@ARTICLE{gebhardt_learning_robust_policies_2018,
  author = {Gregor H. W. Gebhardt and Kevin Daun and Marius Schnaubelt and Gerhard Neumann},
  title = {Learning Robust Policies for Object Manipulation with Robot Swarms},
  journal = {Proceedings of the IEEE International Conference on Robotics and Automation},
  year = {2018},
  pages = {7688-7695},
  crossref = {p11126},
  keywords = {swarm robotics, policy search, kernel methods, kilobots},
  url = {http://www.ausy.tu-darmstadt.de/uploads/Team/GregorGebhardt/LearningRobustPoliciesForObjectManipulationWithRobotSwarms.pdf},
}

@INBOOK{2018:Springer-STAR_ViGiR,
  author = {D. Conner and S. Kohlbrecher and P. Schillinger and A. Romay and A. Stumpf and S. Maniatopoulos and H. Kress-Gazit and O. von Stryk},
  title = {Collaborative autonomy between high-level behaviors and human operators for control of complex tasks with different humanoid robots },
  year = {2018},
  volume = {121},
  pages = {429-494},
  publisher = {Springer},
  editor = {M. Spenko and S. Buerger and K. Iagnemma},
  series = {Springer Tracts in Advanced Robotics},
  booktitle = {The DARPA Robotics Challenge Finals: Humanoid Robots To The Rescue},
  url = {https://www.springer.com/de/book/9783319746654},
  abstract = {This chapter discusses the common reactive high-level behavioral control system used by Team ViGIR and Team Hector on separate robots in the 2015 DARPA Robotics Challenge (DRC) Finals. We present an approach that allows one or more human operators to share control authority with a high-level behavior controller in the form of a finite state machine (automaton). This collaborative autonomy leverages the relative strengths of the robotic system and the (remote) human operators; it increases reliability of the human-robot team performance and decreases the task completion time. This approach is well-suited to disaster scenarios due to the unstructured nature of the environment. The system allows the operators to adjust the robotic system’s autonomy on-the-fly in response to changing circumstances, and to modify pre-defined behaviors as needed. To enable these high-level behaviors, we introduce our system designs for several of the lower-level system capabilities such as footstep planning and template-based object manipulation. We evaluate the proposed approach in the context of our two teams’ participation in the DRC Finals using two different humanoid platforms, and in systematic experiments conducted in the lab afterward. We present a discussion about the lessons learned during the DRC, especially those related to transitioning between operator-centered control and behavior-centered control during competition. Finally, we describe ongoing research beyond the DRC that extends the systems developed during the DRC. All of our described software is available as open source software.},
}

@INPROCEEDINGS{2018:ICRA-Kanoulas,
  author = {D. Kanoulas and A. Stumpf and V.S. Raghavan and C. Zhou and A. Toumpa and O. von Stryk and D.G. Caldwell and N.G. Tsagarakis},
  title = {Footstep planning in rough terrain for bipedal robots using curved contact patches},
  year = {2018},
  month = {21 - 25 May},
  address = {Brisbane, Australia},
  booktitle = {Proc. IEEE Int. Conf. on Robotics and Automation (ICRA)},
  abstract = {Bipedal robots have gained a lot of locomotion capabilities the past few years, especially in the control level. Navigation over complex and unstructured environments using exteroceptive perception, is still an active research topic. In this paper, we present a footstep planning system to produce foothold placements, using visual perception and proper environment modeling, given a black box walking controller. In particular, we extend a state-of-the-art search-based planning approach (ARA*) that produces 6DoF footstep sequences in 3D space for flat uneven terrain, to also handle rough curved surfaces, e.g. rocks. This is achieved by integrating both a curved patch modeling system for rough local terrain surfaces and a flat foothold contact analysis based on visual range input data, into the existing planning framework. The system is experimentally validated using real-world point clouds, while rough terrain stepping demonstrations are presented on the WALK-MAN humanoid robot, in simulation.},
}

@ARTICLE{2018:RAL-Kirchhoff-etal,
  author = {Jérôme Kirchhoff and Oskar von Stryk},
  title = {Velocity estimation for ultra lightweight tendon driven series elastic robots},
  journal = {IEEE Robotics and Automation Letters},
  year = {2018},
  volume = {3},
  number = {2},
  pages = {664-671},
  month = {April},
  doi = {10.1109/LRA.2017.2729663},
  abstract = {Accurate velocity estimation is an important basis for robot control, but especially challenging for highly elastically driven robots. These robots show large swing or oscillation effects if they are not damped appropriately during the performed motion. In this paper, we consider an ultra lightweight tendon driven series elastic robot arm equipped with low-resolution joint position encoders. We propose an adaptive Kalman filter for velocity estimation that is suitable for these kinds of robots with a large range of possible velocities and oscillation frequencies. Based on an analysis of the parameter characteristics of the measurement noise variance, an update rule based on the filter position error is developed that is easy to adjust for use with different sensors. Evaluation of the filter both in simulation and in robot experiments shows a smooth and accurate performance, well suited for control purposes.},
}

@INPROCEEDINGS{2017:GHTC,
  author = {L. Baumgärtner and S. Kohlbrecher and J. Euler and T. Ritter and M. Schmittner and C. Meurisch and M. Mühlhäuser and M. Hollick and O. von Stryk and B. Freisleben},
  title = {Emergency communication in challenged environments via unmanned ground and aerial vehicles},
  year = {2017},
  month = {19-22 Oct.},
  address = {San Jose, CA, USA},
  booktitle = {Proc. IEEE Global Humanitarian Technology Conference (GHTC)},
  doi = {10.1109/GHTC.2017.8239244},
  abstract = {Unmanned ground vehicles (UGVs) and unmanned aerial vehicles (UAVs) are promising assets to support rescue operations in natural or man-made disasters. Most UGVs and UAVs deployed in the field today depend on human operators and reliable network connections to the vehicles. However, network connections in challenged environments are often lost, thus control can no longer be exercised. In this paper, we present a novel approach to emergency communication where semi-autonomous UGVs and UAVs cooperate with humans to dynamically form communication islands and establish communication bridges between these islands. Humans typically form an island with their mobile devices if they are in physical proximity; UGVs and UAVs extend an island"s range by carrying data to a neighboring island. The proposed approach uses delay/disruption-tolerant networking for non-time critical tasks and direct mesh connections for prioritized tasks that require real-time feedback. The developed communication platform runs on rescue robots, commodity mobile devices, and various drones, and supports our operations and control center software for disaster management.},
}

@INPROCEEDINGS{2017:IROS-Missura,
  author = {M. Missura and D. Lee and O. von Stryk and M. Bennewitz},
  title = {The synchronized holonomic model: A framework for efficient motion generation},
  year = {2017},
  month = {24-28 Sept. },
  booktitle = {Prof. IEEE Intl. Conf. on Intelligent Robots and Systems (IROS)},
  doi = {10.1109/IROS.2017.8206025},
  abstract = {We present a simple and efficient mathematical framework suitable for generating motion in the context of a variety of robotic motion tasks ranging from low-level motor control up to high-level locomotion planning. Our concept is based on a one-dimensional second-order model that allows analytic computation of its inverse dynamics while respecting physical constraints. This makes it a particularly useful tool for tasks that are expressed only as a start and goal state, such as animation key frames or way points in path planning. By means of time synchronization, the model extends easily to an arbitrary number of dimensions in a way that the target is reached in all dimensions at the same time. The framework excels in terms of execution time, which lies in the microsecond range even for high-dimensional trajectory generation tasks. We demonstrate our method in two different settings - full-body trajectory generation and path planning - and show its benefits in comparison with current state-of-the-art algorithms.},
}

@INPROCEEDINGS{2017:RC-Ommer,
  author = {Nicolai Ommer and Alexander Stumpf and Oskar von Stryk},
  title = {Real-Time Online Adaptive Feedforward Velocity Control for Unmanned Ground Vehicles},
  year = {2017},
  pages = {to appear},
  publisher = {Springer},
  booktitle = {RoboCup Symposium 2017},
  pdf = {2017_Ommer_adaptive_controller_rc_symposium.pdf},
  abstract = {Online adaptation of motion models enables autonomous robots to move more accurate in case of unknown disturbances. This paper proposes a new adaptive compensation feedforward controller capable of online learning a compensation motion model without any prior knowledge to counteract non-modeled disturbance such as slippage or hardware malfunctions. The controller is able to prevent motion errors a priori and is well suited for real hardware due to high adaptation rate. It can be used in conjunction with any motion model as only motion errors are compensated. A simple interface enables quick deployment of other robot systems as demonstrated in Small Size and Rescue Robot RoboCup leagues.},
}

@INPROCEEDINGS{2017:AIM-Kirchhoff-etal,
  author = {Jérôme Kirchhoff and Oskar von Stryk},
  title = {New insights in synthetic fiber rope elongation and its detection for ultra lightweight tendon driven series elastic robots},
  year = {2017},
  pages = {to appear},
  month = {July 3-7},
  address = {Munich, Germany},
  booktitle = {Proc. IEEE/ASME Int. Conf. on Advanced Intelligent Mechatronics (AIM)},
  abstract = {Selecting transmission components for tendon driven actuation systems can be challenging because of the variety of available solutions. Synthetic fiber ropes have great potential for these systems, but the typically provided characteristics are not always suitable to decide whether a rope should be used in the specific system or not. In this paper, a comparative evaluation of the elongation characteristic regarding different rope materials, manufacturers and temperatures is presented. Further, the influence of guiding pulleys is investigated concerning the application at ultra lightweight tendon driven series elastic robots. The knowledge gained from the performed new rope analysis supports the design process of tendon driven robots. Since tendon elongation influences the control performance and joint torque estimation of the regarded class of robots, a novel observer-based approach for tendon elongation detection is presented and evaluated, which enables to monitor wear for quality assurance and to avoid failures.},
}

@ARTICLE{Ritter_Decentralized_2017,
  author = {Tobias Ritter and Stefan Ulbrich and Oskar von Stryk},
  title = {Decentralized Dynamic Data-Driven Monitoring of Dispersion Processes on Partitioned Domains},
  journal = {Procedia Computer Science},
  year = {2017},
  volume = {108},
  pages = {1632 - 1641},
  note = {International Conference on Computational Science, {ICCS} 2017, 12-14 June 2017, Zurich, Switzerland},
  doi = {10.1016/j.procs.2017.05.033},
  url = {http://www.sciencedirect.com/science/article/pii/S1877050917305501},
  pdf = {2017_Ritter_ICCS.pdf},
  abstract = {The application of mobile sensor-carrying vehicles for online estimating dynamic dispersion processes is extremely beneficial. Based on current estimates that depend on past measurements and forecasts obtained from a discretized PDE-model, the movement of the vehicles can be adapted resulting in measurements at more informative locations. In this work, a novel decentralized monitoring approach based on a partitioning of the spatial domain into several subdomains is proposed. Each sensor is assigned to the subdomain it is located in and is only required to maintain a process and multi-vehicle model related to its subdomain. In this way, vast communication requirements of related centralized approaches and costly full model simulations are avoided making the presented approach more scalable with respect to a larger number of sensor-carrying vehicles and a larger problem domain. The approach consists of a new prediction and update method based on a domain decomposition method and a partitioned variant of the Ensemble Square Root Filter getting along with a minimum exchange of data between sensors on neighboring subdomains. Furthermore, a cooperative vehicle controller is applied in such a way that a dynamic adaption of the sensor distribution becomes possible.},
}

@INPROCEEDINGS{2017:IFAC-Euler,
  author = {J. Euler and O. von Stryk},
  title = {Decentralized Data-Driven Control of Cooperating Sensor- Carrying UAVs in a Multi-Objective Monitoring Scenario},
  year = {2017},
  volume = {50},
  number = {1},
  pages = {15828-15834},
  month = {July 9-14},
  address = {Toulouse, France},
  booktitle = {Proc. 20th IFAC World Congress},
  doi = {10.1016/j.ifacol.2017.08.2316},
  abstract = {For estimating atmospheric dispersion of harmful material, the use of multiple sensor-equipped UAVs for information gathering offers great flexibility, but requires an efficient adaptive sampling strategy that exploits multi-vehicle cooperation. For this purpose, a novel decentralized data-driven online control scheme for cooperating vehicles in multi-objective monitoring scenarios is presented in this paper. In the considered use case, multiple UAVs are to adaptively gather measurements for estimating the parameters of an atmospheric dispersion model. At the same time, they are required to cooperatively patrol predefined checkpoints. Vehicle-specific optimal waypoints for each UAV are determined by sequential optimum design. Following these waypoints leads to a maximized information gain of the acquired measurements, such that the parameter estimate is iteratively improved. On the other hand, checkpoint allocation as well as trajectory planning is provided by a decentralized model-predictive controller based on a discrete-time mixed-integer linear problem formulation. By permanent interaction of parameter estimation, waypoint calculation, and cooperative control, a fully optimization-based, yet efficient and adaptive feedback control approach is obtained. Simulations successfully demonstrate its effectiveness.},
}

@ARTICLE{2017:RAM-Beckerle,
  author = {P. Beckerlea and O. Christ and T. Schürmann and J. Vogt and O. von Stryk and S. Rinderknecht},
  title = {A human-machine-centered design method for (powered) lower limb prosthetics},
  journal = {Robotics and Autonomous Systems},
  year = {2017},
  volume = {95},
  pages = {1-12},
  month = {September},
  doi = {10.1016/j.robot.2017.05.004},
  abstract = {This paper proposes a human-machine-centered approach to lower limb prosthetic design. The approach is based on a profound analysis and modeling of human factors from user and expert survey data. With this knowledge, user demands are considered in the prioritization of technical requirements. To evaluate the design framework, it is applied to the example of the design of a powered prosthetic knee. Key result of this application are a distinct changes in technical requirement priorities that might yield completely different prosthetic designs. Thereby, the potential of the proposed method is substantiated while a practical evaluation is aspect to future studies. Beyond this, the method is easily transferable to other robotic devices operating close to their users, e.g., exoskeletons or teleoperators.},
}

@INPROCEEDINGS{2017:ICRA-Euler,
  author = {J. Euler and O. von Stryk},
  title = {Optimized vehicle-specific trajectories for cooperative process estimation by sensor-equipped UAVs},
  year = {2017},
  month = {29 May-3 June},
  address = {Singapore},
  booktitle = {Proc. IEEE Int. Conf. on Robotics and Automation (ICRA)},
  doi = {10.1109/ICRA.2017.7989386},
  abstract = {This paper presents a sequential optimum design approach for estimating the parameters of an atmospheric dispersion process model based on measurement data gathered by a team of cooperating sensor-equipped UAVs. Locally optimal waypoint sequences that account for each UAV’s possibly heterogeneous motion dynamics are computed by minimizing a suitable optimality criterion. Following these waypoints, the UAVs cooperatively maximize the information gain of the acquired measurements. A decentralized data-driven online control scheme is proposed that couples parameter estimation, waypoint calculation, and vehicle control and enables the UAVs to adaptively observe the dynamic process and iteratively improve the parameter estimate. Simulations demonstrate the effectiveness of the proposed scheme in reducing the error between the estimated and the true dispersion model parameters compared to non-adaptive sensing strategies. In addition, the effect of using different optimality criteria, different numbers and types of UAVs as well as two options for decentralizing the waypoint calculation are investigated.},
}

@ARTICLE{2016:JFR-Romay-etal,
  author = {A. Romay and S. Maniatopoulos and S. Kohlbrecher and P. Schillinger and A. Stumpf and H. Kress-Gazit and O. von Stryk and D. Conner},
  title = {Collaborative autonomy between high-level behaviors and human supervisors for remote manipulation tasks using different humanoid robots},
  journal = {Journal of Field Robotics},
  year = {2017},
  volume = {34},
  number = {2},
  pages = {333-358},
  month = {March},
  note = {First published: 8 September 2016},
  doi = {10.1002/rob.21671},
  url = {http://onlinelibrary.wiley.com/doi/10.1002/rob.21671/full},
  pdf = {2016_RomayEtAl_JFR.pdf},
  abstract = {Team ViGIR and Team Hector participated in the DARPA Robotics Challenge (DRC) Finals, held June 2015 in Pomona, California, along with 21 other teams from around the world. Both teams competed using the same high-level software, in conjunction with independently developed low-level software specific to their humanoid robots. Based on previous work on operator-centric manipulation control at the level of affordances, we developed an approach that allows one or more human operators to share control authority with a high-level behavior controller. This collaborative autonomy decreases the completion time of manipulation tasks, increases the reliability of the human-robot team, and allows the operators to adjust the robotic system’s autonomy on-the-fly. This article discusses the technical challenges we faced and overcame during our efforts to allow the human operators to interact with the robotic system at a higher level of abstraction and share control authority with it. We introduce and evaluate the proposed approach in the context of our two teams’ participation in the DRC Finals. We also present additional, systematic experiments conducted in the lab afterwards. Finally, we present a discussion about the lessons learned while transitioning between operator-centered manipulation control and behavior-centered manipulation control during competition.},
}

@ARTICLE{2016:BBp3-BioinspBiomim,
  author = {M.A.Sharbafi and C. Rode and S. Kurowski and D. Scholz and R. Möckel and K. Radkhah and G. Zhao and A.M. Rashty and O. von Stryk and A. Seyfarth},
  title = {A new biarticular actuator design facilitates control of leg function in BioBiped3},
  journal = {Bioinspiration & Biomimetics},
  year = {2016},
  volume = {11},
  number = {4},
  pages = {046003},
  doi = {10.1088/1748-3190/11/4/046003},
  url = {http://iopscience.iop.org/article/10.1088/1748-3190/11/4/046003},
  abstract = {Bioinspired legged locomotion comprises different aspects, such as (i) benefiting from reduced complexity control approaches as observed in humans/animals, (ii) combining embodiment with the controllers and (iii) reflecting neural control mechanisms. One of the most important lessons learned from nature is the significant role of compliance in simplifying control, enhancing energy efficiency and robustness against perturbations for legged locomotion. In this research, we investigate how body morphology in combination with actuator design may facilitate motor control of leg function. Inspired by the human leg muscular system, we show that biarticular muscles have a key role in balancing the upper body, joint coordination and swing leg control. Appropriate adjustment of biarticular spring rest length and stiffness can simplify the control and also reduce energy consumption. In order to test these findings, the BioBiped3 robot was developed as a new version of BioBiped series of biologically inspired, compliant musculoskeletal robots. In this robot, three-segmented legs actuated by mono- and biarticular series elastic actuators mimic the nine major human leg muscle groups. With the new biarticular actuators in BioBiped3, novel simplified control concepts for postural balance and for joint coordination in rebounding movements (drop jumps) were demonstrated and approved.},
}

@INPROCEEDINGS{2016:Humanoids-Stumpf,
  author = {Alexander Stumpf and Stefan Kohlbrecher and Oskar von Stryk and David C. Conner},
  title = {Open Source Integrated 3D Footstep Planning Framework for Humanoid Robots},
  year = {2016},
  pages = {938-945},
  month = {Nov 15-17},
  address = {Cancún, Mexico},
  booktitle = {Proc. IEEE-RAS Intl. Conf. Humanoid Robots},
  doi = {10.1109/HUMANOIDS.2016.7803385},
  pdf = {2016_Stumpf_footstep_planning_framework_Humanoids.pdf},
  abstract = {Humanoid robots benefit from their anthropomorphic shape when operating in human-made environments. In order to achieve human-like capabilities, robots must be able to perceive, understand and interact with the surrounding world. Humanoid locomotion in uneven terrain is a challenging task as it requires sophisticated world model generation, motion planning and control algorithms and their integration. In recent years, much progress in world modeling and motion control has been achieved. This paper presents one of the very first open source frameworks for full 3D footstep planning available for ROS which integrates perception and locomotion systems of humanoid bipedal robots. The framework is designed to be used for different type of humanoid robots having different perception and locomotion capabilities with minimal implementation effort. In order to integrate with almost any humanoid walking controller, the system can easily be extended with additional functionality that may be needed by low-level motion algorithms. It also considers sophisticated human-robot interaction that enables to direct the planner to generate improved solutions, provides monitoring data to the operator and debugging feedback for developers. The provided software package consists of three major blocks that address world generation, planning and interfacing low-level motion algorithms. The framework has been successfully applied to four different full-size humanoid robots.},
}

@INPROCEEDINGS{CasermanSMC:2016,
  author = {P. Caserman and P. Krabbe and J. Wojtusch and O. von Stryk},
  title = {Real-Time Step Detection Using the Integrated Sensors of a Head-Mounted Display},
  year = {2016},
  booktitle = {Proceedings of IEEE International Conference on Systems, Man, and Cybernetics},
  doi = { 10.1109/SMC.2016.7844777},
  pdf = {SMC_Caserman2016.pdf},
}

@INPROCEEDINGS{WojtuschCybathlon:2016,
  author = {J. Wojtusch and P. Beckerle and T. Schürmann and M. Schumacher and O. Christ and A. Seyfarth and S. Rinderknecht and J. Vogt and O. von Stryk},
  title = {Towards Seamless Integration of Active Assistive Devices into the User"s Body Schema},
  year = {2016},
  booktitle = {Proceedings of the Cybathlon Symposium},
  pdf = {2016_Wojtusch_CYBATHLON.pdf},
  abstract = {Active assistive devices for lower limbs like prostheses or ortheses support the user by providing additional torque to restore and improve locomotion abilities. In order to ultimately achieve their seamless integration into the user’s experience of everyday routine locomotion, they must provide a customized, familiar and predictable behavior that autonomously supports versatile locomotions, which describes formidable challenges for research and development. Moreover from a psychological perspective, the user might regard the device as part of his or her own body, which would mean a successful integration into the body schema. We suggest an integrated investigation of related research questions from psychology, biomechanics, and engineering from the beginning of any development of active assistive devices. Several experimental platforms have been developed by an interdisciplinary group of researchers. They serve as novel research methodologies towards seamless integration of active assistive devices into the user"s body schema. One of the objectives is to investigate how humans incorporate visual, tactile and proprioceptive perception and how to utilize this knowledge in engineering design. The Int2Bot platform is a robot testbed with the shape of a human leg that mimics squatting movements of subjects in order to investigate rubber hand illusion paradigm transferred to lower limbs. Another setup uses a head-mounted display and a treadmill to give subjects the experience of walking through a virtual park. Measures like proprioceptive drift, feeling of presence and agency, body ownership, and location are assessed. Both platforms contribute to a novel prosthesis-user-in-the-loop concept for a holistic, mechanical and perceptive simulation of human gait with different prosthetic concepts. It aims at a user-centered design of assistive devices by utilizing user experience and assessment. First results indicate that optimized variable stiffness actuation and specific visual and auditory stimuli improve the user’s experience.},
}

@ARTICLE{2016:FRAI-Kohlbrecher-etal,
  author = {Stefan Kohlbrecher and Alexander Stumpf and Alberto Romay and Philipp Schillinger and Oskar von Stryk and David C. Conner},
  title = {A comprehensive software framework for complex locomotion and manipulation tasks applicable to different types of humanoid robots},
  journal = {Frontiers in Robotics and AI},
  year = {2016},
  pages = {online},
  doi = {10.3389/frobt.2016.00031},
  url = {http://journal.frontiersin.org/article/10.3389/frobt.2016.00031},
  abstract = {While recent advances in approaches for control of humanoid robot systems show promising results, consideration of fully integrated humanoid systems for solving complex tasks, such as disaster response, has only recently gained focus. In this paper, a software framework for humanoid disaster response robots is introduced. It provides newcomers as well as experienced researchers in humanoid robotics a comprehensive system comprising open source packages for locomotion, manipulation, perception, world modeling, behavior control, and operator interaction. The system uses the Robot Operating System (ROS) as a middleware, which has emerged as a de facto standard in robotics research in recent years. The described architecture and components allow for flexible interaction between operator(s) and robot from teleoperation to remotely supervised autonomous operation while considering bandwidth constraints. The components are self-contained and can be used either in combination with others or standalone. They have been developed and evaluated during participation in the DARPA Robotics Challenge, and their use for different tasks and parts of this competition are described.},
}

@INPROCEEDINGS{2016:AIM-Kirchhoff-etal,
  author = {Jerome Kirchhoff and Oskar von Stryk},
  title = {Robust trajectory tracking control for an ultra lightweight tendon driven series elastic robot arm},
  year = {2016},
  pages = {1297-1304},
  month = {July 12-15},
  address = {Banff, Alberta, Canada},
  booktitle = {Proc. IEEE/ASME Int. Conf. on Advanced Intelligent Mechatronics (AIM)},
  doi = {10.1109/AIM.2016.7576949},
  abstract = {Trajectory tracking control for a tendon driven series elastically actuated robotic arm is considered. This bio-inspired actuation concept enables an ultra lightweight and highly safe robot design that is very well suited for physical human-robot interaction. However, the high elasticity in the joint actuation imposes challenges on robot control, especially for the usual case that no joint torque measurements are available. In this paper, a trajectory tracking controller for this highly compliant robot is presented which does not need explicit joint torque measurements as required by related approaches for robots with elastic joints. A control concept is proposed which aims to be robust against inaccuracies in various model parameters (like robot dynamics, position initialization, drive train stiffness, transmission ratio and friction). It compensates for changes in robot dynamics by equilibrium controlled stiffness. The proposed controller is successfully applied and evaluated in simulated and physical experiments with the robot. },
}

@ARTICLE{2016:KI-Kohlbrecher-etal,
  author = {Stefan Kohlbrecher and Oskar von Stryk},
  title = {From RoboCup Rescue to supervised autonomous mobile robots for remote inspection of industrial plants},
  journal = {KI - Künstliche Intelligenz},
  year = {2016},
  volume = {30},
  number = {3},
  pages = {311–314},
  doi = {doi:10.1007/s13218-016-0446-8},
  url = {http://link.springer.com/article/10.1007/s13218-016-0446-8},
  pdf = {2016-KI_SKo_OvS.pdf},
  abstract = {With increasing capabilities and reliability of autonomous mobile robots, inspection of remote industrial plants in challenging environments becomes feasible. With the ARGOS challenge, oil and gas company TOTAL S.A. initiated an international competition aimed at the development of the first autonomous mobile robot which can safely operate in complete or supervised autonomy over the entire onshore or offshore production site, potentially in hazardous explosive atmospheres and harsh conditions. In this work, the approach of joint Austrian–German Team ARGONAUTS towards solving this challenge is introduced, focussing on autonomous capabilities. These build on functional components developed during prior participation in the RoboCup Rescue Robot League.},
}

@ARTICLE{2016:KI-Romay-etal,
  author = {Alberto Romay and Stefan Kohlbrecher and Oskar von Stryk},
  title = {An object template approach to manipulation for humanoid avatar robots for rescue tasks},
  journal = {KI - Künstliche Intelligenz},
  year = {2016},
  volume = {30},
  number = {3},
  pages = {279-287},
  doi = {10.1007/s13218-016-0445-9},
  url = {http://rdcu.be/ur29},
  pdf = {2016_RomayEtAl_KI.pdf},
  abstract = {Nowadays, the first steps towards the use of remote mobile robots to perform rescue tasks in disaster environments have been made possible. However, these environments still present several challenges for robots, which open new possibilities for research and development. For example, fully autonomous robots are not yet suitable for such tasks with high degree of uncertainty, and pure teloperated robots require high expertise and high mental workload, as well as fast communication to be reliable. In this paper, we discuss a middle ground approach to manipulation, that leverages the strengths and abilities of a human supervisor and a semi-autonomous robot while at the same tackling their weaknesses. This approach is based on the object template concept, which provides an interaction method to rapidly communicate to a remote robot the physical and abstract information for manipulation of the objects of interest. This approach goes beyond current grasp-centered approaches by focusing on the affordance information of the objects and providing flexibility to solve manipulation tasks in versatile ways. Experimental evaluation of the approach is performed using two highly advanced humanoid robots.},
}

@ARTICLE{Ritter_Decentralized_2016,
  author = {Tobias Ritter and Juliane Euler and Stefan Ulbrich and Oskar von Stryk},
  title = {Decentralized Dynamic Data-driven Monitoring of Atmospheric Dispersion Processes},
  journal = {Procedia Computer Science},
  year = {2016},
  volume = {80},
  pages = {919 - 930},
  note = {International Conference on Computational Science 2016, {ICCS} 2016, 6-8 June 2016, San Diego, California, {USA}},
  doi = {10.1016/j.procs.2016.05.382},
  url = {http://www.sciencedirect.com/science/article/pii/S1877050916308584},
  pdf = {2016_Ritter_ICCS.pdf},
  abstract = {Online state and parameter estimation of atmospheric dispersion processes using multiple mobile sensor platforms is a prominent example of Dynamic Data-Driven Application Systems (DDDAS). Based on repeated predictions of a partial differential equation (PDE) model and measurements of the sensor network, estimates are updated and sensor trajectories are adapted to obtain more informative measurements. While most of the monitoring strategies require a central supercomputer, a novel decentralized plume monitoring approach is proposed in this paper. It combines the benefits of distributed approaches like scalability and robustness with the prediction ability of PDE process models. The strategy comprises model order reduction to keep calculations computationally tractable and a joint Kalman Filter with Covariance Intersection for incorporating measurements and propagating state information in the sensor network. Moreover, a cooperative vehicle controller is employed to guide the sensor vehicles to dynamically updated target locations that are based on the current estimated error variance.},
}

@INPROCEEDINGS{2016:ICRA_Schillinger-etal,
  author = {Philipp Schillinger and Stefan Kohlbrecher and Oskar von Stryk},
  title = {Human-Robot Collaborative High-Level Control with Application to Rescue Robotics},
  year = {2016},
  pages = {2796-2802},
  month = {May 16-21},
  note = {Finalist for Best Human-Robot Interaction Paper Award},
  booktitle = {Proc. IEEE Int. Conf. on Robotics and Automation (ICRA)},
  doi = {10.1109/ICRA.2016.7487442},
  url = {ieeexplore.ieee.org/xpl/articleDetails.jsp?reload=true&arnumber=7487442},
  abstract = {Motivated by the DARPA Robotics Challenge (DRC), the application of operator assisted (semi-)autonomous robots with highly complex locomotion and manipulation abilities is considered for solving complex tasks in potentially unknown and unstructured environments. Because of the limited a priori knowledge about the state of the environment and tasks needed to achieve a complex mission, a sufficiently complete a priori design of high level robot behaviors is not possible. Most of the situational knowledge required for such behavior design is gathered only during runtime and needs to be interpreted by a human operator. However, current behavior control approaches only allow for very limited adaptation at runtime and no flexible operator interaction. In this paper an approach for definition and execution of complex robot behaviors based on hierarchical state machines is presented, allowing to flexibly change the structure of behaviors on the fly during runtime through assistance of a remote operator. The efficiency of the proposed approach is demonstrated and evaluated not only in an example scenario, but also by application in two robot competitions.},
}

@ARTICLE{RAL_Wojtusch2016,
  author = {J. Wojtusch and J. Kunz and O. von Stryk},
  title = {MBSlib - An Efficient Multibody Systems Library for Kinematics and Dynamics Simulation, Optimization and Sensitivity Analysis},
  journal = {Robotics and Automation Letters, IEEE},
  year = {2016},
  volume = {1},
  number = {2},
  pages = {954-960},
  keywords = {Biological system modeling;Computational modeling;Heuristic algorithms;Libraries;Mathematical model;Numerical models;Optimization;Calibration and Identification;Direct/Inverse Dynamics Formulation;Multibody Systems;Optimization and Optimal Control;Sensitivity Analysis},
  doi = {10.1109/LRA.2016.2527830},
  url = {http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=7403876},
  pdf = {2016_Wojtusch_RAL.pdf},
  abstract = {The dynamic behavior of many technical and biomechanical systems can be modeled, simulated and optimized by using a multibody systems approach. Systems with many degrees of freedom typically result in complex and high-dimensional multibody systems models that necessitate capable modeling approaches and efficient computational algorithms as well as impede the numerical solution of related optimization problems. In this paper, the efficient and modular multibody systems library MBSLIB for kinematics and dynamics simulation, optimization and sensitivity analysis is presented. MBSLIB provides an intuitive modeling interface, modular software architecture, efficient computational algorithms as well as the computation of derivatives with respect to system states, control variables or model parameters. In combination with gradient-based optimization methods, the derivatives can be used to facilitate the numerical solution of optimization problems significantly. The library is open and can be obtained from the MBSLIB website. These features make MBSLIB a powerful, flexible and lightweight modeling, simulation and optimization library suitable for many technical and biomechanical applications.},
}

@TECHREPORT{2015:ViGIR-Final-Report,
  author = {David Conner and Stefan Kohlbrecher and Alberto Romay and Alexander Stumpf and Spyros Maniatopoulos and Moritz Schappler and Benjamin Waxler },
  title = {Team ViGIR: DARPA Robotics Challenge},
  year = {2015},
  institution = {TORC Robotics, Technical Universita Darmstadt, Cornell University, Leibniz University Hanover},
  url = {http://www.dtic.mil/dtic/tr/fulltext/u2/a623035.pdf},
  abstract = {This report documents Team ViGIR’s efforts in the DARPA Robotics Challenge (DRC) between October 2012 and August 2015. Team ViGIR, a multinational collaborative research and development effort that spanned nine time zones, began as a Track B participant in the simulation-based Virtual Robotics Challenge; after placing in the top six, we began working the Atlas humanoid robotic system developed by Boston Dynamics. Team ViGIR competed in both the DRC Trials and DRC Finals. This report documents our performance, lessons learned along the way, and describes the novel contributions of our team. Specific focus areas include template-based manipulation, footstep planning, and autonomous behavior specification and execution. The software used in the competition and described in this report is being open sourced at http://github.com/team-vigir as part of our commitment to improving the capabilities of humanitarian rescue robotics.},
}

@INPROCEEDINGS{2015:HUM-Romay-Driving,
  author = {A. Romay and A. Stein and M. Oehler and A. Stumpf and S. Kohlbrecher and D.C. Conner and O. von Stryk},
  title = {Open source driving controller concept for humanoid robots: Teams Hector and ViGIR at 2015 DARPA Robotics Challenge Finals},
  year = {2015},
  pages = {video},
  month = {Nov. 3-5},
  address = {Seoul, Korea},
  booktitle = {IEEE-RAS Intl. Conf. on Humanoid Robots},
  pdf = {2015_RomayEtAl_Humanoids_DrivingVideo.mp4},
  abstract = {Among the eight tasks of the DARPA Robotics Challenge (DRC), the driving task was one of the most challenging. Obstacles in the course prevented straight driving and restricted communications limited the situation awareness of the operator. In this video we show how Team Hector and Team ViGIR successfully completed the driving task with dfferent robot platforms, THOR-Mang and Atlas respectively, but using the same software and compliant steering adapter. Our driving user interface presents to the operator image view from cameras and driving aids such as wheel positioning and turn radius path of the wheels. The operator uses a standard computer game joystick which is used to command steering wheel angles and gas pedal pressure. Steering wheel angle positions are generated off-line and interpolated on-line in the robot"s onboard computer. The compliant steering adapter accommodates end-effector positioning errors. Gas pedal pressure is generated by a binary joint position of the robot"s leg. Commands are generated in the operator control station and sent as target positions to the robot. The driving user interface also provides feedback from the current steering wheel position. Video footage with descriptions from the driving interface, robot"s camera and LIDAR perception and external task monitoring is presented.},
}

@INPROCEEDINGS{HUM_Wojtusch2015,
  author = {J. Wojtusch and O. von Stryk},
  title = {HUMOD - A versatile and open database for the investigation, modeling and simulation of human motion dynamics on actuation level},
  year = {2015},
  booktitle = {IEEE-RAS Intl. Conf. on Humanoid Robots},
  doi = {10.1109/HUMANOIDS.2015.7363534},
  pdf = {HUM_Wojtusch2015.pdf},
  abstract = {Collecting high-quality biomechanical measurement data for investigating human motion dynamics with muscle driven actuation, i.e., joint trajectories, ground reaction forces and muscle activities, usually requires experienced examiners, expensive measurement equipment and sophisticated processing. Several published databases offer biomechanical measurement data of various human motions. However, most of these databases are not primarily intended for modeling, simulation and validation of human motion dynamics with muscle driven actuation and do not include ground reaction forces together with muscle activities and detailed anthropometric parameters of the subjects. In this paper, the HUMOD Database, a versatile and quite unique combination of comprehensive biomechanical measurement data and anthropometric parameters with a focus on lower limbs, is introduced. The provided datasets allow to create and validate biomechanical models of the human locomotor system on actuation level and to investigate and simulate human motion dynamics including muscle driven actuation. Besides investigations in biomechanics, the database can be of value especially for the design and development of musculoskeletal humanoid robots and for better understanding and benchmarking human-like robot locomotion. The database contains raw and processed biomechanical measurement data from a threedimensional motion capture system, an instrumented treadmill and an electromyographical measurement system for eight different motion tasks performed by a healthy female and male subject as well as anthropometric parameters for both subjects. The biomechanical measurement data, anthropometric parameters and source code of the applied computational scripts are open and can be obtained free of charge from the HUMOD Database website.},
}

@INPROCEEDINGS{2015:HUM-Romay,
  author = {A. Romay and S. Kohlbrecher and D.C. Conner and O. von Stryk},
  title = {Achieving versatile manipulation tasks with unknown objects by supervised humanoid robots based on object templates},
  year = {2015},
  pages = {to appear},
  month = {Nov. 3-5},
  booktitle = {IEEE-RAS Intl. Conf. on Humanoid Robots},
  pdf = {2015_RomayEtAl_Humanoids.pdf},
  abstract = {The investigations of this paper are motivated by the scenario of a supervised semi-autonomous humanoid robot entering a mainly unknown, potentially degraded human environment to perform highly diverse disaster recovery tasks. For this purpose, the robot must be enabled to use any object it can find in the environment as tool for achieving its current manipulation task. This requires the use of potential unknown objects as well as known objects for new purposes (e.g. using a drill as a hammer). A recently proposed object template manipulation approach is extended to provide a semi-autonomous humanoid robot assisted by a remote human supervisor with the versatility needed to utilize objects in the described manner applying affordances [1] from other previously known objects. For an Atlas humanoid robot it is demonstrated how using a small set of such object templates with well defined affordances can be used to solve manipulation tasks using new unknown objects.},
}

@INPROCEEDINGS{2015:HUM-Scholz,
  author = {D. Scholz and O. von Stryk},
  title = {Efficient design parameter optimization for musculoskeletal bipedal robots combining simulated and hardware-in-the-loop experiments},
  year = {2015},
  pages = {512-518},
  month = {Nov. 3-5},
  booktitle = {IEEE-RAS Intl. Conf. on Humanoid Robots},
  pdf = {2015_HUMANOIDS_Scholz.pdf},
  abstract = {The design and tuning of bio-inspired musculoskeletal bipedal robots with tendon driven series elastic actuation (TD-SEA) including biarticular structures is more complex than for conventional rigid bipedal robots. To achieve a desired dynamic motion goal additional hardware parameters (spring coefficients, rest lengths, lever arms) of both, the TDSEAs and the biarticular structures, need to be adjusted. Furthermore, the biarticular structures add correlations over multiple joints which increase the complexity of tuning of these parameters. Parameter adaption and tuning is needed to fit active and passive dynamics of the actuators and the control system. For the considered class of musculoskeletal bipedal robots no fully satisfying systematic approach to efficiently tune all of these parameters has been demonstrated yet. Conventional approaches for tuning of hardware parameters in rigid robots are either simulation based or use a hardware-in-the-loop optimization. This paper presents a new approach to efficiently optimize these parameters, by combining the advantages of simulation-in-the-loop and hardware-in-the-loop optimizations. Grahical interpretation of suitable metrics, like resulting quality values, are used to interpret the simulation results in order to efficiently guide the hardware experiments. By carefully considering the simulation results and adjusting the sequence of robot experiments based on biomechanical insights, the required number of hardware experiments can be significantly reduced. This approach is applied to the musculoskeletal BioBiped2 robot where the hardware parameters of the elastic actuation of the Gastrocnemius and Soleus structures are optimized. A comparison with a state-of-the-art hardware-in-the-loop optimization method demonstrates the efficiency of the presented approach.},
}

@INPROCEEDINGS{BeckerleICORR:2015,
  author = {P. Beckerle and J. Wojtusch and A. Seyfarth and O. von Stryk and S. Rinderknecht},
  title = {Analyzing and Considering Inertial Effects in Powered Lower Limb Prosthetic Design},
  year = {2015},
  booktitle = {Proceedings of IEEE International Conference on Rehabilitation Robotics},
  pdf = {2015_Beckerle_ICORR.pdf},
  abstract = {Powered lower limb prostheses are designed to restore the biomechanical functionality of missing parts of their users’ bodies. However, they do not yet meet the versatility and efficiency of the biological counterpart. A crucial open issue is how the prosthetic system and its actuator should be designed to achieve an energy efficient operation. This paper proposes a novel methodology for the design and optimization of elastically actuated lower limb prostheses. In contrast to other studies, actuator inertia is considered in this paper. Further, the approach considers the inertial parameters of the prosthesis after initial design to revise the requirements and redesign the system. The design procedure is described and presented for the example of a powered prosthetic knee. In this, considering actuator inertia enables to find optimal stiffness values for walking that are not to be found with common methods and altered optimal values for other gait types. Further, the consideration of the inertial properties of the pre-designed prosthesis in a gait simulation lead to distinctly lower requirements for peak power. For walking those are decreased by about 10% while in running a reduction of over 30% is observed. Analyzing those results, the potential of considering actuator and prosthetic inertia in design and thus the benefits due to the presented method are pointed out.},
}

@INPROCEEDINGS{NollEMBC:2015,
  author = {V. Noll and J. Wojtusch and J. Schuy and M. Grimmer and P. Beckerle and S. Rinderknecht},
  title = {Measurement of Biomechanical Interactions at the Stump-Socket Interface in Lower Limb Prostheses},
  year = {2015},
  booktitle = {Proceedings of the International Conference of the IEEE Engineering in Medicine and Biology Society},
  pdf = {2015_Noll_EMBC.pdf},
  abstract = {Abstract—This paper introduces a novel measuring approach for detecting relative movement between stump and socket in lower limb prostheses. The application of the motion capturing based measuring approach is shown at a single male trans- tibial amputee using a Patella Tendon Bearing (PTB) socket. It further investigates and assesses the feasibility of measuring the relative movement between stump and socket during level walking at different velocities and allocating it to the coinciding loads. Representative results for the two translational degrees of freedom in the sagittal plane are presented and discussed. For the proximodistal (pd) direction, a linear correlation between applied load and relative movement is found, while for the anteroposterior (ap) direction the stump movement is largely influenced by the motion sequence during the respective gait event. Additionally, the effect of walking speed is discussed.},
}

@INCOLLECTION{2015:DyDESS-Euler,
  author = {Juliane Euler and Tobias Ritter and Stefan Ulbrich and Oskar von Stryk},
  title = {Centralized Ensemble-Based Trajectory Planning of Cooperating Sensors for Estimating Atmospheric Dispersion Processes},
  year = {2015},
  volume = {8964},
  publisher = {Springer International Publishing},
  editor = {Sai Ravela and Adrian Sandu},
  series = {Lecture Notes in Computer Science},
  booktitle = {Dynamic Data-Driven Environmental Systems Science},
  doi = {10.1007/978-3-319-25138-7},
  pdf = {2014_EulerEtAl_DyDESS.pdf},
  abstract = {Optimal coordination of multiple sensors is crucial for efficient atmospheric dispersion estimation. The proposed approach adaptively provides optimized trajectories with respect to sensor cooperation and uncertainty reduction of the process estimate. To avoid the time-consuming solution of a complex optimal control problem, estimation and vehicle control are considered separate problems linked in a sequential procedure. Based on a partial differential equation model, the Ensemble Transform Kalman Filter is applied for data assimilation and generation of observation targets offering maximum information gain. A centralized model-predictive vehicle controller simultaneously provides optimal target allocation and collision-free path planning. Extending previous work, continuous measuring is assumed, which attaches more significance to the course of the trajectories. Local attraction points are introduced to draw the sensors to regions of high uncertainty. Moreover, improved target updates increase the sampling efficiency. A simulated test case illustrates the approach in comparison to non-attracted trajectories.},
}

@INPROCEEDINGS{2015:HUM-Schappler-etal,
  author = {M. Schappler and J. Vorndamme and A. Toedtheide and D.C. Conner and O. von Stryk and Sami Haddadin },
  title = {Modeling, identification and joint impedance control of the Atlas arms},
  year = {2015},
  pages = {1052-1059 },
  month = {Nov. 3-5},
  booktitle = {IEEE RAS Intl. Conf. on Humanoid Robots},
  doi = {10.1109/HUMANOIDS.2015.7363499 },
  abstract = {Compliant manipulation has become central to robots that are sought to safely act in and interact with unstructured as well as only partially known environments. In this paper we equip the hydraulically actuated, position controlled arms of the Atlas robot with model-based joint impedance control, including suitable damping design, and experimentally verify the proposed algorithm. Our approach, which originates from the advances in soft-robotics control, relies on high-performance low-level joint torque control. This makes it independent from the actual technology being hydraulic or electromechanical. This paper describes the approach to accurately model the dynamics, and design the optimal excitation trajectory for system identification to enable the specification of model-based feed-forward controls. In conclusion, the implemented controller enables the robot arm to execute significantly smoother motions, be compliant against external forces, and have similar tracking performance as compared to the existing position control scheme. Finally, unknown modeling inaccuracies and contact forces are accurately estimated by a suitable disturbance observer, which will be used in the future to further enhance our controller’s performance.},
}

@INPROCEEDINGS{2015:IROS-Ku-vS,
  author = {S. Kurowski and O. von Stryk},
  title = {A systematic approach to the design of embodiment with application to bio-inspired compliant legged robots},
  year = {2015},
  pages = {3771-3778},
  month = {Sept. 28 - Oct. 02},
  publisher = {IEEE},
  address = {Hamburg, Germany},
  booktitle = {IEEE/RSJ Intl. Conf. on Intelligent Robots and Systems (IROS)},
  doi = {10.1109/IROS.2015.7353906},
  pdf = {2015-IROS_SKu-vS.pdf},
  abstract = {Bio-inspired legged robots with compliant actuation can potentially achieve motion properties in real world scenarios which are superior to conventionally actuated robots. In this paper, a methodology is presented to systematically design and tailor passive and active control elements for elastically actuated robots. It is based on a formal specification of requirements derived from the main design principles for embodied agents as proposed by Pfeifer et al. which are transfered to dynamic model based multi objective optimization problems. The proposed approach is demonstrated and applied for the design of a biomechanically inspired, musculoskeletal bipedal robot to achieve walking and human-like jogging.},
}

@INPROCEEDINGS{delfa2015astrab,
  author = {E. Allouis and R. Marc and J. Gancet and Y.Nevatia and F.Cantori and R.U Sonsalla and M. Fritsche and J. Machowinski and T. Vogele and F.Comin and W. Lewinger and B. Yeomans and C. Saaj and Y.Gao and J.Delfa and P. Weclewski and K. Skocki and B. Imhof and S. Ransom and L. Richter},
  title = {FP7 FASTER project - Demonstration of Multi-platform Operation for Safer Planetary Traverses},
  year = {2015},
  month = {May},
  booktitle = {ASTRA},
  abstract = {As future planetary missions evolve from local exploration in the vicinity of the lander (up to a few km) to more regional operations (with a reach beyond tens of km), the need for a safe and efficient traverse will be greater than ever. To address these challenges, the EU FP7 FASTER project has tackled for the past 4 years the Forward Acquisition of Soil and Terrain data for Exploration Rover which culminated in the successful demonstration of the operational scenario in late 2014 in a representative environment. This paper will briefly recall the selected operational concept for safe traverses for planetary rovers as well as the various sensors created for this project. It will then focus on the latest developments, including the setup and running of the various integration campaigns leading up to the final multi-platform test campaigns at the Airbus DS Mars Yard. Finally, based on the results of the project, it is possible to look ahead to future mission concepts and identify where specific aspects of the FASTER project could contribute to the robustness and safety of future platforms allowing more daring exploration scenarios.},
}

@INPROCEEDINGS{delfa2015astra,
  author = {Juan M. Delfa Victoria and Brian Yeomans and Yang Gao and Oskar von Stryk},
  title = {Autonomous Mission Planning And Execution For Two Collaborative Mars Rovers},
  year = {2015},
  month = {May},
  booktitle = {ASTRA},
  abstract = {One of the most important lessons learnt from more than ten years of robotic exploration in Mars is the high value of autonomy in terms of operations and science return. So far, only a few full-scale experiments to foster autonomy for planetary exploration have been conducted in Europe. One of the most relevant is the recently completed FASTER FP7 framework project, with one of the main scientific contributions being the application of autonomous planning and execution under uncertainty for two collaborative rovers in a Mars scenario where it is not possible to have humans in the loop. This paper presents the results of implementing the QuijoteExpress (abbreviated QE) mission planner and SanchoExpress executive to tackle these problems. QuijoteExpress is a novel platform-independent planner which strengths are performance, plan robustness and expressiveness. QuijoteExpress was able to produce robust collaborative plans for both rovers with only minor tuning under undeterministic and unstructured scenarios. SanchoExpress is a ROS-based, platform-independent timeline executive that can command multiple subsystems in parallel. SanchoExpress (abbreviated SE) can encode platform-dependent knowledge including repair methods for some errors which allow the executive to fix the plan in certain fault scenarios without the need of the replanner, therefore contributing to a more robust execution of the plan. The combined system was found to operate successfully and reliably during the FASTER field trials, enhancing the systems autonomy and enabling complex behaviour to be executed in a robust and fault tolerant manner.},
}

@INBOOK{2015:Soft-Robotics-Book,
  author = {A. Seyfarth and K. Radkhah and O. von Stryk},
  title = {Concepts of Softness for Legged Locomotion and their Assessment},
  year = {2015},
  pages = {120-133},
  publisher = {Springer Verlag},
  editor = {A. Verl and A. Albu-Schäffer and O. Brock and A. Raatz},
  booktitle = {Soft Robotics - Transferring Theory to Application},
  pdf = {2015_Soft_Robotics_Paper.pdf},
  abstract = {In human and animal locomotion, compliant structures play an essential role in the body and actuator design. Recently, researchers have started to exploit these compliant mechanisms in robotic systems with the goal to achieve the yet superior motions and performances of the biological counterpart. For instance, compliant actuators such as series elastic actuators (SEA) can help to improve the energy efficiency and the required peak power in powered prostheses and exoskeletons. However, muscle function is also associated with damping-like characteristics complementing the elastic function of the tendons operating in series to the muscle fibers. Carefully designed conceptual as well as detailed motion dynamics models are key to understanding the purposes of softness, i.e. elasticity and damping, in human and animal locomotion and to transfer these insights to the design and control of novel legged robots. Results for the design of compliant legged systems based on a series of conceptual biomechanical models are summarized. We discuss how these models compare to experimental observations of human locomotion and how these models could be used to guide the design of legged robots and also how to systematically evaluate and compare natural and robotic legged motions.},
}

@Inproceedings{2014_rc_towards_highly_reliable,
  author = {Stefan Kohlbrecher and Florian Kunz and Dorothea Koert and Christian Rose and Paul Manns and Kevin Daun and Johannes Schubert and Alexander Stumpf and Oskar von Stryk},
  title = {Towards Highly Reliable Autonomy for Urban Search and Rescue Robots},
  year = {2015},
  volume = {8992},
  pages = {118-129},
  publisher = {Springer},
  editor = {R.A.C. Bianchi, H.L. Akin, S. Ramamoorthy, K. Sugiura},
  series = {Lecture Notes in Artificial Intelligence (LNAI)},
  booktitle = {RoboCup 2014: Robot World Cup XVIII},
  url = {http://www.springer.com/br/book/9783319186146},
  abstract = {This paper describes the approach used by Team Hector Darmstadt for participation in the 2015 RoboCup Rescue League competition. Participating in the RoboCup Rescue competition since 2009, the members of Team Hector Darmstadt focus on exploration of disaster sites using autonomous Unmanned Ground Vehicles (UGVs). The team has been established as part of a PhD program funded by the German Research Foundation at TU Darmstadt and combines expertise from Computer Science and Mechanical Engineering. We give an overview of the complete system used to solve the problem of reliably finding victims in harsh USAR environments. This includes hardware as well as software solutions and diverse topics like locomotion, SLAM, pose estimation, human robot interaction and victim detection. In 2015, the team focuses on improving the rough terrain motion capabilities of used platforms as well as manipulation capabilities. As a contribution to the RoboCup Rescue community, major parts of the used software have been released and documented as open source software for ROS.},
}

@ARTICLE{2015:JVB,
  author = {C. Mariti and G.G. Muscolo and J. Peters and D. Puig and C.T. Recchiuto and C. Sighieri and A. Solanas and O. von Stryk},
  title = {Developing biorobotics for veterinary research into cat movements},
  journal = {Journal of Veterinary Behavior: Clinical Applications and Research},
  year = {2015},
  volume = {10},
  number = {3},
  pages = {248–254},
  url = {http://www.sciencedirect.com/science/article/pii/S1558787815000052},
  abstract = {Collaboration between veterinarians and other professionals such as engineers and computer scientists will become important in biorobotics research for both scientific achievements and the protection of animal welfare. Particularly, cats are interesting and fascinating animals, but , so far, they have not yet become a significant source of inspiration for new technologies in robotics. This paper suggests a novel approach for the investigation of particular aspects of cat morphology, neurophysiology and behavior, aimed at bridging this gap by focusing on the versatile, powerful locomotion abilities of cats and implementing a robotic tool for the measurements of biological parameters of animals and building cat inspired robotic prototypes. The presented framework suggestswill form the basis for the development of novel hypotheses and models describing biomechanics, locomotion, balancing system, visual perception as well as learning and adaption of cat motor skills and behavior. In subsequent work, the resulting models will be tested and evaluated in simulated and real experiments and validated with specific experimental data gathered from cats. The expected impact of this novel methodology is potentially in multiple areas: the prototype may open new possibilities in robotics, with the investigation of novel dynamic balance This methodology has application in several areas including dynamic models and artificial vision systems. From an ethical point of view, this approach is in line with the 3Rs principles: the detailed and integrated systems will allow us to study a small number of cats (reduction) for the implementation of non-invasive tools such as electromyography and gaze analysis (refinement), which will make the construction of a substitute 41 to experiments on living cats (replacement) easier. For instance, bioinspired prototypes could be used instead of real cats to test whether and how specific visual and physical impairment in cats (up to partial or total blindness, loss of a leg, etc.) change their walking and jumping abilities. This modus operandi may pave the way for a new generation of research in the veterinary field. Moreover, the measurement tools to be developed will constitute an achievement per se, since for the first time visual, muscular and gait analysis of cats will be integrated a 46 nd this will help to improve the rehabilitation procedures for cats and other non-human animals.},
}

@ARTICLE{2014:JFR-ViGIR-DRC-Trials,
  author = {S. Kohlbrecher and A. Romay and A. Stumpf and A. Gupta and O. von Stryk and F. Bacim and D.A. Bowman and A. Goins and R. Balasubramanian and D.C. Conner},
  title = {Human-Robot Teaming for Rescue Missions: Team ViGIR´s Approach to the 2013 DARPA Robotics Challenge Trials},
  journal = {Journal of Field Robotics},
  year = {2015},
  volume = {32},
  number = {3},
  pages = {352-377},
  note = {First published online 4 Dec 2014},
  url = {http://onlinelibrary.wiley.com/doi/10.1002/rob.21558/full},
  pdf = {2014_vigir_jfr_main.pdf},
  abstract = {Team ViGIR entered the 2013 DARPA Robotics Challenge (DRC) with a focus on developing software to enable an operator to guide a humanoid robot through the series of challenge tasks emulating disaster response scenarios. The overarching philosophy was to make our operators full team members and not just simple supervisors. We designed our operator control station (OCS) to allow multiple operators to request and share information as needed to maintain situational awareness under bandwidth constraints, while directing the robot to perform tasks with most planning and control taking place onboard the robot. Given the limited development time we leveraged a number of open source libraries in both our onboard software and our OCS design; this included significant use of the Robot Operating System (ROS) libraries and toolchain. This paper describes the high level approach, including the OCS design and major onboard components, and describes our DRC Trials results. The paper concludes with a number of lessons learned that are being applied to the final phase of the competition and are useful for related projects as well.},
}

@INPROCEEDINGS{2015:IAS_K-Kurowski_vS,
  author = {K. Kurowski and O. von Stryk},
  title = {Online interaction of a human supervisor with multi-robot task allocation},
  year = {2015},
  volume = {302},
  pages = {965-978},
  publisher = {Springer-Verlag},
  editor = {K. Berns, E. Menegatti, N. Michael, H. Yamaguchi},
  series = {Intelligent Systems and Computing},
  address = {Padova, Italy},
  booktitle = {Intelligent Autonomous Systems 13 - Proc. 13th International Conference on Intelligent Autonomous Systems (IAS-13)},
  url = {http://link.springer.com/chapter/10.1007%2F978-3-319-08338-4_70},
  pdf = {2014-IAS_Online-Interaction-HMRTA_K-vS.pdf},
  abstract = {In this paper an approach is presented that allows a human supervisor to efficiently interact with task allocation in a multi-robot team (MRTA). The interaction is based on online modification of the setting of the employed MRTA optimization algorithm during its computation. For the example of a computationally expensive mixed-integer linear programming algorithm it is demonstrated how to achieve up to optimal solution quality, while simultaneously reducing the required calculation time compared to a fully autonomous optimization. The supervisor is enabled to rate feasible, intermediate solutions based on objective or subjective quality criteria and personal expertise. In that way, also suboptimal solutions can be chosen to be satisfactory, and the solver can be terminated without the need to wait for the completion of the computation of the optimal solution. An event based communication concept with queries is used as an efficient means of implementation of the interaction. Furthermore, the supervisor can support the MRTA solver in finding good solutions by defining crucial parts of the solution structure. These intuitive commands are internally translated into constraints and are added to the problem as lazy constraints. This combination of human expertise and state-of-the-art optimization algorithms allows to achieve up to potentially optimal task allocation in much shorter time.},
}

@INPROCEEDINGS{BeckerleRO-MAN:2014,
  author = {P. Beckerle and F. Schültje and J. Wojtusch and O. Christ},
  title = {Implementation, Control and User-Feedback of the Int²Bot for the Investigation of Lower Limb Body Schema Integration},
  year = {2014},
  booktitle = {Proceedings of IEEE International Symposium on Robot and Human Interactive Communication (RO-MAN)},
  pdf = {2014_Beckerle_RO-MAN.pdf},
  abstract = {The integration of prostheses or wearable robotics into the body schema of their users is a fundamental require- ment for the acceptance and control of such artificial devices. Duration and progress of integration are primarily influenced by visual, tactile, and proprioceptive perception. This paper describes the Int 2 Bot, a robot for the assessment of lower limb body schema integration during postural motion. The robot is designed to imitate human squatting movements to investigate the integration of artificial limbs into the body schema. The psychological and technical concepts as well as the mechatronic implementation and control are presented along with interface extensions comprising human knee position sensing and tactile user-feedback. The performance of the robot is examined by experiments excluding and including the human-robot interface and a human user. Those without interface show that the robot itself can perform considerably fast squats with 0.8 Hz, which comes up to maximum human capabilities. The computed torque control achieves good tracking results and fuzzy-based friction compensation further reduces position errors by up to 50%. Yet, results considering the vision-based part of the human-robot interface show that the setup is mainly limited due to delays in motion acquisition with the RGB-D sensor.},
}

@INPROCEEDINGS{SchueltjeRO-MAN:2014,
  author = {F. Schültje and P. Beckerle and M. Grimmer and J. Wojtusch and S. Rinderknecht},
  title = {Comparison of Trajectory Generation Methods for a Human-Robot Interface based on Motion Tracking in the Int²Bot},
  year = {2014},
  booktitle = {Proceedings of IEEE International Symposium on Robot and Human Interactive Communication (RO-MAN)},
  pdf = {2014_SchueltjeEtAlRO-MAN.pdf},
  abstract = {The acceptance of artificial devices like prostheses or other wearable robots requires their integration into the body schemas of the users. Different factors induce, influence and support the integration and acceptance of the device that substitutes or augments a part of the body. Previous studies have shown that the inducing and maintaining factors are visual, tactile and proprioceptive informations as well as their multi- sensory integration. This paper describes the vision-based part of the human-robot interface in the Int 2 Bot, which is a robot for the investigation of lower limb body schema integration during postural movements. The psychological approach and the technical setup of the robot, which is designed to imitate postural movements in the sagittal plane to imitate the human subject while performing squats, are outlined. To realize the imitation, an RGB-D sensor, in form of a Microsoft Kinect, is used to capture the subjects motions without contact and thereby avoid disturbances of body schema integration. For generation of the desired joint trajectories to be tracked by the control algorithm, different methods like an extended Kalman filter, inverse kinematics, an inverse kinematics algorithm us- ing Jacobian transpose and approaches based on kinematic assumptions are presented, evaluated and compared based on human data. Benchmarking the results with data acquired using a professional motion capturing system shows that best overall joint angle estimations are achieved with the extended Kalman filter. Finally, the practical implementation within the robot is presented and the tracking behavior using the trajectories generated with the extended Kalman filter are analyzed.},
}

@ARTICLE{2014:AI-M_RoboCup-Soccer,
  author = {D. Nardi and I. Noda and F. Ribeiro and P. Stone and O. von Stryk and M. Veloso},
  title = {RoboCup Soccer Leagues},
  journal = {AI Magazine},
  year = {2014},
  volume = {35},
  number = {3},
  pages = {77-85},
  doi = {http://dx.doi.org/10.1609/aimag.v35i3.2549},
  url = {http://aaai.org/ojs/index.php/aimagazine/article/view/2549},
  abstract = {RoboCup was created in 1996 by a group of Japanese, American, and European artificial intelligence and robotics researchers with a formidable, visionary long-term challenge: By 2050 a team of robot soccer players will beat the human World Cup champion team. In this article, we focus on RoboCup robot soccer, and present its five current leagues, which address complementary scientific challenges through different robot and physical setups. Full details on the status of the RoboCup soccer leagues, including league history and past results, upcoming competitions, and detailed rules and specifications are available from the league homepages and wikis.},
}

@INPROCEEDINGS{2014:Humanoids-Stumpf,
  author = {A. Stumpf and S. Kohlbrecher and D.C. Conner and O. von Stryk},
  title = {Supervised Footstep Planning for Humanoid Robots in Rough Terrain Tasks using a Black Box Walking Controller},
  year = {2014},
  pages = {287-294},
  month = {Nov 18-20},
  address = {Madrid, Spain},
  booktitle = {Proc. IEEE-RAS Intl. Conf. Humanoid Robots},
  pdf = {2014_Stumpf_footstep_planning_Humanoids.pdf},
  abstract = {In recent years, the numbers of life-size humanoids as well as their mobility capabilities have steadily grown. Stable walking motion and control for humanoid robots are already well investigated research topics. This raises the question how navigation problems in complex and unstructured environments can be solved utilizing a given black box walking controller with proper perception and modeling of the environment provided. In this paper we present a complete system for supervised footstep planning including perception, world modeling, 3D planner and operator interface to enable a humanoid robot to perform sequences of steps to traverse uneven terrain. A proper height map and surface normal estimation are directly obtained from point cloud data. A search-based planning approach (ARA*) is extended to sequences of footsteps in full 3D space (6 DoF). The planner utilizes a black box walking controller without knowledge of its implementation details. Results are presented for an Atlas humanoid robot during participation of Team ViGIR in the 2013 DARPA Robotics Challenge Trials.},
}

@INPROCEEDINGS{2014:Humanoids-Romay,
  author = {A. Romay and S. Kohlbrecher and D.C. Conner and A. Stumpf and O. von Stryk},
  title = {Template-Based Manipulation in Unstructured Environments for Supervised Semi-Autonomous Humanoid Robots},
  year = {2014},
  pages = {979 - 986},
  month = {Nov 18-10},
  address = {Madrid, Spain},
  booktitle = {Proc. IEEE-RAS Intl. Conf. Humanoid Robots},
  pdf = {2014_RomayEtAl_Humanoids.pdf},
  abstract = {Humanoid robotic manipulation in unstructured environments is a challenging problem. Limited perception, communications and environmental constraints present challenges that prevent fully autonomous or purely teleoperated robots from reliably interacting with their environment. In order to achieve higher reliability in manipulation we present an approach involving remote human supervision. Strengths from both human operator and humanoid robot are leveraged through a user interface that allows the operator to perceive the remote environment through an aggregated worldmodel based on onboard sensing, while the robot can efficiently receive perceptual and semantic information from the operator. A template based manipulation approach has been successfully applied to the Atlas humanoid robot; we show real world footage of the results obtained in the DARPA Robotics Challenge Trials 2013.},
}

@TECHREPORT{autonomous_manip_rrl_2014,
  author = {Julia Nitsch and Alexander Buchegger and Dorothea Koert and Christian Rose and Johannes Maurer and Stefan Kohlbrecher and Oskar von Stryk and Gerald Steinbauer},
  title = {Towards Autonomous Manipulation in RoboCup Rescue},
  year = {2014},
  institution = {TU Graz, TU Darmstadt},
  abstract = {This paper presents a generic framework for semi-autonomous manipulation for rescue robots. The presented framework concept is the outcome of the RoboCup short-term visit of team TEDUSAR Graz at Team Hector Darmstadt. },
}

@ARTICLE{2014:Delfa-Acta-Futura,
  author = {J.M. Delfa Victoria and S. Fratini and N. Policella and O. von Stryk and Y. Gao and A. Donati},
  title = {Planning Mars Rovers with Hierarchical Timeline Networks},
  journal = {Acta Futura},
  year = {2014},
  number = {9},
  pages = {21-29},
  doi = {10.2420/AF09.2014.21},
  abstract = {Surface operations in distant bodies like Mars present a lot of challenges. Among them, lack of direct communications and a complex environment are the main drivers that push for more autonomy both on-ground and onboard. This paper presents a timeline, hierarchical, heuristically-based and domain-independent planner called QuijoteExpress oriented to solve highly constrained temporal problems.},
}

@INPROCEEDINGS{2014:IROS-BBp-Sharbafi,
  author = {M.A. Sharbafi and K. Radkhah and O. von Stryk and A. Seyfarth},
  title = {Hopping control for the musculoskeletal bipedal robot BioBiped},
  year = {2014},
  pages = {4868 - 4875},
  month = {September 14-18},
  address = {Chicago, IL, USA },
  booktitle = {2014 IEEE/RSJ International Conference on Intelligent Robots and Systems},
  organization = {IEEE},
  pdf = {2014_Sharbafi_IROS.pdf},
  abstract = {Bipedal locomotion can be divided into primitive tasks, namely repulsive leg behavior (bouncing against gravity), leg swing (protraction and retraction) and body alignment (balancing against gravity). In the bipedal spring-mass model for walking and running, the repulsive leg function is described by a linear prismatic spring. This paper adopts two strategies for swinging and bouncing control from conceptual models for the human-inspired musculoskeletal BioBiped robot. The control approach consists of two layers, velocity based leg adjustment (VBLA) and virtual model control to represent a virtual springy leg between toe and hip. Additionally, the rest length and stiffness of the virtual springy leg are tuned based on events to compensate energy losses due to damping. In order to mimic human locomotion, the trunk is held upright by physical constraints. The controller is implemented on the validated detailed simulation model of BioBiped. Inplace as well as forward hopping and switching between these two gaits are easily achieved by tuning the parameters for the leg adjustment, virtual leg stiffness and injected energy. Furthermore, it is shown that the achieved motion performance of in-place hopping agrees well with that of human subjects.},
}

@INPROCEEDINGS{2014:Ritter-etal,
  author = {T. Ritter and J. Euler and S. Ulbrich and O. von Stryk},
  title = {Adaptive Observation Strategy for Dispersion Process Estimation Using Cooperating Mobile Sensors},
  year = {2014},
  pages = {5302 - 5308},
  month = {Aug 24 - 29},
  address = {Cape Town, South Africa},
  booktitle = {Proceedings of the 19th IFAC World Congress},
  pdf = {2014_RitterEtAl_IFAC.pdf},
  abstract = {Efficient online state estimation of dynamic dispersion processes plays an important role in a variety of safety-critical applications. The use of mobile sensor platforms is increasingly considered in this context, but implies the generation of situation-dependent vehicle trajectories providing high information gain in real-time. In this paper, a new adaptive observation strategy is presented combining state estimation based on partial differential equation models of the dispersion process with a model-predictive control approach for multiple cooperating mobile sensors. In a repeating sequential procedure, based on the Ensemble Transform Kalman Filter, the uncertainty of the current estimate is determined and used to find valuable measurement locations. Those serve as target points for the controller providing optimal trajectories subject to the vehicles’ motion dynamics and cooperation constraints. First promising results regarding accuracy and efficiency were obtained. },
}

@TECHREPORT{2014:hector_rescue_tdp,
  author = {Stefan Kohlbrecher and Johannes Meyer and Thorsten Graber and Karen Petersen and Oskar von Stryk and Uwe Klingauf},
  title = {RoboCupRescue 2014 - Robot League Team Hector Darmstadt (Germany)},
  year = {2014},
  institution = {Technische Universität Darmstadt},
  pdf = {2014_tdp_hector.pdf},
  abstract = {This paper describes the approach used by Team Hector Darmstadt for participation in the 2014 RoboCup Rescue League competition. Participating in the RoboCup Rescue competition since 2009, the members of Team Hector Darmstadt focus on exploration of disaster sites using autonomous Unmanned Ground Vehicles (UGVs). The team has been established as part of a PhD program funded by the German Research Foundation at TU Darmstadt and combines expertise from Computer Science and Mechanical Engineering. We give an overview of the complete system used to solve the problem of reliably finding victims in harsh USAR environments. This includes hardware as well as software solutions and diverse topics like locomotion, SLAM, pose estimation, human robot interaction and victim detection. In 2014, the team focuses on integration of newly acquired highly mobile tracked robot platforms as well as manipulation capabilities. As a contribution to the RoboCup Rescue community, major parts of the used software have been released and documented as open source software for ROS. },
}

@INPROCEEDINGS{2014:ICRA-Radkhah,
  author = {K. Radkhah and O. von Stryk},
  title = {A Study of the Passive Rebound Behavior of Bipedal Robots with Stiff and Different Types of Elastic Actuation},
  year = {2014},
  pages = {5095-5102},
  booktitle = {IEEE Int. Conf. on Robotics and Automation (ICRA)},
  abstract = {One of the most important capabilities of bipedal robots for energy-efficient and dynamic locomotion are shock tolerance and energy storage and release. In this paper, we study three robot models with different leg actuation designs by means of highly detailed multibody system dynamics simulation. For this purpose, we first elaborate on the term of energy-efficient and dynamic two-legged hopping and present a performance index. Subsequently we conduct the same experimental setup for passive rebound and soft landing for all models. Among others it is observed that (1) the envisioned dynamic and energy-efficient locomotion cannot be achieved through stiff actuation, (2) the energy restitution can be maximized without sacrificing the dynamic mobility and (3) such passive rebound experiments are well suited to determining the optimal leg actuation design.},
}

@ARTICLE{BeckerleSMART:2014,
  author = {P. Beckerle and J. Wojtusch and S. Rinderknecht and O. von Stryk},
  title = {Analysis of System Dynamic Influences in Robotic Actuators with Variable Stiffness.},
  journal = {Smart Structures and Systems},
  year = {2014},
  volume = {13},
  number = {4},
  pages = {711-730},
  month = {April},
  doi = {http://dx.doi.org/10.12989/sss.2014.13.4.711},
  pdf = {2014_BeckerleEtAl_SMART.pdf},
  abstract = {In this paper the system dynamic influences in actuators with variable stiffness as contemporary used in robotics for safety and efficiency reasons are investigated. Therefore, different configurations of serial and parallel elasticities are modeled by dynamic equations and linearized transfer functions. The latter ones are used to identify the characteristic behavior of the different systems and to study the effect of the different elasticities. As such actuation concepts are often used to reach energy-efficient operation, a power consumption analysis of the configurations is performed. From the comparison of this with the system dynamics, strategies to select and control stiffness are derived. Those are based on matching the natural frequencies or antiresonance modes of the actuation system to the frequency of the trajectory. Results show that exclusive serial and parallel elasticity can minimize power consumption when tuning the system to the natural frequencies. Antiresonance modes are an additional possibility for stiffness control in the series elastic setup. Configurations combining both types of elasticities do not provide further advantages regarding power reduction but an input parallel elasticity might enable for more versatile stiffness selection. Yet, design and control effort increase in such solutions. Topologies incorporating output parallel elasticity showed not to be beneficial in the chosen example but might do so in specific applications. },
}

@INPROCEEDINGS{ChristSAN:2014,
  author = {O. Christ and J. Wojtusch and P. Beckerle},
  title = {Robotic mirroring of movements in the lower limbs: signal delay of a consumer device sensor.},
  year = {2014},
  booktitle = {Meeting of the Society of Applied Neurosciences (SAN)},
  pdf = {2014_ChristEtAl_SAN.pdf},
}

@INPROCEEDINGS{2013:RoboCup,
  author = {S. Kohlbrecher and J. Meyer and T. Graber and K. Petersen and O. von Stryk and U. Klingauf},
  title = {Hector open source modules for autonomous mapping and navigation with rescue robots},
  year = {2014},
  volume = {8371},
  pages = {624-631},
  publisher = {Springer},
  series = {Lecture Notes in Computer Science},
  booktitle = {RoboCup 2013: Robot World Cup XVII},
  pdf = {2013_RoboCup_Kohlbrecher_open_source_tools.pdf},
  abstract = {Key abilities for robots deployed in urban search and rescue tasks include autonomous exploration of disaster sites and recognition of victims and other objects of interest. In this paper, we present related open source software modules for the development of such complex capabilities which include Hector slam for self-localization and mapping in a degraded urban environment. All modules have been successfully applied and tested originally in the RoboCup Rescue competition. Up to now they have already been re-used and adopted by numerous international research groups for a wide variety of tasks. Recently, they have also become part of the basis of a broader initiative for key open source software modules for urban search and rescue robots.},
}

@INPROCEEDINGS{BeckerleAMAM:2013b,
  author = {P. Beckerle and F. Stuhlenmiller and J. Schuy and J. Wojtusch and S. Rinderknecht and O. von Stryk},
  title = {Friction Compensation and Stiffness Evaluation on a Variable Torsion Stiffness},
  year = {2013},
  booktitle = {International Symposium on Adaptive Motion of Animals and Machines (AMAM)},
  pdf = {2013_BeckerleEtAl_VTS_AMAM.pdf},
}

@MISC{euler13,
  author = {J. Euler and O. von Stryk},
  title = {Optimal Cooperative Control of Mobile Sensors for Dynamic Process Estimation},
  year = {2013},
  note = {Workshop on Robotics for Environmental Monitoring at Robotics: Science and Systems 2013, Jun 24 - 28},
  abstract = {A typical mission for robotic systems in environ- mental monitoring is the identification of dynamic processes like atmospheric dispersion by a group of mobile sensors. Due to this problem’s large-scale and highly dynamic character, an efficient cooperative sampling strategy is required. This paper presents a mathematical concept for estimating the parameters of a Gaussian puff model of the dispersion process based on cooperatively gathered measurement data. The sensors’ cooperative behavior is determined by a distributed model-predictive controller. It combines task allocation and tra- jectory planning in a single mixed-integer problem formulation employing linearly approximated vehicle dynamics models. By integrating the quality of the dispersion model parameters as an additional optimization criterion for the controller, the pro- posed method intends to simultaneously solve both the estimation problem and the cooperative control problem in a near optimal manner. },
}

@INPROCEEDINGS{2013:R-vS_WS-Humanoids,
  author = {K. Radkhah and O. von Stryk},
  title = {The need for a common taxonomy and benchmarks to achieve "human-like" performance in bipedal robot locomotion},
  year = {2013},
  month = {Oct 15},
  booktitle = {Workshop on Benchmarking of Human-Like Robotic Locomotion, IEEE-RAS Humanoids 2013 },
  url = {http://www.h2rproject.eu/humanoids2013},
  pdf = {2013-HUMANOIDS-WS_Radkha&vonStryk.pdf},
  abstract = {A common taxonomy for the term “human-like locomotion” is essential to enhance the progress in the field of bipedal robot locomotion. In literature widespread use of this term can be found implying that human motion is optimal and worthy of imitation. However, a common basic understanding of the fundamental principles and characteristics of human locomotion is yet to be completed. In this talk we review various interpretations of this term in the literature and elaborate briefly on the most relevant characteristics of human motion trajectories. Further, essential methods from modeling and simulation to locomotion performance evaluation are discussed. We present a possible definition for “human-like locomotion” and a general concept for a better comparability of human and robot locomotion performance. The expressed ideas are supported by interim results obtained within the BioBiped project.},
}

@INPROCEEDINGS{BeckerleSMC:2013,
  author = {P. Beckerle and L. Lahnstein and J. Wojtusch and S. Rinderknecht and O. von Stryk},
  title = {Conception and Design of a Hardware Simulator for Restoring Lost Biomechanical Function.},
  year = {2013},
  booktitle = {IEEE International Conference on Systems, Man and Cybernetics (SMC)},
  pdf = {2013_BeckerleEtAl_SMC.pdf},
  abstract = {The Prosthesis-User-in-the-Loop simulator concept represents an approach to integrate users to prosthetic development by a holistic simulation of gait with a prosthesis. It aims at a more user-centered design of lower limb prosthetic devices by utilizing user experience and assessment. As this requires a complex mechanical robot design and sophisticated control strategies that allow for restoring lost biomechanical function, this paper presents the conception and design of a hardware simulator for proof-of-concept studies of those issues. For those investigations, the ankle joints of healthy praticpants are locked mechanically to induce a temporary disability. The task of the simulator is to provide a simulation of physiological gait by artificially restoring ankle functionality. Therefore, the biodynamic behaviour of the locked ankle joint and the enviroment have to be mimicked mechnically. After introducing Prosthesis-User-in-the-Loop simulator idea, the conception of a proof-of-concept simulator is presented. From this, an analytical model is derived and inverse dynamics simulation are used for design. The resulting mechanism is limited to sagittal plane movements and thus has three degrees of freedom. The actuators are dimensioned to meet the requirements of walking motions in the human subject with maximum body height among the test population.},
}

@INPROCEEDINGS{BeckerleAMAM:2013b,
  author = {P. Beckerle and F. Stuhlenmiller and J. Schuy and S. Rinderknecht and O. von Stryk},
  title = {Friction Compensation and Stiffness Evaluation on a Variable Torsion Stiffness.},
  year = {2013},
  booktitle = {International Symposium on Adaptive Motion of Animals and Machines (AMAM)},
  pdf = {2013_BeckerleEtAl_VTS_AMAM.pdf},
}

@INPROCEEDINGS{BeckerleAMAM:2013a,
  author = {P. Beckerle and J. Wojtusch and S. Rinderknecht and O. von Stryk},
  title = {Mechanical Influences on the Design of Actuators with Variable Stiffness.},
  year = {2013},
  booktitle = {International Symposium on Adaptive Motion of Animals and Machines (AMAM)},
  pdf = {2013_BeckerleEtAl_MechInf_AMAM.pdf},
}

@INPROCEEDINGS{BoekerAMAM:2013,
  author = {S. Böker and P. Beckerle and J. Wojtusch and S. Rinderknecht},
  title = {A Novel Design Approach and Operational Strategy for an Active Ankle-Foot Prosthesis.},
  year = {2013},
  booktitle = {International Symposium on Adaptive Motion of Animals and Machines (AMAM)},
  pdf = {2013_BoekerEtAl_AMAM.pdf},
}

@INPROCEEDINGS{BeckerleISPO:2013,
  author = {P. Beckerle and O. Christ and M. Windrich and S. Rinderknecht and J. Vogt and J. Wojtusch},
  title = {A methodological approach to integrate psychological factors to lower limb prosthetic functional design.},
  year = {2013},
  booktitle = {International Society of Prosthetics and Orthotics World Congress (ISPO)},
  pdf = {2013_Beckerle_ISPO.pdf},
  abstract = {As user-centered development (UCD) involves users for an understanding, objective assessment and utilization of their needs, it represents a promising approach to develop improved user-friendly prostheses. Hence, human factors have to be identified and integrated into development. To identify relevant factors and assess the amputees’ requirements, a literature review, questionnaire results and interviews are considered. Further, models of the identified factors’ impacts on the development and Quality Function Deployment (QFD) for the translation from the human understanding to technical design are prepared for evaluation with amputees. The important body scheme integration (BSI) is examined in experiments with unharmed subjects exploring a Rubber Leg Illusion similarly to the Rubber Hand Illusion. Besides BSI, satisfaction and feeling of security (FOS) show to be important factors for UCD. Satisfaction is linked to quality of life (QoL) and time of daily use and influenced by appearance, usability and functional properties of prosthetic components. FOS seems to be an issue of the overall system leading to reliability and balance during use. BSI also affects QoL and might lead to more user-friendly prostheses. Technical functions (enabling) contrary to characteristics from the user’s view (predisposing) seem to be perceived as different properties. The first ones are utilized: Functional units are identified and assessed. Models and QFD are used for their evaluation and translation to technical development. The technical functionality is reviewed and extended based on a comparison of functional and psychological aspects of the units and the overall concept. The elaborated approach should enable to involve users during the whole development process. Yet, it is not validated with a sufficient number of users. Substantiating this approach with sufficient data is necessary – e.g., a comparative analysis to solve conflicting goals. It is promising for the development of future user-friendly prostheses.},
}

@INPROCEEDINGS{WojtuschISPO:2013,
  author = {J. Wojtusch and P. Beckerle and O. von Stryk and S. Rinderknecht},
  title = {A Biomechanical Model for the Estimation of Dynamic Interactions at the Transfemoral Socket Interface.},
  year = {2013},
  booktitle = {International Society of Prosthetics and Orthotics World Congress (ISPO)},
  pdf = {2013_Wojtusch_ISPO.pdf},
  abstract = {For the analysis of the human gait with prosthesis and the design of prosthetic devices, the knowledge of fundamental dynamic interactions at the user-prosthesis interface is required. A direct measurement of these interactions, including forces, torques, and powers, is complex and necessitates additional sensors in the prosthesis. In this work, a biomechanical model for the estimation of dynamic interactions at the transfermoral interface in sagittal plane is presented. By applying an inverse dynamic simulation, the normal force, torque and power at the interface are computed for different gait scenarios and lengths of the residual limb. The biomechanical model consists of multi-body system dynamics models of the legs and the trunk. The sound leg is modeled by three rigid bodies for thigh, shank, and foot as well as three rotatory joints representing the hip, knee, and ankle joint. The model of the leg with prosthesis is obtained by partitioning the rigid body of the thigh into a residual and a prothetic limb and linking both partitions by virtual joints representing the transfemoral interface. The parameters of the residual limb are identified by fitting the inertial specifications to a detailed geometric model of the human thigh. The simulation results provide essential information for gait analysis and prosthesis design. The power characteristics allow to evaluate the effort that has to be expended by the prosthesis user, while the torque characteristics show the influence of different prosthesis lengths on the loads of the residual limb. The normal force characteristics describe the impact of force peaks introduced by ground reactions and are a measure for the pressure distribution at the prosthesis stem. The presented biomachnical model is a first approach towards a comprehensive simulation environment for the human gait with prosthesis and will be further enhanced in accuracy and applicability.},
}

@INPROCEEDINGS{BeckerleAIM:2013,
  author = {P. Beckerle and J. Wojtusch and J. Schuy and B. Strah and S. Rinderknecht and O. von Stryk},
  title = {Power-optimized Stiffness and Nonlinear Position Control of an Actuator with Variable Torsion Stiffness},
  year = {2013},
  pages = {387-392},
  booktitle = {IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM)},
  pdf = {2013_BeckerleEtAl_AIM.pdf},
  abstract = {Introducing compliant actuation to robotic joints is an approach to ensure safety in closer human-machine interaction. Further, the possibility to adjust stiffness can be benificial considering energy storage and the power consumption required to track certain trajectories. The subject of this paper is the stiffness and position control of the Variable Torsion Stiffness (VTS) actuator for application in compliant robotic joints. For the realization of a variable rotational stiffness, the active length of a torsional elastic element in serial configuration between drive and link is adjusted in VTS. After the deduction of an extended drive train model, this paper gives an advanced power analysis clarifying power-optimal settings from previous basic models and identifying additional settings that allow for a more versatile operation. Based on these results that can be generalized to other variable elastic actuator concepts, an optimized strategy for setting stiffness is determined considering the whole system dynamics including natural frequencies as well as antiresonance effects. For position control of VTS in a prototypical implementation, a nonlinear position controller is designed by means of feedback linearization. Although the system is modified significantly by changing drive train stiffness, the stiffness adaptation of the controller ensures the required tracking performance.},
}

@INPROCEEDINGS{SchuyAIM:2013,
  author = { J. Schuy and P. Beckerle and J. Faber and J. Wojtusch and S. Rinderknecht and O. von Stryk},
  title = {Dimensioning and Evaluation of the Elastic Element in a Variable Torsion Stiffness Actuator.},
  year = {2013},
  booktitle = { IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM)},
  pdf = {2013_SchuyEtAl_AIM.pdf},
  abstract = {Variable stiffness joints are essential for robots or biomechanical applications to generate torque with sufficient compliance to ensure safety simultaneously. This paper presents the dimensioning of the elastic element for an actuator with Variable Torsion Stiffness (VTS). Analytical and finite element calculations are compared to experimental evaluation of a splined shaft profile realized in a prototype implementation. Based on simplifications and effects in the real test-rig the results show similar behaviour. Furthermore, an analytical and finite element investigation of four cross-sections with torsional load illustrate optimal utilization of cylindrical geometries considering the torsional stress. In contrast, the low stressed edges of uncylindrical cross-sections are adequate areas to bear additional stresses.},
}

@Techreport{2013:hector_rescue_tdp,
  author = {Thorsten Graber and Stefan Kohlbrecher and Johannes Meyer and Karen Petersen and Oskar von Stryk and Uwe Klingauf},
  title = {RoboCupRescue 2013 - Robot League Team Hector Darmstadt (Germany)},
  year = {2013},
  organization = {Technische Universität Darmstadt},
  pdf = {2013_tdp_hector.pdf},
  abstract = {This paper describes the approach used by Team Hector Darmstadt for participation in the 2013 RoboCup Rescue League competition. Participating in the RoboCup Rescue competition since 2009, the members of Team Hector Darmstadt focus on exploration of disas- ter sites using autonomous Unmanned Ground Vehicles (UGVs). The team has been established as part of a PhD program funded by the German Research Foundation at TU Darmstadt and combines expertise from Computer Science and Mechanical Engineering. We give an overview of the complete system used to solve the problem of reliably finding victims in harsh USAR environments. This includes hardware as well as software solutions and diverse topics like locomotion, SLAM, pose estimation, human robot interaction and victim detection. As a con- tribution to the RoboCup Rescue community, major parts of the used software have been released and documented as open source software for ROS. },
}

@INPROCEEDINGS{2013:IROS,
  author = {K. Petersen and A. Kleiner and O. von Stryk},
  title = {Fast task-sequence allocation for heterogeneous robot teams with a human in the Loop},
  year = {2013},
  pages = {1648 - 1655 },
  month = {Nov 3-8},
  address = {Tokyo, Japan},
  booktitle = {Proc. IEEE/RSJ Intl. Conf. on Intelligent Robots and Systems (IROS)},
  doi = {10.1109/IROS.2013.6696570},
  abstract = {Efficient task allocation with timing constraints to a team of possibly heterogeneous robots is a challenging problem with application, e. g., in search and rescue. In this paper a mixed-integer linear programming (MILP) approach is proposed for assigning heterogeneous robot teams to the simultaneous completion of sequences of tasks with specific requirements such as completion deadlines. For this purpose our approach efficiently combines the strength of state of the art mixed-integer linear programming (MILP) solvers with human expertise in mission scheduling. We experimentally show that simple and intuitive inputs by a human user have substantial impact on both computation time and quality of the solution. The presented approach can in principle be applied to quite general missions for robot teams with human supervision.},
}

@INPROCEEDINGS{2013:SSRR-ViGIR,
  author = {S. Kohlbrecher and D. Conner and A. Romay and F. Bacim and D. Bowman and O. von Stryk},
  title = {Overview of Team ViGIR´s Approach to the Virtual Robotics Challenge},
  year = {2013},
  pages = {1-2},
  month = {Oct 21-26},
  publisher = {IEEE},
  address = {Linkoping, Sweden},
  booktitle = {11th IEEE Intl. Symposium on Safety, Security and Rescue Robotics},
  doi = {10.1109/SSRR.2013.6719382},
  pdf = {2013-IEEE-SSRR_ViGIR_VRC.pdf},
  abstract = {With the DARPA Robotics Challenge (DRC), a call to an ambitious multi-part competition was sent out to the robotics community. In this paper, we briefly summarize the approach for addressing the Virtual Robotics Challenge (VRC) where software for control and supervision of a capable humanoid robot must be developed. Team ViGIR, comprising members from the US and Germany, leveraged previous robotics competition experience and a variety of open source tools, to achieve sixth place in the VRC out of 126 registrants, thereby advancing to the next round of the DRC and obtaining an Atlas robot.},
}

@INPROCEEDINGS{2013CLAWAR2:Radkhah,
  author = {K. Radkhah and O. von Stryk},
  title = {Exploring the Lombard paradox in a bipedal musculoskeletal robot},
  year = {2013},
  pages = {537-546},
  month = {July 14 - 17},
  booktitle = {Proc. Int. Conf. on Climbing and Walking Robots and the Support Technologies for Mobile Machines (CLAWAR)},
  pdf = {2013_CLAWAR_Radkhah-Lombard.pdf},
  abstract = {Towards advanced bipedal locomotion musculoskeletal system design has received much attention in recent years. It has been recognized that designing and developing new actuators with the properties of the human muscle-tendon complex is only one of the many tasks that have to be fulfilled in order to come close to the powerful human musculoskeletal system enabling the human to such versatile dynamic movements that no robot has been capable of replicating yet. But equally important is a technical implementation of the key characteristics of the human musculoskeletal leg system, segmentation and elastic leg behavior enabled by the mono- and biarticular muscles. So far, there has been an overwhelming consensus in biomechanics literature regarding the joint movements caused by biarticular muscles. In reality, however, they are responsible for an additional action during the second half of ground contact during fast dynamic motions in humans that has not yet been addressed by bipedal robot locomotion studies. Using BioBiped1, a bipedal compliant robot with human-inspired mono- and biarticular tendons, we demonstrate by means of a detailed multibody system dynamics simulation how this positive effect subserve energy-efficient dynamic 1D hopping motions and enables us to establish a novel bipedal locomotion model.},
}

@INPROCEEDINGS{2013CLAWAR1:Radkhah,
  author = {K. Radkhah and O. von Stryk},
  title = {Model-based elastic tendon control for electrically actuated musculoskeletal bipeds},
  year = {2013},
  pages = {719 - 728},
  month = {July 14 - 17},
  booktitle = {Proc. Int. Conf. on Climbing and Walking Robots and the Support Technologies for Mobile Machines (CLAWAR)},
  pdf = {2013_CLAWAR_Radkhah-ModelbasedControl.pdf},
  abstract = {Human-inspired musculoskeletal design of bipedal robots offers great potential towards enhanced dynamic and energy-efficient locomotion but imposes also major challenges on their control. In this paper we present an analytical model-based controller that takes into account the system’s complex musculoskeletal actuation dynamics in order to fully exploit the intrinsic dynamics. The effectiveness of the proposed approach is evaluated for hopping-in-place motions on the simulation model of the BioBiped1 robot, a human-inspired musculoskeletal biped featuring a highly compliant tendon-driven actuation system.},
}

@INPROCEEDINGS{2013:ICRA_Mikhailova,
  author = {Inna Mikhailova},
  title = {Energy-based State-Feedback Control of Systems with Mechanical or Virtual Springs},
  year = {2013},
  pages = {accepted for publication},
  month = {May 6-10},
  address = {Karlsruhe, Germany},
  booktitle = {Proc. IEEE Int. Conf. on Robotics and Automation (ICRA)},
}

@INPROCEEDINGS{delfa13Astra,
  author = {Juan Manuel Delfa Victoria and Simone Fratini and Nicola Policella and Oskar von Stryk and Yang Gao},
  title = {QuijoteExpress - A novel APSI planning system for future space robotic missions},
  year = {2013},
  booktitle = {In Proceedings of the 12th Symposium on Advanced Space Technologies in Robotics and Automation (ASTRA)},
  abstract = {Communications delay, an undeterministic/dynamic environment, science return or cost efficiency are some of the reasons that claim for more autonomy on Space Missions. The main effort of previous Mars Rover missions (i.e., MER) have been focused on-board, where at least three systems have been successfully deployed: Autonomous navigation, SPOTTER (dust-devil & cloud detection) and AEGIS (autonomous data collection). Considering the sophistication of future rover payloads (e.g., Exomars Pasteur & Humboldt) and with the lessons learnt from previous rover missions, an advanced planner/replanner represents one of the main building blocks for enabling technology. This paper discusses a possible advanced planner candidate: QuijoteExpress an heuristic-driven planner based on a evolution of the APSI framework, APSI*. APSI is an ESA owned software framework to develop automated planning and scheduling applications. APSI* allows the definition of complex goals using a planning technique called Hierarchical Task Networks (HTN). The human operator can define in this way a plan in terms of complex goals while the planner is in charge of decomposing them into commands. This technique provides several advantages. First, it represents an improvement on the planner performance, as HTN simplifies the search space. The planner does not need to search anymore how to achieve repetitive tasks. Instead, predefined methods specify the different ways to accomplish complex goals. Second, it also simplifies the modeling which is one of the major problems that engineers need to face to deploy automated tools. Finally, it makes plans easier to understand and validate by humans. QuijoteExpress extends the AP2 planner developed in the frame of the ESA Goal Oriented Autonomous Controller Study (GOAC). It is divided in a strategic planner that leads the search and four tactical planners used to fix the plan. In QuijoteExpress, the problem can be evolved to different layers, being each layer more detailed than the previous one. It tries to extract a solution using an iterative repair technique as follows: First, it repairs the present layer by adding / deleting or moving elements of the plan. Once the layer is valid, the planner decomposes the problem to the next level and repeat the process. Besides the use of HTN, QuijoteExpress present other novelties. By analysing the structure of the problem, it can identify independent parts that will be then processed in parallel. This technique aims to improve the performance and might enable other techniques such as distributed computing. To manage the inherent uncertainty of rover missions, QuijoteExpress replaces the concept of valid plan by sufficient plan. It allows the user to represent problems for which some information is missing and the planner to find solutions for such problems. Finally, we have implemented a hierarchical model of a rover to test the new platform.},
}

@INPROCEEDINGS{2013:ICRA_Lens-etal,
  author = {T. Lens and O. von Stryk},
  title = {Design and Dynamics Model of a Lightweight Series Elastic Tendon-Driven Robot Arm},
  year = {2013},
  pages = {4512 - 4518},
  month = {May 6-10},
  address = {Karlsruhe, Germany},
  booktitle = {Proc. IEEE Int. Conf. on Robotics and Automation (ICRA)},
}

@ARTICLE{2012:GAMM,
  author = {M. Friedmann and J. Wojtusch and von Stryk},
  title = {A modular and efficient approach to computational modeling and sensitivity analysis of robot and human motion dynamics},
  journal = {Proceedings in Applied Mathematics and Mechanics},
  year = {2012},
  volume = {12},
  number = {Issue 1},
  pages = {85-86},
  month = {December},
  doi = {10.1002/pamm.201210034},
  url = {http://onlinelibrary.wiley.com/doi/10.1002/pamm.201210034/abstract},
  pdf = {2012_FriedmannEtAl_GAMM.pdf},
  abstract = {In this paper a new class library for the computation of the forward multi-body-system (MBS) dynamics of robots and biomechanical models of human motion is presented. By the developed modular modeling approach the library can be flexibly extended by specific modeling elements like joints with specific geometry or different muscle models and thus can be applied efficiently for a number of dynamic simulation and optimization problems. The library not only provides several methods for solving the forward dynamics problem (like articulated body or composite rigid body algorithms) which can transparently be exchanged. Moreover, the numerical solution of optimal control problems, like in the forward dynamics optimization of human motion, is significantly facilitated by the computation of the sensitivity matrix with respect to the control variables. Examples are given to demonstrate the efficiency of the approach.},
}

@INPROCEEDINGS{delfa12Icaps,
  author = {Juan Manuel Delfa Victoria and Nicola Policella and Yang Gao and Oskar von Stryk},
  title = {Design Concepts for a new Temporal Planning Paradigm},
  year = {2012},
  booktitle = {In Proceedings of the ICAPS Planning & Scheduling for Timelines (PSTL)},
  abstract = {Throughout the history of space exploration, the complexity of missions has dramatically increased, from Sputnik in 1957 to MSL, a Mars rover mission launched in November 2011 with advanced autonomous capabilities. As a result, the mission plan that governs a spacecraft has also grown in complexity, pushing to the limit the capability of human operators to understand and manage it. However, the effective representation of large plans with multiple goals and constraints still represents a problem. In this paper, a novel approach to address this problem is presented. We propose a new planning paradigm named HTLN, intended to provide a compact and understandable representation of complex plans and goals based on Timeline planning and Hierarchical Temporal Networks.We also present the design of a planner based on HTLN, which enables new planning approaches that can improve the performance of present real-world domains.},
}

@INPROCEEDINGS{delfa12Permis,
  author = {Juan Manuel Delfa Victoria and Nicola Policella and Marc Gallant and Oskar von Stryk and Alessandro Donati and Yang Gao},
  title = {Metrics for Planetary Rover Planning & Scheduling Algorithms},
  year = {2012},
  booktitle = {In Proceedings of the Performance Metrics for Intelligent Systems (PerMIS) Workshop},
  abstract = {In addition to its utility in terrestrial-based applications, Automated Planning and Scheduling (P&S) has had a growing impact on space exploration. Such applications require an influx of new technologies to improve performance while not compromising safety. As a result, a reliable method to rapidly assess the effectiveness of new P&S algorithms would be desirable to ensure the fulfillment of all software requirements. This paper introduces RoBen, a mission independent benchmarking tool that provides a standard framework for the evaluation and comparison of P&S algorithms. RoBen considers metrics derived from the model (the system on which the P&S algorithm will operate) as well as user input (e.g., desired problem complexity) to automatically generate relevant problems for quality assessment. A thorough description of the algorithms and metrics used in RoBen is provided, along with the preliminary test results of a P&S algorithm solving RoBen-generated problems.},
}

@INPROCEEDINGS{delfa12SpaceOps,
  author = {Juan Manuel Delfa Victoria and Nicola Policella and Marc Gallant and Alessandro Donati and Reinhold Bertrand and Oskar von Stryk and Yang Gao},
  title = {RoBen: Introducing a Benchmarking Tool for Planetary Rover Planning & Scheduling Algorithms},
  year = {2012},
  booktitle = {Proceedings of the 12th International Conference on Space Operations (Spaceops)},
  abstract = {Automated Planning & Scheduling Systems are nowadays applied in a wide range of spacecraft, from satellites to Mars rovers. The planner is responsible for the generation of valid plans that determine the activities to be performed by the spacecraft, given a set of goals and constraints (the problem), and taking into consideration the status of the spacecraft and environment. Therefore, it represents a critical system that needs to be strictly validated and verified. This paper presents a benchmarking tool called RoBen intended to characterize the performance of timeline planning systems. Using a number of metrics and heuristics, RoBen can generate synthetic problems of a given complexity in order to stress planners at different levels. At the same time, we are looking for properties that could help us to determine when a problem is unsolvable.},
}

@INPROCEEDINGS{community_ssrr_2012,
  author = {Stefan Kohlbrecher and Karen Petersen and Gerald Steinbauer and Johannes Maurer and Peter Lepej and Suzana Uran and Rodrigo Ventura and Christian Dornhege and Andreas Hertle and Raymond Sheh and and Johannes Pellenz},
  title = {Community-Driven Development of Standard Software Modules for Search and Rescue Robots},
  year = {2012},
  booktitle = {Proceedings of the 10th IEEE International Symposium on Safety Security and Rescue Robotics (SSRR 2012)},
  pdf = {2012_SSRR_Kohlbrecher_community_driven_development.pdf},
}

@INPROCEEDINGS{petersen_ssrr_2012,
  author = {Karen Petersen and Oskar von Stryk},
  title = {Application Independent Supervised Autonomy},
  year = {2012},
  booktitle = {Proceedings of the 10th IEEE International Symposium on Safety Security and Rescue Robotics (SSRR 2012)},
  pdf = {petersen_SSRR_2012.pdf},
}

@INPROCEEDINGS{2012:Beckerle-SMC,
  author = {P. Beckerle and O. Christ and J. Wojtusch and J. Schuy and K. Wolff and S. Rinderknecht and J. Vogt and O. von Stryk},
  title = {Design and Control of a Robot for the Assessment of Psychological Factors in Prosthetic Development},
  year = {2012},
  pages = {1485 - 1490},
  month = {Oct. 14-17},
  address = {Seoul},
  booktitle = {IEEE International Conference on Systems, Man, and Cybernetics (SMC)},
  pdf = {2012_BeckerleEtAl_SMC.pdf},
  abstract = {This paper introduces a robotic concept for the assessment of psychological factors in prosthetic design. Its aim is to imitate the postural movements of the participants while those are conducting squatting movements in order to investigate the integration of artificial limbs to the subject"s body scheme. Therefore, the robot mimics the functionality and appearance of the human foot, shank and thigh as well as the ankle and knee joint. To induce a more realistic outer appearance, the hull of a shop-window mannequin is used as cladding. The robot is controlled by a computed torque control combined with a RGB-D sensor for the acquisition of the desired trajectories from the participant. In the test setup one leg of the participant is hidden from his view while the robot stands next to him and imitates the movements of this leg. This paper gives an insight in the theory of body schema integration. The concept of the robot is described and detailed information about the mechanical design and actuator dimensioning in accordance with psychological and biomechanical requirements are given. Furthermore, the concept of the human-machine interface, the control algorithm and simulations based on experimental data from a human subject are presented.},
}

@ARTICLE{2012:Christ-BioEng2,
  author = {O. Christ and P. Beckerle and J. Preller and M. Jokisch and S. Rinderknecht and J. Wojtusch and O. von Stryk and J. Vogt},
  title = {The rubber hand illusion: Maintaining factors and a new perspective in rehabilitation and biomedical engineering?},
  journal = {Biomedical Engineering / Biomedizinische Technik},
  year = {2012},
  volume = {57},
  number = {Suppl. 1},
  pages = {846-849},
  doi = {10.1515/bmt-2012-4297},
  pdf = {2012_ChristEtAl_RHI_BMT.pdf},
  abstract = {Feelings of unrealistic body parts are related to deficits in human information processing and can occur as a part of phantom sensations after amputation [8]. Experimentally induced sensoric illusions like rubber hand illusion (RHI) [1] may help to understand basic information processing and could give new ideas for treatment or the rehabilitation process. Factors that are related to modulate sensoric illusions during movement may help to develop new intervention strategies in the rehabilitation of illusory symptoms. The goal of this study was to review the factors affecting persistence of the RHI effect during movement. We selected 13 keywords and searched in the following www.dimdi.de data bases (CCTR93, CDAR94, CDSR93, DAHTA, DAHTA, EA08, ED93, EM00, EM47, HG05, KP05, KR03, ME00, ME60, PI67, PY81, TV01, TVPP). A total of 160 articles were found. Duplicates were removed and the remaining list was filtered with the objective to explore the influence of active or passive movement during experimentally induced RHI. Then we identified six articles which experimentally examined persistence of RHI during active or passive movements. Results indicate that RHI are maintained during active or passive movements due to visual and temporal congruency. During active movements the RHI is more stable or global than in passive movements or during tactile stimulation. Factors like visual and temporal congruency are related to maintain RHI and are discussed in the rehabilitation of phantom sensations regarding new innovations in the design of prosthetics.},
}

@ARTICLE{2012:Christ-BioEng1,
  author = {O. Christ and M. Jokisch and J. Preller and P. Beckerle and S. Rinderknecht and J. Wojtusch and O. von Stryk and J. Vogt},
  title = {User-Centered Prosthetic Development: Comprehension of Amputees" Needs},
  journal = {Biomedical Engineering / Biomedizinische Technik},
  year = {2012},
  volume = {57},
  number = {Suppl. 1},
  pages = {1098-1101},
  pdf = {2012_ChristEtAl_UCD_BMT.pdf},
  abstract = {The goal of user-centered development (UCD) is an active involvement of the user for a clear understanding of the users" needs. In the context of rehabilitation engineering it is essential to integrate the users" needs into the development methodology. In fact the use or disclaim of assistive device depends on good comfort and satisfaction during application. Especially prostheses are developed to improve amputees’ quality of life up to live independently again. UCD can improve integrating the amputees’ needs into the prosthesis’ properties. For a more detailed view of the prosthesis-users’ needs we developed a questionnaire and collected data from patients regarding their needs using lower limb prostheses. 88 items, describing satisfaction, usability, appearance, functionality and handling of the prosthesis in different motor situations, were generated. Among 65 participants, 29 transfemoral amputees and experienced prosthesis users completed the questionnaire. The results indicate a lack of satisfaction with the prosthesis shaft as well as with different motor functions. Furthermore, the majority feels socially restricted and is dissatisfied with their appearance in public. While the latter is significantly negative correlated with feelings of social restriction, problems during changing gait speed are significantly negative correlated with feelings of certainty and stability during spontaneous movements. Although prostheses are developed to help to improve amputees’ quality of life, the lack in different motor and social issues are noticeable. This indicates that the enhancement of changing gait speed in prostheses may help amputees to feel more certain and natural during walking. From an amputee’s point of view, this could be one important predictor for being more satisfied and a first step for being more independent in life in general. With this first step of UCD, important information for the design of prosthesis in future has been generated.},
}

@ARTICLE{2012:Wolff-OT,
  author = {K. Wolff and P. Beckerle and J. Wojtusch and O. Christ},
  title = {Nutzerfreundliche, energieeffiziente und aktive Beinprothesen},
  journal = {Orthopädie Technik},
  year = {2012},
  pages = {76-79},
  pdf = {2012_WolffEtAl_OT.pdf},
}

@INPROCEEDINGS{2012_Humanoids_Lens,
  author = {Thomas Lens and Jérôme Kirchhoff and Oskar von Stryk},
  title = {Dynamic Modeling of Elastic Tendon Actuators with Tendon Slackening},
  year = {2012},
  pages = {779 - 784},
  month = {Nov. 29 - Dec. 1},
  address = {Osaka, Japan},
  booktitle = {Proceedings of the IEEE/RAS International Conference on Humanoid Robots (HUMANOIDS)},
  pdf = {2012_HUMANOIDS_Lens_PREPRINT.pdf},
  abstract = {This paper presents a new, detailed dynamics model of a novel type of actuators based on tendons with integrated springs that allows for offline adjustment of the stiffness characteristics. Like other cable or belt actuators, the elastic tendon actuator allows to radically reduce the link inertia by placing the motors near the robot base. But by additionally integrating springs in the tendons, the motor and the joint are elastically decoupled, which increases the lifespan of the tendons and the safety of the actuator. A detailed mathematical model of the actuator is derived taking tendon slackening effects into consideration. The result is a degressive stiffness curve that depends on the pretension force of the integrated tendon springs. The derived model is validated against static and dynamic experimental measurement data of a robot arm equipped with elastic tendon actuators.},
}

@INPROCEEDINGS{2012simpar_meyer,
  author = {Johannes Meyer and Alexander Sendobry and Stefan Kohlbrecher and Uwe Klingauf and Oskar von Stryk},
  title = {Comprehensive Simulation of Quadrotor UAVs using ROS and Gazebo},
  year = {2012},
  pages = {400-412},
  booktitle = {3rd Int. Conf. on Simulation, Modeling and Programming for Autonomous Robots (SIMPAR)},
  abstract = {Quadrotor UAVs have successfully been used both in research and for commercial applications in recent years and there has been significant progress in the design of robust control software and hardware. Nevertheless, testing of prototype UAV systems still means risk of damage due to failures. Motivated by this, a system for the comprehensive simulation of quadrotor UAVs is presented in this paper. Unlike existing solutions, the presented system is integrated with ROS and the Gazebo simulator. This comprehensive approach allows simultaneous simulation of diverse aspects such as flight dynamics, onboard sensors like IMUs, external imaging sensors and complex environments. The dynamics model of the quadrotor has been parameterized using wind tunnel tests and validated by a comparison of simulated and real flight data. The applicability for simulation of complex UAV systems is demonstrated using LIDAR-based and visual SLAM approaches available as open source software. },
}

@INPROCEEDINGS{2012DynamicWalking:Radkhah,
  author = {K. Radkhah and O. von Stryk},
  title = {Human-Like Model-Based Motion Generation Combining Feedforward and Feedback Control for Musculoskeletal Robots},
  year = {2012},
  month = {May 21 - 24},
  address = {Pensacola, Florida, USA},
  booktitle = {Proc. 7th Annual Dynamic Walking Conference},
}

@INPROCEEDINGS{2012simpar_scholz,
  author = {Dorian Scholz and Christophe Maufroy and Stefan Kurowski and Katayon Radkhah and Oskar von Stryk and André Seyfarth},
  title = {Simulation and Experimental Evaluation of the Contribution of Biarticular Gastrocnemius Structure to Joint Synchronization in Human-Inspired Three-Segmented Elastic Legs },
  year = {2012},
  volume = {7628},
  pages = {251-260},
  publisher = {Springer},
  editor = {I. Noda and N. Ando and D. Brugali and J.J. Kuffner},
  series = {Lecture Notes in Computer Science},
  booktitle = {3rd Int. Conf. on Simulation, Modeling and Programming for Autonomous Robots (SIMPAR)},
  doi = {10.1007/978-3-642-34327-8_24},
  pdf = {2012_Scholz_SIMPAR.pdf},
  abstract = {The humanoid robot BioBiped2 is powered by series elastic actuators (SEA) at the leg joints. As motivated by the human muscle ar- chitecture comprising monoarticular and biarticular muscles, the SEA at joint level are supported by elastic elements spanning two joints. In this study we demonstrate in simulation and in robot experiments, to what extend synchronous joint operation can be enhanced by introducing elas- tic biarticular structures in the leg, reducing the risk of over-extending individual joints.},
}

@INPROCEEDINGS{euler12,
  author = {J. Euler and A. Horn and D. Haumann and J. Adamy and O. von Stryk},
  title = {Cooperative N-Boundary Tracking in Large Scale Environments},
  year = {2012},
  booktitle = {Proceedings of the IEEE 9th International Conference on Mobile Adhoc and Sensor Systems (MASS)},
  keywords = {adaptive sampling,boundary tracking,cooperative control,large scale environments},
  doi = {10.1109/MASS.2012.6708518},
  url = {http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6708518},
  pdf = {2012_EulerEtAl_WiSARN.pdf},
  abstract = {Monitoring in large scale environments is a typ-ical mission in cooperative robotics. This task requires the exploration of a huge domain by a generally small number of sensor equipped mobile robots. As time restrictions prohibit an exhaustive global search, a sampling strategy is required that allows an efficient spatial mapping of the environment. This paper proposes an adaptive sampling strategy for efficient simultaneous tracking of multiple concentration levels of an atmospheric plume by a team of cooperating unmanned aerial vehicles (UAVs). The approach combines uncertainty and correlation-based concentration estimates to generate sampling points based on already gathered data. The adaptive generation of sampling locations is coupled to a distributed model-predictive controller for planning optimal vehicle trajectories under collision and communication constraints. Simulation results demonstrate that connectivity of all involved vehicles can be maintained and an accurate reconstruction of the plume is obtained efficiently.},
}

@INPROCEEDINGS{2012IROS:lens,
  author = {T. Lens and O. von Stryk},
  title = {Investigation of Safety in Human-Robot-Interaction for a Series Elastic, Tendon-Driven Robot Arm },
  year = {2012},
  pages = {4309-4314},
  booktitle = {IEEE/RSJ Int. Conf. on Intelligent Robots and Systems (IROS)},
  pdf = {2012_IROS_Lens_etal_PREPRINT.pdf},
  abstract = {This paper presents the design of the lightweight BioRob manipulator with spring-loaded tendon-driven actuation developed for safe physical human-robot interaction. The safety of the manipulator is analyzed by an analytical worst-case estimation of impact and clamping forces in the absence of collision detection. As intrinsic joint compliance can pose a threat by storing energy, a safety evaluation method is proposed taking the potential energy stored in the elastic actuation into account. The evaluation shows that the robot arm design constrains the worst case clamping forces to only 25N, while being able to handle loads up to 2kg, and inherits extremely low impact properties, such as an effective mass of less than 0.4kg in non near-singular configurations, enabling safe operation even in case of high velocities. The results are validated in simulation and experiments.},
}

@INPROCEEDINGS{2012IROS:radkhah,
  author = {K. Radkhah and T. Lens and O. von Stryk},
  title = {Detailed Dynamics Modeling of BioBiped´s Monoarticular and Biarticular Tendon-Driven Actuation System },
  year = {2012},
  pages = {4243-4250},
  booktitle = {IEEE/RSJ Int. Conf. on Intelligent Robots and Systems (IROS)},
  abstract = {Bio-inspired, musculoskeletal design of bipedal robots offers great potential towards more human-like robot performance but imposes major challenges on their design and control, as it is challenging to analyze the contribution of each active and passive series elastic tendon to the overall joint, leg and robot dynamics. In this paper, detailed mathematical models of the tendon-driven, series elastically actuated mono- and biarticular structures of the BioBiped1 robot are presented. These enable a systematic analysis of the design space and characteristic curves as well as to derive guidelines for the design of improved prototypes. The derived models are applied to investigate the effects of the active and passive, mono- and biarticular structures on different performance criteria of 1D hopping motions by means of a detailed multi-body system dynamics simulation.},
}

@INPROCEEDINGS{2012:Christ-EMBC,
  author = {O. Christ and J. Wojtusch and P. Beckerle and K. Wolff and J. Vogt and O. von Stryk and S. Rinderknecht},
  title = {Prosthesis-User-in-the-Loop: User-Centered Design Parameters and Visual Simulation},
  year = {2012},
  pages = {1929 - 1932},
  booktitle = {Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)},
  pdf = {2012_ChristEtAl_EMBC.pdf},
  abstract = {After an amputation, processes of change in the body image as well as a change in body scheme have direct influences on the quality of live in every patient. Within this paper, a paradigm of experimental induced body illusion is integrated in a prosthetic hardware simulator concept. This concept combines biodynamical and visual feedback to enhance the quality of rehabilitation and to integrate patients’ needs into the development of prostheses aiming on user-centered solutions. Therefore, user-centered design parameters are deducted. Further, the basic concept of the visual simulation is presented and a possibility for its implementation is given. Finally, issues and conclusions for future work are described.},
}

@INPROCEEDINGS{2012:Wojtusch-EMBC,
  author = {J. Wojtusch and P. Beckerle and O. Christ and K. Wolff and O. von Stryk and S. Rinderknecht and J. Vogt},
  title = {Prosthesis-User-in-the-Loop: A User-Specific Biomechanical Modeling and Simulation Environment},
  year = {2012},
  pages = {4181 - 4184},
  booktitle = {Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)},
  pdf = {2012_WojtuschEtAl_EMBC.pdf},
  abstract = {In this paper, a novel biomechanical modeling and simulation environment with an emphasis on user-specific customization is presented. A modular modeling approach for multi-body systems allows a flexible extension by specific biomechanical modeling elements and enables an efficient application in dynamic simulation and optimization problems. A functional distribution of model description and model parameter data in combination with standardized interfaces enables a simple and reliable replacement or modification of specific functional components. The user-specific customization comprises the identification of anthropometric model parameters as well as the generation of a virtual three-dimensional character. The modeling and simulation environment is associated with Prosthesis-User-in-the-Loop, a hardware simulator concept for the design and optimization of lower limb prosthetic devices based on user experience and assessment. For a demonstration of the flexibility and capability of the modeling and simulation environment, an exemplary application in context of the hardware simulator is given.},
}

@INPROCEEDINGS{fast2012,
  author = {Philipp M. Scholl and Stefan Kohlbrecher and Vinay Sachidananda and Kristof van Laerhoven},
  title = {Fast Indoor Radio-Map Building for RSSI-based Localization Systems},
  year = {2012},
  booktitle = {Demo Paper, International Conference on Networked Sensing Systems},
  pdf = {2012_INSS_Scholl_indoor_radio_map.pdf},
  abstract = {Wireless Indoor localization systems based on RSSI-values typically consist of an offline training phase and online position determination phase. During the offline phase, georeferenced RSSI measurement, called fingerprints, are recorded to build a radiomap of the building. This radiomap is then searched during the position determination phase to estimate another nodes location. Usually the radiomap is build manually, either by users pin-pointing their location on a ready-made floorplan or by moving in pre-specified patterns while scanning the network for RSSI values. This cumbersome process leads to inaccuracies in the radiomap. Here, we propose a system to build the indoor- and radio map simultaneously by using a handheld mapping system employing a laser scanner in an IEEE802.15.4-compatible network. This makes indoor- and radio-mapping for wireless localization less cumbersome, faster and more reliable.},
}

@INPROCEEDINGS{2012:Robotik_Lens_etal,
  author = {T. Lens and A. Karguth and O. von Stryk},
  title = {Safety Properties and Collision Behavior of Robotic Arms with Elastic Tendon Actuation},
  year = {2012},
  booktitle = {Proceedings of the German Conference on Robotics (ROBOTIK)},
  pdf = {2012_ROBOTIK_Lens_etal_PREPRINT.pdf},
  abstract = {Applications with physical human-robot interaction require a high level of safety even in case of software or hardware failures. This paper highlights the advantages of combining tendon actuation with transmission elasticity to maximize safety for robotic arms sharing workspaces with humans. To this end, the collision behavior of combinations of tendon or joint and elastic or stiff actuation with geared electrical motors as reliable actuators is compared using the lightweight BioRob arm as robotic platform in simulation. For the comparison a worst case scenario is assumed in which the robot arm is accelerated with maximum supply voltage over its joint range and collides with maximum end-effector velocity. The study shows that the robot arm achieves end-effector velocities as high as 6m/s and that elastic tendon actuation reduces the end-effector impact energy and force by up to 90% compared to stiff joint actuation. A considerable reduction of the gearbox stress is also achieved. In addition, the effect of motor current fuses limiting the motor torques is evaluated. It is shown that for the given high speed scenario, torque limiting devices can be effective to prevent excessive clamping forces in case of failure, but can not reduce the impact peak force without heavily compromising the robot dynamics. The main design criterion for safety should therefore be lightweight link design and compliant actuation, which can be achieved by using elastic tendon actuation. The paper concludes with the comparison of safety properties of robotic arms in research and industry.},
}

@INPROCEEDINGS{2012:IEEE-BioRob_VTS,
  author = {J. Schuy and P. Beckerle and J. Wojtusch and S. Rinderknecht and O. von Stryk},
  title = {Conception and evaluation of a novel variable torsion stiffness for biomechanical applications},
  year = {2012},
  pages = {713 - 718},
  booktitle = {4th IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics (BioRob)},
  pdf = {2012_SchuyEtAl_BioRob.pdf},
  abstract = {Abstract—This paper proposes a novel variable torsion stiffness (VTS) aiming on biomechanical applications like prosthetic knee joints. By varying the effective length of a torsional elastic element via a relocatable counter bearing, the stiffness of a rotational joint is adjusted. This functional concept is described in detail by the authors as well as the design of such VTS joints. Additionally, analytical models for the transfer behaviour of drivetrain and stiffness control are derived. These are used for a simulative evaluation of a pendulum driven by a VTS unit. Based on the results of this simulation, the power requirements of VTS are analysed. Furthermore, an analysis of its structural strength is presented. For practical comprehensibility, the example of the design of a prosthetic knee joint is taken up for several times in this paper. Finally, the concept, modeling and design of VTS as well as the simulation results are concluded and discussed in a final assessment and in comparison to other contemporary concepts.},
}

@TECHREPORT{2012:rescue_tdp,
  author = {Thorsten Graber and Stefan Kohlbrecher and Johannes Meyer and Karen Petersen and Oskar von Stryk and Uwe Klingauf},
  title = {RoboCupRescue 2012 - Robot League Team Hector Darmstadt (Germany)},
  year = {2012},
  institution = {Technische Universität Darmstadt},
  pdf = {2012_tdp_hector.pdf},
  abstract = {This paper describes the approach used by Team Hector Darmstadt for participation in the 2012 RoboCup Rescue League competition. Participating in the RoboCup Rescue competition since 2009, the members of Team Hector Darmstadt focus on exploration of disaster sites using autonomous Unmanned Ground Vehicles (UGVs). The team has been established as part of a PhD program funded by the German Research Foundation at TU Darmstadt and combines expertise from Computer Science and Mechanical Engineering. We give an overview of the complete system used to solve the problem of reliably finding victims in harsh USAR environments. This includes hardware as well as software solutions and diverse topics like locomotion, SLAM, pose estimation, human robot interaction and victim detection. As a contribution to the RoboCup Rescue community, major parts of the used software have been released and documented as open source software for ROS.},
}

@TECHREPORT{2012:dd_tdp,
  author = {J. Kuhn and S. Kohlbrecher and K. Petersen and D. Scholz and J. Wojtusch and O. von Stryk},
  title = {Team Description for Humanoid KidSize League of RoboCup 2012 },
  year = {2012},
  institution = {Technische Universität Darmstadt},
  pdf = {2012_tdp_hum.pdf},
  abstract = {This paper describes the hardware and software design and developments of the kidsize humanoid robot systems of the Darmstadt Dribblers in 2012. The robots are used as a vehicle for research in humanoid robotics and teams of cooperating, autonomous robots. The Humanoid League of RoboCup provides an ideal testbed for investigation of topics like stability, control and versatility of humanoid locomotion, behavior control of autonomous humanoid robots and robot teams with many degrees of freedom and many actuated joints, perception and world modeling based on very limited human-like, external sensing abilities as well as benchmarking of autonomous robot performance. The methodologies developed by the Darmstadt Dribblers to address reflex and cognitive control layers, image processing, perception, world modeling, behavior and motion control, robot simulation, monitoring, debugging and bio-inspired humanoid robot bodyware are briefly discussed. },
}

@INPROCEEDINGS{2011_ROBIO_Klug_Musculoskeletal_System_Human_Arm,
  author = {S. Klug and T. Lens and M. Nogler and O. von Stryk},
  title = {The musculoskeletal system of the human arm - More than the sum of its parts},
  year = {2011},
  pages = {639-643},
  booktitle = {IEEE International Conference on Robotics and Biomimetics (ROBIO)},
  abstract = {Biological systems show outstanding performance in the control of highly redundant and nonlinear systems. The complexity of these systems has raised questions about sufficient strategies of planning and controlling movements. Although many aspects of the musculoskeletal system, like nonlinear muscle properties, redundant actuation, and mechanically coupled joints, seem to make things more complicate from a purely technical point of view, this complexity has positive influence on the control. In this paper we show first aspects on how the nonlinear characteristics of the musculoskeletal system of the human arm may influence and even support the control of movements.},
}

@ARTICLE{petersen_intsys2011,
  author = {K. Petersen and O. von Stryk},
  title = {An Event-based Communication Concept for Human Supervision of Autonomous Robot Teams},
  journal = {International Journal on Advances in Intelligent Systems},
  year = {2011},
  volume = {4},
  number = {3 and 4},
  pages = {357 - 369},
  url = {http://www.thinkmind.org/index.php?view=article&articleid=intsys_v4_n34_2011_24},
  pdf = {2011_petersen_intsys.pdf},
}

@INCOLLECTION{2011:Abele_etal_TUForschen,
  author = {E. Abele and J. Bauer and M. Friedmann and M. Pischan and C. Reinl and O. von Stryk},
  title = {Einsatz von Robotern in der spanenden Fertigung},
  year = {2011},
  volume = {1/2011},
  pages = {44 - 49},
  publisher = {TU Darmstadt},
  booktitle = {Wissenschaftsmagazin forschen},
  pdf = {AbeleBauerFriedmannPischanReinlStryk_TUFoschen_2011.pdf},
  abstract = {For milling of complex work pieces with required accuracies of less than 0.1 mm five-axis machine tools are used in industrial practice. Industrial robots are by far more cost-efficient but they are achieving less machining accuracy due to their elastic resilience. Deviations can be simulated and corrected with a mathematical model, that reproduces static and dynamic interactions of robot and milling process. The challenge: High accuracy can only be achieved, if model parameters are known precisely at any time.},
}

@INCOLLECTION{2011:TUD-Forschung,
  author = {T. Hemker and H. De Gersem and S. Koch and O. von Stryk},
  title = {Bessere Synchrotron-Magnete durch simulationsbasierte Optimierung},
  year = {2011},
  number = {2/2011},
  pages = {58-62},
  publisher = {TU Darmstadt},
  editor = {M. Schaefer},
  series = {forschung},
  booktitle = {Computational Engineering},
  url = {http://www.tu-darmstadt.de/vorbeischauen/publikationen/forschung/index_3136.de.jsp},
  pdf = {2011-Forschen_02_2011_S58-62.pdf},
  abstract = {Während die numerische Optimierung von kontinuierlichen Parametern supraleitender Magnete basierend auf elektromagnetischen Feldsimulationen trotz hoher Rechenzeitanforderungen schon fast alltäglich ist, stellt die für ein optimales Design notwendige, simultane Berücksichtigung auch diskreter Parameter und der damit verbundene, hohe zusätzliche Rechenaufwand enorme Schwierigkeiten dar. Eine neue, methodische Vorgehensweise zu deren Überwindung wird vorgestellt und zur Entwicklung von besonders leistungsfähigen, supraleitenden Magneten für das neue internationale Beschleunigerzentrum FAIR erfolgreich angewendet.},
}

@ARTICLE{griffin2011,
  author = {J. D. Griffin and K. R. Fowler and G. A. Gray and T. Hemker and M. D. Parno},
  title = {Derivative-Free Optimization Via Evolutionary Algorithms Guiding Local Search},
  journal = {Pacific Journal of Optimization},
  year = {2011},
  volume = {7},
  number = {3},
  pages = {425-443},
  month = {September},
  url = {http://www.ybook.co.jp/online2/oppjo/vol7/p425.html},
  pdf = {2010-griffin_etal.pdf},
  abstract = {In this paper, we describe the technical details of HOPSPACK (Hybrid Optimization Parallel Search Package), a new software platform which facilitates combining multiple optimization routines into a single, tightly-coupled, hybrid algorithm that supports parallel function evaluations. The framework is designed such that existing optimization source code can be easily incorporated with minimal code modification. By maintaining the integrity of each individual solver, the strengths and code sophistication of the original optimization package are retained and exploited.},
}

@INPROCEEDINGS{KohlbrecherMeyerStrykKlingaufFlexibleSlamSystem2011,
  author = {S. Kohlbrecher and J. Meyer and O. von Stryk and U. Klingauf},
  title = {A Flexible and Scalable SLAM System with Full 3D Motion Estimation},
  year = {2011},
  pages = {155-160},
  month = {November 1-5},
  address = {Kyoto, Japan},
  booktitle = {Proc. IEEE International Symposium on Safety, Security and Rescue Robotics (SSRR)},
  organization = {IEEE},
  doi = {10.1109/SSRR.2011.6106777},
  pdf = {2011_SSRR_KohlbrecherMeyerStrykKlingauf_Flexible_SLAM_System.pdf},
  abstract = {For many applications in Urban Search and Rescue (USAR) scenarios robots need to learn a map of unknown environments. We present a system for fast online learning of occupancy grid maps requiring low computational resources. It combines a robust scan matching approach using a LIDAR system with a 3D attitude estimation system based on inertial sensing. By using a fast approximation of map gradients and a multi-resolution grid, reliable localization and mapping capabilities in a variety of challenging environments are realized. Multiple datasets showing the applicability in an embedded hand-held mapping system are provided. We show that the system is sufficiently accurate as to not require explicit loop closing techniques in the considered scenarios. The software is available as an open source package for ROS.},
}

@INPROCEEDINGS{2011:KohlbrecherStumpfVonStryk_WsHumSoc,
  author = {S. Kohlbrecher and A. Stumpf and O. von Stryk},
  title = {Grid-Based Occupancy Mapping and Automatic Gaze Control for Soccer Playing Humanoid Robots},
  year = {2011},
  month = {Oct. 26th - Oct. 28th},
  address = {Bled},
  booktitle = {Proc. 6th Workshop on Humanoid Soccer Robots at the 2011 IEEE-RAS Int. Conf. on Humanoid Robots},
  keywords = {World Modeling, RoboCup, Probabilistic Robotics, State Estimation},
  pdf = {2011_Humanoids_Kohlbrecher_Stumpf_Stryk_Grid_Based_Occupancy_Mapping_and_Automatic_Gaze_Control_for_Soccer_Playing_Humanoid_Robots.pdf},
  abstract = {With advances in walking abilities of autonomous soccer playing humanoid robots, the world modeling and state estimation problem moves into focus, as only sufficiently accurate and robust modeling allows to leverage improved locomotion capabilities. A novel approach for dense grid-based obstacle mapping in dynamic environments with an additional application for automatic gaze control is presented in this paper. It is applicable for soccer playing humanoid robots with external sensing limited to human-like vision and strongly limited onboard computing abilities. The proposed approach allows fusion of information from different sources and efficiently provides a single consistent and robust world state estimate despite strong robot hardware limitations.},
}

@INPROCEEDINGS{2011:AMAM-BioBiped,
  author = {C. Maufroy and H.-M. Maus and K. Radkhah and D. Scholz and O. von Stryk and A. Seyfarth},
  title = {Dynamic leg function of the BioBiped humanoid robot},
  year = {2011},
  month = {Oct. 11-14},
  address = {Osaka, Japan},
  booktitle = {Proc. 5th Int. Symposium on Adaptive Motion of Animals and Machines (AMAM)},
  pdf = {2011-AMAM2011-MAUFROY-preprint.pdf},
  abstract = {This contribution presents the concept and design of the first robot of the BioBiped series, aiming to transfer biomechanical insights regarding the mechanics and control of human walking and running to bipedal robot design and actuation. These are supported by preliminary experiments with the robot, where synchronous and alternate hopping motions could be successfully realized. This demonstrates that the robot design has the potential to develop dynamic gait patterns such as walking and running.},
}

@INPROCEEDINGS{2011:Humanoids-BioBiped1,
  author = {D. Scholz and S. Kurowski and K. Radkhah and O. von Stryk},
  title = {Bio-inspired motion control of the musculoskeletal BioBiped1 robot based on a learned inverse dynamics model},
  year = {2011},
  month = {Oct. 26-28},
  address = {Bled, Slovenia},
  booktitle = {Proc. 11th IEEE-RAS Int. Conf. on Humanoid Robots (HUMANOIDS)},
  pdf = {2011_Humanoids_Scholz_Kurowski_Radkhah_Stryk_Bio-Inspired_Motion_Control_of_the_Musculoskeletal_BioBiped1_Robot_Based_on_a_Learned_Inverse_Dynamics_Model.pdf},
  abstract = {Based on the central hypothesis that a humanoid robot with human-like walking and running performance requires a bio-inspired embodiment of the musculoskeletal functions of the human leg as well as of its control structure, a bio-inspired approach for joint position control of the BioBiped1 robot is presented in this paper. This approach combines feedforward and feedback control running at 1 kHz and 40 Hz, respectively. The feed-forward control is based on an inverse dynamics model which is learned using Gaussian process regression to account for the robot’s body dynamics and external influences. For evaluation the learned model is used to control the robot purely feed-forward as well as in combination with a slow feedback controller. Both approaches are compared to a basic feedback PD-controller with respect to their tracking ability in experiments. It is shown, that the combined approach yields good results and outperforms the basic feedback controller when applied to the same set-point trajectories for the leg joints.},
}

@ARTICLE{parno2011,
  author = {M. Parno and K. Fowler and T. Hemker},
  title = {Applicability of Surrogates to Improve Efficiency of Particle Swarm Optimization for Simulation-based Problems},
  journal = {Engineering Optimization},
  year = {2011},
  pages = {online},
  doi = {10.1080/0305215X.2011.598521},
  abstract = {Particle swarm optimization (PSO) is a population-based, heuristic technique based on social behaviour that performs well on a variety of problems including those with non-convex, non-smooth objective functions with multiple minima. However, the method can be computationally expensive in that a large number of function calls is required. This is a drawback when evaluations depend on an off-the-shelf simulation program, which is often the case in engineering applications. An algorithm is proposed which incorporates surrogates as a stand-in for the expensive objective function, within the PSO framework. Numerical results are presented on standard benchmarking problems and a simulation-based hydrology application to show that this hybrid can improve efficiency. A comparison is made between the application of a global PSO and a standard PSO to the same formulations with surrogates. Finally, data profiles, probability of success, and a measure of the signal-to-noise ratio of the the objective function are used to assess the use of a surrogate.},
}

@INPROCEEDINGS{iros2011:radkhah,
  author = {K. Radkhah and O. von Stryk},
  title = {Actuation requirements for hopping and running of the musculoskeletal robot BioBiped1},
  year = {2011},
  pages = {4811-4818},
  booktitle = {IEEE/RSJ Int. Conf. on Intelligent Robots and Systems (IROS)},
  pdf = {2011_Radkhah_iros.pdf},
  abstract = {Actuation with variable elasticity is considered a key property for the realization of human-like bipedal locomotion. Also, an intelligent and self-stable mechanical system is indispensable. While much effort of current research has been devoted to the development of variable impedance joint actuators, this paper deals with the important question of how to determine the actuation requirements of a compliant, musculoskeletal robot that is targeted at fast dynamic motions. In a step-by-step approach, design decisions for the elastic humanoid robot BioBiped1 are presented. Using multibody system dynamics models and simulations, incorporating bidirectional series elastic actuator models and a realistic ground contact model, we analyze the actuation requirements of the employed electrical motors for computer generated hopping and human data based running motions. The numerical simulation results are accompanied by videos of the dynamics simulations. Recent experiments on the real hardware have indicated that the selected motor-gear units and elastic transmissions support the desired dynamic motion goals.},
}

@INPROCEEDINGS{2011:Lens-etal,
  author = {T. Lens and K. Radkhah and O. von Stryk},
  title = {Simulation of Dynamics and Realistic Contact Forces for Manipulators and Legged Robots with High Joint Elasticity},
  year = {2011},
  pages = {34-41},
  booktitle = {Proc. 15th International Conference on Advanced Robotics (ICAR)},
  pdf = {2011_icar_lens-rdkhh_preprint.pdf},
  abstract = {In this paper, multibody system dynamics simulation for manipulators and legged robots with high joint elasticities, particularly with focus on collision modeling, is addressed. We present the architecture of a newly developed toolbox in conjunction with a detailed discussion of a realistic contact, friction and stiction model, which is validated with real measurement data of a bouncing ball. The work presented is driven and inspired by two concrete robot developments in the authors" group: the manipulator BioRob and the biped BioBiped. The libraries are used to develop kinematic and kinetic models of these bio-inspired and highly elastic robots. Models and simulation of both robots are discussed, as well as occurring forces during collisions of the BioRob-X4 arm with the ground. We are also able to demonstrate good agreement of ground contact forces measured during slow jogging motion of a human subject with simulation results obtained with BioBiped1.},
}

@TECHREPORT{2011:rescue_tdp,
  author = {Thorsten Graber and Stefan Kohlbrecher and Johannes Meyer and Karen Petersen and Oskar von Stryk},
  title = {RoboCupRescue 2011 - Robot League Team Hector Darmstadt (Germany)},
  year = {2011},
  institution = {Technische Universität Darmstadt},
  pdf = {2011_tdp_hector.pdf},
  abstract = {The team Hector Darmstadt has been established from a PhD program funded by the German Research Foundation at TU Darmstadt.It combines expertise from Computer Science and Mechanical Engineering. The team successfully participates in the RoboCup Rescue League since 2009, with a focus on autonomous robots. Several team members have already contributed in the past to highly successful teams in the RoboCup Four-Legged and Humanoid League and in UAV competitions.},
}

@TECHREPORT{2011:dd_tdp,
  author = {M. Friedmann and J. Kuhn and S. Kohlbrecher and K. Petersen and D. Scholz and D. Thomas and J. Wojtusch and O. von Stryk},
  title = {Darmstadt Dribblers - Team Description for Humanoid KidSize League of RoboCup 2011},
  year = {2011},
  institution = {Technische Universität Darmstadt},
  pdf = {2011_tdp_hum.pdf},
  abstract = {This paper describes the hardware and software design and developments of the kidsize humanoid robot systems of the Darmstadt Dribblers in 2011. The robots are used as a vehicle for research in humanoid robotics and teams of cooperating, autonomous robots. The Humanoid League of RoboCup provides an ideal testbed for investigation of topics like stability, control and versatility of humanoid locomotion, behavior control of autonomous humanoid robots and robot teams with many degrees of freedom and many actuated joints, perception and world modeling based on very limited human-like, external sensing abilities as well as benchmarking of autonomous robot performance. The methodologies developed by the Darmstadt Dribblers to address reflex and cognitive control layers, image processing, perception, world modeling, behavior and motion control, robot simulation, monitoring and debugging are briefly discussed.},
}

@INPROCEEDINGS{2011:Reinl_etal_AIM,
  author = {C. Reinl and M.Friedmann and J.Bauer and M. Pischan and E. Abele and O. von Stryk},
  title = {Model-based Off-line Compensation of Path Deviation for Industrial Robots in Milling Applications},
  year = {2011},
  booktitle = {IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM)},
}

@ARTICLE{hemker2011,
  author = {T. Hemker and C. Werner},
  title = {DIRECT using local search on surrogates},
  journal = {Pacific Journal of Optimization},
  year = {2011},
  volume = {7},
  number = {3},
  pages = {443-466},
  month = {September},
  url = {http://www.ybook.co.jp/online2/oppjo/vol7/p443.html},
  pdf = {2011_hemker.pdf},
  abstract = {The solution of noisy nonlinear optimization problems with nonlinear constraints and derivative information is becoming increasingly important, as many practical applications can be described by this type of problem in e.g., engineering applications. Existing local optimization methods show good convergence properties. However, they often depend on sufficiently good starting points and/or the approximation of gradients. In turn, global derivative free methods, which need no starting values to be initialized, require many evaluations of the objective function, particularly in the vicinity of the solution. A derivative free optimization algorithm is developed that combines advantages of both local and global methods. The DIRECT algorithm, which is often used for problems where no prior knowledge is available as kind of a brute force start, is extended by an inner loop using a surrogate based optimization method. The local search on the surrogate function determines better candidates for sampling than the hypercube center points chosen by DIRECT, especially if constraints are arising. This inner loop needs no additional evaluation of the original problem. Standard test problems and a computational more expensive test problem are chosen to show the performance of the new algorithm.},
}

@INPROCEEDINGS{2011:KuhnReinlVonStryk_IFAC_WC11,
  author = {J. Kuhn and C. Reinl and O. von Stryk},
  title = {Predictive Control for Multi-Robot Observation of Multiple Moving Targets Based on Discrete-Continuous Linear Models},
  year = {2011},
  month = {Aug 28 - Sep 2},
  address = {Milano, Italy},
  booktitle = {Proceedings of the 18th IFAC World Congress},
  pdf = {2011-IFAC-KuhnReinlVonStryk.pdf},
  abstract = {The observation of multiple moving targets by cooperating mobile robots is a key problem in many security, surveillance and service applications. In essence, this problem is characterized by a tight coupling of target allocation and continuous trajectory planning. Optimal control of the multi-robot system generally neither permits to neglect physical motion dynamics nor to decouple or successively process target assignment and trajectory planning. In this paper, a numerically robust and stable model-predictive control strategy for solving the problem in the case of discrete-time double-integrator dynamics is presented. Optimization based on linear mixed logical dynamical system models allows for a flexible weighting of different aspects and optimal control inputs for settings of moderate size can be computed in real-time. By simulating sets of randomly generated situations, one can determine a maximum problem size solvable in real-time in terms of the number of considered robots, targets, and length of the prediction horizon. Based on this information, a decentralized control approach is proposed. },
}

@INBOOK{2011:Bauer_etal_ProcessMaschineInteractions,
  author = {J. Bauer and M. Friedmann and T. Hemker and M. Pischan and C. Reinl and E. Abele and O. von Stryk},
  title = {Analysis of Industrial Robot Structure and Milling Process Interaction for Path Manipulation},
  year = {2011},
  pages = {245-263 },
  publisher = {Springer},
  editor = {Prof. Dr.-Ing. Berend Denkena},
  series = {Lecture Notes in Production Engineering},
  booktitle = {Process Machine Interactions},
  abstract = {Industrial robots are used in a great variety of applications for handling, welding, assembling and milling operations. Especially for machining operations, industrial robots represent a cost-saving and flexible alternative compared to standard machine tools. Reduced pose and path accuracy, especially under process force load due to the high mechanical compliance, restrict the use of industrial robots for machining applications with high accuracy requirements. In this chapter, a method is presented to predict and compensate path deviation of robots resulting from process forces. A process force simulation based on a material removal calculation is presented. Furthermore, a rigid multi-body dynamic system’s model of the robot is extended by joint elasticities and tilting effects, which are modeled by spring-damper-models at actuated and additional virtual axes. By coupling the removal simulation with the robot model the interaction of the milling process with the robot structure can be analyzed by evaluating the path deviation and surface structure. With the knowledge of interaction along the milling path a general model-based path correction strategy is introduced to significantly improve accuracy in milling operations.},
}

@ARTICLE{2011:Abele_etal_JMST,
  author = {E. Abele and J. Bauer and T. Hemker and R. Laurischkat and H. Meier and S. Reese and O. von Stryk},
  title = {Comparison and Validation of Implementations of a Flexible Joint Multibody Dynamics System Model for an Industrial Robot},
  journal = {CIRP Journal of Manufacturing Science and Technology},
  year = {2011},
  volume = {4},
  number = {1},
  pages = {38-43},
  doi = {10.1016/j.cirpj.2011.01.006},
  abstract = {In this paper, different implementations of elastic joint models of industrial robots are described and compared established in ADAMS and SimMechanics. The models are intended to be used for path prediction under process force load due to Roboforming and High Speed Cutting, respectively. The computational results have been compared and showed good agreement. In experiments of robot forming and robot milling the measured and simulated path deviations according to the process force are compared. The experiments are descriped and the results are discussed within the paper as a basis of a next step model based compensation of the path deviation.},
}

@INPROCEEDINGS{petersen:2011,
  author = {K. Petersen and O. von Stryk},
  title = {Towards a General Communication Concept for Human Supervision of Autonomous Robot Teams},
  year = {2011},
  pages = {228 -- 235},
  booktitle = {Proceedings of the Fourth International Conference on Advances in Computer-Human Interactions (ACHI)},
  pdf = {2011_petersen.pdf},
}

@ARTICLE{2011:IJHR-BioBiped,
  author = {K. Radkhah and C. Maufroy and M. Maus and D. Scholz and A. Seyfarth and O. von Stryk},
  title = {Concept and design of the BioBiped1 robot for human-like walking and running},
  journal = {International Journal of Humanoid Robotics},
  year = {2011},
  volume = {8},
  number = {3},
  pages = {439-458},
  keywords = {Hopping; running; jogging; walking; biped; biomechanics; humanoid locomotion; compliance; mechanical elasticity; series elastic actuation},
  doi = {10.1142/S0219843611002587},
  url = {http://www.worldscinet.com/ijhr/08/0803/S0219843611002587.html},
  pdf = {2011_RadkhahEtAl_ijhr.pdf},
  abstract = {Biomechanics research shows that the ability of the human locomotor system depends on the functionality of a highly compliant motor system that enables a variety of different motions (such as walking and running) and control paradigms (such as flexible combination of feedforward and feedback controls strategies) and reliance on stabilizing properties of compliant gaits. As a new approach of transferring this knowledge into a humanoid robot, the design and implementation of the first of a planned series of biologically inspired, compliant, and musculoskeletal robots is presented in this paper. Its three-segmented legs are actuated by compliant mono- and biarticular structures, which mimic the main nine human leg muscle groups, by applying series elastic actuation consisting of cables and springs in combination with electrical actuators. By means of this platform, we aim to transfer versatile human locomotion abilities, namely running and later on walking, into one humanoid robot design. First experimental results for passive rebound, as well as push-off with active knee and ankle joints, and synchronous and alternate hopping are described and discussed. BioBiped1 will serve for further evaluation of the validity of biomechanical concepts for humanoid locomotion.},
}

@INPROCEEDINGS{Meyer:2010:WorldModel,
  author = {J. Meyer and P. Schnitzspan and S. Kohlbrecher and K. Petersen and O. Schwahn and M. Andriluka and U. Klingauf and S. Roth and B. Schiele and O. von Stryk},
  title = {A Semantic World Model for Urban Search and Rescue Based on Heterogeneous Sensors},
  year = {2011},
  pages = {180 -- 193},
  editor = {Ruiz-del-Solar, Javier and Chown, Eric and Ploeger, Paul G.},
  series = {Lecture Notes in Computer Science, Lecture Notes in Artificial Intelligence},
  booktitle = {RoboCup 2010: Robot Soccer World Cup XIV},
  url = {https://springerlink3.metapress.com/content/n515v876ll57334l/resource-secured/?target=fulltext.pdf&sid=yyw2tr55m2on31z0hpufyw55&sh=www.springerlink.com},
  pdf = {2010_rcs_worldmodel.pdf},
}

@INPROCEEDINGS{petersen:2010,
  author = {K. Petersen and G. Stoll and O. von Stryk},
  title = {A Supporter Behavior for Soccer Playing Humanoid Robots},
  year = {2011},
  pages = {386 -- 396},
  editor = {Ruiz-del-Solar, Javier and Chown, Eric and Ploeger, Paul G.},
  series = {Lecture Notes in Computer Science, Lecture Notes in Artificial Intelligence},
  booktitle = {RoboCup 2010: Robot Soccer World Cup XIV},
  url = {https://springerlink3.metapress.com/content/fqqv74t28m65742n/resource-secured/?target=fulltext.pdf&sid=yyw2tr55m2on31z0hpufyw55&sh=www.springerlink.com},
  pdf = {2010_rcs_supporter.pdf},
}

@INCOLLECTION{2011:KhelilReinlAyariShaikhSzczytowskiAliSuri_PCN,
  author = {Abdelmajid Khelil and Christian Reinl and Brahim Ayari and Faisal Karim Shaikh and Piotr Szczytowski and Azad Ali and Neeraj Suri},
  title = {Wireless Sensor Cooperation for a Sustainable Quality of Information},
  year = {2011},
  publisher = {John Wiley & Sons, Ltd., UK.},
  editor = {Mohammad S. Obaidat and Mieso Denko and Isaac Woungang},
  chapter = {6},
  booktitle = {Pervasive Computing and Networking},
}

@INBOOK{Khelil_etal_Reinl_2011,
  author = {Abdelmajid Khelil and Christian Reinl and Faisal Karim Shaikh and Azad Ali and Neeraj Suri },
  title = {Delay-Tolerant Monitoring of Mobility-Assisted Wireless Sensor Networks},
  year = {2011},
  pages = {---},
  month = {November},
  publisher = {CRC Press, Taylor & Francis Group},
  editor = {Athanasios Vasilakos, Yan Zhang, Thrasyvoulos Spyropoulos},
  booktitle = {Delay Tolerant Networks: Protocols and Applications},
  pdf = {2011_Kehlil_etal_DTN_preprint.pdf},
}

@INPROCEEDINGS{2010_ICRA_Workshop:Lens,
  author = {Thomas Lens and Oskar von Stryk and Christian Trommer and Andreas Karguth},
  title = {BioRob Arm: Antagonistic Series Elastic Actuation for Inherent Safe Human-Robot Interaction},
  year = {2010},
  month = {May 3--8},
  booktitle = {Workshop on New Variable Impedance Actuators for the Next Generation of Robots, IEEE International Conference on Robotics and Automation (ICRA)},
}

@INPROCEEDINGS{2010SIMPAR:Maufroy,
  author = {C. Maufroy and M. Maus and K. Radkhah and D. Scholz and A. Seyfarth and O. von Stryk},
  title = {First Results for the BioBiped1 Robot Designed towards Human-Like Walking and Running},
  year = {2010},
  month = {November 15-18},
  address = {Darmstadt, Germany},
  booktitle = {Workshop on Biomechanical Simulation of Humans and Bio-Inspired Humanoids, Simulation, Modeling, and Programming for Autonomous Robots (SIMPAR)},
  pdf = {2010_Maufroy_BH2.pdf},
}

@INPROCEEDINGS{2010ICRAWorkshop:Radkhah,
  author = {K. Radkhah and S. Kurowski and T. Lens and O. v. Stryk},
  title = {An Extended Antagonistic Series Elastic Actuator for a Biologically Inspired Four-Legged Robot},
  year = {2010},
  month = {May 3 - 8},
  address = {Anchorage, Alaska, USA},
  booktitle = {Workshop on New Variable Impedance Actuators for the Next Generation of Robots, IEEE International Conference on Robotics and Automation (ICRA)},
}

@INPROCEEDINGS{2010:ThomasScholzTemplerVonStryk_WsHumSim,
  author = {Dirk Thomas and Dorian Scholz and Simon Templer and Oskar von Stryk},
  title = {Sophisticated Offline Analysis of Teams of Autonomous Mobile Robots},
  year = {2010},
  month = {December},
  address = {Nashville, TN},
  booktitle = {Proc. 5th Workshop on Humanoid Soccer Robots at the 2010 IEEE-RAS Int. Conf. on Humanoid Robots},
  keywords = {Robot Team Analysis, RoboCup},
  pdf = {2010_humanoids_soccer_workshop-team_analysis-thomas-scholz-templer-stryk.pdf},
  abstract = {Debugging control software for an autonomous mobile robot is a dif?cult and time consuming task. But it gets even harder, when analyzing a whole team of robots and their team behavior. The quality of the robots" decisions based on their current knowledge cannot be judged anymore by merely looking at their actions from the outside. In this paper an approach for collecting intrinsic and extrinsic data of a team of robots during full operation and analyzing this data of?ine is described. Since the amount of data to be collected is quite large a method for automated and semi-automated analysis is shown - making it possible to detect known problems in an automated process and mark potentially interesting events for manual review. Furthermore a solution to reuse existing single robot debugging tools on teams of robots, without rewriting each tool, is presented. },
}

@INPROCEEDINGS{2010:IWK-Karguth-vonStryk,
  author = {M. Schweitzer and C. Trommer and A. Karguth and J. Kunz and T. Lens and O. v. Stryk},
  title = {Safe Human Interaction with the Compliant Robot Arm BioRob},
  year = {2010},
  booktitle = {55. Internationales Wissenschaftliches Kolloquium 2010 der TU Ilmenau, TU Ilmenau (Hrsg.)},
  pdf = {2010-IWK-Schweizer_etal_Safe_Human_Interaction_BioRob_PREPRINT.pdf},
}

@TECHREPORT{2010:rescue_tdp,
  author = {Mykhaylo Andriluka and Stefan Kohlbrecher and Johannes Meyer and Karen Petersen and Paul Schitzspan and Oskar von Stryk},
  title = {RoboCupRescue 2010 - Robot League Team Hector Darmstadt (Germany)},
  year = {2010},
  institution = {Technische Universität Darmstadt},
  pdf = {2010_rescue_tdp.pdf},
}

@INPROCEEDINGS{2010:KohlbrecherVonStryk_WsHumSoc,
  author = {S. Kohlbrecher and O. von Stryk},
  title = {Modeling Observation Uncertainty for Soccer Playing Humanoid Robots},
  year = {2010},
  month = {Dec. 6 - Dec. 8},
  address = {Nashville},
  booktitle = {Proc. 5th Workshop on Humanoid Soccer Robots at the 2010 IEEE-RAS Int. Conf. on Humanoid Robots},
  keywords = {World Modeling, RoboCup, Probabilistic Robotics, State Estimation},
  pdf = {Humanoids10_Kohlbrecher_Stryk_Modeling_Observation_Uncertainty.pdf},
  abstract = {In recent years, humanoid robot soccer robots have shown increasingly robust and fast locomotion, making perception, world modeling and behavior control important. In this paper, we present the world modeling approach of the Darmstadt Dribblers humanoid robot team, which won the competitions in the RoboCup Humanoid KidSize League in 2009 and 2010. The paper focuses on modeling observation uncertainties originating from different contributing factors centrally in one module. This allows different state estimators to use this data in a consistent way, independently of the specific state estimation approach used.},
}

@INPROCEEDINGS{andriluka:2010_iros,
  author = {Mykhaylo Andriluka and Paul Schnitzspan and Johannes Meyer and Stefan Kohlbrecher and Karen Petersen and Oskar von Stryk and Stefan Roth and Bernt Schiele},
  title = {Vision Based Victim Detection from Unmanned Aerial Vehicles},
  year = {2010},
  pages = {1740 - 1747 },
  month = {Oct. 18 - 22},
  booktitle = {Proceedings of IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)},
  pdf = {2010_iros_andriluka-etal.pdf},
}

@PROCEEDINGS{2010:SIMPAR-Proc,
  author = {},
  title = {Simulation, Modeling, and Programming for Autonomous Robots (SIMPAR 2010)},
  year = {2010},
  volume = {6472},
  publisher = {Springer},
  editor = {N. Ando and S. Balakirsky and T. Hemker and M. Reggiani and O. von Stryk},
  series = {Lecture Notes in Artificial Intelligence},
  doi = {10.1007/978-3-642-17319-6},
  url = {http://dx.doi.org/10.1007/978-3-642-17319-6},
  abstract = {Proceedings of the Second International Conference on Simulation, Modeling and Programming for Autonomous Robots, SIMPAR 2010, Darmstadt, Germany, November 15-18, 2010.},
}

@TECHREPORT{2010:dd_tdp,
  author = {M. Friedmann and T. Hemker and S. Kohlbrecher and K. Petersen and S. Petters and K. Radkhah and M. Risler and D. Scholz and D. Thomas and O. von Stryk},
  title = {Darmstadt Dribblers - Team Description for Humanoid KidSize League of RoboCup 2010},
  year = {2010},
  institution = {Technische Universität Darmstadt},
  pdf = {2010-tdp-hum.pdf},
  abstract = {This paper describes the hardware and software design of the kidsize humanoid robot systems of the Darmstadt Dribblers in 2010. The robots are used as a vehicle for research in control of locomotion and behavior of autonomous humanoid robots and robot teams with many degrees of freedom and many actuated joints. The Humanoid League of RoboCup provides an ideal testbed for such aspects of dynamics in motion and autonomous behavior as the problem of generating and maintaining statically or dynamically stable bipedal locomotion is predominant for all types of vision guided motions during a soccer game. A modular software architecture as well as further technologies have been developed for ecient and eective implementation and test of modules for sensing, planning, behavior, and actions of humanoid robots.},
}

@INPROCEEDINGS{2010:SIMPAR-Lens,
  author = {T. Lens and J. Kunz and O. von Stryk},
  title = {Dynamic Modeling of the 4 DoF BioRob Series Elastic Robot Arm for Simulation and Control},
  year = {2010},
  volume = {6472},
  pages = {411-422},
  publisher = {Springer},
  series = {Lecture Notes in Artificial Intelligence},
  booktitle = {Simulation, Modeling, and Programming for Autonomous Robots (SIMPAR 2010)},
  doi = {10.1007/978-3-642-17319-6_38},
  pdf = {2010-SIMPAR-Lens_etal_PREPRINT.pdf},
  abstract = {This paper presents the modeling of the light-weight BioRob robot arm with series elastic actuation for simulation and controller design. We describe the kinematic coupling introduced by the cable actuation and the robot arm dynamics including the elastic actuator and motor and gear model. We show how the inverse dynamics model derived from these equations can be used as a basis for a position tracking controller that is able to sufficiently damp the oscillations caused by the high, nonlinear joint elasticity. We presents results from simulation and brieföy describe the implementation for a real world application.},
}

@INPROCEEDINGS{rdkhh-kurowski:2010,
  author = {K. Radkhah and S. Kurowski and T. Lens and O. von Stryk},
  title = {Compliant Robot Actuation by Feedforward Controlled Emulated Spring Stiffness},
  year = {2010},
  volume = {6472},
  pages = {497-508},
  publisher = {Springer},
  booktitle = {Simulation, Modeling, and Programming for Autonomous Robots (SIMPAR)},
  pdf = {2010_simpar_rdkhh_preprint.pdf},
  abstract = {Existing legged robots lack energy-inefficiency, performance and adaptivity when confronted with situations that animals cope with on a routine basis. Bridging the gap between artificial and natural systems requires not only better sensorimotor and learning capabilities but also a corresponding motion apparatus and intelligent actuators. Current actuators with online adaptable compliance pose high requirements on software control algorithms and sensor systems. We present a novel actuation mechanism and technique that allows for a virtual stiffness change of a deployed extended series elastic actuator without posing high energy requirements. The performance limits of the approach are assessed by comparing to an active and a passive compliant methodology. For this purpose we use a 2-degrees-of-freedom arm with and without periodic load representing a 2-segmented leg with and without ground contact. The simulation results indicate that the method is suited for the use in legged robots. },
}

@INPROCEEDINGS{2010:IROS-Thomas-vonStryk,
  author = {D. Thomas and O. von Stryk},
  title = {Efficient Communication in Autonomous Robot Software},
  year = {2010},
  month = {Oct. 18 - 22},
  address = {Taipei, Taiwan},
  booktitle = {Proc. IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)},
  pdf = {2010-IROS-Thomas-vonStryk.pdf},
  abstract = {Software for autonomous robots solving challenging tasks in research or application is becoming increasingly complex. System integration has to deal with various different functional components. To decouple those components from each other and to enable a modular and reuseable software architecture a robot middleware is typically used. But this intermediate layer introduces significant additional overhead during run-time. In this work a methodology is described to utilize specific application characteristics to improve communication efficiency between different robot software modules. By composing several components in a single thread memory copying or locking operations can be avoided, when data is exchanged between those parts. The optimization can be achieved without compromising the advantages of a communication layer. Still the modifications are transparent to the maybe already existing components. Experimental results in the scenario of autonomous soccer-playing humanoid robots are presented and exhibit remarkable reduction in communication overhead. Furthermore this approach can be implemented in or on-top of other communication layers.},
}

@INPROCEEDINGS{2010:SIMPAR_Friedmann_etal,
  author = {Martin Friedmann and Karen Petersen and Oskar von Stryk},
  title = {Evaluation and Enhancement of Common Simulation Methods for Robotic Range Sensors},
  year = {2010},
  volume = {6472},
  pages = {63-74},
  publisher = {Springer},
  series = {Lecture Notes in Artificial Intelligence},
  booktitle = {Simulation, Modeling, and Programming for Autonomous Robots (SIMPAR 2010)},
  pdf = {2010-SIMPAR_Friedmann-etal.pdf},
  abstract = {Distance sensors are an important class of external sensors used in many autonomous robots. Thus it is of importance to provide proper simulation for these sensors to enable software-in-the-loop testing of a robot"s control software. Two different methods for distance calculation are commonly applied for the simulation of such sensors, namely reading back the depth buffer from 3D renderings and the calculation of ray-object-intersections. Many simulators impose restrictions on either method, none of the widely used robot simulators reviewed in this paper currently considers material dependent simulation of the distances measured. In this paper extended versions of both methods are presented which provide additional information on the object perceived by distance sensors. Several methods for incorporating distance- and object-information into a complete distance-sensor simulation-module are discussed. Implementations of either method are compared for their performance depending on the sensor resolution on dierent computer systems. These measurements show, that the break even of the methods strongly depends on the hardware, thus stressing the importance of providing either method in a robot simulation in a transparent way in order to obtain optimal performance of the simulation.},
}

@INPROCEEDINGS{2010:SIMPAR_Sachidananda_Etal,
  author = {Vinay Sachidananda and Diego Costantini and Christian Reinl and Dominik Haumann and Karen Petersen and Parag S. Mogre and Abdelmajid Khelil},
  title = {Simulation and Evaluation of Mixed-Mode Environments: Towards Higher Quality of Simulations},
  year = {2010},
  pages = {133 - 143},
  publisher = {Springer},
  booktitle = {Simulation, Modeling, and Programming for Autonomous Robots (SIMPAR 2010)},
  pdf = {2010_simpar_quosim.pdf},
}

@INPROCEEDINGS{2010:biorob_radkhah,
  author = {K. Radkhah and T. Lens and A. Seyfarth and O. von Stryk},
  title = {On the Influence of Elastic Actuation and Monoarticular Structures in Biologically Inspired Bipedal Robots},
  year = {2010},
  pages = {389-394},
  booktitle = {Proc. 2010 IEEE International Conference on Biomedical Robotics and Biomechatronics (BIOROB)},
  pdf = {2010_biorob_rdkhh_preprint.pdf},
  abstract = {Implementing the intrinsically compliant and energy-efficient leg behavior found in humans for humanoid robots is a challenging task. Control complexity and energy requirements are two major obstacles for the design of legged robots. Past projects revealed that the control complexity can be drastically reduced by designing mechanically intelligent systems with self-stabilization structures. Breaking through the latter obstacle can be achieved by the development and use of compliant actuators. Mechanical elasticity and its online adaptation in legged systems are generally accepted as the technologies to achieve human-like mobility. However, elastic actuation does not necessarily result in energy-efficient systems. We show that mechanical elasticity, although being worthwhile, can have negative effects on the performance of drives. We present a methodology that introduces both elasticity and energy-efficiency to a bipedal model. To this end, we report on the influence of monoarticular structures and demonstrate that these structures have the potential to both take us a step further toward the goal of realizing human-like locomotion and reduce the energy consumption. },
}

@INPROCEEDINGS{2010:AbeleBauerPrischanStrykFriedmannHemker,
  author = {E. Abele and J. Bauer and M. Pischan and O. v. Stryk and M. Friedmann and T. Hemker},
  title = {Prediction of the Tool Displacement for Robot Milling Applications using Co-Simulation of an Industrial Robot and a Removal Process},
  year = {2010},
  month = {jun},
  booktitle = {CIRP 2nd International Conference Process Machine Interactions},
  organization = {CIRP },
  keywords = {Milling, Industrial Robot, Machine Process Interaction, Material removal simulation},
  pdf = {2010-PMI_preprint.pdf},
  abstract = {Industrial robots are used in a great variety of applications for handling, welding and milling operations. They represent a cost-saving and flexible alternative for machining applications. A reduced pose and path accuracy, especially under process force load due to the high mechanical compliance, restrict the use of industrial robots for further machining applications. In this paper a method is presented to predict the resulting path deviation of the robot under process force. A process force simulation based on a material removal calculation is proposed. The presented material removal simulation allows the calculation of the chip geometry even in complex cutter work piece engagement conditions. The removal simulation is validated by means of conducted milling tests. By coupling the removal simulation with a robot model the path deviation can be predicted. },
}

@TECHREPORT{griffin2010,
  author = {Joshua D. Griffin and Kathleen R. Fowler and Genetha A. Gray and Thomas Hemker and Matthew D. Parno},
  title = {Derivative-Free Optimization Via Evolutionary Algorithms Guiding Local Search},
  year = {2010},
  institution = {Sandia National Laboratories},
  pdf = {2010-griffin_etal.pdf},
  abstract = {In this paper, we describe the technical details of HOPSPACK (Hybrid Optimization Parallel Search Package), a new software platform which facilitates combining multiple optimization routines into a single, tightly-coupled, hybrid algorithm that supports parallel function evaluations. The framework is designed such that existing optimization source code can be easily incorporated with minimal code modification. By maintaining the integrity of each individual solver, the strengths and code sophistication of the original optimization package are retained and exploited.},
}

@INPROCEEDINGS{Radkhah_Clawar:2010,
  author = {K. Radkhah and D. Scholz and A. Anjorin and M. Rath and O. von Stryk },
  title = {Simple yet effective technique for robust real-time instability detection for humanoid robots using minimal sensor input},
  year = {2010},
  pages = {680-689},
  month = {Aug. 31 - Sep. 03},
  address = {Nagoya, Japan},
  booktitle = {13th International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines (CLAWAR)},
  pdf = {2010_clawar_rdkhh_preprint.pdf},
  abstract = {Legged locomotion of autonomous humanoid robots is advantageous but also challenging since it inherently suffers from high posture instability. External disturbances such as collisions with other objects or robots in the environment can cause a robot to fall. Many of the existing approaches for instability detection and falling prevention include a large number of sensors resulting in complex multi-sensor data fusion and are not decoupled from the walking motion planning. Such methods can not simply be integrated into an existing low-level controller for real-time motion generation and stabilization of a humanoid robot. A procedure that is both easily implementable using a minimal number of affordable sensors and capable of reliable detection of posture instabilities is missing to date. We propose a simple, yet reliable balance control technique consisting of a filtering module for the used data from two-axes-gyroscopes and -accelerometers located at the trunk, an instability classification algorithm, and a lunge step module. The modules are implemented on our humanoid robots which participate at the yearly RoboCup competitions in the humanoid kid-size league of soccer playing robots. Experimental results show that the approach is suited for real-time operation during walking. },
}

@INPROCEEDINGS{2010:ISR-Lens_etal,
  author = {T. Lens and J. Kunz and C. Trommer and A. Karguth and O. von Stryk},
  title = {BioRob-Arm: A Quickly Deployable and Intrinsically Safe, Light- Weight Robot Arm for Service Robotics Applications},
  year = {2010},
  pages = {905-910},
  month = {Jun},
  address = {Munich, Germany},
  booktitle = {41st International Symposium on Robotics (ISR 2010) / 6th German Conference on Robotics (ROBOTIK 2010)},
  pdf = {2010-ISR_Robotik_Lens_etal_preprint.pdf},
  abstract = {Using conventional rigid industrial manipulators for service robotics applications typically demands huge efforts for safety measurements resulting in high installation and operation costs. We present how the BioRob robot arm is based on a combination of compliant actuation and lightweight mechanical design to obtain the flexibility, mobility and, most important, the inherent safety properties needed to implement effective and safe service robotics applications. We discuss the sensors and control structure used to damp the oscillations caused by the significant joint compliance of the arm and to obtain the accuracy needed for the intended applications. The concluding example of a typical pick and place application with teaching by manual guidance illustrates the benefits of the BioRob design for service robotics applications.},
}

@INPROCEEDINGS{radkhah_ISR:2010,
  author = {K. Radkhah and M. Maus and D. Scholz and A. Seyfarth and O. von Stryk},
  title = {Towards Human-Like Bipedal Locomotion with Three-Segmented Elastic Legs},
  year = {2010},
  pages = {696-703},
  month = {Jun 7-9},
  address = {Munich, Germany},
  booktitle = {41st International Symposium on Robotics (ISR)/ 6th German Conference on Robotics (ROBOTIK)},
  pdf = {2010_isr_rdkhh_preprint.pdf},
  abstract = {The long-term goal of the recently launched project BioBiped is to develop autonomous bipedal robots that are capable of energy-efficient multi-modal locomotion. In this paper we give a brief review of the important insights and techniques gained in previous and current projects leading to a new generation of human-like robots. Furthermore, we present the hardware design and the applied principles for the bipedal robot with three-segmented elastic legs that is currently under development. In the latter part of the paper we describe optimization methods that yield optimal parameter sets for tuning the walking and running gaits for a robot prototype with the same kinematic leg design. },
}

@ARTICLE{2010:RAS-KienervonStryk,
  author = {J. Kiener and O. von Stryk},
  title = {Towards cooperation of heterogeneous, autonomous robots: a case study of humanoid and wheeled robots},
  journal = {Robotics and Autonomous Systems},
  year = {2010},
  volume = {58},
  number = {7},
  pages = {921-929},
  keywords = {Heterogeneous multi-robot team; autonomous humanoid robot; task distribution and allocation; behavior control; robot middleware; robot simulator},
  doi = {10.1016/j.robot.2010.03.013},
  url = {http://www.sciencedirect.com/science/article/pii/S0921889010000710},
  pdf = {2010-KienervonStryk.pdf},
  abstract = {In this paper a case study of cooperation of a strongly heterogeneous autonomous robot team, composed of a highly articulated humanoid robot and a wheeled robot with largely complementing and some redundant abilities is presented. By combining strongly heterogeneous robots the diversity of achievable tasks increases as the variety of sensing and motion abilities of the robot system is extended compared to a usually considered team of homogeneous robots. A number of methodologies and technologies required to achieve the long-term goal of cooperation of heterogeneous autonomous robots are discussed including modeling tasks and robot abilities, task assignment and redistribution, robot behavior modeling and programming, robot middleware and robot simulation. Example solutions and their application to the cooperation of autonomous wheeled and humanoid robots are presented in this case study. The scenario describes a tightly coupled cooperative task, where the humanoid robot and the wheeled robot track a moving ball, which is to be approached and kicked by the humanoid robot into a goal. The task can be fulfilled successfully by combining the abilities of both robots.},
}

@ARTICLE{2010:IJMMS-Radkhah-etal,
  author = {K. Radkhah and T. Hemker and O. von Stryk},
  title = {Self-calibration for industrial robots with rotational joints},
  journal = {Int. J. Mechatronics and Manufacturing Systems},
  year = {2010},
  volume = {3},
  number = {3/4},
  pages = {187-209},
  pdf = {2010_ijmms_rdkhh_preprint.pdf},
}

@INPROCEEDINGS{2009_ReinlVonStryk_GMA140,
  author = {Christian Reinl and Oskar von Stryk},
  title = {MILP-basierte Optimalsteuerung kooperativer Multi-Vehikel-Systeme},
  year = {2009},
  pages = {138 - 150},
  month = {Sept},
  note = {ISBN 978-3-9502451-4-1},
  publisher = {Technische Universit"at Wien, Institut f"ur Automatisierungs- und Regelungstechnik},
  editor = {Andreas Kugi, Boris Lohmann},
  booktitle = {GMA-Fachausschuss 1.40 "Theoretische Verfahren der Regelungstechnik" Tagungsband},
  organization = {VDI/VDE-Gesellschaft Mess- und Automatisierungstechnik},
  pdf = {2009-GMA_Reinl_Stryk.pdf},
}

@INPROCEEDINGS{2009:ScholzFriedmannVonStryk_WsHumSoc,
  author = {D. Scholz and M. Friedmann and O. von Stryk},
  title = {Fast, Robust and Versatile Humanoid Robot Locomotion with Minimal Sensor Input},
  year = {2009},
  month = {Dec. 7 - Dec. 10},
  address = {Paris},
  booktitle = {Proc. 4th Workshop on Humanoid Soccer Robots at the 2009 IEEE-RAS Int. Conf. on Humanoid Robots},
  keywords = {Humanoid Motion Generation, RoboCup},
  pdf = {Humanoids09_Scholz_Friedmann_Stryk_MotionGeneration.pdf},
  abstract = {The generation of fast and robust locomotion is one of the crucial problems to be solved for a competitive autonomous humanoid soccer robot. During the last decades many different approaches to solve this problem have been investigated. In this paper a simplified yet powerful approach for generation of locomotion for an autonomous humanoid robot is described. It is based on an open loop trajectory generation with an overlying gyroscope-based closed loop postural stabilization. Unlike other widely used approaches in humanoid robotics the trajectory generation is completely decoupled from the stabilization algorithm, thus simplifying design, implementation and testing of either algorithm. The only sensor required for postural stabilization is a two axis gyroscope in the robot"s hip. No further sensors like foot-ground contact or force sensors, which are typically applied in many other approaches, are required. Nevertheless the presented approach exhibits remarkable performance. Furthermore this approach can be implemented easily in many available robots without complex modifications of the hardware. Experimental results for various types of locomotion are presented for two different robots used in the 2009 RoboCup Humanoid KidSize competition.},
}

@INPROCEEDINGS{radkhah_Robio:2009,
  author = {K. Radkhah and S. Kurowski and O. von Stryk},
  title = {Design Considerations for a Biologically Inspired Compliant Four-Legged Robot },
  year = {2009},
  pages = {598-603},
  month = {Dec 19-23},
  note = {Finalist for Best Paper Award in Biomimetics},
  address = {Guilin, Guangxi, China},
  booktitle = {Proc. 2009 IEEE International Conference on Robotics and Biomimetics (ROBIO)},
  url = {http://ieeexplore.ieee.org/search/freesrchabstract.jsp?tp=&arnumber=5420606&queryText%3Drobio+Design+Considerations+for+a+Biologically+Inspired+Compliant+Four-Legged+Robot%26openedRefinements%3D*%26searchField%3DSearch+All},
  pdf = {2009_robio_rdkhh_preprint.pdf},
  abstract = {In this paper we summarize some basic principles of legged locomotion in animals and then discuss the application of the principles to the design and fabrication of a four-legged robot. The here presented model combines ideas for better locomotion of robots both in the biologically inspired, mechanically intelligent structure and in the bionic controller. The movement of the legs is triggered by bionic drives with a setup similarly to biological muscles. The robot is characterized by several different gaits and an animal like locomotion without using feedback control. It has four legs, each having three joints of which two are actuated. During the development we also paid attention to the technical realization of the model. Special techniques to reduce the weight of the robot such as the achievement of different motions by changing the spring stiffness by means of intelligent control instead of an additional motor were also focused on during the development. Two novel features of our four-legged concept comprise the possibility of easily changing the spring stiffness deployed in the bionic drives of the joints and the way of this adjustment which requires neither complex computation nor additional motor. This feature allows the smooth transition to different gaits without necessarily having to change the controller parameters.},
}

@TECHREPORT{2009:dd_tdp,
  author = {M. Friedmann and K. Petersen and S. Petters and K. Radkhah and Dorian Scholz and D. Thomas and O. von Stryk},
  title = {Darmstadt Dribblers: Team Description for Humanoid KidSize League of RoboCup 2009},
  year = {2009},
  institution = {Technische Universit"at Darmstadt},
  pdf = {2009-tdp-hum.pdf},
  abstract = {This paper describes the hardware and software design of the kidsize humanoid robot systems of the Darmstadt Dribblers in 2009. The robots are used as a vehicle for research in control of locomotion and behavior of autonomous humanoid robots and robot teams with any degrees of freedom and many actuated joints. The Humanoid League of RoboCup provides an ideal testbed for such aspects of dynamics in motion and autonomous behavior as the problem of generating and maintaining statically or dynamically stable bipedal locomotion is predominant for all types of vision guided motions during a soccer game. A modular software architecture as well as further technologies have been developed for efficient and effective implementation and test of modules for sensing, planning, behavior, and actions of humanoid robots. },
}

@TECHREPORT{Parno2009,
  author = {M. D. Parno and K. R. Fowler and T. Hemker},
  title = {Framework for Particle Swarm Optimization with Surrogate Functions},
  year = {2009},
  number = {TUD-CS-2009-0139},
  institution = {Technische Universit\"at Darmstadt, Department of Computer Science},
  pdf = {Parno2009.pdf},
  abstract = {Particle swarm optimization (PSO) is a population-based, heuristic minimization technique that is based on social behavior. The method has been shown to perform well on a variety of problems including those with nonconvex, nonsmooth objective functions with multiple local minima. However, the method can be computationally expensive in that a large number of function calls is required to advance the swarm at each optimization iteration. This is a significant drawback when function evaluations depend on output from an off-the-shelf simulation program, which is often the case in engineering applications. To this end, we propose an algorithm which incorporates surrogate functions, which serve as a stand-in for the expensive objective function, within the PSO framework. We present numerical results to show that this hybrid approach can improve algorithmic efficiency.},
}

@INPROCEEDINGS{radkhah:2009,
  author = {K. Radkhah and T. Hemker and M. Friedmann and O. von Stryk},
  title = {Towards the deployment of industrial robots as measurement instruments - An extended forward kinematic model incorporating geometric and nongeometric effects },
  year = {2009},
  pages = {124-129},
  month = {Jul. 14 - Jul. 17},
  address = {Singapore, Singapore},
  booktitle = {Proc. 2009 IEEE/ASME Conference on Advanced Intelligent Mechatronics (AIM)},
  url = {http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F5211950%2F5229709%2F05230028.pdf%3Farnumber%3D5230028&authDecision=-203},
  abstract = {In the area of mounting and spot-welding of body-in-white, absolutely accurate robots are installed as measuring instruments, replacing expensive coordinate and other external measuring machines. Measurement technologies based on industrial robots play an increasingly important role. Such applications require highly accurate robots. Prior to deployment of highly accurate robot, however, it needs to be ensured that the implemented robot model fits the real model. Robot calibration can offer a significant opportunity to improve the positioning accuracy and to cut production costs. Existing calibration approaches fail to capture geometric and elastic effects occurring in the robot forward kinematics. Therefore, in this work an extended forward kinematic model incorporating both geometric and elastic effects has been developed in which the positioning accuracy of a manipulator, with or without an accurate internal robot model in the robot controller, is improved. },
}

@ARTICLE{2009:RAS-FPvS,
  author = {M. Friedmann and K. Petersen and O. von Stryk},
  title = {Adequate motion simulation and collision detection for soccer playing humanoid robots},
  journal = {Robotics and Autonomous Systems},
  year = {2009},
  volume = {57},
  pages = {786-795},
  doi = {10.1016/j.robot.2009.03.008},
  url = {http://dx.doi.org/10.1016/j.robot.2009.03.008},
  pdf = {2009_friedmann_RAS.pdf},
  abstract = {In this paper a humanoid robot simulator based on the multi-robot simulation framework (MuRoSimF) is presented. Among the unique features of this simulator is the scalability in the level of physical detail in both the robot"s motion and sensing systems. It facilitates the development of control software for humanoid robots which is demonstrated for several scenarios from the RoboCup Humanoid Robot League. Different requirements exist for a humanoid robot simulator. E.g., testing of algorithms for motion control and postural stability require high fidelity of physical motion properties whereas testing of behavior control and role distribution for a robot team requires only a moderate level of detail for real-time simulation of multiple robots. To meet such very different requirements often different simulators are used which makes it necessary to model a robot multiple times and to integrate different simulations with high-level robot control software. MuRoSimF provides the capability of exchanging the simulation algorithms used for each robot transparently, thus allowing a trade-off between computational performance and fidelity of the simulation. It is therefore possible to choose different simulation algorithms which are adequate for the needs of a given simulation experiment, for example, motion simulation of humanoid robots based on kinematical, simplified dynamics or full multi-body system dynamics algorithms. In this paper also the sensor simulation capabilities of MuRoSimF are revised. The methods for motion simulation and collision detection and handling are presented in detail including an algorithm which allows the real-time simulation of the full dynamics of a 21 DOF humanoid robot. Merits and drawbacks of the different algorithms are discussed in the light of different simulation purposes. The simulator performance is measured and illustrated in various examples, including comparison with experiments of a physical humanoid robot.},
}

@ARTICLE{2009:ReinlGlockerStryk_AT,
  author = {C. Reinl and M. Glocker and O. von Stryk},
  title = {Optimalsteuerung kooperierender Mehrfahrzeugsysteme (Optimal Control of Cooperative Multi-Vehicle Systems)},
  journal = {at-Automatisierungstechnik},
  year = {2009},
  volume = {57},
  number = {6},
  pages = {296-305},
  doi = {10.1524/auto.2009.0778},
  url = {http://www.atypon-link.com/OLD/doi/pdfplus/10.1524/auto.2009.0778},
  pdf = {2009-reinl-vonstryk-AT.pdf},
  abstract = {Nichtlineare hybride dynamische Systemmodelle kooperativer Optimalsteuerungsprobleme ermöglichen eine enge und formale Kopplung von diskreter und kontinuierlicher Zustandsdynamik, d.h. von dynamischer Rollen-, Aktionszuweisung mit wechselnder physikalischer Fahrdynamik. In den resultierenden gemischt-ganzzahligen Mehrphasen-Optimalsteuerungsproblemen können Beschränkungen an diskrete und kontinuierliche Zustands- und Steuervariablen berücksichtigt werden, z.B. Formations- oder Kommunikationsanforderungen. Zwei numerische Verfahren werden untersucht: ein Dekompositionsansatz mit Branch-and-Bound und direktem Kollokationsverfahren sowie die Approximation durch große, gemischt-ganzzahlige lineare Optimierungsaufgaben. Die Verfahren werden auf exemplarische Problemstellungen angewendet: Die simultane Wegpunktreihenfolge- und Trajektorienoptimierung von Luftfahrzeugen sowie die Optimierung von Rollenverteilung und Trajektorien im Roboterfußball. Nonlinear hybrid dynamical systems for modeling optimal cooperative control enable a tight and formal coupling of discrete and continuous state dynamics, i.e. of dynamic role and task assignment with switching dynamics of motions. In the resulting mixed-integer multi-phase optimal control problems constraints on the discrete and continuous state and control variables can be considered, e.g., formation or communication requirements. Two numerical methods are investigated: a decomposition approach using branch-and- bound and direct collocation methods as well as an approximation by large-scale, mixed-integer linear problems. Both methods are applied to example problems: the optimal simultaneous waypoint sequencing and trajectory planning of a team of aerial vehicles and the optimization of role distribution and trajectories in robot soccer.},
}

@TECHREPORT{2009:rescue_tdp,
  author = {Micha Andriluka and Martin Friedmann and Stefan Kohlbrecher and Johannes Meyer and Karen Petersen and Christian Reinl and Peter Schau{ss} and Paul Schnitzspan and Armin Strobel and Dirk Thomas and Oskar von Stryk},
  title = {RoboCupRescue 2009 - Robot League Team: Darmstadt Rescue Robot Team (Germany)},
  year = {2009},
  institution = {Technische Universit"at Darmstadt},
  pdf = {2009_rescue_tdp.pdf},
  abstract = {The Darmstadt Rescue Robot Team is a new team established from a PhD program funded by the German Research Foundation at TU Darmstadt. It combines expertise from Computer Science and Mechanical Engineering. Several team members have already contributed in the past to highly successful teams in the RoboCup four-legged and humanoid leagues. },
}

@INPROCEEDINGS{2008:RCS-BeckerRisler,
  author = {D. Becker and M. Risler},
  title = {Mutual localization in a team of autonomous robots using acoustic robot detection},
  year = {2009},
  volume = {5399},
  pages = {35-48},
  publisher = {Springer Verlag},
  editor = {L. Iocchi and H. Matsubara and A. Weitzenfeld and C. Zhou},
  series = {Lecture Notes in Artificial Intelligence},
  booktitle = {RoboCup 2008: Robot Soccer World Cup XII},
  pdf = {rc08_becker_risler_preprint.pdf},
  abstract = {In order to improve self-localization accuracy we are exploring ways of mutual localization in a team of autonomous robots. Detecting team mates visually usually leads to inaccurate bearings and only rough distance estimates. Also, visually identifying teammates is not possible. Therefore we are investigating methods of gaining relative position information acoustically in a team of robots. The technique introduced in this paper is a variant of code-multiplexed communication (CDMA, code division multiple access). In a CDMA system, several receivers and senders can communicate at the same time, using the same carrier frequency. Well-known examples of CDMA systems include wireless computer networks and the Global Positioning System, GPS. While these systems use electro-magnetic waves, we will try to adopt the CDMA principle towards using acoustic pattern recognition, enabling robots to calculate distances and bearings to each other. First, we explain the general idea of cross-correlation functions and appropriate signal pattern generation. We will further explain the importance of synchronized clocks and discuss the problems arising from clock drifts. Finally, we describe an implementation using the Aibo ERS-7 as platform and briefly state basic results, including measurement accuracy and a runtime estimate. We will briefly discuss acoustic localization in the specific scenario of a RoboCup soccer game.},
}

@ARTICLE{2008_hemker_ijr,
  author = {T. Hemker and H. Sakamoto and M. Stelzer and O. von Stryk},
  title = {Efficient walking speed optimization of a humanoid robot},
  journal = {International Journal of Robotics Research},
  year = {2009},
  volume = {28},
  number = {2},
  pages = {303 - 314},
  month = {Feb.},
  doi = {10.1177/0278364908095171},
  url = {http://dx.doi.org/10.1177/0278364908095171},
  pdf = {2009_hemker_ijr.pdf},
  abstract = {The development of optimized motions of humanoid robots that guarantee a fast and also stable walking is an important task especially in the context of autonomous soccer playing robots in RoboCup. We present a walking motion optimization approach for the humanoid robot prototype HR18 which is equipped with a low dimensional parameterized walking trajectory generator, joint motor controller and an internal stabilization. The robot is included as hardware-in-the-loop to define a low dimensional black-box optimization problem. In contrast to previously performed walking optimization approaches we apply a sequential surrogate optimization approach using stochastic approximation of the underlying objective function and sequential quadratic programming to search for a fast and stable walking motion. This is done under the conditions that only a small number of physical walking experiments should have to be carried out during the online optimization process. For the identified walking motion for the considered 55 cm tall humanoid robot we measured a forward walking speed of more than 30 cm/sec. With a modified version of the robot even more than 40 cm/sec could be achieved in permanent operation.},
}

@ARTICLE{2009:IJRR-Seyfarthetal,
  author = {A. Seyfarth and R. Tausch and M. Stelzer and F. Iida and A. Karguth and O. von Stryk},
  title = {Towards bipedal jogging as a natural result for optimizing walking speed for passively compliant three-segmented legs},
  journal = {International Journal of Robotics Research},
  year = {2009},
  volume = {28},
  number = {2},
  pages = {257-265},
  note = {see also the video},
  pdf = {2009-Seyfarthetal.pdf},
  abstract = {Elasticity in conventionally built walking robots is an undesired side-effect that is suppressed as much as possible because it makes control very hard and thus complex control algorithms must be used. The human motion apparatus, in contrast, shows a very high degree of flexibility with sufficient stability. In this research we investigate how compliance and damping can deliberately be used in humanoid robots to improve walking capabilities. A modular robot system consisting of rigid segments, joint modules and adjustable compliant cables spanning one or two joints is used to configure a human-like biped. In parallel, a simulation model of the robot was developed and analyzed. Walking motion is gained by oscillatory out-of-phase excitations of the hip joints. An optimization of the walking speed has been performed by improving the viscoelastic properties of the leg and identifying the appropriate hip control parameters. A good match was found between real robot experiments and numerical simulations. At higher speeds, transitions from walking to running are found in both the simulation as well as in the robot.},
}

@INPROCEEDINGS{2008:Stelzer_ECCOMAS,
  author = {M. Stelzer and O. von Stryk},
  title = {Motion dynamics and optimization of humans and a biologically inspired biped robot},
  year = {2008},
  month = {June 30 –July 5},
  address = {Venice, Italy},
  booktitle = {Proc. 8th.World Congress on Computational Mechanics (WCCM8) & 5th European Congress on Computational Methods in Applied Sciences and Engineeering (ECCOMAS 2008)},
  keywords = {Human kicking motion, human jumping motion, forward dynamics optimization, multibody system dynamics modeling, optimal control, direct collocation},
  url = {http://congress.cimne.com/eccomas/eccomas2008/pdfs/a1758.pdf},
  pdf = {2008_Stelzer_ECCOMAS.pdf},
}

@PROCEEDINGS{2008:SIMPAR-Proc,
  author = {},
  title = {Simulation, Modeling, and Programming for Autonomous Robots (SIMPAR 2008)},
  year = {2008},
  volume = {5325},
  publisher = {Springer Verlag},
  editor = {S. Carpin and I. Noda and E. Pagello and M. Reggiani and O. von Stryk},
  series = {Lecture Notes in Artificial Intelligence},
  url = {http://www.springer.com/computer+science/ai/book/978-3-540-89075-1},
  abstract = {This book constitutes the refereed proceedings of the First International Conference on Simulation, Modeling, and Programming for Autonomous Robots, SIMPAR 2008, held in Venice, Italy, in November 2008. The 29 revised full papers and 21 revised poster papers presented were carefully reviewed and selected from 42 submissions. The papers address all current issues of robotics applications and simulation environments thereof, such as 3D robot simulation, reliability, scalability and validation of robot simulation, simulated sensors and actuators, offline simulation of robot design, online simulation with real­time constraints, simulation with software/hardware-in-the-loop, middleware for robotics, modeling framework for robots and environments, testing and validation of robot control software, standardization for robotic services, communication infrastructures in distributed robotics, interaction between sensor networks and robots, human robot interaction, and multi­robot. The papers are organized in topical sections on simulation, programming, and applications.},
}

@INPROCEEDINGS{2008:SIMPAR-WS-Friedmann-etal,
  author = {M. Friedmann and S. Petters and M. Risler and H. Sakamoto and D. Thomas and O. von Stryk},
  title = {New Autonomous, Four-Legged and Humanoid Robots for Research and Education},
  year = {2008},
  number = {ISBN 978-88-95872-01-8},
  pages = {570-579},
  month = {November 3-4},
  editor = {Emanuele Menegatti},
  address = {Venice (Italy)},
  booktitle = {Workshop Proceedings of SIMPAR 2008, Intl. Conf. on Simulation, Modeling and Programming for Autonomous Robots},
  url = {http://www.simpar-conference.org/},
  pdf = {2008-SIMPAR-WS-Friedmann-etal.pdf},
  abstract = {Prototype models of new, fully programmable, autonomous four-legged and humanoid robots are presented as powerful standard platforms for research and education. They are based on an open and modular concept for hardware and software and exhibit a multitude of interfaces, sensors and powerful motion capabilities.},
}

@INPROCEEDINGS{2008-Petters-etal-Testing-Simpar,
  author = {S. Petters and D. Thomas and M. Friedmann and O. von Stryk},
  title = {Multilevel testing of control software for teams of autonomous mobile robots},
  year = {2008},
  number = {5325},
  pages = {183-194},
  month = {November},
  publisher = {Springer},
  editor = {S. Carpin et al.},
  series = {Lecture Notes in Artificial Intelligence},
  booktitle = {Simulation, Modeling and Programming for Autonomous Robots (SIMPAR 2008)},
  url = {http://dx.doi.org/10.1007/978-3-540-89076-8_20},
  pdf = {2008-SIMPAR_PettersThomasFriedmannVonStryk.pdf},
  abstract = {Developing control software for teams of autonomous mobile robots is a challenging task, which can be facilitated using frameworks with ready to use components. But testing and debugging the resulting system as teached in modern software engineering to be free of errors and tolerant to sensor noise in a real world scenario is to a large extend beyond the scope of current approaches. In this paper multilevel testing strategies using the developed frameworks RoboFrame and MuRoSimF are presented. Testing incorporating automated tests, online and offline analysis and software-in-the-loop (SIL) tests in combination with real robot hardware or an adequate simulation are highly facilitated by the two frameworks. Thus the efficiency of validation of complex real world applications is improved. In this way potential errors can be identified early in the development process and error situations in real world operations can be reduced significantly.},
}

@INPROCEEDINGS{pmi:2008,
  author = {E. Abele and J. Bauer and S. Rothenbücher and M. Stelzer and O. von Stryk},
  title = {Prediction of the Tool Displacement by Coupled Models of the Compliant Industrial Robot and the Milling Process},
  year = {2008},
  pages = {223-230},
  month = {3-4 September},
  address = {Hannover, Gemany},
  booktitle = {Proceedings of the International Conference on Process Machine Interactions},
  pdf = {2008-PMI_preprint.pdf},
}

@INPROCEEDINGS{radkhah:2008,
  author = {K. Radkhah and T. Hemker and O. von Stryk},
  title = {A Novel Self-Calibration Method for Industrial Robots Incorporating Geometric and Nongeometric Effects},
  year = {2008},
  pages = {864-869},
  month = {Aug. 05 - Aug. 08},
  address = {Takamatsu, Japan},
  booktitle = {Proc. IEEE International Conference on Mechatronics and Automation (ICMA)},
  url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=4798870&isnumber=4798708},
  abstract = {We propose a novel problem formulation for the solution of the nonlinear least squares appearing in the static calibration of the parameters of an industrial robot with rotational joints. A further contribution of the presented work is the use of an extended forward kinematic model incorporating both geometric and nongeometric parameters. These novelties facilitate the use of industrial robots as measurement systems. Both the automobile and the general industry are interested in the use of highly accurate robots that can be deployed as measurement instruments, e.g. for noticing incorrectly welded points early in the production process. Existing approaches are disadvantageous because of (1) the use of additional external measurement systems, and (2) the difficult, time-consuming, and cost-intensive determination of the robot base. Instead of absolute measurement data, we make use of relative measurement data by means of a camera attached to the robot flange. In tests based on data generated from simulation of a real experimental setup, we obtain absolute accuracies after calibration better than $\pm$ \unit[100]{$\mu$m}. This work lays the foundations for a cost-minimal and effective realization of a robot as a measurement instrument. },
}

@TECHREPORT{2008:dd_tdp,
  author = {M. Friedmann and K. Petersen and S. Petters and K. Radkhah and D. Thomas and O. von Stryk},
  title = {Darmstadt Dribblers: Team Description for Humanoid KidSize League of RoboCup 2008},
  year = {2008},
  institution = {Technische Universität Darmstadt},
  pdf = {2008-tdp-hum.pdf},
  abstract = {This paper describes the hardware and software design of the kidsize humanoid robot systems of the Darmstadt Dribblers in 2008. The robots are used as a vehicle for research in control of locomotion and behavior of autonomous humanoid robots and robot teams with many degrees of freedom and many actuated joints. The Humanoid League of RoboCup provides an ideal testbed for such aspects of dynamics in motion and autonomous behavior as the problem of generating and maintaining statically or dynamically stable bipedal locomotion is predominant for all types of vision guided motions during a soccer game. A modular software architecture as well as further technologies have been developed for efficient and effective implementation and test of modules for sensing, planning, behavior, and actions of humanoid robots. },
}

@INPROCEEDINGS{2008:SIMPAR-FriedmannPetersenvonStryk,
  author = {M. Friedmann and K. Petersen and O. von Stryk},
  title = {Simulation of multi-robot teams with flexible level of detail},
  year = {2008},
  number = {5325},
  pages = {29-40},
  month = {November},
  note = {Best Paper Award},
  publisher = {Springer},
  editor = {S. Carpin et al.},
  series = {Lecture Notes in Artificial Intelligence},
  address = {Venice, Italy},
  booktitle = {Simulation, Modeling and Programming for Autonomous Robots (SIMPAR 2008)},
  url = {http://dx.doi.org/10.1007/978-3-540-89076-8_7},
  pdf = {2008-SIMPAR_FriedamnnPetersenVonStryk.pdf},
  abstract = {A key methodology for the development of autonomous robots is testing using simulated robot motion and sensing systems. An important issue when simulating teams of heterogeneous autonomous robots is performance versus accuracy. In this paper the multi-robot-simulation framework (MuRoSimF) is presented which allows the flexible and transparent exchange and combination of the algorithms used for the simulation of motion and sensing systems of each individual robot in a scenario with individual level of realism. It has already been used successfully for the simulation of several types of legged and wheeled robots equipped with cameras and laser scanners. In this paper the core functionalities of MuRoSimF are presented. Existing algorithms for simulation of the robots’ motions are revised. Newly added features including the execution of the simulation on multi core CPUs and two different algorithms for the simulation of laser scanners are presented. The performance of these features is tested in an urban scenario using wheeled robots.},
}

@TECHREPORT{2008:RoboCup-TDP-GermanTeam,
  author = {David Becker and Jörg Brose and Daniel Göhring and Matthias Jüngel and Max Risler and Thomas Röfer},
  title = {GermanTeam 2008 - The German National RoboCup Team},
  year = {2008},
  institution = {DFKI Bremen, TU Darmstadt, HU Berlin},
  pdf = {2008-tdp-GermanTeam.pdf},
}

@INPROCEEDINGS{cirpicme:2008,
  author = {E. Abele and J. Bauer and C. Bertsch and R. Laurischkat and H. Meier and S. Reese and M. Stelzer and O. von Stryk},
  title = {Comparison of Implementations of a Flexible Joint Multibody Dynamic System Model for an Industrial Robot},
  year = {2008},
  booktitle = {6th CIRP International Conference on Intelligent Computation in Manufacturing Engineering, 23-25 July, Naples, Italy},
  pdf = {ICME2008_preprint.pdf},
}

@ARTICLE{wtonline2008,
  author = {E. Abele and J. Bauer and M. Stelzer and O. von Stryk},
  title = {Wechselwirkungen von Fräsprozess und Maschinenstruktur am Beispiel des Industrieroboters},
  journal = {WT-online},
  year = {2008},
  pages = {733 - 737},
  pdf = {2008-wtonline_preprint.pdf},
  abstract = {Entwicklung von Modellkomponenten für eine Offlinekompensation der spanenden Bearbeitung mit Industrierobotern Industrieroboter werden bereits heute zur spanenden Bearbeitung eingesetzt. Die durch den Zerspanprozess hervorgerufenen Kräfte erzeugen sowohl eine statische Abdrängung als auch eine niederfrequente Schwingung des Fräswerkzeuges. Dies wirkt sich negativ auf die Bauteilqualität aus. Über eine Offlinekompensation der statischen Abdrängung vor der Fräsbearbeitung kann das Roboterprogramm entsprechend abgeändert werden, sodass der statische Fehler reduziert wird. Hierzu wird ein Strukturmodell des Roboters sowie die Modellierung des Fräsprozesses benötigt, welche im Folgenden vorgestellt werden. Interaction of the milling process and the machine structure in case of the industrial robot Industrial robots are already used for operations such as milling. Due to the milling process and its process forces a static displacement and a low frequent oscillation of the Tool Centre Point is induced. This has negative effects on the work piece quality. With an offline compensation of the static displacement, the robot program can be modified in order to reduce the static error. This implies a model of the robot structure and of the milling process which will be presented in this article.},
}

@INPROCEEDINGS{2008-Kropf-etal-MMULATOR,
  author = {Matthias Kropff and Christian Reinl and Kim Listmann and Karen Petersen and Katayon Radkhah and Faisal Karim Shaikh and Arthur Herzog and Armin Strobel and Daniel Jacobi and Oskar von Stryk},
  title = {MM-ulator: Towards a Common Evaluation Platform for Mixed Mode Environments},
  year = {2008},
  number = {5325},
  pages = {41-52},
  month = {November},
  publisher = {Springer},
  editor = {S. Carpin et al.},
  series = {Lecture Notes in Artificial Intelligence},
  booktitle = {Simulation, Modeling, and Programming for Autonomous Robots (SIMPAR)},
  url = {{http://www.springerlink.com/content/62ph40794m636833/?p=72406ae46a8d4364bc570589871af29d&pi=7}},
  pdf = {2008_SIMPAR_Kropf_etal.pdf},
  abstract = {We investigate the interaction of mobile robots, relying on information provided by heterogeneous sensor nodes, to accomplish a mission. Cooperative, adaptive and responsive monitoring in Mixed-Mode Environments (MMEs) raises the need for multi-disciplinary research initiatives. To date, such research initiatives are limited since each discipline focusses on its domain specific simulation or testbed environment. Existing evaluation environments do not respect the interdependencies occurring in MMEs. As a consequence, holistic validation for development, debugging, and performance analysis requires an evaluation tool incorporating multi-disciplinary demands. In the context of MMEs, we discuss existing solutions and highlight the synergetic benefits of a common evaluation tool. Based on this analysis we present the concept of the MM-ulator: a novel architecture for an evaluation tool incorporating the necessary diversity for multi-agent hard-/software-in-the-loop simulation in a modular and scalable way.},
}

@INPROCEEDINGS{2008:Robotik2008-Klugetal,
  author = {Sebastian Klug and Thomas Lens and Oskar von Stryk and Bernhard Möhl and Andreas Karguth},
  title = {Biologically Inspired Robot Manipulator for New Applications in Automation Engineering},
  year = {2008},
  number = {2012},
  month = {June 11-12},
  publisher = {VDI Wissensforum GmbH},
  series = {VDI-Berichte},
  address = {Munich, Germany},
  booktitle = {Proceedings of Robotik 2008},
  pdf = {2008-Robotik2008-Klugetal.pdf},
  owner = {FG SIM, TUD},
  abstract = {The fast growing interest in flexible, versatile and mobile robotic manipulators demands for robots with inherent high passive safety suited for direct human-robot interaction. To gain access to these new applications in the field of automation engineering where close vicinity and direct cooperating with humans are required, the ""BioRob"" project demonstrates the applicability of a new biologically inspired, lightweight and elastic ""bionic"" robot manipulator specifically designed for safe human-robot interaction. This paper presents the mechanical design and controller structure used for the new demonstrators with up to four compliant joints. The advantages of the design and potential application areas for the manipulator are discussed.},
}

@INPROCEEDINGS{robotik2008_ptw_sim,
  author = {M. Stelzer and O. von Stryk and E. Abele and J. Bauer and M. Weigold},
  title = {High speed cutting with industrial robots: Towards model based compensation of deviations},
  year = {2008},
  pages = {143-146},
  booktitle = {Proceedings of Robotik 2008, 11-12 June, Munich, Germany},
  pdf = {robotik2008_sim_ptw_preprint.pdf},
}

@INPROCEEDINGS{2008:RislervonStryk,
  author = {M. Risler and O. von Stryk},
  title = {Formal behavior specification of multi-robot systems using hierarchical state machines in XABSL},
  year = {2008},
  month = {May 12-16},
  address = {Estoril, Portugal},
  booktitle = {AAMAS08-Workshop on Formal Models and Methods for Multi-Robot Systems},
  pdf = {2008_RislerVonStryk.pdf},
  abstract = {This paper presents the latest developments of the Extensible Agent Behavior Specification Language (XABSL), a modular and scalable tool for engineering complex multiagent behavior. It is based on hierarchical finite state machines. By the new extensions the development of cooperative multi agent behavior is supported through language elements which allow to conveniently specify how the state machines of multiple agents interact. Basic properties of XABSL are illustrated in direct comparison with Petri Net Plans and the COLBERT language using examples of basic robot behavior. More complex examples from robot soccer are used to illustrate the new extensions of XABSL. The complete system is available online on the XABSL website (http://www.xabsl.de).},
}

@INPROCEEDINGS{2008:ReinlRuhStolzenburgStryk,
  author = {C. Reinl and F. Ruh and F. Stolzenburg and O. von Stryk},
  title = {Multi-Robot Systems Optimization and Analysis Using MILP and CLP },
  year = {2008},
  month = {May 12-16},
  address = {Estoril, Portugal},
  booktitle = {AAMAS08-Workshop on Formal Models and Methods for Multi-Robot Systems},
  pdf = {2008_ReinlRuhStolzenburgStryk.pdf},
  abstract = {Formal methods for multi-robot system analysis, specially logic-based methods, operate on discrete models. Optimization methods for simultaneous trajectory and task allocation, namely mixed integer dynamic optimization, operate on hybrid dynamical models which take into account a model of the motion dynamics of the physical robot. In this paper, ongoing work towards a coherent treatment of both approaches is described. A benchmark problem from robot soccer is introduced and used as an illustrative example.},
}

@INCOLLECTION{2008:InsectMimetics-Moehl-etal,
  author = {B. Möhl and S. Klug and T. Lens and O. von Stryk},
  title = {Elasticity in insect wings: applications to compliant robot joints (in Japanese)},
  year = {2008},
  pages = {798- 806},
  month = {October},
  note = {ISBN-13: 978-4-86043-197-6},
  publisher = {NTS Inc.},
  editor = {M. Matsukaze},
  series = {Advanced Biomimetics Series 3},
  booktitle = {Insect Mimetics (in Japanese) 昆虫ミメティックス},
}

@INCOLLECTION{2008:StelzervonStryk,
  author = {M. Stelzer and O. von Stryk},
  title = {Walking, running and kicking of humanoid robots and humans},
  year = {2008},
  pages = {175-192 and 337},
  publisher = {Springer Verlag},
  editor = {M.H. Breitner and G. Denk and P. Rentrop},
  booktitle = {From Nano to Space - Applied Mathematics Inspired by Roland Bulirsch},
  pdf = {2008-Stelzer-vonStryk.pdf},
  abstract = {In this paper key aspects and several methods for modeling, simulation, optimization and control of the locomotion of humanoid robots and humans are discussed. Similarities and differences between walking and running of humanoid robots and humans are outlined. The presented methods are different steps towards the ultimate goals of understanding and predicting human motion by validated simulation models and of developing humanoid robots with human like performance in walking and running. Numerical and experimental results are presented for model-based optimal control as well as for hardware-in-the-loop optimization of humanoid robot walking and for forward dynamics simulation and optimization of a human kicking motion.},
}

@ARTICLE{2008:IJHR-Friedmann-etal,
  author = {M. Friedmann and J. Kiener and S. Petters and H. Sakamoto and D. Thomas and O. von Stryk},
  title = {Versatile, high-quality motions and behavior control of a humanoid soccer robot},
  journal = {International Journal of Humanoid Robotics},
  year = {2008},
  volume = {5},
  number = {3},
  pages = {417-436},
  month = {September},
  url = {http://www.worldscinet.com/ijhr/05/0503/S02198436080503.html},
  pdf = {2008_FriedmannKienerPettersThomasStrykSakamoto.pdf},
  abstract = {Autonomous soccer games represent an extraordinary challenge for autonomous humanoid robots which must act fast and stable while carrying all needed onboard computers, sensors and batteries. In this paper, the development and system integration of hardware and software modules of the 55 cm tall, autonomous humanoid soccer robot Bruno is described to cope with this challenge. Altough based on a "minimalistic" design which only uses gyroscopes in the hip but not foot-ground contact sensors for control of balance, versatile and high-quality walking motions have been developed. Fast forward walking of about 1.5 km/h has been obtained using an efficient sequential surrogate optimization method and walking through uneven terrain with a newly designed passively compliant foot sole. Further modules of the software and control architecture which are needed for an adaptive selection of different motions and autonomous robot behavior are briefly described. Experimental results are reported which have been obtained under the conditions of a live competition. The robot"s hardware is mainly based on standard components which can therefore be easily adapted by new designers as no comparable, standard humanoid robot platforms are available.},
}

@ARTICLE{2007:OptEng-HemkerFowlervonStryk,
  author = {T. Hemker and K.R. Fowler and M.W. Farthing and O. von Stryk},
  title = {A mixed-integer simulation-based optimization approach with surrogate functions in water resources management},
  journal = {Optimization and Engineering},
  year = {2008},
  volume = {9},
  number = {4},
  pages = {341-360},
  month = {December},
  doi = {10.1007/s11081-008-9048-0},
  pdf = {2008_hemker_opte.pdf},
  abstract = {Efficient and powerful methods are needed to overcome the inherent difficulties in the numerical solution of many simulation-based engineering design problems. Typically, expensive simulation codes are included as black-box function generators; therefore, gradient information that is required by mathematical optimization methods is entirely unavailable. Furthermore, the simulation code may contain iterative or heuristic methods, low-order approximations of tabular data, or other numerical methods which contribute noise to the objective function. This further rules out the application of Newton-type or other gradient-based methods that use traditional finite difference approximations. In addition, if the optimization formulation includes integer variables the complexity grows even further. In this paper we consider three different modeling approaches for a mixed-integer nonlinear optimization problem taken from a set of water resources benchmarking problems. Within this context, we compare the performance of a genetic algorithm, the implicit filtering algorithm, and a branch-and-bound approach that uses sequential surrogate functions. We show that the surrogate approach can greatly improve computational efficiency while locating a comparable, sometimes better, design point than the other approaches.},
}

@INPROCEEDINGS{2007:RCS-FriedmannPetersenvonStryk,
  author = {M. Friedmann and K. Petersen and O. von Stryk},
  title = {Tailored real-time simulation for teams of humanoid robots},
  year = {2008},
  volume = {5001},
  pages = {425-432},
  publisher = {Springer-Verlag},
  editor = {U. Visser and F. Ribeiro and T. Ohashi and F. Dellaert},
  series = {Lecture Notes in Computer Science/Artificial Intelligence},
  address = {Berlin/Heidelberg},
  booktitle = {RoboCup 2007: Robot Soccer World Cup XI},
  doi = {http://www.springerlink.com/content/41251kv140217484/},
  url = {http://www.springer.com/computer/artificial/book/978-3-540-68846-4},
  pdf = {2007_RoboCupSymposium_FriedmannPetersenVonStryk_preprint.pdf},
  abstract = {Developing and testing the key modules of autonomous humanoid soccer robots (e.g., for vision, localization, and behavior control) in software-in-the-loop (SIL) experiments, requires real-time simulation of the main motion and sensing properties. These include humanoid robot kinematics and dynamics, the interaction with the environment, and sensor simulation, especially the camera properties. To deal with an increasing number of humanoid robots per team the simulation algorithms must be very efficient. In this paper, the simulator framework MuRoSimF (Multi-Robot-Simulation-Framework) is presented which allows the flexible and transparent integration of different simulation algorithms with the same robot model. These include several algorithms for simulation of humanoid robot motion kinematics and dynamics (with O(n) runtime complexity), collision handling, and camera simulation including lens distortion. A simulator for teams of humanoid robots based on MuRoSimF is presented. A unique feature of this simulator is the scalability of the level of detail and complexity which can be chosen individually for each simulated robot and tailored to the requirements of a specific SIL test. Performance measurements are given for real-time simulation on a moderate laptop computer of up to six humanoid robots with 21 degrees of freedom, each equipped with an articulated camera.},
}

@INPROCEEDINGS{radkhah:2007,
  author = {K. Radkhah and D. Kulic and E. Croft },
  title = {Dynamic Parameter Identification for the CRS A460 Robot},
  year = {2007},
  pages = {3842 - 3847},
  month = {Oct. 29 - Nov. 2},
  address = {San Diego, CA},
  booktitle = {IEEE/RSJ Int. Conf. on Intelligent Robots and Systems (IROS)},
  url = {http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F4398943%2F4398944%2F04399314.pdf%3Farnumber%3D4399314&authDecision=-203},
  pdf = {2007_iros_rdkhh_preprint.pdf},
  abstract = {Dynamic Parameter Identification is a useful tool for developing and evaluating robot control strategies. However, a multi degree of freedom robot arm has many parameters, and the process of determining them is challenging. Much research has been done in this area and experimental methods have been applied on several robot arms. To our knowledge, there is currently no set of inertial parameters, either by modelling or by estimation, available for the CRS A460/A465 arm, a popular laboratory table top robot. In this paper we review and compare a number of methods for dynamic parameter identification and for generating trajectories suitable for estimating the identifiable dynamic parameters of a given robot. We then present a step by step process for dynamic parameter identification of a serial manipulator, and demonstrate this process by experimentally identifying the dynamic parameters of the CRS A460 robot.},
}

@INPROCEEDINGS{2007:RCS-JuengelRisler,
  author = {Matthias Jüngel and Max Risler},
  title = {Self-Localization Using Odometry and Horizontal Bearings to Landmarks},
  year = {2007},
  note = {to appear},
  publisher = {Springer},
  editor = {U. Visser and F. Ribeiro and T. Ohashi and F. Dellaert},
  series = {Lecture Notes in Artificial Intelligence},
  booktitle = {RoboCup 2007: Robot Soccer World Cup XI},
  pdf = {2007-RCS-JuengelRisler.pdf},
}

@INPROCEEDINGS{2007:FriedmannPetersenVonStryk_WsHumSoc,
  author = {M. Friedmann and K. Petersen and O. v. Stryk},
  title = {Adequate Motion Simulation and Collision Detection for Soccer Playing Humanoid Robots},
  year = {2007},
  month = {Nov. 29 - Dec. 1},
  address = {Pittsburgh, PA, USA},
  booktitle = {Proc. 2nd Workshop on Humanoid Soccer Robots at the 2007 IEEE-RAS Int. Conf. on Humanoid Robots},
  url = {http://www.humanoidsoccer.org/ws07/program.html},
  pdf = {2007-HumanoidsWSHumSoccer-FPvS.pdf},
  abstract = {In this paper a humanoid robot simulator built with the Multi-Robot-Simulation-Framework (MuRoSimF) is presented. Among the unique features of the this simulator is the scalability in the level of physical detail in both the robot’s motion and sensing systems. It facilitates the development of control software for humanoid robots which is demonstrated for several scenarios from the RoboCup Humanoid Robot League. Different requirements exist for a humanoid robot simulator. E.g., testing of algorithms for motion control and postural stability require high fidelity of physical motion properties where as testing of behavior control and role distribution for a robot team requires only a moderate level of detail for real-time simulation of multiple robots. To meet such very different requirements often different simulators are used which makes it neccessary to model a robot multiple times and to integrate different simulations with high-level robot control software. MuRoSimF provides the capability of exchanging the simulation algorithms used for each robot transparently, thus allowing a trade-off between computational performance and fidelity of the simulation. It is therefore possible to choose different simulation algorithms which are adequate for the needs of a given simulation experiment, for example, motion simulation of humanoid robots based on kinematical, simplified dynamics or full multibody system dynamics algorithms. In this paper the sensor simulation capabilities of MuRoSimF are revised and the algorithms for motion simulation and collision detection and handling are presented in detail. An algorithm is presented which allows the real time simulation of the full dynamics of a 21 DOF humanoid robot. Special consideration is given to the merits and drawbacks of the different algorithms depending on the scenario. The simulation’s performance is measured and comparisons with the experimental performance of the humanoid robots are given.},
}

@TECHREPORT{2007:RoboCup-TDP-GermanTeam,
  author = {T. Röfer and J. Brose and D. Göhring and M. Jüngel and T. Laue and M. Risler},
  title = {GermanTeam 2007 - The German National RoboCup Team},
  year = {2007},
  institution = {DFKI Bremen and TU Darmstadt and HU Berlin and Universität Bremen},
  pdf = {2007-tdp-GermanTeam.pdf},
}

@ARTICLE{hemker_et_al_2008,
  author = {T. Hemker and H. De Gersem and O. von Stryk and T. Weiland},
  title = {Mixed-Integer Nonlinear Design Optimization of a Superconductive Magnet},
  journal = {IEEE Transactions on Magnetics},
  year = {2007},
  volume = {44},
  number = {6},
  pages = {1110-1113},
  month = {June},
  pdf = {2007_hemker_ieee_tm.pdf},
  abstract = {The numerical optimization of continuous parameters in electrotechnical design using electromagnetic field simulation is already standard. When integer-valued variables are involved, the complexity of the optimization problem rises drastically. In this paper, we describe a new sequential surrogate optimization approach for simulation-based mixed-integer nonlinear programming problems. We apply the method for the optimization of combined integer- and real-valued geometrical parameters of the coils of a superconductive magnet.},
}

@INPROCEEDINGS{2007:IROS-WS-Architectures-PettersThomasvonStryk,
  author = {S. Petters and D. Thomas and O. von Stryk},
  title = {RoboFrame - A Modular Software Framework for Lightweight Autonomous Robots},
  year = {2007},
  month = {Oct. 29},
  address = {San Diego, CA, USA},
  booktitle = {Proc. Workshop on Measures and Procedures for the Evaluation of Robot Architectures and Middleware of the 2007 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems},
  url = {http://wiki.robot-standards.org/index.php/IROS_2007_WS},
  pdf = {2007-iros-workshop-pettersthomasvonstryk.pdf},
  abstract = {The complexity of autonomous robot systems has increased dramatically in recent years. Besides an increased variety of robots, sensors, actuators, onboard computers and intelligent algorithms, the architecture of the software has gained crucial relevance with respect to the efficiency for adopting a robotic system to new hardware, new software or new tasks. For evaluation of different robot architectures and middleware not only a set of set of evaluation criterias is required. At least equally important for an evaluation is to define a representative set of the boundary conditions, i.e., different types of robots, tasks and scenarios as well as robot programmers. How the different criteria of an evaluation will be weighted also depends on these boundary conditions. To address the special needs of heterogeneous teams of autonomous lightweight robots, the software framework RoboFrame has been developed. Its main characteristics are platform independency, modularity and high efficiency. It is also bundled with a library of common components for robot control software, which provides much more support to the robot programmer than a robot middleware system alone. },
}

@INPROCEEDINGS{2007:ReinlVonStryk_RoboMat,
  author = {C. Reinl and O. von Stryk},
  title = {Optimal Control of Cooperative Multi-Robot Systems Using Mixed-Integer Linear Programming},
  year = {2007},
  pages = {145 - 151},
  month = {Sept. 17-19},
  editor = {Centro Internacional de Mathematica},
  address = {Coimbra, Portugal},
  booktitle = {Proc. RoboMat 2007},
  url = {http://labvis.isr.uc.pt/robomat/},
  pdf = {2007-ReinlVonStryk_ROBOMAT.pdf},
  abstract = {A new planning method for optimal control of multi-robot systems is discussed which accounts for the (continuous) physical locomotion dynamics of the robots and its tight coupling to the distribution and allocation of (discrete) subtasks to the robots to fulfill a joint mission. The point of departure is a nonlinear and nonconvex hybrid optimal control problem (HOCP) formulation which incorporates a detailed hybrid automaton model. Because of the many difficulties involved in solving this problem like large computational times and the lack of good or global convergence properties it is transcribed into a mixed- integer linear program (MILP). This can be solved much more efficiently using existing algorithms. The proposed approach is outlined for an example problem of cooperative soccer robots. The MILP solution itself may serve either as a good initial solution estimate for a method addressing the nonlinear HOCP or may later become the kernel of a model predictive control method for cooperative multi-robot systems. Despite the promising results obtained so far a variety of open questions yet remains to be answered including the ”best” way of transcribing HOCP to MILP with respect to both computational efficiency and good HOCP solution approximation. },
}

@INPROCEEDINGS{2007:AMS-Friedmannetal,
  author = {M. Friedmann and S. Petters and M. Risler and H. Sakamoto and D. Thomas and O. von Stryk},
  title = {A new, open and modular platform for research in autonomous four-legged robots},
  year = {2007},
  pages = {254 - 260},
  month = {18 - 19 Oct.},
  publisher = {Springer Verlag},
  editor = {K. Berns and T. Luksch},
  series = {Informatik aktuell},
  address = {Kaiserslautern},
  booktitle = {Autonome Mobile Systeme 2007},
  pdf = {2007_AMS_Friedmann_EtAl_preprint.pdf},
  abstract = {In this paper the design goals for a new, open and modular, four-legged robot platform are described that was developed in reaction to the open call for a standard platform issued by the RoboCup Federation in 2006. The new robot should have similar motion and sensing capabilities like the previously used Sony AIBO plus several new ones. The hardware and software should be open, modular and reconfigurable. The robot should be resonably priced and allow annually upgrades.},
}

@INPROCEEDINGS{2007:IROS-Kiener-vonStryk,
  author = {J. Kiener and O. von Stryk},
  title = {Cooperation of heterogeneous, autonomous robots: A case study of humanoid and wheeled robots},
  year = {2007},
  pages = {959-964},
  month = {Oct. 29 - Nov. 2},
  address = {San Diego, CA, USA},
  booktitle = {Proc. IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)},
  pdf = {2007-IROS-KienervonStryk.pdf},
  abstract = {In this paper we present a case study of cooperation of a strongly heterogeneous robot team, composed of a highly articulated humanoid robot and a wheeled robot with largely complementing and some competing capabilities. By combining two strongly heterogeneous robots the diversity of accomplishable tasks increases as the variety of sensors and actuators in the robot systems is extended compared with a team consisting of homogeneous robots. The scenario describes a tightly cooperative task, where the humanoid robot and the wheeled robot follow for a long distance a ball, which is kicked finally by the humanoid robot into a goal. The task can be fulfilled successfully by combining the abilities of both robots. For task distribution and allocation, a newly developed objective function is presented which is based on a proper modeling of the sensing, perception, motion and onboard computing capabilities of the cooperating robots. Aspects of reliability and fault tolerance are considered.},
}

@INPROCEEDINGS{2007:ReinlVonStryk_ROBOCOMM,
  author = {Christian Reinl and Oskar von Stryk},
  title = {Optimal Control of Multi-Vehicle Systems Under Communication Constraints Using Mixed-Integer Linear Programming},
  year = {2007},
  month = {Oct. 15-17},
  address = {Athens, Greece},
  booktitle = {Proceedings of the. First International Conference on Robot Communication and Coordination (RoboComm)},
  keywords = {connectivity network, mobile communication network, linearized optimal control, mixed-integer linear optimal control, cooperative multi-vehicle system},
  pdf = {2007-ReinlVonStryk_ROBOCOMM.pdf},
  abstract = {A new planning method for optimal cooperative control of heterogeneous multi-vehicle systems is investigated which enables to account for each vehicle’s nonlinear physical motion dynamics in a structured environment as well as for connectivity constraints of wireless communication. A general formulation as nonlinear hybrid optimal control problem (HOCP) is presented. A transformation technique is proposed to reduce the large computational efforts for solving HOCPs towards a future online application of this approach. Hereby the general problem is transcribed to a linearized mixed-integer linear programming problem (MILP) which can be solved much more efficiently. The proposed approach is successfully applied to the numerical solution of a representative, cooperative monitoring problem involving heterogeneous vehicles and conditions.},
}

@TECHREPORT{2007:RoboCup-TDP-Dribblers,
  author = {M. Friedmann and J. Kiener and S. Petters and D. Thomas and O. von Stryk},
  title = {Darmstadt Dribblers: Team Description for Humanoid KidSize League of RoboCup 2007},
  year = {2007},
  note = {11 pages},
  institution = {Technisch Universität Darmstadt},
  pdf = {2007-tdp-hum.pdf},
  abstract = {This paper describes the hardware and software design of the kidsize humanoid robot systems of the Darmstadt Dribblers in 2007. The robots are used as a vehicle for research in control of locomotion and behavior of autonomous humanoid robots and robot teams with many degrees of freedom and many actuated joints. The Humanoid League of RoboCup provides an ideal testbed for such aspects of dynamics in motion and autonomous behavior as the problem of generating and maintaining statically or dynamically stable bipedal locomotion is predominant for all types of vision guided motions during a soccer game. A modular software architecture as well as further technologies have been developed for efficient and effective implementation and test of modules for sensing, planning, behavior, and actions of humanoid robots.},
}

@INPROCEEDINGS{2007:Compumag-Hemkeretal,
  author = {T. Hemker and O. von Stryk and H. De Gersem and T. Weiland},
  title = {Simulation-based design improvement of a superconductive magnet by mixed-integer nonlinear surrogate optimization},
  year = {2007},
  pages = {449-450},
  month = {June 24-28},
  address = {Aachen, Germany},
  booktitle = {16th Intl. Conf. on the Computation of Electromagnetic Fields - Compumag 2007},
  pdf = {2007_hemker_compumag.pdf},
  abstract = {The numerical optimization of continuous parameters in electrotechnical design using electromagnetic field simulation is already standard. In this paper, we describe a new sequential surrogate optimization approach for simulation-based mixed-integer nonlinear programming problems. We apply the method for the optimization of combined integer- and real-valued geometrical parameters of the coils of a superconductive magnet.},
}

@INPROCEEDINGS{2007:AIM-Kratzetal,
  author = {R. Kratz and M. Stelzer and M. Friedmann and O. von Stryk},
  title = {Control approach for a novel high power-to-weight ratio SMA muscle scalable in force and length},
  year = {2007},
  month = {September 4-7},
  address = {Zürich, CH},
  booktitle = {IEEE/ASME Intl. Conf. on Advanced Intelligent Mechatronics (AIM)},
  pdf = {2007-AIM-Kratz-etal.pdf},
  abstract = {The development of a control approach for a novel, soundless, lightweight and multifunctional shape memory alloy (SMA) actuator scalable in force and length for personal assistance or home-help robots is presented in this paper. The SMA actuator is based on lightweight bundles of thin wires of prestrained shape memory alloy that change their length when heated above their transformation temperature. The design approach of the actuator allows arranging the point of actuation in any direction and ensures a short cool down time to guarantee a frequency of contraction/stress cycles that is high enough to allow fast joint motions. This is needed for the generation of fast joint motions. For the use of the actuator the novel control approach has been experimentally validated. The approach uses the resistance of the actuator as a linear position encoder and there are no additional external sensors needed. The application of the new actuator to a novel lightweight humanoid robot is outlined. One advantage of the actuator over electric motors lies in the large variety of user-defined points of actuation of the in pull-force and length free scalable actuators and the high power-to-weight ratio. The results demonstrate that it is possible to build a large humanoid robot actuated with SMA actuator in a new way.},
}

@INPROCEEDINGS{biomed:2006,
  author = {M. Stelzer and O. von Stryk},
  title = {Human Kicking Motion Using Efficient Forward Dynamics Simulation and Optimization},
  year = {2007},
  volume = {15},
  pages = {192--196},
  publisher = {Springer, Berlin},
  editor = {F. Ibrahim and N. A. Abu Osman and J. Usman and N. A. Kadri},
  booktitle = {3rd Kuala Lumpur International Conference on Biomedical Engineering 2006: Biomed 2006, 11-14 December 2006, Kuala Lumpur, Malaysia},
  doi = {10.1007/978-3-540-68017-8},
  pdf = {biomed2006_preprint.pdf},
}

@ARTICLE{2006:JBiomech-Stelzer,
  author = {M. Stelzer and O. von Stryk},
  title = {A novel approach to efficient forward dynamics simulation and optimization of human motion and its application},
  journal = {Journal of Biomechanics},
  year = {2006},
  volume = {39},
  number = {Suppl. 1},
  pages = {S45-S46},
  doi = { http://dx.doi.org/10.1016/S0021-9290(06)83057-5},
}

@TECHREPORT{2006:RoboCup-TDP-GermanTeam,
  author = {Thomas Röfer and Jörg Brose and Eike Carls and Jan Carstens and Daniel Göhring and Matthias Jüngel and Tim Laue and Tobias Oberlies and Sven Oesau and Max Risler and Michael Spranger and Christian Werner and Jörg Zimmer},
  title = {GermanTeam 2006 - The German National RoboCup Team},
  year = {2006},
  institution = {DFKI Bremen and Universität Bremen and TU Darmstadt and HU Berlin},
  pdf = {2006-tdp-GermanTeam.pdf},
}

@INPROCEEDINGS{icmmb:2006,
  author = {M. Stelzer and O. von Stryk},
  title = {Applications of Efficient Forward Dynamics Simulation in Biomechanics},
  year = {2006},
  booktitle = {Proceedings of the XVth International Conference on Mechanics in Medicine and Biology, Singapore},
  pdf = {icmmb2006_preprint.pdf},
}

@INPROCEEDINGS{2006:HumanoidsSoccerWS-DarmstadtDribblersandHajimeTeam,
  author = {M. Friedmann and J. Kiener and S. Petters and H. Sakamoto and D. Thomas and O. von Stryk},
  title = {Versatile, high-quality motions and behavior control of humanoid soccer robots},
  year = {2006},
  pages = {9-16},
  month = {Dec. 4-6},
  address = {Genoa, Italy},
  booktitle = {Proc. Workshop on Humanoid Soccer Robots of the 2006 IEEE-RAS Int. Conf. on Humanoid Robots},
  url = {http://www.dei.unipd.it/~emg/whs2006/schedule.html},
  pdf = {2006-HumanoidsHSR-WS-DarmstadtDribblersandHajimeTeam.pdf},
  abstract = {Many different and high-quality humanoid otions have been developed based on a tailored, 55cm tall humanoid robot kinematics and design using 21 servo motors and inertial sensors for stabilization. These include fast forward walking of about 1.5 km/h in permanent operation, multidirectional walking capabilities, a variety of standard and spectacular kicks, standing up motions as well as motions displaying an emotional state of the robot. While all robot motions are executed in real-time on a controller board an adaptive selection of different motions and autonomous robot behavior are controlled by hierarchical state machine executed on an onboard Pocket PC. Information about the current state of the dynamic environment in a soccer game is obtained from two directed cameras with wide and narrow angles. During RoboCup 2006 the robot demonstrated the fastest walking of all kid- and teen-size humanoid robots on regular terrain as well as in the rough terrain challenge. Also a large variety of different motions as well as individual and team behaviors during successful autonomous soccer games have been demonstrated including the scoring of a goal with the first autonomously performed backheel kick of a humanoid robot.},
}

@INPROCEEDINGS{2006:ROBIO-Friedmannetal,
  author = {M. Friedmann and J. Kiener and S. Petters and D. Thomas and O. von Stryk},
  title = {Modular software architecture for teams of cooperating, heterogeneous robots},
  year = {2006},
  pages = {613-618},
  month = {December 17-20},
  address = {Kunming, China},
  booktitle = {Proc. IEEE International Conference on Robotics and Biomimetics (ROBIO)},
  pdf = {2006-Friedmann_etal_ROBIO_preprint.pdf},
  abstract = {For teams of cooperating autonomous lightweight robots with challenging dynamical locomotion properties a platform independent modular software architecture and platform independent modules for sensor data processing, planning and motion control have been developed. The software architecture allows high level communication between modules on different abstraction levels of the control architecture within one robot system as well as communication between different and heterogeneous robots and computers using wireless network. Very different behavior control paradigms may be realized on the basis of the developed architecture. The application to teams of cooperating small and medium size humanoid robots is investigated in this paper. Scenarios for inter robot communication and cooperative task accomplishment are described.},
}

@INPROCEEDINGS{2006:ROBIO-Kratzetal,
  author = {R. Kratz and S. Klug and M. Stelzer and O. von Stryk},
  title = {Biologically inspired reflex based stabilization control of a humanoid robot with artificial {SMA} muscles},
  year = {2006},
  pages = {1089-1094},
  month = {December 17-20},
  address = {Kunming, China},
  booktitle = {Proc. IEEE International Conference on Robotics and Biomimetics (ROBIO)},
  pdf = {preprint_robio_2006.pdf},
  abstract = {Suddenly occurring collisions or unintentional motions represent a high safety risk in robotics and must be prevented. Especially for humanoid robots, the influence of disturbances that occur unexpectedly during bipedal locomotion are difficult to compensate. A model based online control approach for stabilization of a humanoid robot with many degrees of freedom may require too much time for computing and implementing an adequate compensating motion. In addition, such a control approach usually requires accurate sensor information about the type and magnitude of the disturbance. The goal of the present paper is a reflex based online stabilization control of a humanoid robot actuator based on artificial SMA muscles. The design of a humanoid robot actuated with SMA muscles allows a lightweight robot design and simplifies the direct implementation of reflexes. The reflex that is integrated into the robot depends on an evaluation of the pressure distribution of the feet. An instable position of the center of mass of the robot leads to a known specific pressure disturbance that should be avoided. The experiments show that the implementation of a reflex for the actuators in the calf leads to a stabilization of the entire robot. Additional reflexes are required when the strength or speed of disturbances are increased, such as in the upper leg or arms.},
}

@ARTICLE{2006:ZAMM_Stelzer_vonStryk,
  author = {Maximilian Stelzer and Oskar von Stryk},
  title = {Efficient Forward Dynamics Simulation and Optimization of Human Body Dynamics},
  journal = {ZAMM - Journal of Applied Mathematics and Mechanics},
  year = {2006},
  volume = {86},
  number = {10},
  pages = {828-840},
  keywords = {Forward dynamics simulation, forward dynamics optimization, multibody systems, optimal control, biomechanics, human motion},
  doi = {10.1002/zamm.200610290},
  pdf = {2006-Stelzer-vonStryk-ZAMM_pre.pdf},
  abstract = {The modeling of the time dependent, dynamic behavior of the human musculoskeletal system results in a large scale mechanical multibody system. This consists of submodels for the skeleton, wobbling masses, muscles and tendons as redundant actuators. Optimization models are required for the simulation of the muscle groups involved in a motion. In contrast to the inverse dynamics simulation the forward dynamics simulation enables to consider very general problem statements in principle. The paper presents a new approach to the forward dynamics simulation and optimization of human body dynamics which overcomes the enormous computational cost of current approaches for solving the resulting optimal control problems. The presented approach is based on a suitable modeling of the dynamics of the musculoskeletal system in combination with a tailored direct collocation method for optimal control. First numerical results for a human kick demonstrate an improvement in computational time of two orders of magnitude when compared to standard methods.},
}

@INCOLLECTION{2006:BionikGothavonStryk,
  author = {O. von Stryk},
  title = {Ihr intelligenter 'Personal Robot' im Jahr 2050: Haushaltshilfe, Terminator oder Fußballspieler?},
  year = {2006},
  pages = {48-50},
  publisher = {Stiftung Schloss Friedenstein Gotha},
  editor = {Museum der Natur Gotha},
  address = {Gotha, Germany},
  booktitle = {Bionik - Vom Ursaurier zum laufenden Roboter},
}

@INPROCEEDINGS{2006:IROSLoetzschRislerJuengel,
  author = {M. Lötzsch and M. Risler and M. Jüngel},
  title = {XABSL - A Pragmatic Approach to Behavior Engineering},
  year = {2006},
  pages = {5124-5129},
  month = {October 9-15},
  address = {Beijing, China},
  booktitle = {Proceedings of IEEE/RSJ International Conference of Intelligent Robots and Systems (IROS)},
  pdf = {2006-IROSLoetzschRislerJuengel.pdf},
  abstract = {This paper introduces the Extensible Agent Behavior Specification Language (XABSL) as a pragmatic tool for engineering the behavior of autonomous agents in complex and dynamic environments. It is based on hierarchies of finite state machines (FSM) for action selection and supports the design of longterm and deliberative decision processes as well as of short-term and reactive behaviors. A platform-independent execution engine makes the language applicable on any robotic platform and together with a variety of visualization, editing and debugging tools, XABSL is a convenient and powerful system for the development of complex behaviors. The complete source code can be freely downloaded from the XABSL website (http://www.informatik.huberlin.de/ki/XABSL/). The language has been successfully applied on many robotic platforms, mainly in the domain of RoboCup robot soccer. It gave the GermanTeam the crucial advantage over other teams to become the 2004 and 2005 world champion in the Four-Legged League and helped the team CoPS Stuttgart to become third in the Middle Size League in 2004.},
}

@INPROCEEDINGS{2006:IFAC-MVS-Friedmann-etal,
  author = {M. Friedmann and J. Kiener and S. Petters and D. Thomas and O. von Stryk },
  title = {Reusable architecture and tools for teams of lightweight heterogeneous robots},
  year = {2006},
  pages = {51-56},
  month = {October 2-3},
  address = {Salvador, Brazil},
  booktitle = {Proc. 1st IFAC Workshop on Multivehicle Systems},
  pdf = {2006-IFAC-MVS-FriedmannKienerPettersThomasvonStryk.pdf},
  abstract = {The software framework RoboFrame has been designed to meet the special requirements for teams of lightweight autonomous heterogeneous robot systems. Due to platform abstraction and modern object oriented design, it allows the reuse of components of common robot control software. It can also efficiently be implemented on new platforms and enables different control architectures for different tasks. For the exemplary application in autonomous robot soccer teams configurable and portable algorithms for vision, world modeling, behavior and motion control have been developed on top of the framework. For debugging, controlling and monitoring, an extendable graphical user interface and a generic simulator package have been implemented around the framework. Based on these instruments, different applications for homogeneous and heterogeneous robot teams can be realized in short time.},
}

@INPROCEEDINGS{2006:IFAC-MVS-GlockerReinlvonStryk,
  author = {M.Glocker and C. Reinl and O. von Stryk},
  title = {Optimal task allocation and dynamic trajectory planning for multi-vehicle systems using nonlinear hybrid optimal control},
  year = {2006},
  pages = {38-43},
  month = {October 2-3},
  address = {Salvador, Brazil},
  booktitle = {Proc. 1st IFAC-Symposium on Multivehicle Systems},
  pdf = {2006-IFAC-MVS-GlockerReinlvonStryk.pdf},
  abstract = {Based on a nonlinear hybrid dynamical systems model a new planning method for optimal coordination and control of multiple unmanned vehicles is investigated. The time dependent hybrid state of the overall system consists of discrete (roles, actions) and continuous (e.g. position, orientation, velocity) state variables of the vehicles involved. The evolution in time of the system’s hybrid state is described by a hybrid state automaton. The presented approach enables a tight and formal coupling of discrete and continuous state dynamics, i.e. of dynamic role and action assignment and sequencing as well as of the physical motion dynamics of a single vehicle modeled by nonlinear differential equations. The planning problem of determining optimal hybrid state trajectories that minimize a cost function as time or energy for optimal multi-vehicle cooperation subject to constraints including the vehicle’s motion dynamics is transformed to a mixed-binary dynamic optimization problem being solved numerically. The numerical method consists of an inner iteration where multiphase optimal control problems are solved using a direct collocation method and an outer iteration based on a branch-and-bound search of the discrete solution space. The approach presented in this paper is applied to the scenarios of optimal simultaneous waypoint or target sequencing and dynamic trajectory planning for a team of unmanned aerial vehicles in a plane and to optimal role assignment and physics-based trajectories in robot soccer.},
}

@INPROCEEDINGS{2006:CLAWARHemkeretal,
  author = {T. Hemker and H. Sakamoto and M. Stelzer and O. von Stryk},
  title = {Hardware-in-the-loop optimization of the walking speed of a humanoid robot},
  year = {2006},
  pages = {614-623},
  month = {September 11-14},
  address = {Brussels, Belgium},
  booktitle = {CLAWAR 2006: 9th International Conference on Climbing and Walking Robots},
  pdf = {2006-Hemker_etal_CLAWAR_pre.pdf},
  abstract = {The development of optimized motions of humanoid robots that guarantee a fast and also stable walking is an important task especially in the context of autonomous soccer playing robots in RoboCup. We present a walking motion optimization approach for the humanoid robot prototype HR18 which is equipped with a low dimensional parameterized walking trajectory generator, joint motor controller and an internal stabilization. The robot is included as hardware-in-the-loop to define a low dimensional black-box optimization problem. In contrast to previously performed walking optimization approaches we apply a sequential surrogate optimization approach using stochastic approximation of the underlying objective function and sequential quadratic programming to search for a fast and stable walking motion. This is done under the conditions that only a small number of physical walking experiments should have to be carried out during the online optimization process. For the identified walking motion for the considered $55$ cm tall humanoid robot we measured a forward walking speed of more than $30$ cm/sec. With a modified version of the robot even more than $40$ cm/sec could be achieved in permanent operation.},
}

@INPROCEEDINGS{2006:CLAWARSeyfarthetal,
  author = {A. Seyfarth and R. Tausch and M. Stelzer and F. Iida and A. Karguth and O. von Stryk},
  title = {Towards bipedal running as a natural result of optimizing walking speed for passively compliant three-segmented legs},
  year = {2006},
  pages = {396-401},
  month = {September 12-14},
  address = {Brussels, Belgium},
  booktitle = {CLAWAR 2006: 9th International Conference on Climbing and Walking Robots},
  pdf = {2006-Seyfarth_etal_CLAWAR_pre.pdf},
  abstract = {Elasticity in conventionally built walking robots is an undesired side-effect that is oppressed as much as possible because it makes control very hard, and thus complex control algorithms must be used. The human motion apparatus, in contrast, shows a very high degree of flexibility with suffcient stability. In this research we investigate how elasticities and damping can sensibly be used in humanoid robots to improve walking capabilities. A modular robot system consisting of rigid segments, joint modules and adjustable elastic strings spanning one or more joints is used to configure a human-like biped. In parallel, a complex simulation model of the robot has been established. Walking motion is gained by oscillatory out-of-phase excitations of the hip joints. An optimization of the walking speed has been performed by improving the viscoelastic properties of the leg and identifying the appropriate hip control parameters. Experiments on the real robot very well matched the numerical results. At higher speeds, transitions from walking to running are found in both the simulation as well as in the robot.},
}

@INPROCEEDINGS{2006:IFACKratzStelzervStryk,
  author = {R. Kratz and M. Stelzer and O. von Stryk},
  title = {Macroscopic SMA wire bundle actuator/sensor system: design, measurement, control approach},
  year = {2006},
  month = {September 12-14},
  address = {Heidelberg},
  booktitle = {Proc. 4th IFAC-Symposium on Mechatronic Systems},
  pdf = {preprint_mechatronics_2006.pdf},
}

@INCOLLECTION{2006:MoehlvonStryk-Bionikbuch,
  author = {Bernhard Möhl and Oskar von Stryk},
  title = {Menschen aus Stahl},
  year = {2006},
  pages = {174-180},
  publisher = {Bionik Media},
  editor = {K.G. Blüchel and F. Malik},
  booktitle = {Faszination Bionik - Die Intelligenz der Schöpfung},
}

@INPROCEEDINGS{2006_hemker_CMWR,
  author = {T. Hemker and K.R. Fowler and O. von Stryk},
  title = {Derivative-Free Optimization Methods for Handling Fixed Costs in Optimal Groundwater Remediation Design},
  year = {2006},
  pages = {electronic resource},
  month = {19-22 June},
  editor = {P.J. Binning and P. Engesgaard and H. Dahle and G. Pinder and W.G. Gray},
  booktitle = {Proc. of the CMWR XVI - Computational Methods in Water Resources},
  pdf = {2006-Hemker_etal_CMWR_pre.pdf},
  abstract = {Groundwater remediation design problems are routine in water resource management. The starting point for such a design problem is to formulate an objective function that represents a measure of the manager´s goal. For example, in plume migration control, we need to determine the cost to design a well field to alter the direction of groundwater flow and thereby control the destination of a contaminant. Constraints must be specified to ensure that the plume is captured, the physical domain is protected, and the wells operate under realistic conditions. Optimization algorithms must work in conjunction with groundwater flow and possibly contaminant transport simulators to determine the minimal cost well design subject to the constraints, but typically these numerical simulation codes have been developed for many years and have usually not been designed to meet the specific needs of optimization methods as, e.g., providing gradient information. Decision variables can be real-valued, in the case of pumping rates and well locations, or integer valued in the case of the number of wells in the design. In this work we focus on formulations that include a fixed installation cost as well as an operating cost, resulting in a simulation-based nonlinear mixed-integer optimization problem. The motivation is that our preliminary studies have shown that convergence to an unsatisfactory, local minimum with many wells operating at low pumping rates is common when the fixed cost is ignored. The challenge in the fixed cost formulation is the integer variable for the number of wells in the design. Removing a well from the design space leads to a large decrease in cost meaning optimizers must be equipped to either handle a mixed-integer or approximate mixed integer, black-box problem and discontinuities in the objective function. Moreover since evaluation of the objective function requires numerical results from a simulation, derivative information is unavailable. Gradient based optimization methods are not appropriate for these applications, hence methods that rely only on function values are more appealing. We compare three methods for handling the installation cost on a hydraulic capture benchmarking problem proposed in the literature. All the approaches described below do not use the gradient of the objective function, only function values for minimization. In one approach, we use penalty coefficients proposed in the literature for the installation term to transform the discontinuous problem into a continuous one. In another approach, we bypass including the number of wells as a decision variable by defining an inactive-well threshold. In the course of the optimization, if a well rate falls in this threshold, the well is removed from the design space, leading to large discontinuities in the objective function. For the two above formulations, we use the implicit filtering algorithm, a method which uses a sequence of finite difference gradients, for minimization. In the third approach, we use sequential stochastic modeling to build surrogate functions to approximate the original objective function. With this procedure the use of a branch and bound technique becomes possible to solve the mixed integer problem in contrast to methods working directly on the simulation results, which impedes relaxation of integer variables. We present promising preliminary numerical results on the benchmarking problem and point the way towards improvement and future work. },
}

@INPROCEEDINGS{2006:ACTUATORKratzStelzervonStryk,
  author = {R. Kratz and M. Stelzer and O. von Stryk},
  title = {Design, measurement experiments and application of a macroscopic shape memory alloy actuator system},
  year = {2006},
  month = {June 14-15},
  address = {Bremen, Germany},
  booktitle = {ACTUATOR 2006 - 10th International Conference on New Actuators},
  pdf = {preprint_actuator_2006.pdf},
  abstract = {Prestrainend shape memory alloys (SMA) change their length when heated above their transformation temperature. Based on this property various micro-technical actuators have been developed in the past. This paper presents the design of novel macroscopic SMA actuators scalable in force and length. Our design approach allows arranging the point of actuation in any direction and ensures a short cool down time to guarantee a high frequency of contraction/stress cycles. The use of the new actuator also necessitates a novel control approach. A model to describe the actuators behavior has been developed and experimentally validated. It offers the possibility of using the resistance of the actuator as a linear position encoder and provides a basis for the control approach of the actuator. The application to a new bipedal walking robot demonstrates one envisioned future use of the actuators. One advantage over electric motors lies in the large variety of user-defined points of actuation of the scalable actuators on a mechanical structure. This allows generating joint movements without the common restrictions holding for electric motors on the possible point of actuation. },
}

@INPROCEEDINGS{2006BioRob:KlugvonStrykMoehl,
  author = {S. Klug and O. von Stryk and B. Möhl},
  title = {Design and Control Mechanisms for a 3 DOF Bionic Manipulator},
  year = {2006},
  number = {210},
  month = {February 20-22},
  address = {Pisa, Italy},
  booktitle = {Proc. 1st IEEE / RAS-EMBS Intl. Conf. on Biomedical Robotics and Biomechatronics (BioRob)},
  url = {http://www.biorob.de},
  pdf = {2006-BioRob-Klug-vonStryk-Moehl.pdf},
  abstract = {Functionality and design of a bionic robot arm consisting of three joints driven by elastic and compliant actuators derived from biologically inspired principles are presented. In the first design standard springs with linear characteristics are utilized in combination with electrical drives. Different control approaches for the bionic robot arm are presented, discussed and evaluation in numerical simulations and experiments with regards to the long-term goal of a natural-like control perfomance.},
}

@INPROCEEDINGS{MATHMOD2006,
  author = {R. Höpler and M. Stelzer and O. von Stryk},
  title = {Object-Oriented Dynamics Modeling of Walking Robots for Model-Based Trajectory Optimization and Control},
  year = {2006},
  number = {30},
  editor = {I. Troch and F. Breitenecker},
  series = {ARGESIM Reports},
  booktitle = {Proc. 5th MATHMOD Vienna, February 8-10},
  pdf = {2006-MATHMOD.pdf},
  abstract = {Modeling walking robot dynamics is an intricate subject when dealing with optimization and model based control. When modeled as multibody systems with a free floating base walking robots lead to high dimensional equation systems. Walking involves frequent changes in the kinematic structure due to varying contact situations. However, specialized algorithms that treat the contacts separately and thus can make use of the tree structure of the system can be used. This paper discusses the dynamics algorithms used and discusses the development and application of objectoriented modeling and implementation techniques to achieve a representation of the mechanical model amenable to the various requirements by legged robot applications. Optimal control techniques are involved to generate optimal walking trajectories of a biped and a quadruped robot. Numerical results are shown.},
}

@INPROCEEDINGS{2006_hemker_CEM,
  author = {T. Hemker and M. Glocker and H. De Gersem and O. von Stryk and Th. Weiland},
  title = {Mixed-integer simulation-based optimization for a superconductive magnet design},
  year = {2006},
  pages = {125-127},
  month = {4-6 April},
  booktitle = {Sixth International Conference on Computational Elektromagnetics, Proceedings, 4-6 April 2006 in Aachen},
  organization = {VDE},
  pdf = {2006-Hemker_etal_CEM_pre.pdf},
  abstract = {The optimization of continuous parameters in electrotechnical designs using electromagnetic field simulation is already standard. Typically, the simulation tools only carry out evaluations of the objective function and do not provide gradient information. If in addition to continuous design parameters also integer design parameters have to be optimized, only computational expensive random search methods like genetic algorithms are well known. In this paper, we present a new sequential modeling approach to solve mixed-integer simulation-based optimiza-tion problems for an electrotechnical design problem for superconductive magnets. Each step of this approach uses stochastic modeling techniques to predict the simulation output by a surrogate function. The surrogate function treats the integer variables as real-valued ones. New promising parameter con-figurations are predicted by a “branch-and-bound” method, which solves the purely continuous subproblems by classical optimization methods for continuous and differentiable functions. The additional information of these simulation runs improves the quality of the surrogate function step by step. The proposed approach is applied to optimize the distribution of coil blocks and coil windings of a superconduc-tive magnet such that a maximal homogeneity of the magnetic field in the aperture is achieved.},
}

@TECHREPORT{2005:RoboCup-TDP-GermanTeam,
  author = {Thomas Röfer and Ronnie Brunn and Stefan Czarnetzki and Marc Dassler and Matthias Hebbel and Matthias Jüngel and Thorsten Kerkhof and Walter Nistico and Tobias Oberlies and Carsten Rohde and Michael Spranger and Christine Zarges},
  title = {GermanTeam 2005 - The German National RoboCup Team},
  year = {2005},
  institution = {Universität Bremen and TU Darmstadt and HU Berlin and Universität Dortmund},
  pdf = {2005-tdp-GermanTeam.pdf},
}

@TECHREPORT{GT:2005,
  author = {T. Röfer and T. Laue and M. Weber and H.-D. Burkhard and M. Jüngel and D. Göhring and J. Hoffmann and B. Altmeyer and T. Krause and M. Spranger and O. von Stryk and R. Brunn and M. Dassler and M. Kunz and T. Oberlies and M. Risler and U. Schwiegelshohn and M. Hebbel and W. Nistico and S. Czarnetzki and T. Kerkhof and M. Meyer and C. Rohde and B. Schmitz and M. Wachter and T. Wegner and C. Zarges},
  title = {GermanTeam 2005},
  year = {2005},
  institution = {HU-Berlin and U-Bremen and TU-Darmstadt and U-Dortmund},
  pdf = {2005-GermanTeamReport.pdf},
  abstract = {The GermanTeam is a joint project of four German universities in the Four-Legged League. This report describes the software developed for the RoboCup 2005 in Osaka. It presents the software architecture of the system as well as the methods that were developed to tackle the problems of motion, image processing, object recognition, self-localization, and robot behavior. The approaches for both playing robot soccer and mastering the challenges are presented. In addition to the software actually running on the robots, this document will also give an overview of the tools the GermanTeam used to support the development process. The report serves as detailed documentation of the work that has been done and aims at enabling other researchers to make use of it. In an extensive appendix, several topics are described in detail, namely the installation of the software, how it is used, the implementation of inter-process communication, streams, and debugging mechanisms, and the approach of the GermanTeam to model the behavior of the robots.},
}

@INCOLLECTION{2005:SpringerVideoRettig-etal,
  author = {U. Rettig and R. Bulirsch and O. von Stryk and R.H.W. Hoppe},
  title = {Modeling, simulation and control of electrorheological fluid dampers},
  year = {2005},
  publisher = {Springer-Verlag},
  editor = {H.-J. Bungartz, R.-P. Mundani, A.C. Frank},
  series = {Springer VideoMATH},
  type = {DVD, Video, PAL},
  booktitle = {Bubbles, Jaws, Moose Tests, and More: The Wonderful World of Numerical Simulation},
  abstract = {This video introduces the mathematical challenges in modeling, simulation and control of new continuously controllable shock absorbers based on electrorheological fluids (ERF) within automobiles. The basic mode of operation of an ERF is demonstrated by an experiment. Simulations demonstrate the interaction between controllable shock absorbers with a wide range of characteristics, the road and the multibody system of the motor vehicle. Mathematical questions considered during this project concern modeling, parameter estimation, optimal control and dynamic simulation. Parametric models predicting the dynamic behavior of the damper characteristics must be developed but also validated and calibrated by ERF flow simulations and experimental results. New optimal control strategies based on quarter car or half car models enable almost optimal use of the ERF shock absorbers with respect to dring safety and comfort. A well known driving maneuver, performed in three different configurations, demonstrates the innovative potential of optimally controlled ERF shock absorbers. The simulation is based on a full vehicle dynamics model augmented with the new ERF shock absorbers and the new optimal controllers, and it includes complex submodels not only for the vehicle"s multibody system, drive train, axle kinematics and tires but also for the driver and the road.},
}

@INPROCEEDINGS{ASIM:2005,
  author = {R. Höpler and M. Stelzer and O. von Stryk},
  title = {Object-oriented dynamics modeling for simulation, optimization and control of walking robots},
  year = {2005},
  pages = {588--593},
  month = {September 12-15},
  booktitle = {Proc. 18th Symposium on Simulation Technique, ASIM, Erlangen},
  pdf = {2005-ASIM.pdf},
}

@INCOLLECTION{2005:GlockerMartinvonStryk,
  author = {Markus Glocker and Alexander Martin and Oskar von Stryk},
  title = {Optimale kooperative Steuerung von Mehrflugzeugsystemen},
  year = {2005},
  number = {3/2005},
  pages = {14-18},
  publisher = {Technische Universität Darmstadt},
  editor = {Uwe Klingauf},
  series = {thema Forschung},
  address = {Darmstadt},
  booktitle = {thema Forschung - Im Aufwind: Luftverkehr},
  url = {http://www.tu-darmstadt.de/aktuell/thema-forschung/},
  pdf = {2005-forschung03-a3.pdf},
  abstract = {Die Untersuchung und Optimierung von Koordination und Flugtrajektorien zur Erhöhung von Kapazität und Sicherheit im Luftverkehr unter Berücksichtigung von Freiflugphasen und neuen Möglichkeiten der Flugregelung führt bei realitätsnaher Modellierung der Flugzeugdynamik auf eine gänzlich neue Klasse von diskret-kontinuierlichen dynamischen Optimierungsproblemen. Damit können die simultane Optimierung von Flugtrajektorien und Landereihenfolge bei Flughäfen ebenso beschrieben werden wie die Koordination und Trajektorienoptimierung einer Flotte unbemannter Flugsysteme zur Verkehrsüberwachung oder Aufklärung bei Katastrophen. Erste Ansätze für numerische Berechnungsverfahren werden diskutiert und an Beispielen illustriert.},
}

@INPROCEEDINGS{2005:ButzEhmann,
  author = {T. Butz and M. Ehmann},
  title = {Virtuelle Rundenzeitoptimierung mittels realistischer Rennfahrzeugsimulation},
  year = {2005},
  month = {13.-14. Oktober 2005},
  publisher = {TÜV Süd Gruppe},
  address = {Garching},
  booktitle = {Proc. race.tech},
  pdf = {2005-racetech_Butz_Ehmann.pdf},
  abstract = {Der Einsatz von maßeschneiderten Fahrdynamik-Simulationspaketen ist Stand der Technik bei der Entwicklung von Rennfahrzeugen. Neben dem virtuellen Prototypenbau können schnelle Simulationsmodelle zu Konzeptuntersuchungen und zur Optimierung einzelner Fahrzeugkomponenten dienen. Die Entwicklung von Fahrdynamikreglern wird während des gesamten Entwicklungszyklus unterstützt, vom ersten Entwurf des Regelalgorithmus bis hin zu Funktionstests und Abstimmung des Steuergeräts in Echtzeitumgebungen, wo eine Implementierung des Reglers in Software oder Hardware mittels Sensoren und Aktuatoren mit der Vollfahrzeugsimulation verbunden ist. Zur Simulation der Rennfahrzeugdynamik wird neben einem präisen physikalischen Fahrzeugmodell ein Fahrermodell benötigt, das das virtuelle Fahrzeug im fahrdynamischen Grenzbereich präzise langs zeitoptimaler Führungsgrößen für die Ideallinie und das Geschwindigkeitsprofil führen kann. In diesem Beitrag wird eine Strategie zur Rundenzeitoptimierung vorgestellt, in der eine näherungsweise optimale Startlösung für die Sollgeschwindigkeit durch den Einsatz von nichtlinearen Optimierungsverfahren iterativ verbessert wird. Ergebnisse der Optimierung und die Grenzen der Vorgehensweise werden diskutiert.},
}

@INPROCEEDINGS{kiener05,
  author = { Jutta Kiener and Sebastian Petters and Dirk Thomas and Martin Friedmann und Oskar von Stryk},
  title = {Architektur und Komponenten für ein heterogenes Team kooperierender, autonomer humanoider Roboter},
  year = {2005},
  number = {19},
  pages = {3 - 10},
  month = {08 - 09 December},
  publisher = {Springer},
  editor = {P. Levi and M. Schanz and R. Lafrenz and V. Avrutin},
  series = {Informatik aktuell},
  address = {Stuttgart},
  booktitle = {Autonome Mobile Systeme 2005 },
  organization = {Gesellschaft f\"ur Informatik},
  pdf = {2005-ams-kiener-vonStryk.pdf},
  abstract = {Für ein kooperierendes Team autonomer, humanoider Roboter, das derzeit aus insgesamt vier unterschiedlichen, ca. 37 - 68 cm großen Robotertypen besteht, werden eine plattformübergreifende, modulare Softwarearchitektur sowie plattformübergreifende und individuelle Module zur Sensordatenverarbeitung, Planung und Bewegungssteuerung entwickelt. Das entwickelte funktionale Framework ermöglicht die Kommunikation der Softwaremodule, d.h. Algorithmen für die unterschiedlichen Aufgaben innerhalb der Architektur untereinander, sowie die Kommunikation per WLAN zwischen verschiedenen Rechnern und Robotern. Als Anwendungsszenario für die Teamkooperation in einer dynamischen und strukturierten Umgebung wird Roboterfußball untersucht. Die entwickelten Methoden wurden im Juli 2005 von den Darmstadt Dribblers beim RoboCup in Osaka bei der Premiere von Teamspielen in der Humanoid Robot League eingesetzt. Daneben werden Kooperationsszenarien von heterogenen Robotersystemen bestehend aus vierbeinigen und humanoiden Robotern untersucht.},
}

@INPROCEEDINGS{StelzervonStryk2005,
  author = {Maximilian Stelzer and Oskar von Stryk},
  title = {From Robots to Humans: Towards Efficient Forward Dynamics Simulation and Optimization Exploiting Structure and Sensitivity Information},
  year = {2005},
  booktitle = {Proceedings of ECCOMAS Multibody Dynamics 2005, Advances in Computational Multibody Dynamics, Madrid, June 21-24},
  pdf = {stelzer_vonstryk_ECCOMAS2005_final_pre.pdf},
}

@INPROCEEDINGS{RettigvonStryk:2005,
  author = {U. Rettig and O. von Stryk},
  title = {Optimal and robust damping control for semi-active vehicle suspension},
  year = {2005},
  pages = {paper no. 20-316},
  month = {August 7-12},
  address = {Eindhoven, The Netherlands},
  booktitle = {5th EUROMECH Nonlinear Dynamics Conference (ENOC)},
  pdf = {2005-enoc-rettig-vstryk-preprint.pdf},
  abstract = {The paper focusses on optimal control issues arising in semi-active vehicle suspension motivated by the application of continuously controllable ERF-shock absorbers. Optimality of the damping control is measured by an objective consisting of a weighted sum of criteria related to safety and comfort which depend on the state variables of the vehicle dynamics model. In the case of linear objectives and linear quarter or half car dynamics models the well-known linear quadratic regulators can be computed. However, to account for maximum robustness with respect to unknown perturbations, e.g., by the ground, linear robust-optimal H-infinity controllers are investigated which can be computed iteratively. The linear H-infinity controller can be viewed as the solution of a linear dynamic zero-sum differential game. Thus, a nonlinear H-infinity controller can be obtained in principle as the solution of a nonlinear zero-sum dynamic game problem. Such a problem formulation enables to consider nonlinear vehicle dynamics as well as nonlinear objectives and constraints. A computational method is discussed which computes approximations of robust-optimal trajectories for nonlinear damping control. The method is based on a reformulation of the dynamic game and the application of a control and state parameterization approach in combination with sparse nonlinear programming methods. Numerical results for the different approaches and their validation by software-in-the-loop simulation using a full motor vehicle dynamics model are presented. },
}

@ARTICLE{RoefervonStryk:2005,
  author = {Th. Röfer and O. von Stryk},
  title = {Softwarearchitektur: Ein Erfolgsfaktor beim Roboterfußball!},
  journal = {OBJEKTspektrum},
  year = {2005},
  volume = {2005},
  number = {4},
  pages = {31-32},
  month = {July/August},
  abstract = {Seit 1997 wird jährlich der RoboCup, die Fußballweltmeisterschaft autonomer Roboter, in mehreren Ligen laufender, rollender oder simulierter Roboter ausgetragen. Am RoboCup 2004 in Lissabon, an dem 346 Teams aus 37 Ländern teilnahmen, hat erstmals ein deutsches Team den Weltmeistertitel in der Liga der vierbeinigen Roboter gewonnen. Das GermanTeam will den Titel auch beim diesjährigen RoboCup im Juli in Osaka verteidigen.},
}

@INPROCEEDINGS{ButzStryk:2005,
  author = {T. Butz and O. von Stryk},
  title = {Optimal control based modeling of vehicle driver properties},
  year = {2005},
  number = {SAE Paper 2005-01-0420},
  month = {April 11-14},
  address = {Detroit, MI},
  booktitle = {Society of Automotive Engineers (SAE) 2005 World Congress},
  pdf = {2005-ButzvonStryk.pdf},
  abstract = {In this paper, we present a two-level driver model for the use in real-time vehicle dynamics applications. On the anticipation level of this model, nominal trajectories for the path and the speed profile of the vehicle along a given course are determined by reducing the driving task to a parametric optimal control problem and using an efficient direct collocation method for its solution. Typical optimality criteria and control-state constraints serve to depict driving properties of different driver types. On the stabilization level, a nonlinear position controller guides the full vehicle dynamics model along the prescribed trajectories in real-time. This synthetic driver model allows easy implementation of different driving strategies to simulate a wide range of driver types and vehicles. The expediency of the proposed model is shown by comparing simulation results with measured data from several drivers performing ISO double lane changes with a passenger car.},
}

@INPROCEEDINGS{2005AMAM:KlugMoehlvonStrykBart,
  author = {S. Klug and B. Möhl and O. von Stryk and O. Barth},
  title = {Design and application of a 3 DOF bionic robot arm},
  year = {2005},
  month = {September 25-30},
  note = {in press},
  address = {Ilmenau, Germany},
  booktitle = {Proc. 3rd Intl. Symposium on Adaptive Motion in Animals and Machines (AMAM)},
  url = {http://www.biorob.de},
  pdf = {2005-AMAM-Klug-Moehl-vonStryk-Barth.pdf},
  abstract = {Regarding to concrete industrial applications, we examined the functionality and the systematic design of a bionic robot arm developed and driven by biologically inspired principles. Based on a laboratory model a scalable multi-bodydynamics-simulation model has bin developed. Although it is driven by elastically coupled linkages which require additional control efforts for oscillation damping, we can show possible advantages of a lighter and bending relieved structure and a significant reduction of danger in case of collisions.},
}

@INPROCEEDINGS{AMAM2005,
  author = {M. Stelzer and O. von Stryk},
  title = {Efficient forward dynamics simulation and optimization of locomotion: from legged robots to biomechanical systems},
  year = {2005},
  month = {September 25-30},
  booktitle = {Proc. 3rd Intl. Symposium on Adaptive Motion in Animals and Machines (AMAM)},
  pdf = {2005-AMAM-Stelzer-vonStryk.pdf},
}

@TECHREPORT{DD:2005,
  author = {M. Friedmann and J. Kiener and R. Kratz and T. Ludwig and S. Petters and M. Stelzer and O. von Stryk and D. Thomas},
  title = {Darmstadt Dribblers 2005: Humanoid Robot (Team Description Paper)},
  year = {2005},
  note = {10 pages},
  institution = {Technische Universität Darmstadt},
  pdf = {2005-tdp-hum-darmstadt-dribblers.pdf},
  abstract = {This paper describes the hardware and software design of the two humanoid robot systems of the Darmstadt Dribblers. The robots are used as a vehicle for research in control of locomotion and behavior of humanoid robots with many degrees of freedom and many actuated joints. The Humanoid League of RoboCup provides an ideal testbed for such aspects of dynamics in motion and autonomous behavior as the problem of generating and maintaining statically or dynamically stable bipedal locomotion is predominant for all types of motions during a soccer game. A new modular software architecture has been developed for efficient and effective implementation and test of modules for sensing, planning, behavior, and actions.},
}

@ARTICLE{KlugMoehlvonStrykBarth:2005,
  author = {S. Klug and B. Möhl and O. von Stryk and O. Barth},
  title = {Der bionische Roboterarm},
  journal = {Konstruktion},
  year = {2005},
  pages = {48-49},
  month = {May},
}

@ARTICLE{2004:ATZ-worlwide_Butz-et-al,
  author = {T. Butz and M. Ehmann and O. von Stryk and T.-M. Wolter},
  title = {Realistic road modelling for the real-time simulation of vehicle dynamics},
  journal = {ATZ worldwide},
  year = {2004},
  volume = {106},
  number = {2},
  pages = {11-13},
  month = {February},
  url = {http://link.springer.com/article/10.1007%2FBF03224646},
  abstract = {The computer-aided development of vehicle dynamics control units makes growing demands on the simulation environment. In addition to a detailed model of the vehicle, the realistic simulation of driving dynamics requires a model that can represent various road geometries and conditions. The following article presents a complex road model that is implemented in the ve-Dyna Advanced Road from the company Tesis Dynaware GmbH. The efficient implementation permits both fast PC applications and real-time simulation on suitable hardware.},
}

@INPROCEEDINGS{Glocker:04,
  author = {M. Glocker},
  title = {A decomposition approach for optimal control problems with integer inner point state constraints},
  year = {2004},
  volume = {4},
  number = {1},
  pages = {608-609},
  month = {Dec.},
  note = {Beitrag zur GAMM-Jahrestagung 2004 in Dresden, eingereicht zur Veröffentlichung in PAMM},
  booktitle = {Proceedings in Applied Mathematics and Mechanics (PAMM)},
  pdf = {2004-Glocker.pdf},
  abstract = {A large class of optimal control problems for hybrid dynamic systems can be formulated as mixed-integer optimal control problems (MIOCPs). A decomposition approach is suggested to solve a special subclass of MIOCPs with mixed integer inner point state constraints. It is the intrinsic combinatorial complexity of the discrete variables in addition to the high nonlinearity of the continuous optimal control problem that forms the challenges in the theoretical and numerical solution of MIOCPs. During the solution procedure the problem is decomposed at the inner time points into a multiphase problem with mixed integer boundary constraints and phase transitions at unknown switching points. Due to a discretization of the state space at the switching points the problem can be decoupled into a family of continuous optimal control problems (OCPs) and a problem similar to the asymmetric group traveling salesman problem (AGTSP). The OCPs are transcribed by direct collocation to large-scale nonlinear programming problems, which are solved efficiently by an advanced SQP method. The results are used as weights for the edges of the graph of the corresponding TSP-like problem, which is solved by a Branch-and-Cut-and-Price (BCP) algorithm. The proposed approach is applied to a hybrid optimal control benchmark problem for a motorized traveling salesman.},
}

@INPROCEEDINGS{2004:NandyvonStryk,
  author = {S. Nandy and O. von Stryk},
  title = {Towards EKF for humanoid robot navigation by sensor error modelling and sensor error fusion},
  year = {2004},
  pages = {59-67},
  editor = {S. N. Shome, J. Basu and G. P. Sinha},
  booktitle = {Proc. National Conference on Advanced Manufacturing & Robotics},
}

@TECHREPORT{2004:RoboCup-TDP-GermanTeam,
  author = {Thomas Röfer and Ronnie Brunn and Ingo Dahm and Matthias Hebbel and Jan Hoffmann and Matthias Jüngel and Tim Laue and Martin Lötzsch and Walter Nistico and Michael Spranger},
  title = {GermanTeam 2004 - The German National RoboCup Team},
  year = {2004},
  institution = {Universität Bremen and TU Darmstadt and HU Berlin and Universität Dortmund},
  pdf = {2004-tdp-GermanTeam.pdf},
}

@INCOLLECTION{tropea:bionik2004,
  author = {M. Stelzer and O. von Stryk},
  title = {Laufbewegungen bei Roboter, Tier und Mensch: Analyse, Modellierung, Simulation und Optimierung},
  year = {2004},
  pages = {145-158},
  publisher = {Springer-Verlag},
  editor = {T. Rossmann and C. Tropea},
  booktitle = {Bionik},
  url = {http://www.springeronline.com/sgw/cda/frontpage/0,11855,1-185-22-32104490-detailsPage%253Dppmmedia%257CaboutThisBook%257CaboutThisBook,00.html},
}

@INPROCEEDINGS{MechRob:2004,
  author = {R. Höpler and M. Stelzer and O. von Stryk},
  title = {Object-oriented dynamics modeling for legged robot trajectory optimization and control},
  year = {2004},
  pages = {972-977},
  month = {Sept. 13-15},
  publisher = {Sascha Eysoldt Verlag},
  address = {Aachen},
  booktitle = {Proc. IEEE Intl. Conf. on Mechatronics and Robotics (MechRob)},
  pdf = {2004-IEEE-MechRob.pdf},
  abstract = {This paper discusses the development and application of object-oriented modeling and implementation techniques to achieve a representation of the mechanical model amenable to the various requirements by legged robot applications. This leads to a uniform, modular, and flexible code generation while reaping the performance of efficient domain-specific articulated body algorithms. Trajectory optimization problems of bipedal and quadrupedal robots are investigated as applications. It is shown how a high-level specification of multibody dynamics models using component libraries serves as a basis for generation of a number of modules forming an ìoverall computational dynamics model. The selected examples illustrate how one copes with the emerging complexity by integrating various modules for, e.g., equations of motion, non-linear boundary conditions, symmetry and transition conditions, for multiple phases during motion. Variations of the mechanical structure, e.g., contact conditions can be treated either by multiple models or by reconfiguration of one model. Numerical results are presented for time- and energy-optimal trajectories of full three-dimensional models of a humanoid robot and a Sony four-legged robot. },
}

@INPROCEEDINGS{HoeplerStelzervonStryk:2004,
  author = {R. Höpler and M. Stelzer and O. von Stryk},
  title = {Integrated, object-oriented dynamics modeling for design, trajectory optimization and control of legged robots},
  year = {2004},
  month = {March 1-4},
  address = {Halle (Saale), Germany},
  booktitle = {EUROMECH Colloquium 452 on Advances in Simulation Techniques for Applied Dynamics},
}

@TECHREPORT{Kiener:2004,
  author = {J. Kiener},
  title = {Direkte und Inverse Kinematik eines sechsgelenkigen humanoiden Roboterarms},
  year = {2004},
  note = {Interner Bericht},
  institution = {Technische Universität Darmstadt, Fachgebiet Simulation und Systemoptimierung},
}

@TECHREPORT{DD:2004,
  author = {J. Kiener and M. Stelzer and O. von Stryk},
  title = {Darmstadt Dribblers 2004: Humanoid Robot (Team Description Paper)},
  year = {2004},
  note = {9 pages},
  institution = {Technische Universität Darmstadt},
  url = {http://www.sim.informatik.tu-darmstadt.de/},
  pdf = {2004-tdp-hum04.pdf},
  abstract = {This paper describes the design and implementation of the first humanoid robot prototype of the Darmstadt Dribblers, which participated in the Humanoid League of RoboCup for the first time in 2004. The robot is used as a vehicle for research in control of locomotion and behavior of humanoid robots with many degrees of freedom and many actuated joints. For humanoid robots highly nonlinear physical dynamical effects must be considered on all levels of a reactive-deliberative control architecture realizing autonomous robot behaviour. The Humanoid League of RoboCup provides an ideal testbed as the problem of generating and maintaining statically or dynamically stable bipedal locomotion is predominant for all types of motions during a soccer game. The team has evolved from the Darmstadt Dribbling Dackels team which continuously has participated as part of the German Team in the Sony Four-Legged League since 2001.},
}

@TECHREPORT{GT:2004,
  author = {T. Röfer and T. Laue and H.-D. Burkhard and J. Hoffmann and M. Jüngel and D. Göhring and M. Lötzsch and U. Düffert and M. Spranger and B. Altmeyer and V. Goetzke and O. von Stryk and R. Brunn and M. Dassler and M. Kunz and M. Risler and M. Stelzer and D. Thomas and S. Uhrig and U. Schwiegelshohn and I. Dahm and M. Hebbel and W. Nistico and C. Schumann and M. Wachter},
  title = {GermanTeam 2004, Technical Report of the RocoCup-Team in the Sony Legged Robot League},
  year = {2004},
  note = {299 pages},
  institution = {HU-Berlin and U-Bremen and TU-Darmstadt and U-Dortmund},
  pdf = {2004-GermanTeamReport.pdf},
  abstract = {The GermanTeam is a joint project of four German universities in the Sony Legged Robot League. This report describes the software developed for the RoboCup 2004 in Lisbon. It presents the software architecture of the system as well as the methods that were developed to tackle the problems of motion, image processing, object recognition, self-localization, and robot behavior. The approaches for both playing robot soccer and mastering the challenges are presented. In addition to the software actually running on the robots, this document will also give an overview of the tools the GermanTeam used to support the development process.
The report serves as detailed documentation of the work that has been done and aims at enabling other researchers to make use of it. In an extensive appendix, several topics are described in detail, namely the installation of the software, how it is used, the implementation of inter-process communication, streams, and debugging mechanisms, and the approach of the GermanTeam to model the behavior of the robots.},
}

@ARTICLE{Butz-etal:2004,
  author = {T. Butz and M. Ehmann and T.-M. Wolter and O. von Stryk},
  title = {Realistische Straßenmodellierung für die Fahrdynamiksimulation in Echtzeit},
  journal = {ATZ - Automobiltechnische Zeitschrift},
  year = {2004},
  volume = {2/2004, Jahrgang 106},
  pages = {118-125},
  url = {http://link.springer.com/article/10.1007%2FBF03221604},
  pdf = {2004-Butz-Ehmann-vStryk-Wolter.pdf},
  abstract = {Die rechnergestützte Entwicklung von Kraftfahrzeugsteuergeräten stellt wachsende Anforderungen an die eingesetzte Simulationsumgebung. Neben einem detaillierten Fahrzeugmodell wird für die realistische Berechnung der Fahrdynamik ein Trassenmodell benötigt, mit dem sich verschiedene Straßengeometrien und -bedingungen abbilden lassen. Der folgende Beitrag skizziert ein komplexes Straßenmodell, das in der ve-Dyna Advanced Road der Tesis Dynaware GmbH umgesetzt ist. Die effiziente Implementierung gestattet schnelle PC-Anwendungen ebenso wie Echtzeitsimulationen auf geeigneter Hardware.},
}

@INPROCEEDINGS{BussHardtetal.Humanoids:2003,
  author = {M. Buss and M. Hardt and J. Kiener and M. Sobotka and M. Stelzer and O. von Stryk and D. Wollherr},
  title = {Towards an autonomous, humanoid, and dynamically walking robot: modeling, optimal trajectory planning, hardware architecture, and experiments},
  year = {2003},
  month = {30 Sept - 3 Oct},
  address = {Karlsruhe/Munich, Germany},
  booktitle = {Proc. 3rd IEEE-RAS International Conference on Humanoid Robots (Humanoids2003)},
  pdf = {2003-Humanoids-Buss-etal.pdf},
  abstract = {The complete development process for achieving walking motion with a recently constructed humanoid robot is discussed. The desired motion is based on the solution of an optimal control problem whose constraints depend upon the high-dimensional nonlinear multibody system dynamics of a 17~DoF humanoid and physical contact constraints with the environment. On-line control strategies are developed for tracking the precalculated trajectories. Experimental walking results with the humanoid robot are presented.},
}

@TECHREPORT{ZulaufKieferEffenberger:2003,
  author = {A. Zulauf and M. Kiefer and J. Effenberger},
  title = {Entwicklung eines Roboterarms und eines Kamerasystems für einen mobilen Roboter},
  year = {2003},
  type = {Studienarbeit},
  institution = {Technische Universität Darmstadt, Fachgebiet Simulation und Systemoptimierung},
}

@INPROCEEDINGS{wollherr:aim03,
  author = {D. Wollherr and M. Buss and M. Hardt and O. von Stryk},
  title = {Research and Development Towards an Autonomous Biped Walking Robot},
  year = {2003},
  pages = {968-973},
  address = {Kobe, Japan},
  booktitle = {Proceedings of the IEEE/ASME International Conference on Advanced Intelligent Mechatronics AIM2003},
  url = {http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1225473},
  pdf = {2003-AIM-Wollherr-etal.pdf},
  abstract = {Methods for modeling, simulation and optimization of the dynamics, stability, and performance of humanoid robots are presented in this paper. Optimal control trajectory following by joint-level control combined with an online compensation method using Jacobians is proposed. The kinematic design, dynamic properties, hard- and software architecture for an autonomous biped, and experimental results are presented.},
}

@BOOK{vonStryk:Habil,
  author = {O. von Stryk},
  title = {Numerical Hybrid Optimal Control and Related Topics},
  year = {2003},
  publisher = {Habilitationsschrift, Technische Universität München},
  editor = { },
  address = {München, Germany},
}

@TECHREPORT{GT:2003,
  author = {T. Röfer and H.-D. Burkhard and U. Düffert and J. Hoffmann and D. Göhring and M. Jüngel and M. Lötzsch and O. von Stryk and R. Brunn and M. Kallnik and M. Kunz and S. Petters and M. Risler and M. Stelzer and I. Dahm and M. Wachter and K. Engel and A. Osterhues and C. Schumann and J. Ziegler},
  title = {GermanTeam 2003},
  year = {2003},
  note = {199 pages},
  type = {Technical Report of the RocoCup-Team in the Sony Legged Robot League},
  institution = {Humboldt-Universität Berlin and Universität Bremen and Technische Universität Darmstadt and Universität Dortmund},
  owner = {SIM},
  abstract = {The GermanTeam is a joint project of several German universities in the Sony Legged Robot League. This report describes the software developed for the RoboCup 2003 in Padova. It presents the software architecture of the system as well as the methods that were developed to tackle the problems of motion, image processing, object recognition, self-localization, and robot behavior. The approaches for both playing robot soccer and mastering the challenges are presented. In addition to the software actually running on the robots, this document will also give an overview of the tools the GermanTeam used to support the development process.
In an extensive appendix, several topics are described in detail, namely the installation of the software, how it is used, the implementation of inter-process communication, streams, and debugging mechanisms, and the approach of the GermanTeam to model the behavior of the robots.},
}

@INPROCEEDINGS{PAMM:2003,
  author = {A. Helm and M. Hardt and R. Höpler and O. von Stryk},
  title = {Development of a toolbox for model-based real-time simulation and analysis of legged robots},
  year = {2003},
  volume = {2},
  number = {1},
  pages = {130-131},
  month = {25 March},
  booktitle = {PAMM - Proceedings in Applied Mathematics and Mechanics},
  doi = {10.1002/pamm.200310050},
  url = {http://www3.interscience.wiley.com/cgi-bin/jhome/91016652},
  pdf = {2003-PAMM-HHvSH.pdf},
  abstract = {Multibody systems such as legged robots require sophisticated and efficient methods for their modeling, control and simulation. This paper discusses the development of a software library based on modern tools such as C++, OpenGL and XML for highly efficient dynamics modeling. A primary focus lies on modularity permitting its easy extensibility in connection with different actuation and contact models, optimization algorithms, localized and centralized on-line control schemes as well as animation and simulation environments.},
}

@INPROCEEDINGS{ICRA:2003,
  author = {M. Hardt and O. von Stryk and D. Wollherr and M. Buss},
  title = {Development and control of autonomous, biped locomotion using efficient modeling, simulation, and optimization techniques},
  year = {2003},
  pages = {1356-1361},
  month = {Sept. 14-19},
  address = {Taipeh, Taiwan},
  booktitle = {Proc. IEEE Int. Conf. on Robotics and Automation (ICRA)},
  url = {http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F8794%2F27829%2F01241780.pdf%3Farnumber%3D1241780&authDecision=-203},
  pdf = {2003-ICRA-Hardt-etal.pdf},
  abstract = {Methods for modeling, simulating and optimizing the dynamics, stability and performance of legged robot locomotion are discussed in this paper. It is demonstrated how these tools are used in the design, implementation and operation of a humanoid robot. The selection and integration of fundamental hard- and software needed for autonomous operation and high agility is presented for a recently developed fully-actuated 17 DoF humanoid. The results are additionally reported from simulations and gait optimizations completed during its development using a 3D dynamic biped model coupled with multiple physical and stability constraints.},
}

@INPROCEEDINGS{RC:2002,
  author = {M. Hardt and O. von Stryk},
  title = {The role of motion dynamics in the design, control and stability of bipedal and quadrupedal robots},
  year = {2003},
  volume = {2752},
  pages = {206-223},
  month = {June 24-25},
  publisher = {Springer-Verlag},
  editor = {G.A. Kaminka and P.U. Lima and R. Rojas},
  series = {Lecture Notes in Artificial Intelligence},
  address = {Fukuoka, Japan},
  booktitle = {RoboCup 2002 International Symposium (Robot Soccer World Cup VI)},
  pdf = {2002-robocup-hardt-vonstryk.pdf},
  abstract = {Fundamental principles and recent methods for investigating the nonlinear dynamics of legged robot motions with respect to control, stability and design are discussed. One of them is the still challenging problem of producing dynamically stable gaits. The generation of fast walking or running motions require methods and algorithms adept at handling the nonlinear dynamical effects and stability issues which arise. Reduced, recursive multibody algorithms, a numerical optimal control package, and new stability and energy performance indices are presented which are well-suited for this purpose. Difficulties and open problems are discussed along with numerical investigations into the proposed gait generation scheme. Our analysis considers both biped and quadrupedal gaits with particular reference to the problems arising in soccer-playing tasks encountered at the RoboCup where our team, the Darmstadt Dribbling Dackels, participates as part of the German Team in the Sony Legged Robot League.},
}

@TECHREPORT{GTTDP:2003,
  author = {I. Dahm and U. Düffert and J. Hoffmann and M. Jüngel and M. Kallnik and M. Lötzsch and M. Risler and T. Röfer and M. Stelzer and J. Ziegle},
  title = {German Team 2003},
  year = {2003},
  note = {4 Seiten},
  type = {Team Description Paper},
  institution = {Humboldt-Universität Berlin, Universität Bremen, Technische Universität Darmstadt},
  pdf = {2003-GermanTeam2003.pdf},
  owner = {SIM},
  abstract = {The GermanTeam participates as a national team in the Sony Legged Robot League. It currently consists of students and researchers from the following four universities: the Humboldt-Universität zu Berlin, the Universität Bremen, the Technische Universität Darmstadt, and the Universität Dortmund. The members of the GermanTeam participate as separate teams in the national contests such as RoboCup German Open, but jointly line up for the international RoboCup championship as a single team. To support this cooperation and concurrency, the GermanTeam introduced an architecture that provides mechanisms for parallel development. The entire information processing and control of the robot is divided into modules that have well-defined tasks and interfaces. For each module, many different solutions can be developed. Solutions for a module can be switched at runtime. Currently, for most modules various solutions exist. Approaches to a problem can thereby easily be compared and benchmarked.
This paper gives a brief overview of the current work of all four universities in the GermanTeam.},
}

@INCOLLECTION{VoegelvonStrykBulirschWolterChucholowski2003,
  author = {M. Vögel and O. von Stryk and R. Bulirsch and T.-M. Wolter and C. Chucholowski},
  title = {An optimal control approach to real-time vehicle guidance},
  year = {2003},
  pages = {84-102},
  publisher = {Springer-Verlag},
  editor = {W. Jäger and H.-J. Krebs},
  booktitle = {Mathematics - Key Technology for the Future},
  pdf = {2003-voegel-vonstryk-bulirsch-etal.pdf},
  owner = {SIM},
  abstract = {A newly developed two-level driver model is presented. On the anticipation level, optimal control problems for a reduced vehicle dynamics model are solved repeatedly on a moving prediction horizon to yield near optimal setpoint trajectories for the full model. On the stabilization level, a nonlinear position controller is developed to accurately track the setpoint trajectories with a full motor vehicle dynamics model in real-time. The formulation of the optimal control problems on the anticipation level is based on a nonlinear single track model which is extended by a complex tire model and further nonlinear model details such as to match the main properties of the full vehicle dynamics model. The optimal control problems are solved efficiently by a recently developed sparse direct collocation method. Numerical results for various vehicle maneuvers are presented, including a time-optimal double lane change at high speed.},
}

@INPROCEEDINGS{StelzerHardtvonStryk2003,
  author = {M. Stelzer and M. Hardt and O. von Stryk},
  title = {Efficient dynamic modeling, numerical optimal control and experimental results for various gaits of a quadruped robot},
  year = {2003},
  pages = {601-608},
  month = {Sept. 17-19},
  booktitle = {CLAWAR 2003: 6th International Conference on Climbing and Walking Robots, Catania, Italy},
  pdf = {2003-stelzer-hardt-vonstryk.pdf},
  owner = {SIM},
  abstract = {Numerical simulation and optimization of gaits for quadruped robots based on nonlinear multibody dynamics models of legged locomotion have made progress recently. A fully threedimensional dynamical model of Sony’s four-legged robot is used to state an optimal control problem for a symmetric, dynamically stable gait. The optimal control problem is solved by a sparse direct collocation method. Numerical problems related to the high-index differential algebraic equations of motion are avoided by substituting the differential algebraic equations by an equivalent set of reduced dynamics ordinary differential equations. Numerical and experimental results validate the model and the methods used for gait generation.},
}

@ARTICLE{HardtvonStryk2003,
  author = {M. Hardt and O. von Stryk},
  title = {Dynamic modeling in the simulation, optimization and control of legged robots},
  journal = {ZAMM - Journal of Applied Mathematics and Mechanics },
  year = {2003},
  volume = {83},
  number = {10},
  pages = {648-662},
  url = {http://www.wiley-vch.de/publish/en/journals/alphabeticIndex/2233/},
  pdf = {2003-zamm7a-preprint.pdf},
  owner = {SIM},
  abstract = {Fundamental principles and recent methods for investigating the nonlinear dynamics of legged robot motions with respect to control, stability and design are discussed. One of them is the still challenging problem of producing dynamically stable gaits. The generation of fast walking or running motions requires methods and algorithms adept at handling the nonlinear dynamical effects and stability issues which arise. Reduced, recursive multibody algorithms, a numerical optimal control method, and new stability and energy performance indices are presented which are well-suited for this purpose.Difficulties and open problems are discussed along with numerical investigations into the proposed gait generation scheme. Our analysis considers both biped and quadrupedal gaits. },
}

@INCOLLECTION{TF:2002,
  author = {M. Hardt and M. Stelzer and O. von Stryk},
  title = {Modellierung und Simulation der Dynamik des Laufens bei Roboter, Tier und Mensch},
  year = {2002},
  volume = {2/2002},
  pages = {56-63},
  publisher = {Technische Universität Darmstadt},
  booktitle = {thema Forschung},
  url = {http://www.tu-darmstadt.de/for/thema_forschung/thema-forschung.tud},
  pdf = {2002-TUDForschung-hardt-stelzer-vonstryk.pdf},
  abstract = {In den neunziger Jahren des zwanzigsten Jahrhunderts begann weltweit das wissenschaftliche und kommerzielle Interesse an Laufmaschinen und laufenden Robotern (z.B. Honda P3, Sony AIBO) stark anzuwachsen. Konstruktion, Steuerung und Regelung laufender Roboter sind um ein Vielfaches aufwendiger zu realisieren als beispielsweise die Fortbewegung auf Rädern. Die Fortbewegung auf Beinen ermöglicht jedoch das Schreiten über Hindernisse und Gräben, das Treppen steigen und allgemein eine gleichmäßige Fortbewegung über unebenem Untergrund durch Kompensation von Unebenheiten durch Anpassung von Schrittlänge und -höhe. Auch besteht auf weichem Grund ein geringeres Risiko des Einsinkens gegenüber Rädern. Computerbasierte Modellierung und Simulation bietet neben Theorie und Experiment einen neuen Zugang zum Verständnis und zur Lösung vieler noch offener, grundlegender Fragen im Verständnis der Dynamik des Laufens bei Mensch, Tier und Roboter.},
}

@INCOLLECTION{TF:2002-2,
  author = {T. Butz and C. Chucholowski and M. Ehmann and U. Rettig and O. von Stryk and T.-M. Wolter},
  title = {Test und Validierung von Fahrdynamikregelungen mittels Hardware- und Software-in-the-Loop Simulation},
  year = {2002},
  volume = {1/2002},
  pages = {45-50},
  publisher = {Technische Universität Darmstadt},
  booktitle = {thema Forschung},
}

@INPROCEEDINGS{IFAC:2002,
  author = {M. Hardt and O. von Stryk},
  title = {Increasing stability in dynamic gaits using numerical optimization},
  year = {2002},
  pages = {1636-1641},
  month = {July 21-26},
  publisher = {Elsevier Science},
  address = {Barcelona, Spain},
  booktitle = {Proc. 15th IFAC World Congress on Automatic Control},
  keywords = {walking, path planning, dynamic stability, robot dynamics, optimization problems, nonlinear programming, numerical methods},
  url = {http://www.ifac2002.org/},
  pdf = {2002-ifac-hardt-vonstryk.pdf},
  abstract = {Optimal gait planning is applied in this work to the problem of improving stability in quadruped locomotion. In many settings, it is desired to operate legged machines at high performance levels where rapid velocities and a changing environment make stability of utmost concern. Since gait planning still remains a vital component of legged system control design, an efficient method of determining periodic paths is presented which optimize a dynamic stability criterion. Efficient recursive multibody algorithms are used with numerical optimal control software to solve the minimax performance stability criteria.},
}

@INPROCEEDINGS{GlockervonStryk:2002,
  author = {M. Glocker and O. von Stryk},
  title = {Hybrid optimal control of motorized traveling salesmen and beyond},
  year = {2002},
  pages = {987-992},
  month = {July 21-26},
  publisher = {Elsevier Science},
  address = {Barcelona, Spain},
  booktitle = {Proc. 15th IFAC World Congress on Automatic Control},
  keywords = {nonlinear hybrid dynamical systems, mixed-integer optimal control, branch-and-bound, direct collocation transcription, sparse sequential quadratic programming, motorized traveling salesmen, genetic algorithm},
  url = {http://www.ifac2002.org/},
  pdf = {2002-ifac-glocker-vonstryk.pdf},
  abstract = {Numerical methods for optimal control of hybrid dynamical systems are considered where the discrete dynamics and the nonlinear continuous dynamics are tightly coupled. A decomposition approach for numerically solving general mixed-integer continuous optimal control problems (MIOCPs) is discussed. In the outer optimization loop a branch-and-bound binary tree search is used for the discrete variables. The multiple-phase optimal control problems for the continuous state and control variables in the inner optimization loop are solved by a sparse direct collocation transcription method. A genetic algorithm is applied to improve the performance of the branch-and-bound approach by providing a good initial upper bound on the MIOCP performance index. Results are presented for motorized traveling salesmen problems, new benchmark problems in hybrid optimal control.},
}

@INPROCEEDINGS{LNCSE:2002,
  author = {T. Butz and O. von Stryk and C. Chucholowski and S. Truskawa and T.-M. Wolter},
  title = {Modeling techniques and parameter estimation for the simulation of complex vehicle structures},
  year = {2002},
  volume = {21},
  pages = {333-340},
  publisher = {Springer-Verlag},
  editor = {M. Breuer, F. Durst, C. Zenger},
  series = {Lecture Notes in Computational Science and Engineering},
  booktitle = {High Perfomance Scientific and Engineering Computing},
  pdf = {2002-butz-etal.pdf},
}

@ARTICLE{ZAMM:2002,
  author = {T. Butz and O. von Stryk},
  title = {Modelling and simulation of electro- and magnetorheological fluid dampers},
  journal = {ZAMM: Zeitschrift für Angewandte Mathematik und Mechanik},
  year = {2002},
  volume = {82},
  number = {1},
  pages = {3-20},
  url = {http://www.wiley-vch.de/publish/en/journals/alphabeticIndex/2233/},
  pdf = {2002-ZAMM-Butz-vonStryk.pdf},
  abstract = {Electro- and magnetorheological fluids are smart, synthetic fluids changing their viscosity from liquid to semi-solid state within milliseconds if a sufficiently strong electric or magnetic field is applied. When used in suitable devices, they offer the innovative potential of very fast, adaptively controllable interfaces between mechanical devices and electronic control units. This paper gives an overview on the basic properties of electro- and magnetorheological fluids and discusses various phenomenological models for whole devices and their applications. Numerical simulation results are presented for the passive suspension of a quarter vehicle model.},
}

@INPROCEEDINGS{BussHardtvonStryk:2002,
  author = {M. Buss and M. Hardt and O. von Stryk},
  title = {Numerical solution of hybrid optimal control problems with applications in robotics},
  year = {2002},
  pages = {2077-2082},
  month = {July 21-26},
  publisher = {Elsevier Science},
  address = {Barcelona, Spain},
  booktitle = {Proc. 15th IFAC World Congress on Automatic Control},
  keywords = {hybrid optimal control, mechatronics, underactuated robots},
  url = {http://www.ifac2002.org/},
  pdf = {2002-ifac-buss-hardt-vonstryk.pdf},
  abstract = {Numerical solution techniques for a class of hybrid (discrete event / continuous variable) optimal control problems (HOCP) are described, and their potential use in robotic applications is demonstrated. HOCPs are inherently combinatorial due to their discrete event aspect which is one of the main challenges when numerically solving for optimal hybrid trajectories. One may associate a continuous nonlinear multi-phase problem with each possible discrete state sequence. Two solution techniques for obtaining suboptimal solutions are presented (both based on numerical direct collocation): one fixes interior point constraints on a grid, another uses branch-and-bound. Numerical results of a robotic multi-arm transport task and an underactuated robot are presented.},
}

@INPROCEEDINGS{KONDISK:2002,
  author = {M. Buss and M. Glocker and M. Hardt and O. von Stryk and R. Bulirsch and G. Schmidt},
  title = {Nonlinear hybrid dynamical systems: modeling, optimal control, and applications},
  year = {2002},
  volume = {279},
  pages = {311-335},
  publisher = {Springer-Verlag},
  editor = {S. Engell, G. Frehse, E. Schnieder},
  series = {Lecture Notes in Control and Information Sciences (LNCIS)},
  address = {Berlin, Heidelberg},
  booktitle = {Modelling, Analysis and Design of Hybrid Systems},
  pdf = {2002-kondisk.pdf},
  abstract = {Nonlinear hybrid dynamical systems are the main focus of this paper. A modeling framework is proposed, feedback control strategies and numerical solution methods for optimal control problems in this setting are introduced, and their implementation with various illustrative applications are presented. Hybrid dynamical systems are characterized by discrete event and continuous dynamics which have an interconnected structure and can thus represent an extremely wide range of systems of practical interest. Consequently, many modeling and control methods have surfaced for these problems. This work is particularly focused on systems for which the degree of discrete/continuous interconnection is comparatively strong and the continuous portion of the dynamics may be highly nonlinear and of high dimension. The hybrid optimal control problem is defined and two solution techniques for obtaining suboptimal solutions are presented (both based on numerical direct collocation for continuous dynamic optimization): one fixes interior point constraints on a grid, another uses branch-and-bound. These are applied to a robotic multi-arm transport task, an underactuated robot arm, and a benchmark motorized traveling salesman problem.},
}

@INPROCEEDINGS{IROS:2002,
  author = {D. Wollherr and M. Hardt and M. Buss and O. von Stryk},
  title = {Actuator selection and hardware realization of a small and fast-moving autonomous humanoid robot},
  year = {2002},
  pages = {2491-2496},
  month = {Sept. 30 - Oct. 4},
  address = {Lausanne, Switzerland},
  booktitle = {Proc. 2002 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems (IROS)},
  url = {http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1041643},
  pdf = {2002-iros-wollherr-hardt-buss-vonstryk.pdf},
  abstract = {This paper discusses the design concept and system development of a small and relatively fast walking, autonomous humanoid robot with 17 degrees-offreedom (DoF). The selection of motor size and gear ratios is based on numerical optimization of detailed multibody dynamics and optimal control corresponding to fast steps of the robot with an envisioned target speed of more than 0.5m/s. In this paper the design considerations based on numerical optimal control studies and the mechanical realization of the robot are presented including first investigations on the achievable performance of a decentralized, microcontrollerbased control architecture.},
}

@INPROCEEDINGS{hardt:clawar02,
  author = {M. Hardt and D. Wollherr and M. Buss and O. von Stryk},
  title = {Design of an autonomous fast-walking humanoid robot},
  year = {2002},
  pages = {391-398},
  month = {Sept. 25-27},
  publisher = {Bury St. Edmunds and London, UK: Professional Engineering Publishing},
  editor = {P. Bidaud and F.B. Amar},
  address = {Paris, France},
  booktitle = {CLAWAR: International Conference on Climbing and Walking Robots},
  pdf = {2002-clawar-hardt-wollherr-buss-vonstryk.pdf},
  abstract = {The design considerations for a small, relatively fast walking, autonomous humanoid robot are presented. The robot must be energy efficient but also produce sufficient torque to reach greater speeds. On the basis of previous investigations into gait optimization for multilegged systems, dynamical modeling and nonlinear optimization tools are used for design optimization and choosing the motor size and gear ratios. Gait trajectories for relatively fast steps and different prototypes were calculated. The design decisions are described for the humanoid robot with 6 degrees-of-freedom (DoF) in each leg and 2 DoF in each arm based on numerical results and preliminary investigations with a 4 DoF test robot.},
}

@TECHREPORT{GT:2002,
  author = {H.-D. Burkhard and U. Düffert and J. Hoffmann and M. Jüngel and M. Lötzsch and R. Brunn and M. Kallnik and N. Kuntze and M. Kunz and S. Petters and M. Risler and O. v. Stryk and N. Koschmieder and T. Laue and T. Röfer and K. Spiess and A. Cesarz and I. Dahm and M. Hebbel and W. Nowak and J. Ziegler},
  title = {German Team 2002},
  year = {2002},
  note = {178 Seiten},
  type = {Technical Report of the RocoCup-Team in the Sony Legged Robot League},
  institution = {Humboldt-Universität Berlin, Universität Bremen, Technische Universität Darmstadt},
}

@ARTICLE{vonStrykGlocker:2001,
  author = {O. von Stryk and M. Glocker},
  title = {Numerical mixed-integer optimal control and motorized traveling salesmen problems},
  journal = {APII-JESA (Journal europeen des systemes automatises - European Journal of Control)},
  year = {2001},
  volume = {35},
  number = {4},
  pages = {519-533},
  pdf = {2001-vonstryk-glocker.pdf},
  abstract = {A general approach for the numerical solution of hybrid, mixed-integer optimal control problems is presented. In an outer level iteration a branch-and-bound procedure is applied to search the entire feasible discrete variable space. An inner level iteration contains for each actual value of the discrete variable a continuous nonlinear optimal control problem with its nonlinear dynamics defined in multiple phases and phase transitions occuring at unknown switching points (events) which must be solved numerically subject to nonlinear constraints. For this purpose, a robust and efficient direct collocation method is employed that parameterizes both the continuous state and control variables and exploits the sparse structure in the resulting nonlinearly constrained optimization problems. The proposed approach is successfully applied to two new hybrid optimal control benchmark problems for a motorized traveling salesman and for a team of two cooperating, motorized salesmen.},
}

@INPROCEEDINGS{ISNM:2001,
  author = {U. Rettig and O. von Stryk},
  title = {Numerical optimal control strategies for semi-active vehicle suspension with electrorheological fluid dampers},
  year = {2001},
  volume = {138},
  pages = {221-241},
  publisher = {Birkhäuser Verlag},
  editor = {K.-H. Hoffmann, R.H.W. Hoppe, V. Schulz},
  series = {International Series in Numerical Mathematics},
  booktitle = {Fast Solution of Discretized Optimization Problems},
  pdf = {2001-rettig-vonstryk.pdf},
}

@INPROCEEDINGS{CACE:2001,
  author = {A. Kröner and T. Kronseder and G. Engl and O. von Stryk},
  title = {Dynamic optimization for air separation plants},
  year = {2001},
  pages = {433-438},
  month = {May 27-30},
  publisher = {Elsevier},
  editor = {R. Gani, S.B. Jorgensen},
  address = {Kolding, Dänemark},
  booktitle = {Proc. European Symposium on Computer Aided Process Engineering (ESCAPE-11)},
}

@INPROCEEDINGS{LNCSE:2001,
  author = {T. Kronseder and O. von Stryk and R. Bulirsch and A. Kröner},
  title = {Towards nonlinear model-based predictive optimal control of large-scale process models with application to air separation plants},
  year = {2001},
  pages = {385-410},
  publisher = {Springer Verlag},
  editor = {M. Grötschel, S.O. Krumke, J. Rambau},
  address = {Heidelberg},
  booktitle = {Online Optimization of Large Scale Systems},
  url = {http://www.zib.de/dfg-echtzeit/Publikationen/Preprints/Preprint-01-14.html},
  pdf = {2001-kronseder-etal.pdf},
}

@INPROCEEDINGS{LNAI:2002,
  author = {R. Brunn and U. Düffert and M. Jüngel and T. Laue and M. Lötzsch and S. Petters and M. Risler and T. Röfer and K. Spiess and A. Sztybryc},
  title = {GermanTeam 2001},
  year = {2001},
  volume = {2377},
  pages = {705-708},
  publisher = {Springer-Verlag},
  editor = {A. Birk, A. Coradeschi, S. Tadokoro},
  booktitle = {RoboCup 2001: Robot Soccer World Cup V. - Lecture Notes in Artificial Intelligence},
  pdf = {2001-GermanTeam2001.pdf},
  abstract = {The GermanTeam is the successor of the Humboldt Heroes who already participated in the Sony Legged Robot League competitions in 1999 and 2000. Because of the strong interest of other German universities, in March 2001, the GermanTeam was founded. It consists of students and researchers of five universities: Humboldt-Universität zu Berlin, Universität Bremen, Technische Universität Darmstadt, Universität Dortmund, and Freie Universität Berlin. However, for the system presented in this document, the Humbold Heroes only had reinforcements from Bremen and Darmstadt. The two other universities will actively participate with the beginning of the winter semester.},
}

@INPROCEEDINGS{AISDG:2001,
  author = {M.H. Breitner and U. Rettig and O. von Stryk},
  title = {On optimal missile guidance upgrades with dynamic Stackelberg game linearizations},
  year = {2001},
  volume = {6},
  pages = {277-294},
  publisher = {Boston, Basel, Berlin: Birkhäuser},
  editor = {E. Altman, O. Pourtallier},
  booktitle = {Advances in Dynamic Games and Applications. Annals of the International Society of Dynamic Games},
}

@TECHREPORT{GT:2001,
  author = {H.-D. Burkhard and U. Düffert and M. Jüngel and M. Lötzsch and N. Koschmieder and T. Laue and T. Röfer and K. Spiess and O. von Stryk and A. Sztybryc and R. Brunn and M. Risler},
  title = {GermanTeam 2001},
  year = {2001},
  note = {41 Seiten},
  type = {Technical Report of the RocoCup-Team in the Sony Legged Robot League},
  institution = {Humboldt-Universität Berlin, Universität Bremen, Technische Universität Darmstadt},
  pdf = {2001-GermanTeam2001report.pdf},
  abstract = {The GermanTeam is a joint project of several German universities in the Sony Legged Robot League. This report describes the software developed for the RoboCup 2001 in Seattle. It presents the software architecture of the system as well as the methods that were developed to tackle the problems of motion, image processing, object recognition, self-localization, and robot behavior. The approaches for both playing robot soccer and mastering the challenges are presented. In addition to the software actually running on the robots, this document will also give an overview of the tools the GermanTeam used to support the development process.},
}

@INPROCEEDINGS{LNCSE:2001-2,
  author = {T. Binder and L. Blank and H.G. Bock and R. Bulirsch and W. Dahmen and M. Diehl and T. Kronseder and W. Marquardt and J.P. Schlöder and O. von Stryk},
  title = {Introduction to model based optimization of chemical processes on moving horizons},
  year = {2001},
  pages = {295-339},
  publisher = {Springer Verlag},
  editor = {M. Grötschel and S.O. Krumke and J. Rambau},
  address = {Heidelberg},
  booktitle = {Online Optimization of Large Scale Systems},
  pdf = {2001-binder-etal.pdf},
}

@INPROCEEDINGS{2000:Glocker-vonStryk-SFB255,
  author = {M. Glocker and O. von Stryk},
  title = {Trajectory optimization of a shuttle mounted robot},
  year = {2000},
  pages = {71-82},
  month = {Oct 7-8, 1999},
  publisher = {Sonderforschungsbereich 255},
  address = {Greifswald},
  booktitle = {Optimalsteuerungsprobleme in der Luft- und Raumfahrt (Optimal Control Problems in Aeronautics and Astronautics)},
  organization = {Technische Universitaet Muenchen},
  pdf = {2000-Glocker-vonStryk-SFB.pdf},
  abstract = {Optimal path planning for a shuttle mounted remote manipulator system is investigated. Shuttle, robot and load are modelled as a multi-body system of rigid bodies whereby computer-aided modelling is used to dervive the equations of motion. Minimum time and minimum energy trajectories of the robot are investigated which re-establish the shuttle"s attitude at the beginning of the maneuver also at the end. The resulting constrained optimal control problems are solved by a recent version of the optimal control software DIRCOL [12] which is based on discretization of state and control variables, collocation and nonlinear programming (NLP). An improvement of internal gradient approximations, the full utilization of the discretized problem structure as well as of the sparsity of the NLP Jacobian are important factors improving the efficiency and robustness of the method. The resulting NLPs are solved by a recent version of the large-scale SQP method SNOPT [5]. A three-dimensional animation of the space robot trajectories is obtained using the graphics library SIGMA [1].},
}

@INPROCEEDINGS{vonStrykGlocker:2000,
  author = {O. von Stryk and M. Glocker},
  title = {Decomposition of mixed-integer optimal control problems using branch and bound and sparse direct collocation},
  year = {2000},
  pages = {99-104},
  month = {September 18-19},
  publisher = {Shaker},
  editor = {S. Engell, S. Kowalewski, J. Zaytoon},
  address = {Aachen},
  booktitle = {ADPM 2000 - The 4th International Conference on Automation of Mixed Processes: Hybrid Dynamic Systems},
  pdf = {2000-vonstryk-glocker.pdf},
  abstract = {A large class of optimal control problems for hybrid dynamic systems can be formulated as mixed-integer optimal control problems (MIOCPs). It is the intrinsic combinatorial complexity, in addition to the nonlinearity of the continuous, multi-phase optimal control problems that is largely responsible for the challenges in the theoretical and numerical solution of MIOCPs. We present a new decomposition approach to numerically solving fairly general MICOPs with binary control variables. A Branch and Bound (B&B) technique is applied to efficiently search the entire discrete solution space performing a truncated binary tree search for the discrete variables maintaining upper and lower bounds on the performance index. The partially relaxed binary variables at an inner node define an optimal control problem with dynamic equations defined in multiple phases. Its global solution provides a lower bound on the performance index for all nodes of the subtree. If the lower bound for a given subtree is greater than the current global upper bound then that entire subtree need no longer be searched. The many optimal control problems with nonlinear, continuous state dynamics defined in multiple phases subject to nonlinear constraints are solved most efficiently by a sparse direct collocation transcription. Hereby, the multi-phase optimal control problem is transcribed to a sparse, large-scale nonlinear programming problem being solved efficiently by a tailored SQP method. Despite the high efficiency of the sparse direct collocation method, the efficiency of the decomposition technique for MIOCPs strongly depends on the determination of good lower and upper bounds on the performance index being used to fathoming entire subtrees throughout the binary tree search. The proposed approach is successfully applied to two new benchmark problems for hybrid optimal control: a motorized traveling salesman and a team of two cooperating, motorized salesmen.},
}

@INPROCEEDINGS{LAM:2000,
  author = {R.H.W. Hoppe and G. Mazurkevitch and U. Rettig and O. von Stryk},
  title = {Modeling, simulation and control of electrorheological fluid devices},
  year = {2000},
  pages = {251-276},
  note = {Preprint SFB-438-9917, Sonderforschungsbereich 438, Technische Universität München -- Universität Augsburg (1999), 26 S.},
  publisher = {Springer-Verlag},
  editor = {H.-J. Bungartz, R.H.W. Hoppe, Chr. Zenger},
  booktitle = {Lectures on Applied Mathematics},
  url = {http://www-lit.mathematik.tu-muenchen.de/veroeff/html/SFB/992.34006.html},
  pdf = {1999-hoppe-etal.pdf},
}

@ARTICLE{HeimvonStryk:2000,
  author = {A. Heim and O. von Stryk},
  title = {Trajectory optimization of industrial robots with application to computer-aided robotics and robot controllers},
  journal = {Optimization},
  year = {2000},
  volume = {47},
  pages = {407-420},
  pdf = {1999-heimvstryk.pdf},
}

@INPROCEEDINGS{CLAWAR:2000,
  author = {M. Hardt and O. von Stryk},
  title = {Towards optimal hybrid control solutions for gait patterns of a quadruped},
  year = {2000},
  pages = {385-392},
  month = {Oktober 2 - 4},
  publisher = {Bury St. Edmunds and London, UK: Professional Engineering Publishing},
  editor = {M. Armada, P. Gonzalez de Santos},
  address = {Madrid},
  booktitle = {Proc. CLAWAR 2000 - 3rd International Conference on Climbing and Walking Robots},
  url = {http://www.iai.csic.es/clawar2000/},
  pdf = {2000-clawar.pdf},
  abstract = {We consider the problem of finding optimal gaits for a quadruped robot. Paths are sought which minimize the actuation energy required for walking in an attempt to approximate natural motion. The number of possible gaits for a quadruped is quite large when one considers varied orders of leg motion, different liftoff times, and various ground contact combinations for the legs. The problem is treated as a fully nonlinear optimal hybrid path planning problem on a 22-dimensional state space. Modeling aspects, our numerical approach, and experimental results are discussed in this paper.},
}

@INPROCEEDINGS{LNCS:2000,
  author = {T. Butz and O. von Stryk and T.-M. Wolter},
  title = {A parallel optimization scheme for parameter estimation in motor vehicle dynamics},
  year = {2000},
  volume = {1900},
  pages = {829-834},
  publisher = {Springer-Verlag},
  editor = {A. Bode and T. Ludwig and W. Karl and R. Wismüller},
  series = {Lecture Notes in Computer Science},
  booktitle = {Euro-Par 2000 - Parallel Processing},
  pdf = {2000-butz_etal.pdf},
}

@ARTICLE{SIAM:2000,
  author = {T. Butz and O. von Stryk and M. Vögel and T.-M. Wolter and C. Chucholowski},
  title = {Parallel parameter estimation in full motor vehicle dynamics},
  journal = {Cover story of SIAM News/Applications on Advanced Architecture Computers},
  year = {2000},
  volume = {33},
  number = {4},
  pages = {1-5},
  month = {May},
  note = { The video of the article is also available from the SIAM website (http://www.siam.org/siamnews/05-00/animations/)},
  pdf = {2000-siamnews.pdf},
}

@ARTICLE{BussvonStrykBulirschSchmidt:2000,
  author = {M. Buss and O. von Stryk and R. Bulirsch and G. Schmidt},
  title = {Towards hybrid optimal control},
  journal = {at-Automatisierungstechnik},
  year = {2000},
  volume = {48},
  number = {9},
  pages = {448-459},
  url = {http://www.oldenbourg.de/cgi-bin/roabstracts?A=1494},
  pdf = {2000-at.pdf},
  abstract = {In this article a general class of hybrid optimal control problems with continuous and discrete state variables and control inputs is defined. After a brief review of conventional optimal control, major novel challenges resulting from the hybrid nature are discussed. Some application problems are comparatively easy to solve because of the fixed or known sequence of discrete events; however, if the number and the sequence of discrete phases is not known a priori, the solution must then be found among a combinatorial number of possible sequence candidates. The article presents several preliminary approaches to the (numerical) solution of hybrid optimal control problems by hybrid dynamic programming, by decomposition using branch-and-bound, or fixing transversality conditions to obtain suboptimal solutions. The last two methods rely on the capabilities of the direct collocation method DIRCOL to solving multi-phase optimal control problems robustly and efficiently. Results obtained by the proposed methods are presented in two examples: an underactuated robotic system with a holding brake as the discrete component, and a hybrid, motorized traveling salesman problem. },
}

@INPROCEEDINGS{1999:Hardt-WS,
  author = {M. Hardt and K. Kreutz-Delgado and J. Helton and O. von Stryk},
  title = {Obtaining minimum energy biped walking gaits with symbolic models and numerical optimal control},
  year = {1999},
  pages = {1-19},
  booktitle = {Prof. Workshop Biomechanics Meets Robotics, Modelling and Simulation of Motion},
  pdf = {1999_Hardt-etal_10.1.1.43.6189.pdf},
}

@TECHREPORT{DIRCOL,
  author = {O. von Stryk},
  title = {User`s Guide for DIRCOL (Version 2.1): A direct collocation method for the numerical solution of optimal control problems},
  year = {1999},
  month = {November},
  address = {Technische Universität Darmstadt},
  institution = {Fachgebiet Simulation und Systemoptimierung},
  pdf = {1999-dircol-2.1-guide-short.pdf},
}

@ARTICLE{vonStrykVoegel:1999,
  author = {O. von Stryk and M. Vögel},
  title = {A guidance scheme for full car dynamics simulations},
  journal = {ZAMM: Zeitschrift für angewandte Mathematik und Mechanik},
  year = {1999},
  volume = {79},
  number = {Suppl. 2},
  pages = {363-364},
  pdf = {1998-gamm.pdf},
}

@TECHREPORT{vonStryk-CCG:1999,
  author = {O. von Stryk},
  title = {Numerische Verfahren zur Parameteridentifikation in Mehrkörpersystemen},
  year = {1999},
  month = {March 8-11},
  note = {64 pages},
  institution = {Manuskript zum Lehrgang TV 1.03 der Carl-Cranz-Gesellschaft e.V., Weßling-Oberpfaffenhofen},
}

@INPROCEEDINGS{LNCSE:1999-2,
  author = {G. Engl and A. Kröner and T. Kronseder and O. von Stryk},
  title = {Numerical simulation and optimal control of air separation plants},
  year = {1999},
  volume = {8},
  pages = {221-231},
  publisher = {Springer-Verlag},
  editor = {H.-J. Bungartz, F. Durst, Chr. Zenger},
  booktitle = {High Performance Scientific and Engineering Computing. Lecture Notes in Computational Science and Engineering},
  pdf = {1998-fortwihr-linde.pdf},
}

@INPROCEEDINGS{LNCSE:1999,
  author = {C. Chucholowski and M. Vögel and O. von Stryk and T.-M. Wolter},
  title = {Real time simulation and online control for virtual test drives of cars},
  year = {1999},
  volume = {8},
  pages = {157-166},
  publisher = {Springer-Verlag},
  editor = {H.-J. Bungartz, F. Durst, Chr. Zenger},
  booktitle = {High Performance Scientific and Engineering Computing. Lecture Notes in Computational Science and Engineering},
  pdf = {1998-fortwihr-tesis.pdf},
}

@ARTICLE{vonStryk:1998,
  author = {O. von Stryk},
  title = {Optimal control of multibody systems in minimal coordinates},
  journal = {ZAMM: Zeitschrift für Angewandte Mathematik und Mechanik},
  year = {1998},
  volume = {78},
  number = {Suppl. 3},
  pages = {1117-1120},
  pdf = {1997-gamm.pdf},
}

@TECHREPORT{KoslikRillvonStrykZampieri:1998,
  author = {B. Koslik and G. Rill and O. von Stryk and D. Zampieri},
  title = {Active suspension design for a tractor by optimal control methods},
  year = {1998},
  note = {23 S., Eingereicht bei: Optimal Control, Applications and Methods},
  type = {Preprint SFB-438-9801},
  institution = {Sonderforschungsbereich 438, Technische Universität München - Universität Augsburg},
  keywords = {optimal active suspension; steady-state LQR problem; closed-loop solution; open-loop solution; direct transcription method},
  pdf = {1998-tractor.pdf},
  abstract = {An active suspension system for improving the ride comfort and safety of a tractor is investigated. The underlying planar dynamic tractor model and a suitable objective for optimal suspension are introduced. The problem of optimal active suspension leads to a linear-quadratic optimal control problem. Classical Linear-Quadratic Regulator (LQR) theory provides a closed-loop control for the steady state problem which is optimal only for an initial disturbance input from the road. A direct transcription method can handle more general disturbances and models but provides only an open-loop solution, where the time history of the optimal control is given along the optimal trajectory for one type of deterministic disturbance and initial value only. Simulation results for two different road disturbances are given comparing both approaches.},
}

@INPROCEEDINGS{HeimvonStryketal:1996,
  author = {A. Heim and O. von Stryk and H.J. Pesch and H. Schäffler and K. Scheuer},
  title = {Parameteridentifikation, Bahnoptimierung und Echtzeitsteuerung von Robotern in der industriellen Anwendung},
  year = {1997},
  pages = {551-564},
  publisher = {Springer},
  editor = {K.-H. Hoffmann and T. Lohmann and W. Jäger and H. Schunck},
  booktitle = {Mathematik - Schlüsseltechnologie für die Zukunft},
  pdf = {1996-bmbf.pdf},
}

@INPROCEEDINGS{BreitnerRettigvonStryk:1997,
  author = {M.H. Breitner and U. Rettig and O. von Stryk},
  title = {Robust optimal control with large neural networks emulated on the neuro-computer board SYNAPSE-PC},
  year = {1997},
  pages = {487-492},
  publisher = {Wissenschaft & Technik, Berlin},
  editor = {A. Sydow},
  booktitle = {Application in Modelling and Simulation},
}

@INPROCEEDINGS{AnzillvonStryk:1994,
  author = {W. Anzill and O. von Stryk},
  title = {Optimum design of microwave oscillators with minimized phase noise},
  year = {1996},
  pages = {301-306},
  publisher = {J. Wiley & Sons Ltd and B. G. Teubner},
  editor = {H. Neunzert},
  booktitle = {Progress in Industrial Mathematics at ECMI 94},
  pdf = {1994-ecmi.pdf},
}

@TECHREPORT{HeimvonStryk:1996,
  author = {A. Heim and O. von Stryk},
  title = {Documentation of PAREST - A multiple shooting code for optimization problems in differential-algebraic equations},
  year = {1996},
  note = {31 Seiten},
  type = {Report TUM-M9616},
  institution = {Mathematisches Institut, Technische Universität München},
  pdf = {1996-parest.pdf},
}

@ARTICLE{AnzillvonStrykBulirschRusser:1994,
  author = {W. Anzill and O. von Stryk and R. Bulirsch and P. Russer},
  title = {Phase noise minimization of microwave oscillators by optimal design},
  journal = {IEEE MTT-S Digest, Orlando, Florida, USA},
  year = {1995},
  pages = {1565-1568},
  pdf = {1995-mtts.pdf},
}

@ARTICLE{BreitnerKoslikvonStrykPesch:1994,
  author = {M. H. Breitner and B. Koslik and O. von Stryk and H. J. Pesch},
  title = {Iterative design of economic models via simulation, optimization and modeling},
  journal = {Mathematics and Computers in Simulation},
  year = {1995},
  volume = {39},
  pages = {527-532},
  month = {Feb. 2-4},
  pdf = {1994-vienna.pdf},
}

@BOOK{1994:vonStrykDISSVDI,
  author = {O. von Stryk},
  title = {Numerische Lösung optimaler Steuerungsprobleme: Diskretisierung, Parameteroptimierung und Berechnung der adjungierten Variablen.},
  year = {1994},
  number = {441},
  publisher = {VDI Verlag},
  editor = { },
  series = {Fortschritt-Berichte VDI, Reihe 8: Meß-, Steuer- und Regelungstechnik},
  address = {Düsseldorf},
  pdf = {1994-diss.pdf},
  pdf_short = {1994-diss-abstract.pdf},
}

@INPROCEEDINGS{vonStrykSchlemmer:1993,
  author = {O. von Stryk and M. Schlemmer},
  title = {Optimal control of the industrial robot Manutec r3},
  year = {1994},
  volume = {115},
  pages = {367-382},
  publisher = {Basel: Birkhäuser},
  editor = {R. Bulirsch, D. Kraft},
  booktitle = {Computational Optimal Control, International Series of Numerical Mathematics},
  pdf = {1993-manutec.pdf},
}

@INPROCEEDINGS{vonStryk:1994,
  author = {O. von Stryk},
  title = {Optimization of dynamic systems in industrial applications},
  year = {1994},
  pages = {347-351},
  month = {Sep. 20-23},
  editor = {H. J. Zimmermann},
  address = {Aachen, Germany},
  booktitle = {Proc. 2nd European Congress on Intelligent Techniques and Soft Computing (EUFIT)},
  pdf = {1994-eufit.pdf},
}

@ARTICLE{KiehlvonStryk:1994,
  author = {M. Kiehl and O. von Stryk},
  title = {Generalized necessary conditions for optimal control problems of Bolza type: theory and application},
  journal = {ZAMM: Zeitschrift für Angewandte Mathematik und Mechanik},
  year = {1994},
  volume = {74},
  number = {6},
  pages = {T591-T593},
  pdf = {1994-ZAMM_Kiehl-vonStryk.pdf},
}

@INCOLLECTION{vonStrykPeschBulirsch:1993,
  author = {O. von Stryk and H. J. Pesch and R. Bulirsch},
  title = {Zeit ist Geld? Nicht für Roboter! },
  year = {1993},
  number = {6},
  pages = {22-23},
  publisher = {Technische Universität München},
  booktitle = {Sonderreihe: Forschung für Bayern},
  pdf = {1993-forbay.pdf},
}

@INPROCEEDINGS{vonStryk:1993,
  author = {O. von Stryk},
  title = {Numerical solution of optimal control problems by direct collocation},
  year = {1993},
  volume = {111},
  pages = {129-143},
  publisher = {Birkhäuser},
  editor = {R. Bulirsch and A. Miele and J. Stoer and K. H. Well},
  series = {International Series of Numerical Mathematics},
  address = {Basel},
  booktitle = {Optimal Control - Calculus of Variations, Optimal Control Theory and Numerical Methods},
  pdf = {1991-dircol.pdf},
  abstract = {By an appropriate discretization of control and state variables, a constrained optimal control problem is transformed into a finite dimensional nonlinear program which can be solved by standard SQP-methods~\cite{Gilletal1986}. Convergence properties of the discretization are derived. From a solution of this method known as direct collocation, these properties are used to obtain reliable estimates of adjoint variables. In the presence of active state constraints, these estimates can be significantly improved by including the switching structure of the state constraint into the optimization procedure. Two numerical examples are presented.},
}

@INPROCEEDINGS{BreitnerKoslikvonStrykPesch:1993,
  author = {M. H. Breitner and B. Koslik and O. von Stryk and H. J. Pesch},
  title = {Optimal control of investment, level of employment and stockkeeping},
  year = {1993},
  pages = {60-63},
  publisher = {Heidelberg: Physica Verlag},
  editor = {A. Bachem and U. Derigs and M. Jünger and R. Schrader},
  booktitle = {Operations Research "93},
  pdf = {1993-koeln.pdf},
}

@INPROCEEDINGS{BulirschNerzPeschvonStryk:1991,
  author = {R. Bulirsch and E. Nerz and H. J. Pesch and O. von Stryk},
  title = {Combining direct and indirect methods in optimal control: range maximization of a hang glider},
  year = {1993},
  volume = {111},
  pages = {273-288},
  publisher = {Basel: Birkhäuser},
  editor = {R. Bulirsch and A. Miele and J. Stoer and K.-H. Well},
  booktitle = {Optimal Control - Calculus of Variations, Optimal Control Theory and Numerical Methods, International Series of Numerical Mathematics},
  pdf = {1993-ISNM_range_maximization.pdf},
  abstract = {When solving optimal control problems, indirect methods such as multiple shooting suffer from difficulties in finding an appropriate initial guess for the adjoint variables. For, this initial estimate must be provided for the iterative solution of the multipoint boundary-value problems arising from the necessary conditions of optimal control theory. Direct methods such as direct collocation do not suffer from this problem, but they generally yield results of lower accuracy and their iteration may even terminate with a non-optimal solution. Therefore, both methods are combined in such a way that the direct collocation method is at first applied to a simplified optimal control problem where all inequality constraints are neglected as long as the resulting problem is still well-defined; Because of the larger domain of convergence of the direct method, an approximation of the optimal solution of this problem can be obtained easier. The fusion between direct and indirect methods is then based on a relationship between the Lagrange multipliers of the underlying nonlinear programming problem to be solved by the direct method and the adjoint variables appearing in the necessary conditions which form the boundary-value problem to be solved by the indirect method. Hence, the adjoint variables, too, can be estimated from the approximation obtained by the direct method. This first step then facilitates the subsequent extension and completition of the model by homotopy techniques and the solution of the arising boundary-value problems by the indirect multiple shooting method. Proceeding in this way, the high accuracy and reliability of the multiple shooting method, especially the precise computation of the switching structure and the possibility to verify many necessary conditions, is preserved while disadvantages caused by the sensitive dependence on an appropriate estimate of the solution are considerably cut down. This procedure is described in detail for the numerical solution of the maximum-range trajectory optimization problem of a hang glider in an upwind which provi~des an example for a control problem where appropriate initial estimates for the adjoint variables are hard to find.},
}

@ARTICLE{vonStrykBulirsch:1992,
  author = {O. von Stryk and R. Bulirsch},
  title = {Direct and indirect methods for trajectory optimization},
  journal = {Annals of Operations Research},
  year = {1992},
  volume = {37},
  pages = {357-373},
  pdf = {1992-directindirect.pdf},
}

@ARTICLE{KiehlvonStryk:1992,
  author = {M. Kiehl and O. von Stryk},
  title = {Real-time optimization of a hydroelectric power plant},
  journal = {Computing},
  year = {1992},
  volume = {49},
  pages = {171-191},
  pdf = {1992-KiehlvonStryk.pdf},
}