@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{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.},
}

@PHDTHESIS{2015:PhD-Thesis-Scholz,
  author = {Dorian Scholz},
  title = {On the Design and Development of Musculoskeletal Bipedal Robots},
  year = {2015},
  month = {August 18},
  school = {Technische Universitaet Darmstadt, Department of Computer Science},
  url = {http://tuprints.ulb.tu-darmstadt.de/5628/},
}

@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.},
}

@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: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.},
}

@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.},
}

@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{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{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. },
}

@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{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{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. },
}

@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.},
}

@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. },
}

@MASTERSTHESIS{scholz2008,
  author = {Dorian Scholz},
  title = {Modulare und plattformunabhängige dynamische Bewegungserzeugung für autonome mobile humanoide Roboter},
  year = {2008},
  school = {Technische Universitaet Darmstadt, Department of Computer Science},
  keywords = {Bewegungserzeugung, Humanoid Motion Generation},
  pdf = {2008-scholz.pdf},
  abstract = {Im Rahmen dieser Diplomarbeit wurde eine Software zur Echtzeitsteuerung und -regelung von Robotern entwickelt. Zum Einsatz kommt die Software auf einem Mikrocontroller zur Ansteuerung der Aktoren und Sensoren auf humanoiden Robotern. Implementiert wurde ein plattformunabhängiges Basissystem und Bib- liotheken zur Plattformabstraktion für mehrere Systeme. Unterstützte Plattformen sind zwei verschiedene Mikrocontroller-Systeme, sowie PCs mit Windows oder Linux und ein Simulator. Das System ist modular aufgebaut und beinhaltet mehrere Bewegungsmodule. Einen Schwerpunkt bilden das Laufmodul und die Balanceregelung. Weiterhin wurde zu Debugging- und Visualisierungszwecken eine gra?sche Benutzerober?äche implementiert, die mit dem System über eine serielle Verbindung kommuniziert.},
}