Modeling and control of dynamically walking bipedal robots

Abstract

Today’s bipedal robots still cannot compete with humans regarding efficiency, velocity, and robustness of locomotion. Thus, this paper suggests a control concept for dynamic walking based on insights into human motion control. Key features include exploitation of passive dynamics, hierarchical control, and reflexes, while not requiring a full dynamical model.Walking stability is achieved by a set of postural reflexes based on the motion of the extrapolated center of mass. It shows that only a small number of joints must be simultaneously actively actuated during the different phases of walking. Besides the control concept, the anthropomorphic biped model and its properties like compliant actuation are presented as they prove to be essential for the walking performance. Specifically, the approach requires non self-locking and torque-controllable joints with parallel elasticity and low friction, similar to the human muscle-tendon system. The approach is validated for 3D dynamic walking within a physical simulation framework. Results show an efficient, fluent, and fast gait that can cope with considerable disturbances. The resulting joint trajectories show significant resemblance to human walking data.