Bipedal Locomotion Control Based on Simultaneous Trajectory and Foot Step Planning

This paper proposes a trajectory planner for bipedal locomotion that determines a center-of-mass (CoM) trajectory, footsteps, and step durations simultaneously. Trajectory planning based on a linear inverted pendulum model is formulated as a nonlinear constraint satisfaction problem. The proposed iterative constraint solving algorithm is able to solve this problem in a short amount of time so that trajectory replanning at every walking step is possible. Unlike existing planning methods that determine footsteps and a CoM trajectory sequentially under fixed walking period, the proposed planner can produce complex walking patterns that fully utilize the interdependency of these physical quantities. The proposed trajectory planner and a trajectory tracking controller is implemented on a real robot and their performance is evaluated.