Footstep Modification Including Step Time and Angular Momentum Under Disturbances on Sparse Footholds

Abstract

Maintaining dynamic balance is an important requirement for bipedal robots. To deal with large disturbances, the footsteps need to be modified depending on the disturbance. Currently, there are few methods that determine footsteps by considering foothold constraints and the balance of the robot. In this paper, we propose a footstep modification method that considers the steppable region. In certain situations, robots cannot maintain balance due to the limitations of the landing position on sparse footholds, such as stepping stones. Therefore, our proposed method modifies not only the step position, but also the step timing and the angular momentum, and balance can be maintained even on the footholds where the steppable region is strictly limited. These walking parameters are analytically calculated by representing the steppable region as convex hulls and applying our previously utilized method. We verified the effectiveness of the proposed method in an experiment where a life-sized humanoid robot walked on stepping stones consisting of unsteady blocks and was able to recover when pushed.