A reactive stepping algorithm based on preview controller with observer for biped robots

Abstract

Reactive stepping is an important utility to regain balance when bipedal walking motions are disturbed. This paper sheds light on the reasons for humanoid robots to fall down. It presents a method to calculate modifications of predefined foot placements with the objective to minimize deviations of the Zero Moment Point from a reference without interrupting the walk. The calculation is in closed-form, and is embedded into a well-evaluated preview controller with observer based on the 3D Linear Inverted Pendulum Mode (3D-LIPM). Experiments in simulation and on a physical robot prove the benefit of the proposed system.