Periodic stability for 2-D biped dynamic walking on compliant ground

Abstract

The improvement of stability for dynamic biped walking is motivated by the potential use of humanoid robot in complex environment. This paper focuses on the effect of ground compliance on the periodic stability of dynamic walking. Firstly, the compliant ground is equivalent to a spring-damper system, and the coupling dynamics model of robot-ground system is modelled as a rigid planar kinematic chains in contact with a stiffness-damping system. Based on it, two differential equations are obtained to describe the dynamic walking process in one cycle which is separated into a swing phase followed by an impact phase. Subsequently, a stable gait is planned under rigid assumption and transplanted to the walking under compliant ground condition. The effect of ground compliance on the gait during the swing phases is analyzed under 15 kinds of ground conditions, respectively and effect on it during impact phase is analyzed under 12 kinds of ground conditions. Finally, the periodic stability under the effect of ground compliance is analyzed with 6 kinds of ground conditions, and the effect of ground compliance on the periodic stability of dynamic walking is concluded.