Walking stability in bipedal robots

Abstract

Stable walking is one of the most important measurement indexes for the movement of bipedal robots.After reviewing the traditional gait stability criterion based on zero moment point (ZMP),the authors analyzed the relationship between ZMP and the center of pressure (COP),and concluded that the ZMP of a bipedal robot is the COP of that bipedal robot if there is neither viscous force nor adsorption force between the biped robot and its horizontal footing.After analyzing differences in humanoid walking gaits caused by differences in supporting surfaces,the authors proposed a method for describing the supporting surface in a way that satisfies regional descriptions of support polygons under conditions of multipoint contact.Based on comprehensive consideration of the position of ZMP/COP and the center of gravity (COG) in the supporting surface,criteria for comprehensive stability were put forward.The results of simulations and experiments show that this method is more accurate than traditional criteria for comprehensive evaluation of a gait's stability.