Pseudo virtual passive dynamic walking and effect of upper body as counterweight

This paper investigates the effect of an upper body on efficient dynamic bipedal walking utilizing its natural dynamics. We introduce an upper body as a one-link torso and add it to a simple biped model by means of a bisecting hip mechanism (BHM). We first mathematically analyze the effect of the upper body with the BHM as a counterweight and discuss how it affects natural swinging motion of the swing leg. Second, we propose a simple method for generating efficient dynamic bipedal gait imitating the property of virtual passive dynamic walking, and numerically analyze the gait efficiency. Simulation results show that the walking system exhibits period-doubling bifurcation, and we discuss how the efficiency changes in the multiple-period gait.