Underactuated virtual passive dynamic walking with an upper body

Achieving energy-efficient dynamic walking has become one of the main subjects of research on robotic bipedal locomotion. Approaches based on passive-dynamic walkers can accomplish bipedal locomotion. However, passive dynamic walking has only been studied with the legs, and the effect of an upper body has not been clarified. This paper investigates the effect of an upper body on the efficiency and stability of dynamic bipedal locomotion based on observations. We first investigated a suitable upper body, which was a simple 1-link torso with a bisecting hip mechanism that would not destroy natural dynamics of the biped model. Second, we analyzed the robot's driving mechanism and chose underactuated virtual passive dynamic walking as the method for generating an efficient dynamic gait. We confirmed that efficient dynamic walking was possible with a specific resistance of 0.01 and investigated the effect of the physical parameters of the upper body through numerical simulations.