Yet another humanoid walking - passive dynamic walking with torso under simple control

Passive Dynamic Walking (PDW) has been receiving increasing attention as a simple walking method with no or less control, therefore no or less energy consumption. To the best of our knowledge, there are no PDW models with a torso although there have been already many studies on PDW. This paper presents the first step towards applying the PDW principle to humanoid robots by adding a torso to a conventional PDW model. The computer simulation shows that, only with a simple PD control applied between the torso and the stance leg to stand the torso up, the walking of the PDW robot converges at a stable gait cycle. Three attempts to reduce the torque to stand the torso up succeeded. Changing the mechanical properties of the robot itself with the same controller makes it possible to suppress the torque to stand the torso up: changing the posture of the torso, adding the soft leg tips, and changing the curvature of the sole. Computer simulation results are shown and discussion is given.