PDAC-based Underactuated 3D Bipedal Walking- Stabilization of PDAC Constants and Walking Direction Control-

Abstract — This paper proposes a three-dimensional biped dynamic walking algorithm based on Passive Dynamic Au-tonomous Control (PDAC) which is previously proposed. The robot dynamics is modeled as an autonomous system of a three-dimensional inverted pendulum by applying the PDAC concept that is based on the assumption of point contact of the robot foot and the virtual constraint as to robot joints. Due to autonomy, there are two conservative quantities named “PDAC constant”, that determine the velocity and direction of the biped walking. We also propose the convergence algorithm to make PDAC constant converge to arbitrary value, so that walking velocity and direction is controllable. Numerical simulation results validate proposed algorithm. I