Whole-body walking pattern using pelvis-rotation for long stride and arm swing for yaw angular momentum compensation

A long stride can enable a humanoid robot achieve fast and stable walking. For a long stride, the kinematics of the robot should be fully utilized, and walking with pelvic rotation can be a solution. A rotational trajectory of pelvis considering kinematic limitations is needed for pelvis-rotation walking. When the robot walks with a long stride while rotating the pelvis, the yaw momentum may be larger than that when walks with the pelvis fixed. This is caused by the rotation of the pelvis and leg motion, and hence, walking with pelvic rotation may become unstable. In this paper, we propose to control the lower body of a robot as a redundant system with leg joints and a waist joint for walking with pelvic rotation. The position of the base frame to implement the redundant system for the lower body of the robot is also proposed. In addition, the a quadratic programming (QP) controller is formulated to enable arm swing for yaw momentum compensation while controlling the lower body. The feasibility of the proposed control method was verified using a simulation and an experiment of walking with a long stride while rotating the pelvis using a QP controller and compensating the yaw momentum by means of arm swing.