Decoupling COG control for redundant biped robot based on null-space disturbance observer

Describes a method to control the center of gravity (COG) of the legs of a biped robot. Each leg is endowed with 4 joints, so that the robot has a redundancy in each leg. In the redundant system, the position and posture of the leg can be controlled independently, with decoupling controller. In the paper, three types of disturbance observer are applied at a controller, and then the decoupled controller is established. Both decoupled motions of the tiptoe and COG are achieved with the disturbance observers