Null space damping method for robust controlled redundant manipulator

This paper describes a decoupling control and null space damping strategy of redundant manipulator by disturbance observer. In the robot based on the joint space disturbance observer, equivalent mass matrix, which represents the virtual mass of the manipulator in operational space, is defined independently of the dynamics of the manipulator. And the disturbance force is defined in workspace. So the disturbance observer in workspace and jointspace can be applied to the redundant manipulator simultaneously. This feature makes it easy to realize the decoupling force controller and to simplify the inverse kinematics problem including the null space damping. Several numerical results are shown to confirm the validity of the proposed method.