Vibration suppression control of redundant manipulator with flexible structure by considering nullspace motion

A redundant manipulator is useful for posture control while maintaining the desired end-effector position by using its redundancy. This makes it possible to perform agile motions such as obstacle avoidance while achieving the target task. However, as the number of degrees of freedom of motion increases, the stiffness of the redundant manipulator decreases, which induces unacceptable vibration in manipulator motion. To address this issue, this paper describes a strategy of vibration suppression by using a workspace observer and resonance ratio control based on nullspace control. The validity of the proposed approach is confirmed by simulations and experiments.