Hybrid impedance control of redundant manipulators: An approach to decouple task space and null space motions

In this paper, an approach to resolve the kinematic redundancy and to contr ol the motion/force of redundant manipulators is presented using the concep t of a quasi-coordinate. Using this factorization, we can transform the joi nt space dynamics into a new decoupled form with dimensional consistency. T hen by extracting the minimal null-motion component to control the internal motion of redundant manipulator, inertial decoupling of the task space and null-space motions for redundant manipulator is achieved. Combining the ex tracted null-motion component and task space variables, an extended Jacobia n is constructed and using this extended Jacobian, we devise a new hybrid i mpedance controller for redundant manipulator. The unique feature of this c ontroller is the ability to directly control the null space motion which is known to have strong effect on performance of task space motion. Some nume rical examples are given to demonstrate the performance of the proposed con trol method.