A robust impedance control strategy for redundant manipulator

In this paper, an impedance control strategy for a redundant manipulator based on a workspace observer is proposed. The calculation of the impedance controller becomes more complicated as the number of the degree-of-freedom increases because the pseudo inverse Jacobian matrix is generally used. To improve this problem, the disturbance observer is applied to each joint to eliminate the dynamical effects. This makes it easy to realize virtual impedance control in the joint space. Furthermore the workspace observer is applied to obtain the decoupled impedance response in the workspace. In this case, virtual impedance of each joint works as null space effect in the workspace response. This means that our approach realizes the null space impedance effect without much effort to calculate the null space term (I-J⁺ J). The validity of the proposed method is confirmed by the experimental results in the 3-link planar redundant manipulator