Experiments on impedance control of redundant manipulators

In the paper, the authors present experimental results of force control using a planar 4 DOF redundant robot. A globally stable impedance force control law is used to control force and trajectory in the operational space. Redundancy is solved by the gradient optimization technique using a dynamically consistent pseudo-inverse. In the authors´ case, they implemented three optimization criteria-obstacle avoidance, torque optimization and singularity avoidance. The desired null space motion is controlled with a new formulation of the null space velocity controller, that assures globally stable behaviour in null space.