Experiments in force control of robotic manipulators

A new classification scheme for robotic force control algorithms is presented. It is shown that algorithms can be categorized according to whether they are joint-based or cartesian-based. Further, they can be grouped according to whether the innermost servo loop is based on torque, velocity, or position. For useful force control, closing an inner loop on position can greatly increase disturbance rejection while also allowing for a split rate servo controller to minimize the computational burden. Experimental results from the implementation of a new force feedback method are presented. This cartesian-based method uses an inner loop closed on position and has been implemented on an AdeptOne robot. Bias force application, force searching, and selective compliance about a synthetic remote center compliance (RCC) have all been implemented. Excellent results in free space and in hard contact have been achieved. This technique has been successfully used to assemble parts having 0.001 inch clearances.