An adaptive force position regulator for robot manipulators

An adaptive force/position regulator for robot manipulators in contact with an elastically compliant surface is proposed in this paper. The controller consists of a PD action on the position loop, a PI action on the force loop, together with estimated gravity compensation and desired contact force feedforward. The closed-loop system is shown to have a unique equilibrium state and asymptotic stability in the neighbourhood of this state is proven via the classical Lyapunov method. To cope with imperfect gravity compensation, the controller is made adaptive with respect to a suitable set of parameters in the gravity term. Numerical case studies are developed for a three-joint elbow manipulator.