Sliding-Mode Force Control of Manipulators

Abstract

Department of Electrical and Control EngineeringNational Chiao Tung UniversityHsinchu, Taiwan, R.O.C.(Received March 3, 1998; Accepted August 3, 1998)ABSTRACTThis paper presents robust motion and force control of a robotic manipulator to deal with systemand environment uncertainties using the sliding mode approach. The dynamic model is modified to containtwo sets of state variables, where one describes the constrain motion and the other describes the uncon-strained motion. This force control scheme is a position-based sliding mode technique and consists oftwo feedback loops. A simple force compensator in the outer loop modifies the end-effector positionbased on the sensed contact force and the desired force. A sliding mode controller in the inner loop producesthe joint torque required to track the modified trajectory. This algorithm is able to achieve excellent positionand force with unknown environmental stiffness. Simulation results are included to demonstrate the successof the proposed controller.Key Words: sliding mode, force componsator, force control, robot