Observer based robust force control in cooperative motion systems

This paper is concerned with the realization of a robust force control scheme in the cooperative motion of multiple manipulator systems. The derivation of the control scheme is based on the adoption of a disturbance force observer to the motion control system which is decomposed into trajectory and internal (grasping) force control subsystems. The force disturbance observer provides the system's robustness by compensating the disturbances of system including the variation of system parameters and also by enhancing the decoupled trajectory and internal force motion controllers. The effectiveness of the proposed systems is verified by several experimental results using two units of SCARA manipulators grasping an object and moving the object according to the desired trajectory in free motion condition as well as in the existence of external interaction force.