An adaptive sliding-mode approach for force/motion control of manipulators under holonomic constraints

This paper deals with the sliding-mode position/force control of constrained-manipulator systems, in which the constraints are supposed to be holonomic. An adaptive version of the controller is used for an on-line estimation of the unknown parameters. Because of this, no a priori knowledge of the bounds of unknown parameters is required. The algorithm guarantees asymptotic stability of the global system, a zero tracking error for both position and force vectors and robustness against parameter uncertainties and external disturbances. If the model of the system is well-known, force feedback is not necessary to achieve zero-error force convergence. Through a small modification of the control law, the chattering phenomenon associated with the torques applied to joints is avoided.