Decoupling force and position control in constrained motion with friction

This paper deals with the force/position control of constrained mechanical systems subjected to uncertainties and disturbances of various nature, including friction. The hybrid control problem with continuous active forces and discontinuous friction disturbance is addressed in the paper by exploiting the robustness properties of the second-order sliding-mode control algorithms. An algorithm of this kind is proved to be effective to avoid complex stick-slip phenomena and to attain, by suitably choosing the sliding surfaces, a dynamic decoupling of the force and position control tasks during constrained motion with friction.