Regulation and force control using sliding modes to reduce rebounds in a mechanical system subject to a unilateral constraint

In this study, a control algorithm is proposed, based on the sliding-mode technique, to regulate a single degree of freedom mechanical system subject to a unilateral constraint. The system may be in non-constrained motion at some time or in constrained motion at some other time. The system motion can be divided in three phases: free motion, constrained motion and transition (from non-constrained to constrained motion and vice versa). Only one control law is designed for the system, regardless of the motion phase. It is shown that the non-linear system is globally asymptotically stable and achieves zero steady-state position error. Numerical and experimental results show the performance of the proposed controller.