Variable structure controller for robot manipulators using time-varying sliding surface

The authors propose a variable-structure controller with a time-varying sliding surface for robot manipulators. The time-varying sliding surface ensures the existence of a sliding mode from an initial state, whereas the conventional sliding surface cannot achieve performance robust against parameter variations and disturbances before the sliding mode occurs. Therefore, the error transient can be fully prescribed in advance for all time. The overall system is globally exponentially stable. The efficiency of the proposed method for trajectory tracking has been demonstrated by simulations