Sliding mode controller with filtered signal for robot manipulators using virtual plant controller

A sliding mode control scheme that guarantees smoothness of the control signal and exponential error convergence is proposed for robot manipulators. The proposed method inserts a low pass filter (LPF) in front of the plant, and the virtual controller is designed for the virtual plant-the combination of the LPF and the robot manipulator. The virtual control signal contains high frequency components because of a switching function. The real control signal, however, always shows a smooth curve since it is an output of the LPF. In addition to the smoothness of the control signal always being assured, the overall system is in sliding mode at all times, i.e. its performance is always invariant under the existence of parameter uncertainties and external disturbances. The closed-loop system is shown to be globally exponentially stable. (C) 1997 Elsevier Science Ltd.