Variable structure controller with chattering alleviation

A variable structure control scheme that guarantees the smoothness of the control signal and the exponential error convergence for robot manipulators is proposed. The proposed method inserts a low pass filter (LPF) in front of the plant, and a virtual controller is designed for the virtual plant-a combination of the LPF and the robot manipulator. The virtual control signal contains high frequency components due to the switching function. The real control signal, however, always shows a smooth curve since it is an output of the LPF. In addition to the assured smoothness of the control signal, the overall system is in the sliding mode all the time, 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