Robust control of a MEMS optical switch using fuzzy sliding mode

In this Paper, in order to improve the performance of sliding mode controller, a fuzzy logic sliding mode controller is proposed. The slope of sliding surface is changed based on error and its derivative by a fuzzy logic and reached to the predetermined slope. This decreases reaching phase and speeds up system´s response, and with increasing the slope of the sliding surface, final tracking error decreases. For eliminating the chattering phenomenon, instead of using saturation function, a fuzzy logic algorithm based on surface function is designed. So chattering problem as a result of uncertainty and disturbance is eliminated. In both fuzzy logics, Mamdani-type fuzzy inference is used. Proposed controller is applied to control of a nonlinear MEMS optical switch which is subjected to disturbance. The performance of this controller is compared to sliding mode controller which has same parameters and simulation results indicate the superior performance of the proposed controller.