Adaptive fuzzy variable structure control of induction motors

In variable structure sliding mode control schemes, one has to adjust the controller gains in order to obtain an acceptable response. The controller gains are required to be readjusted under variation of the disturbance load torque and/or of the parameters of the induction motor. To compensate automatically for the uncertainties experienced by the system, the controller gains are adjusted by a fuzzy inference mechanism. Furthermore, an adaptive fuzzy sliding mode controller is proposed. It combines the merits of sliding mode control, fuzzy inference mechanism and the adaptive algorithm. First, a sliding mode controller is designed, and then a fuzzy inference mechanism is used to compensate for the uncertainties experienced by the system by adjusting the reaching rates of the sliding mode controller. Finally an adaptation algorithm is used to adjust the centers of the fuzzy sets in order to reduce the control effort and chattering. Simulation results verify the effectiveness of the proposed algorithm.