In this paper, we present a speed fuzzy sliding mode control for a direct torque controlled double star induction motor (DSIM). Direct torque control (DTC) uses only a couple of hysteresis comparators to perform both torque and flux dynamic control. The proposed control scheme utilizes a fuzzy sliding mode controller (FSMC) for the speed control. The FSMC is formed with the robustness of sliding mode control (SMC) and the smoothness of fuzzy logic (FL). Few fuzzy rules are used for this strategy control. The sliding mode control is used to achieve robust performance against parameter variations and external disturbances. The problem with this conventional controller is that it has large chattering on the torque and the drive is very noisy. In order to reduce chattering, the sign function is substituted with a fuzzy control law which draws the system state variables into prespecified bounds of sliding mode surface. The computer simulations are conducted to demonstrate the satisfactory tracking performance and robustness of the control with reduced chattering problem.

Keywords: Double star induction motor (DSIM), Direct torque control (DTC), Sliding mode control (SMC), Fuzzy logic controller (FLC), Fuzzy sliding mode controller (FSMC), Flux and torque estimators