Asynchronous Motor DTC System Based On Sliding Mode And Fuzzy Control

With the development of the control strategy for AC motor drives, the direct torque control(DTC) scheme has aroused the concern of scholars. It has the fast torque response and simple control structure, excellent dynamic and static performance, etc. DTC does not require complicated rotating coordinate transformation, but based on the error of flux linkage and torque directly on the flux and torque control. However, the high current and torque ripple is the major problem of traditional DTC.To solve the current and torque ripple problem of traditional DTC, a fuzzy torque hysteresis controller is designed to adjust the bandwidth of torque hysteresis controller based on fuzzy control strategy. Besides, the sliding mode control(SMC) strategy is applied to the system to reduce the current and torque ripple. Although the SMC strategy effectively makes up the shortcomings of the traditional DTC, it also introduces the chattering phenomenon of the system. In this paper, an adaptive sliding mode controller is designed to reduce the chattering phenomenon and the current and torque ripple. And we build the Matlab/Simulink model to verify the effectiveness of the proposed control system. The main content of this paper is as follows:First, we review the research status and background of this topic.Second, the basic principle of induction motor DTC system is introduced. Then, we build the Matlab/Simulink model of traditional DTC system.Third, a fuzzy torque hysteresis controller is designed to replace the traditional three-level torque hysteresis controller based on fuzzy control strategy. The comparison experiments are done in Matlab/Simulink environment and the results show that the controller can effectively reduce the torque ripple of the system.Fourth, the theory of the sliding mode control is introduced. A sliding mode speed controller is designed to replace the traditional PID controller. Then, an adaptive sliding mode controller is presented to reduce the chattering phenomenon of the system based on the adaptive and sliding mode control strategy. The simulation results show that the presented strategy can effectively reduce the chattering and the torque ripple of the system.At last, a sliding load torque observer is used to enhance the load disturbance rejection ability of the control system based on sliding mode control strategy. The presented observer has a good control performance and disturbance rejection ability.The simulation and experiments results show that the proposed scheme has a good control effect and good application prospect.