Research On Permanent Magnet Synchronous Motor Speed Control System Based On Improved Sliding Mode Variable Structure

In industrial production,permanent magnet synchronous motor(PMSM)are widely used due to their simple structure,high power density and fast dynamic response.The traditional motor speed control systems are controlled by PI control,but are susceptible to environmental influence.Sliding mode variable structure because of its insensitivity to parameter disturbance and strong robustness,it gradually replaces the PI control application in the motor speed control system.However,the traditional sliding mode variable structure method will cause the system to vibrate,affect the control effect,it is attach great significance to design a high-performance motor speed control system based on sliding mode control.Based on the traditional sliding mode control method,an improved method of the speed control system is proposed to achieve the goal of fast response,no overshoot,strong anti-interference ability and no error in tracking the given speed.Firstly,on the basis of reading a large number of literature,a fast power reaching law with variable exponent is designed.In the classical control system,the control effect of variable exponential fast power reaching law is simulated and compared with that of exponential and power reaching law.The superiority of variable exponential fast power reaching law is verified.Based on the improved reaching law,the sliding mode speed controller of PMSM speed control system is designed,and the stability is verified.The simulation model of the improved sliding mode speed controller is built.Then,the sliding mode observer(SMO)in the traditional position sensorless control has the phenomenon of buffeting when detecting the back electromotive force and affects the estimation accuracy of the rotor.The characteristics of the function curve of the saturation function,hyperbolic tangent function and combined power fumction are analyzed.It is concluded that the characteristics of the combined power function are more in line with the characteristics of sliding mode control.So the combined power function is chosen to replace the symbolic function to design the improved sliding mode observer,and the discrete sliding mode observer model is built.Because the fractional order theory can provide multiple characteristics of self-adjustment,the combination of fractional order-phase locked loop(FO-PLL)is used instead of the inverse tangent function to estimate the rotor position.Finally,the proposed improved method is verified by simulation in MATLAB/Simulink.The simulation results show that the permanent magnet synchronous motor speed control system based on improved sliding mode speed controller has good dynamic and static performance in tracking speed,suppressing chattering and eliminating external load disturbance.It has strong robustness and self-control adaptability.The position sensoless control technology based on improved sliding mode observer and fractional phase-locked loop has smaller back-EMF chattering and smoother curve than traditional position sensorless control technology.The error between rotor position estimation and actual value is small.It is indicating that the improved method has high observation accuracy.