Speed Control Of Permanent Magnet Synchronous Motor Based On Sliding Mode Variable Structure

In recent years,due to the decline in the price of rare earth materials,permanent magnet synchronous motor(PMSM)has become the mainstream of the field of motor drive.It is widely used in vehicles,aerospace and medical fields.Conventionally,PI is generally used to control the speed of permanent magnet synchronous motor.However,PI is very susceptible to changes in motor parameters and external interference because of the strong coupling and non-linearity.So it cannot meet the high requirement of accuracy in some occasions.Sliding mode control begin to replace the PI based on its strong robustness and it has aroused the concern of researchers.In this paper,to improve the permanent magnet synchronous motor control performance,sliding mode speed controller is designed according to the principle of sliding mode control.The main contents are as follows.The Simulink simulation model of permanent magnet synchronous motor is built according to the mathematical model of PMSM and the realization process of vector control.This paper presents a new approximation law based on the analysis of the principle of sliding mode control to weaken the chattering.By comparison with constant velocity law,the theory is analyzed and the stability is also proved.The simulation verifies its superiority to traditional PI control.In this paper,the influence of external disturbance on the performance of the motor is analyzed,and a method of estimating the external disturbance is proposed by using the extended state observer.The control performance can be improved effectively by compensate for the disturbance.To reduce the influence of moment of inertia on the control performance,this paper presents a new method to estimate the moment of inertia by observer.The bad consequences caused by the change of moment of inertia is effectively eliminated by applying the estimated value to design the controller.To verify the validity of the proposed method,a test stand is set up.By the comparison experiment,the effectiveness is proved.