Research On Sensorless Control Strategy Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor(PMSM)is widely used in electric vehicles,aerospace,deep sea exploration and other fields in recent years because of its high power factor,simple structure and easy control.As one of the classical control algorithms,PI algorithm is often used to design PMSM speed controller,but the control algorithm can not fully meet the complex and variable system.Obtaining accurate rotor speed and position information is an important condition to ensure the efficient control of the motor.The traditional method uses mechanical sensors to obtain the rotor speed and position,but the existence of mechanical sensors will not only increase the production cost of the control system,but also reduce the control accuracy of the system.In order to overcome the above two problems,this paper studies the PMSM speed control system and sensorless control technology.Based on the basic structure of PMSM and the corresponding relationship between physical parameters,the decoupling equations of PMSM in different coordinate systems are deduced,the rotor flux oriented control strategy based on PMSM is established,and the mathematical model based on SVPWM technology is established.The principle of sliding mode reaching law is described,and the defects of traditional exponential reaching law are analyzed.Based on the traditional exponential reaching law,an improved variable speed reaching law is proposed,which can suppress chattering and improve starting speed,and solve the problems existing in the traditional exponential reaching law.Based on the improved variable speed reaching law,a speed controller is designed,which is effectively applied in PMSM speed control system.The PMSM sliding mode observer is studied,and the defects of traditional sliding mode observer are pointed out.By using sigmoid function,variable cut-off frequency low-pass filter and PLL algorithm to improve the traditional observer,an improved sliding mode observer is constructed.The simulation models of the improved sliding mode observer and the traditional sliding mode observer are built respectively.Through the comparative analysis of the simulation results,it can be seen that the improved sliding mode observer can effectively improve the accuracy of rotor speed and position estimation,which verifies the superiority of the control strategy proposed in this paper.