Research On Speed Sensorless Control Technology Of PMSM Based On Improved MRAS

Permanent Magnet Synchronous Motor has a lot of advantages which include steady state for a long time,small volume and high power density,and has generous application prospects in electric vehicles,industrial manufacturing and some related fields.With the gradual expansion of application fields,the mechanical sensors used to detect PMSM rotor speed and position information are subject to many limitations,making it difficult to use in high temperature and harsh environments.Therefore,this thesis takes the surface-mount PMSM as the research object,and studies the speed sensorless detection technology and its high-performance control method.First,the mathematical model of PMSM in the rotating coordinate system is established,and on this basis,the Model Reference Adaptive System(MRAS)is applied to the sensorless estimation strategy of the motor.Aiming at these problems of poor robustness and changeless errors between rotational speed and position estimates and actual values of traditional MRAS observers,the super-distortion sliding mode algorithm is introduced into the adaptive mechanism of MRAS to improve the robustness of the observer and reduce the inherent speed error;furthermore,the switching function in the super-distortion sliding mode algorithm is replaced by a saturation function,and an adaptive coefficient is introduced into its integral term,which can effectively suppress the chattering phenomenon of the sliding mode algorithm.Through simulation analysis,the superiority of the improved MRAS observer is verified.Secondly,for the problem of poor dynamic performance and robust performance of the speed control system in the case of sensorless,an improved reaching law sliding mode control method is proposed.This programme reconstructs the exponential part of the power reaching law,and combines this part with the exponential reaching law,so that the velocity of the system in the reaching phase is accelerated,and the dynamics response of the system is improved;and the velocity of the system is slowed down in the sliding phase,which is more beneficial to reduce the chattering.Based on the state equation constructed with the speed error as the state quantity,the PMSM speed loop controller is redesigned,the simulation system model is built,and the superiority of the improved sliding mode controller is verified.Finally,in order to verify the effectiveness of the research method,a PMSM experimental platform with TMS320F28335 digital control chip as the core is built,the hardware electrocircuit is designed,and the control method programme is written.The speed sensorless control method studied in this thesis is tested on a 2.1k W motor.The experimental results show that the sensorless control method has high-precision velocity estimation,good dynamic response and strong robustness,the correctness of theoretical analysis and simulation is further verified.