Research On Rotor Position Hybrid Detection And Encoder Correction Of Permanent Magnet Synchronous Motor

With the acceleration of urbanization in China,elevator industry is enjoying the prosperity for development.Permanent magnet synchronous motor has become the mainstream of the elevator field due to its high power density,simple structure and good speed performance.It is the key to realize the good performance of PMSM and keep torque stable by detecting rotor position precisely.In this thesis,PMSM control system based on sinusoidal photoelectric encoder is studied.Issues on PMSM rotor position detection,zero-setting of the absolute position signal and calibration of reference signal generated by the encoder are deeply researched.Besides,simulation and experiments are conducted to verify the feasibility of the proposed method.The physical model PMSM is firstly established.Based on the model,establishment methods are revealed for three-phase static coordinate system,two-phase stationary coordinate and synchronous rotating coordinate system.Then mathematical models of PMSM in the three coordinate systems are derived,on basis of which,the principle of vector control strategy and SVPWM modulation technology is described in detail.The working principle of sinusoidal photoelectric encoder is elaborated,and absolute and incremental detection methods for PMSM rotor position are induced based on output signals of the encoder.The comparison of the two methods shows that there is strong complementarity between the two methods in accuracy and convenience and a hybrid detection method for PMSM rotor position is then proposed.The issue of encoder correction is researched emphatically,the nature of which is revealed,and corresponding solutions are proposed.Encoder correction includes the zero-setting of absolute position signals and the calibration of reference signal.The nature of the former is to acquire the initial phase angle between absolute position signals and PMSM rotor actual position;the latter is to get mechanical angle of PMSM rotor corresponding to the reference signal.PMSM rotor is pre-located at aknown position by a stator current vector and the zero-setting of absolute position signals can be conducted by comparing rotor actual position with the result of absolute detecting method.Then reference signal can be pre-calibrated via absolute detecting method,and the result of pre-calibration will be optimized by the angle between current vectors in d-q,thus accomplishing the calibration of reference signal.Finally,methods for PMSM rotor position detection and encoder correction are verified thorough simulations and experiments.Results show that the proposed method can acquire the initial phase angle of absolute position signals and the position of reference signal accurately,thus accomplishing encoder correction effectively,and that the hybrid detecting method of rotor position can ensure PMSM start smoothly and run accurately.