Analysis of Rotor Anisotropy and Position Tracking Error Prediction for Surface-Mounted PMSM Under High Frequency Signal Injection

Conventional high frequency (HF) signal injection methods utilize saturation-induced inductance saliency to extract rotor position in surface-mounted permanent magnet synchronous motor (SPMSM). However, special attention needs to be paid to the resistance saliency caused by rotor eddy current loss, especially in the motor with a small inductance saliency ratio. Taking a 24-slot/4-pole SPMSM as an example, this research investigates the rotor anisotropic features and position tracking error under HF signal injection. Firstly, a parallel equivalent circuit is established to decouple the HF current responses, and the position tracking error under inductance- and resistance-based saliency tracking methods can be derived. Secondly, four finite element analysis models equipped with different rotor configurations are designed to compare the effects of rotor anisotropic features on position tracking accuracy. Thirdly, the HF signals are injected into the four models, and the current responses are analyzed by Fourier analysis. The simulation results demonstrate that the rotor loss has an impact on the HF impedance, leading to the phase shift of the negative sequence current and static position tracking error. Furthermore, through the solution of the HF equivalent impedance, the inverse model can accurately predict the tracking error caused by rotor anisotropy. Finally, the proposed tracking error prediction method is validated on an SPMSM platform and demonstrated high-accuracy prediction results. In short, the proposed method contributes to evaluating the anisotropic properties of the analyzed motor and enables accurate prediction of the position tracking error.