Rotor Initial Position Estimation Method of SMPMSM with Polarity Detection Based on Cross-Coupling Inductance Variation

This paper proposes an initial rotor position estimation method for a surface-mounted permanent magnet synchronous motor(SMPMSM) with very weak saliency. By injecting the high frequency voltage signal twice at different d-q axes apart 45°, the rotor position can be estimated by an arctangent calculation without any angle observer. After that, the ambiguity between d and -d axis can be solved by looking at the variation of the cross-coupling inductance of SMPMSM under additional signal injection. The method is simple, fast, and straightforward. It can estimate the rotor position within 30 ms in 8° electric angle error bound. It can be applied to the starting of SMPMSM in model based sensorless control or torque control of SMPMSM using an incremental encoder. The effectiveness of the proposed method has been verified through an experimental test.