Arbitrary injection for permanent magnet synchronous machines with multiple saliencies

This paper presents a position estimation method for a Permanent Magnet Synchronous Machine (PMSM) with multiple comparably strong saliences at low and zero speed. An anisotropy harmonics model is compared to the machines anisotropy found through the current measurement, the result of which is defined as the error. Then a minimization rule for this error is derived and employed to construct a nonlinear observer for the rotor position. In contrast to previous literature, this approach employs the saliency angle and its magnitude and is thereby able to estimate the rotor position regardless of the ratio between the anisotropy harmonics. The approach is verified in simulation and experiments.