Improved initial rotor position estimation of IPMSM using amplitude demodulation method based on HF carrier signal injection

For interior permanent magnet synchronous motor (IPMSM) drives, high-frequency (HF) rotating voltage signal injection method is widely employed to estimate the initial rotor position. However, conventional demodulation method based on current phase is complex and susceptible to filters and digital control delays, an amplitude demodulation algorithm is proposed in this paper. With the proposed method, the initial rotor position can be demodulated from the amplitude of three phase current, including magnetic position and polarity. Meanwhile, the current amplitude is calculated by recursive DFT method, which requires a negligible memory space. Furthermore, a simple way is presented on exacting rotor position without filters, which is immune from filters and digital control delays. For magnetic polarity detection, a novel method is investigated based on magnetic saturation effect, which has the advantages of high signal-to-noise ratio (SNR) and no extra signal injection. Finally, the experimental results on a IPMSM indicate that the proposed method can obtain the initial rotor position with high precise and good robustness while comparing to the conventional method.