Digital demodulation for fast set-up of sensorless PMSM electrical drives based on magnetic anisotropy

This paper presents a demodulation algorithm applied to the sensorless control of permanent magnet synchronous motors (PMSM). The sensorless control technique reported in this paper is based on the injection of high frequency voltages to the stator so that the motor currents contain information on the rotor position. This information is then extracted by an appropriate demodulation technique. The presented demodulation algorithm is based on spectral analysis of the signal produced by the sensorless control technique because this is fully characterized and presents not ambiguous correlation between current harmonic content and rotor position. The most important feature of the demodulation algorithm is the fast setup in applying to PMSM drives because it does not need all the usual preliminary calibrations and tunings that characterize instead other algorithms such as down-sampling demodulation. In this paper the proposed demodulation is justified by a theoretical point of view and finally validated by experimental results carried up under various operating conditions for a synchronous motor electrical drive.