New digital demodulator for sensorless control of electrical drives with Permanent Magnet Synchronous Motors

This paper deals a new digital demodulator algorithm for sensorless control of interior permanent magnet synchronous motors (IPMS) based on the estimation of speed and rotor angular position. To this aim a signal similar to that generated by a resolver connected to the shaft of the motor is obtained injecting high frequency stator currents. A new digital algorithm has been designed and set up to demodulate the above signal whose implementation can be carried out on the same DSP that processes the whole control algorithm. The proposed demodulator scheme is presented and justified on the theoretic point of view. Simulations results finally validate the effectiveness of the demodulator within the sensorless control algorithm in all the operating conditions concerning the whole speed and load torque ranges. The carried out simulations have been compared with results of other simulations of a sensorless control algorithm previously implemented and experimentally validated by the authors.