Research on low speed control of permanent magnet synchronous motor based on state observer

This paper presents an instantaneous speed detection method of permanent magnet synchronous motor (PMSM) based on state observer. When a low resolution incremental-type encoder is used for speed detection, the conventional detection methods will lead delay and error which readily cause instability of the control system, in particular, when the number of pulses is few in one detection period. By using the observed rotor speed, the control system performance can be greatly improved in very low speed range, even with low resolution encoder. In practice, it is very difficult to keep the parameters of the observer and the actual system consistent with each other at any time, so this paper analyzes and demonstrates it is very robust to parameter variations. To further improve the accuracy of the observed speed in very low speed, a novel prediction method of the rotor position is designed, the simulation results are given, and the validity of this method is proved.