Simulation Research on Sensorless Speed Control System of Permanent Magnet Synchronous Motor Based on SMO

The vector control system of permanent magnet synchronous motor based on sliding mode observer (SMO) is studied in this paper. On the basis of analyzing the traditional sliding mode observer, an improved sliding mode observer is proposed. Firstly, by using the hyperbolic tangent function instead of the traditional symbol function, the chattering of the system is suppressed. Secondly, a low pass filter which has the variable cutoff frequency along with the rotor speed is designed to reduce the phase delay. Then, by using Kalman filter, it could make back EMF information more smoothly. Finally, in order to obtain accurate position and velocity information, the method of phase-locked loop (PLL) is proposed to estimate the position and speed of the rotor. The simulation results show that the new algorithm can not only improve the accuracy of the position and speed estimation of the rotor but reduce the chattering of the system.