Sensorless Vector Control Using a Novel Sliding Mode Observer for PMSM Speed Control System

A novel sliding mode observer with estimated back-EMF(electromotive force) feeding back to the calculation of stator current observation was designed and implemented.In order to simplify the hardware structure of the speed control system,a low pass filter with a cut-off frequence changing with the rotor speed was designed.The adaptive algorithm of the back-EMF gain was proposed based on the analysis of the novel sliding mode observer's stability,and the compensation of estimated rotor position error could be realized through regulating the feedback gain.The permanent magnet synchronous motor(PMSM) speed estimation function was achieved by a phase-locked loop(PLL).A PMSM sensorless vector control system based on the novel sliding mode observer was set up and experiments are implemented on the platform.The experimental results verified that the estimation method based on the novel sliding mode observer could accurately estimate the rotor position and speed at very low speed.Speed sensorless vector control system had the characteristics of a wide speed range and robustness.Furthermore,the algorithm of the sensorless control was simple and easily achieved.