Speed control of permanent magnet motors using sliding mode observers for induced EMF position and speed estimation

This paper presents a speed control system for a permanent magnet synchronous motor (PMSM) in which the sliding mode technique is used to estimate the induced EMF, rotor position and speed. The electrical dynamic equations of PMSM are modified to obtain the sliding mode observer model and then the variables are estimated by using only measured stator currents and voltages. Firstly, the observer of the induced EMF is implemented using analog devices. Taking the output signals of this observer, the estimated speed and position variables are numerically calculated. Information on the induced EMF is used for the implementation of feedforward action in the current loop. Speed and position information are used for speed loop control and variable transformations, respectively. Simulation results of these observers are presented. Experimental results confirm the good performance of the closed loop speed control using the proposed observer