Sliding mode speed observer of induction motor

This paper describes a new approach to the estimation of the induction motor speed from the measured terminal voltages and currents for speed sensorless sliding mode torque and flux control. The produced torque is explicitly continuous output variable of control. The magnitude and orientation angle of the induction motor´s rotor flux are determined by the output of the sliding mode closed loop flux observer based on the estimation of the extended electromotive force. The described technique is very simple and robust to variations of motor parameters. Furthermore, pure integration of sensed variables, in principle, is not required at all. Therefore, this new method can achieve much wider bandwidth speed control then previous speed sensorless drives. The effectiveness is verified by simulations and experiments.