A novel MRAS based speed sensorless control of induction motor

Speed and torque control of an induction motor is usually attained by application of a speed or position sensor. However, speed and position sensors require the additional mounting space, reduce the reliability in harsh environments and increase the cost of the motor. Various control algorithms have been proposed for the elimination of speed and position sensors. This paper investigates a novel speed sensorless control of an induction motor. The proposed control strategy is based on MRAS (model reference adaptive system) using state observer model with current error feedback and rotor current model as two models for flux estimation. The rotor speed is estimated so that the difference between the outputs of state observer model and rotor current model may be zero. This algorithm may overcome several shortages of conventional MRAS: integrator problems, small EMF at low speed, and relatively large sensitivity to resistance variation. The proposed algorithm is verified through simulation and experiment.