Survey of speed sensorless controls for IM drives

Many works for induction motor (IM) drive systems without a speed sensor were proposed. These researches use different techniques, to estimate the motor speed, such as PLL, MRAS, observers, Kalman filter, RLS, neural networks, etc. These approaches and others have made it possible to control IM speed with the estimated speed values. However, the performance and sensitivity of such drives to parameters variations, as well as their ease of tuning and implementation are crucial to their use in industry. This paper analyzes these techniques and the corresponding merits and demerits as well as their feasibility for estimating the motor speed.