Analysis of Observability Conditions for AC Induction Machine Sensorless Control

AC induction motors become very popular for motion control applications due to their simple and reliable construction. There are applications in which speed sensors should be omitted, to achieve cost reduction. In such a situation, we have to solve the task of state reconstruction only from voltage and currents measurements - design so called sensorless control algorithm. In the current paper, we present a simplified AC induction machine model suitable for speed observer design together with its observability analysis. Conditions of speed and rotor resistance observability are defined.