Inertia identification for the speed observer of the low speed control of induction machines

This paper presents a control method for induction machines in a low speed range with an instantaneous speed observer and inertia identification. When a low resolution incremental-type encoder is used for the speed detection, only the average speed in the interval of the encoder pulses is observed, and it usually makes the speed controller unstable at the very low speed range. This paper, therefore, proposes a low speed control method with a speed observer which is implemented by the disturbance observer using a low precision shaft encoder. Furthermore, to improve the performance of the speed controller, the authors perform the identification of the inertia which is estimated by the periodic test signal. They show that this proposed method is superior to the conventional method by comparing simulation and experimental results.