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

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