Sensorless control of AC motors at zero speed

The paper presents a review of the main approaches to sensorless control of AC motor drives, pointing out the problems related to zero speed operations. A general sensorless vector control technique able to drive different kinds of AC motors at low and zero speed is then presented. The proposed control scheme exploits the anisotropy of the machines and does not require the knowledge of any motor parameter allowing low cost implementation. Experimental results on some prototypes with different AC motors are presented to evaluate the consistence of the proposed technique