Sensorless field oriented control of a PM motor including zero speed

This paper presents a simple control method for controlling permanent magnet synchronous motors (PMSM) in a wide speed range without a shaft sensor. The method estimates the stator flux by integration of the measured BEMF signal. To compensate for the offset in the BEMF the offset is estimated. The control method is made robust at zero and low speed by changing the direct vector current component to a value different from zero. In order to verify the applicability of the method the controller has been implemented and tested on a 800 W motor