Adaptive sensorless field oriented control of PM motors 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. An adaptive observer is used for estimation of the rotor position and speed of a permanent magnet synchronous motors (PMSM). The observer compensates for voltage offsets and permanent magnet strength variations. The adaptation structure for estimating the strength of the permanent magnet is determined from a Lyapunov stability proof. 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.