Rotating High Frequency Injection and Ellipse Fitting Technique for Ringed-Pole Motor Sensorless Control

In this paper a sensorless control scheme is proposed for low-speed operation of the ringed-pole motor: a modified surface permanent magnet synchronous motor in which a copper turn has been wound around each rotor pole. This modification makes the motor suitable for high frequency injection methods. This paper investigates the application of the rotating voltage injection technique to the ringed-pole motor. Differently from the conventional demodulation approach, the measured currents are processed with a recursive ellipse fitting technique. The position is obtained in real-time from the parameters of the estimated ellipse. The proposed sensorless control scheme is discussed and validated with simulations.