2011 Volume 131 Issue 2 Pages 208-218
This paper presents an observer-based position sensorless control method involving signal injection, which is appicable over a wide range of speeds. An extended electromotive force (EEMF) observer is suitable for salient-pole synchronous motors because the position information of EMF and saliency are considered. Signal injection is needed to make use of the position information of saliency at low speeds. However, observers consist of a low-pass filter. Therefore, the position information of saliency has not been used for the EEMF observer.
In this study, a signal injection method that does not cause a torque ripple is applied to make effective use of the EEMF observer at low speeds. The signal frequency can be selected such that it lies within the bandwidth of the observer. In this paper, a position estimation method based on heterodyne detection and involving the use of an EEMF observer with a filter is proposed. The proposed technique makes it possible to extend the operating range of the EEMF observer to lower speeds. The validity of the proposed control method is confirmed by experiments.