Position sensorless drives for sinusoidal permanent magnet motors

In the field of electric motor control, extensive efforts have been devoted to the development of position sensorless motor drives. These sensorless drives are advantageous because they permit a significant system cost reduction. Owing to academic and industrial research that span over the past decades, various position sensorless techniques have been invented and can be classified under two categories, namely, those that work only at high speed and those that work only at low speed. In fact, as of today, there are no sensorless techniques that single-handedly permit operation over the entire speed range. This thesis incorporates a review of the literature that has been published in the field of position sensorless motor drives. As part of the thesis research, both a high speed and a low speed sensorless algorithm were developed. The theory behind those algorithms, as well as simulated and experimental results underlining their performance, is presented. The novelty of this thesis lies in the development of a fusion algorithm. The algorithm seamlessly fuses the information generated by the high and low speed sensorless algorithm. The resulting sensorless drive, based on novel fusion algorithm, permits position sensorless operation over the entire speed range. Experimental results show that the position estimation error obtained from this fusion algorithm is smaller, in most of the speed spectrum, than that obtained from the low speed or high speed algorithms alone. The scope of the thesis is specifically restricted to sinusoidal permanent magnet motors, which are favorable in many applications because of their small size and high power efficiency.