Sensorless Control of PM Motor Drives - a Technology Status Review

The control of Brushless Permanent Magnet Motors require rotor position information that can be measured by means of a position sensor. The motion sensorless control aims at eliminating the motor position sensor and its corresponding electronic conditioning circuits, cabling and connectors. Besides a clear cost reduction, the motion sensorless drives have better reliability when compared with their position sensor-based counterparts. The research conducted in the last two decades has provided many different solutions that are used in many applications. Nevertheless, the literature reports just a few survey papers dealing with this important topic. This paper intends providing a comprehensive review of the sensorless control solutions, including the machine influence on the sensorless drive performance.