Self-sensing methods for PM motors in mechatronic applications

In order to control the speed and/or position of permanent magnet (PM) motors, they require position sensors. Basically, the auto-commutation needs 3 sensors for a 3-phase motor. In micro-motors, as there is no space for the sensors, self-sensing must be used. In any case, suppression of the sensors enhances the overall reliability. The motor becomes a sensor itself and electromagnetic phenomena are explored to detect the rotor position. These phenomena are magnetic saturation, back-EMF, eddy currents and/or magnetic anisotropy. The present paper will describe the technique used to detect the rotor position in PM motors used in mechatronic applications such as solar aircraft, stepper motors for automotive systems, etc.