Self-sensing methods to drive micro-machines

Synchronous motors require sensors in order to control these devices in speed and/or position. Basically, the auto-commutation needs 3 sensors for a 3-phase type actuator. In micro-motors, as there is no more room to place the sensors, self-sensing approach must be used. The motor becomes a sensor it-self and electromagnetic phenomena are analyzed to detect the position of the rotor. These phenomena are magnetic saturation, back-EMF detection, Eddy current analysis and/or magnetic anisotropy variation. The present paper will describe the technique used to drive a micro-motor for Pico-satellite purpose.