An inductive position sensor with switched reluctance motor structure

Position sensors like hall sensors, optical encoder and electromagnetic sensors are widely used in motor drive systems for providing reliable rotor positions for the motors like switched reluctance motors and brushless DC motors. However, the position measurement effects of most traditional sensors are highly dependent on the operational environmental conditions. In this paper, a method of using the switched reluctance motor (SRM) to mimic an inductive rotor position sensor is presented. Based on the high frequency signal injection method, the unsaturated phase inductance of the sensor motor can be calculated indirectly for position estimation. The sensor motor has been tested for providing position signals for a coaxial motor drive. Experimental results verify the validity of the proposed method. This work shows that the new sensor possesses the robust structure and the basic electromagnetic characteristic of a SRM, which is able to be used in many harsh environmental application conditions.