Torque and position estimation in switched reluctance motors using embedded magnetic field sensors

A new method for controlling switched reluctance motors based on direct measurement of air-gap magnetic fields is presented in this dissertation. Direct measurement of magnetic fields in an operating electric motor has not been previously possible due to the small air-gap dimensions and curved surfaces associated with switched reluctance machines. This research presents the results of developing a giant magnetoresistive (GMR) device that is based on copper-cobalt nanowires. Using the signals derived from air-gap GMR sensors, the instantaneous motor torque is computed from a discrete version of the Maxwell stress tensor that has been derived for real-time applications. In addition, the rotor position is determined by processing the air-gap magnetic field with real-time wavelet transforms, thereby eliminating the need for a separate rotor shaft position sensor. Inclusion of the air-gap magnetic field sensors is developed on a thin substrate such that there is no need to modify the design of the motor to accommodate the sensor installation. Experimental results from air-gap magnetic flux values are provided.