Novel electromagnetic rotor position sensor for brushless DC machine in aviation and aerospace industry

In order to implement an aviation or aerospace brushless DC machine servo control system in a high-temperature hostile environment, a novel electromagnetic rotor position sensor was designed. Concentrated excitation coils were symmetrically mounted at the middle of the stator inner circumference notches and the pickup ones were wound around the stator teeth. The rotor outer circumference was cut to form sunken right-angled sectors at the corresponding positions of the magnetic S poles on the machine rotor. With the magnetic field excited by a relatively high frequency sinusoidal current, the detected signals were modulated by the machine rotor position, as the total mutual inductance between one pickup coil and all the excitation ones varied as a function of the sensor rotor position. As all magnetic iron cores were laminated from new soft magnetic alloy ultra-thin sheet, the excitation current frequency may be increase to 100 KHz. Moreover a linear model and an equivalent-magnetic-circuit model were set up and based on the later, the sensor geometry parameters were optimized by a simulated annealing algorithm. An infinite element analysis was done in ANSYS software program and an experiment system was also built up. Both the simulation and the experiment results revealed the validity and reliability of the whole scheme.