Brushless d.c. motor with rfid rotor magnet position sensing

Abstract

A brushless D.C. motor has a rotor with a plurality of magnets secured to a mounting surface. Each magnet has an RFID tag secured to a magnet surface, with each RFID tag having stored therein a unique identification character serving to identify the magnet. A stator has a plurality of pole teeth separated by slots, each pole tooth having a power coil wound thereabout. A plurality of RFID interrogation antennae are mounted adjacent the pole teeth. An RFID reader generates r.f. interrogation signals broadcast by the antennae to the RFID tags. The RFID tags respond by broadcasting the unique identification character whenever an interrogation signal is sensed as the tag enters the region of a pole tooth. This position and magnet identification information is received by the RFID reader, which processes the information and sends it to a motor controller and driver unit, which supplies operating power to the individual power coils. The coils are connected in either a conventional star configuration or individually to the electrical power source to provide improved commutation control of the motor. After assembly, the motor is calibrated to eliminate mechanical, electrical and magnetic irregularities by operating the motor in a generator mode, examining the emf generated by the power coils, and developing compensating parameters to alter the driving signals for the power coils.