Amazon.com, Inc.
Sensor-less motor reversal apparatus

Abstract:

Described is a sensor-less motor reversal ("SLMR") apparatus that aids the reversal of motor rotation of a bidirectional motor, such as a brushless DC motor of an aerial vehicle. The SLMR includes an RPM dependent clutch that is rotated by a drive shaft of the motor and that engages an engageable shaft of the SLMR apparatus during a low RPM range of the motor during which indirect measurement of the RPM of the motor through a back-EMF of the motor is unreliable. As the engageable shaft increases in RPM, energy is stored by an energy storage mechanism of the SLMR. As the RPM of the motor decreases as part of a motor reversal, the energy stored by the energy storage mechanism is discharged and aids in the transition of the reversal of the motor from positive to negative, or negative to positive. As described, the SLMR apparatus is stateless.