US 12,074,552 B2
Dual encoder system for electric motor
Cosma Pabouctsidis, Geneva (CH); and Steven C. Bartz, Deephaven, MN (US)
Assigned to Nidec Motor Corporation, St. Louis, MO (US)
Filed by Nidec Motor Corporation, St. Louis, MO (US)
Filed on Dec. 14, 2021, as Appl. No. 17/550,937.
Claims priority of application No. 20210100782 (GR), filed on Nov. 9, 2021.
Prior Publication US 2023/0142572 A1, May 11, 2023
Int. Cl. H02P 3/22 (2006.01); G01D 3/08 (2006.01); G01D 5/14 (2006.01); H02P 29/02 (2016.01)
CPC H02P 29/02 (2013.01) [G01D 5/145 (2013.01)] 17 Claims
OG exemplary drawing
 
1. A dual encoder system for use on an electric motor to generate feedback information for controlling the electric motor, the dual encoder system comprising:
a single magnet mounted on a shaft of the electric motor;
a single printed circuit board mounted on the electric motor;
a first encoder mounted on the single printed circuit board and cooperating with the single magnet to generate and provide a first encoder information to a motor controller regarding one or more operational characteristics of the electric motor; and
a second encoder mounted on the single printed circuit board and cooperating with the single magnet to generate and provide a second encoder information to a safety controller regarding the one or more operational characteristics of the electric motor,
wherein the safety controller is configured to receive the first encoder information from the motor controller, compare the second encoder information to the first encoder information, and brake the electric motor if the second encoder information is different from the first encoder information,
wherein the safety controller performs progressive multi-stage braking of the electric motor by activating a torque-off system to disable the motor controller to cause the electric motor to coast to a stop;
after a first delay period, activating a multi-phase shorting system to divert power from the plurality of stator windings of the electric motor and thereby shorten a time period required for the electric motor to stop; and
after a second delay period, activating an electromechanical brake system to mechanically brake the electric motor and thereby further shorten the time period required for the electric motor to stop.