US 11,750,124 B2
Low-speed sensorless brushless motor control in a power tool
Shailesh P. Waikar, Perry Hall, MD (US); Zhi Qu, Bellevue, WA (US); Wing Lin, Bel Air, MD (US); and John C. Vanko, Timonium, MD (US)
Assigned to Black & Decker Inc., New Britain, CT (US)
Filed by Black & Decker Inc., New Britain, CT (US)
Filed on Jun. 22, 2022, as Appl. No. 17/846,485.
Application 17/846,485 is a continuation of application No. 16/853,123, filed on Apr. 20, 2020, granted, now 11,374,514.
Claims priority of provisional application 62/955,586, filed on Dec. 31, 2019.
Claims priority of provisional application 62/838,560, filed on Apr. 25, 2019.
Prior Publication US 2022/0329180 A1, Oct. 13, 2022
Int. Cl. H02P 6/182 (2016.01); H02P 6/17 (2016.01); B25D 11/06 (2006.01); B25F 5/02 (2006.01); H02P 6/06 (2006.01); H02P 6/18 (2016.01); H02P 6/28 (2016.01)
CPC H02P 6/182 (2013.01) [B25D 11/064 (2013.01); B25F 5/02 (2013.01); H02P 6/06 (2013.01); H02P 6/17 (2016.02); H02P 6/186 (2013.01); H02P 6/28 (2016.02); H02P 2203/03 (2013.01); H02P 2203/09 (2013.01); H02P 2209/07 (2013.01)] 14 Claims
OG exemplary drawing
 
1. A power tool comprising:
a brushless motor having a stator defining a plurality of phases, a rotor rotatable relative to the stator, and a plurality of power terminals electrically connected to the plurality of phases;
a power unit having a plurality of power switches connected electrically between a power source and the plurality of motor terminals and operable to deliver power to the motor; and
a control unit interfaced with the power unit to output a drive signal to one or more of the plurality of motor switches to drive the plurality of phases of the motor over a plurality of sectors of the rotor rotation, the control unit being configured to detect an initial position of the rotor, commutate the motor beginning at the initial position of the rotor using a low-speed motor commutation scheme until an output speed of the rotor exceeds a speed threshold, and commutate the motor based on a back-electromotive force (back-EMF) voltage of the motor after the output speed of the rotor exceeds the speed threshold,
wherein in the low-speed commutation scheme, the control unit applies a first plurality of voltage pulses to a present sector of the plurality of sectors and a second plurality of voltage pulses to a next sector of the plurality of sectors, and detects a transition of the rotor from the present sector to the next sector based on motor current measurements associated with the first plurality of voltage pulses and the second plurality of voltage pulses, wherein the control unit is configured to compare slopes of the motor current measurements and detect the transition of the rotor from the present sector to the next sector when the current measurement associated with one of the first plurality of voltage pulses has a larger slope than the current measurement associated with a corresponding one of the second plurality of voltage pulses.