Patent ID: 8587230
Filing Date: 2013-11-19
Classification: B25B,B25F,H02P

Abstract:
1. A power tool comprising: a housing; a brushless DC motor housed inside the housing, the motor comprising a rotor, a stator, and at least one sensor positioned to sense a state of the rotational position of the rotor inside the stator; a power supply; an input unit actuated by a user comprising a variable-speed actuator; and a control unit configured to control commutation of the motor through a plurality of power switches coupled to the power supply, the control unit receiving a current sensor state from the sensor and a user-selected speed from the variable-speed actuator, the control unit further configured to determine whether the motor has reversed direction using the user-selected speed and the current sensor state and to disable commutation of the motor if the motor has reversed direction until a proper current sensor state is received from the sensor.