Method and system for prevention of motor reversal
AssigneeBlack & Decker Inc.
InventorsPradeep M. Pant, James Goble
Life of this patent
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Abstract
A power tool includes a brushless DC motor housed inside a tool housing, an input unit, and a control unit. The motor includes 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 control unit controls commutation of the motor through a series of power switches coupled to the power supply. The control unit receives a current sensor state from the sensor and a user-selected speed from the input unit and determines whether the motor has reversed direction using the user-selected speed and the current sensor state. The control unit disables commutation of the motor if the motor has reversed direction until a proper current sensor state is received from the sensor.
Claims10
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.
A method of commutating a brushless DC motor in a power tool, the brushless 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, the method comprising:
- receiving a user-selected speed from a variable-speed actuator;
- receiving a current sensor state from the sensor;
- determining whether the motor has reversed direction using the user-selected speed and the current sensor state;
- and
- disabling commutation of the motor if the motor has reversed direction until a proper current sensor state is received from the sensor.
Dependencies are inferred from the claim text.