Power tool and control method thereof

A method for controlling a power tool, comprising:

• detecting, by a controller, a parameter indicating a workload of a brushless motor, and determining an operational status of the power tool based on the parameter;
• and
• controlling, by the controller, in response to determining that the parameter is less than a set threshold, the brushless motor to maintain a first target rotational speed;
• or
• controlling, by the controller, in response to determining that the parameter is greater than or equal to the set threshold, the brushless motor to maintain a second target rotational speed,
• wherein:
• the first target rotational speed is greater than the second target rotational speed;
• and
• the controlling, by the controller, the brushless motor to maintain the first target rotational speed, or the controlling, by the controller, the brushless motor to maintain the second target rotational speed comprises:
• calculating, by the controller, an actual motor rotational speed of the brushless motor, and
• increasing, by the controller, in response to determining that the actual motor rotational speed is less than the first target rotational speed or the actual motor rotational speed is less than the second target rotational speed, a pulse-width modulation (PWM) duty cycle and/or a conduction angle for driving the brushless motor, wherein an adjustment priority of the PWM duty cycle is higher than an adjustment priority of the conduction angle;
• or
• the controlling, by the controller, the brushless motor to maintain the first target rotational speed, or the controlling, by the controller, the brushless motor to maintain the second target rotational speed comprises:
• calculating, by the controller, an actual motor rotational speed of the brushless motor, and
• increasing, by the controller, in response to determining that the actual motor rotational speed is less than the first target rotational speed or the actual motor rotational speed is less than the second target rotational speed, a pulse-width modulation (PWM) duty cycle and/or a conduction angle for driving the brushless motor, wherein an adjustment priority of the PWM duty cycle is higher than an adjustment priority of the conduction angle.

A power tool comprising:

• a brushless motor comprising a stator and a rotor;
• an inverter circuit comprising a plurality of switch components, wherein the plurality of switch components are configured to perform a switch action to control driving of the brushless motor;
• and
• a controller electrically connected to the inverter circuit and the brushless motor, the controller comprising a load detection module configured to detect a parameter indicating a workload of the brushless motor,
• wherein:
• in response to the parameter being greater than or equal to a set threshold, the controller is configured to control the brushless motor to maintain a target rotational speed,
• in response to the parameter being less than the set threshold, the controller is configured to control the brushless motor in an open-loop mode, and the brushless motor has a maximum rotational speed under a control in the open-loop mode,
• the maximum rotational speed under the control in the open-loop mode is greater than the target rotational speed, and
• the controller is configured to:
• adjust a pulse-width modulation (PWM) duty cycle and/or a conduction angle of a switch component of the plurality of switch components, so that the brushless motor maintains the target rotational speed, and
• increase the PWM duty cycle and/or the conduction angle of the switch component in response to the parameter being greater than or equal to the set threshold and an actual motor rotational speed being less than the target rotational speed, and wherein an adjustment priority of the PWM duty cycle is higher than an adjustment priority of the conduction angle;
• or
• decrease the conduction angle and/or the PWM duty cycle of the switch component in response to the parameter being greater than or equal to the set threshold and an actual motor rotational speed is greater than the target rotational speed, and wherein an adjustment priority of the conduction angle is higher than an adjustment priority of the PWM duty cycle.