Cutting tool and control method

A power tool, comprising:

• a cutting element;
• an electric motor configured to drive the cutting element to perform a cutting function and comprising a stator having a plurality of windings and a rotor;
• a driver circuit electrically connected to the electric motor to drive the electric motor to run;
• and
• a controller configured to estimate an angular position of the rotor based on a working parameter of the electric motor and output a drive signal to the driver circuit based on the angular position of the rotor to control rotation of the electric motor;
• wherein, at a start stage, the controller is configured to output a first control instruction to control the electric motor to restart when an abnormal start of the electric motor is detected and the first control instruction comprises an instruction to acquire the angular position of the rotor with a high-frequency signal injection method;
• wherein the controller comprises a rotational speed collection unit configured to acquire an initial rotational speed value of the electric motor at the start stage of the electric motor, the controller is configured to restart the electric motor when the initial rotational speed value is less than or equal to a first preset threshold, the working parameter of the electric motor comprises the rotational speed value and the current value, and the controller is configured to cause the electric motor to enter the normal speed regulating stage when the rotational speed value of the electric motor is greater than or equal to the second preset threshold and the current value of the electric motor is less than or equal to the preset current threshold or to otherwise input the first control instruction so as to restart the electric motor.

A control method of a cutting tool, wherein the cutting tool comprises an electric motor having a rotor, a driver circuit electrically connected to the electric motor, and a controller electrically connected to the electric motor and the driver circuit separately, the control method comprising:

• acquiring a working parameter of the electric motor;
• estimating an angular position of the rotor according to the working parameter of the electric motor at a start stage of the electric motor;
• outputting a drive signal to the driver circuit according to the angular position of the rotor so that the driver circuit drives the electric motor to rotate;
• acquiring an initial rotational speed value of the electric motor at the start stage of the electric motor;
• restarting the electric motor when the initial rotational speed value is less than or equal to a first preset threshold;
• and
• causing the electric motor to enter the normal speed regulating stage when the rotational speed value of the electric motor is greater than or equal to the second preset threshold and the current value of the electric motor is less than and equal to the preset current threshold or otherwise inputting the first control instruction so as to restart the electric motor.