Electric motor system and motor control method

A method for controlling operation of a brushless direct-current motor having an output shaft for transmitting torque, the motor rotating at a given rotational speed in a steady operational state thereof, and stopping rotation while being energized in a hold state thereof,

• the method comprising:
• acquiring a measured rotational position of the motor shaft;
• acquiring a targeted rotational position of the motor shaft;
• calculating a difference between the measured and targeted rotational positions of the motor shaft;
• generating a control signal based on the calculated difference through a combination of control actions, including at least a proportional action and an integral action employing a proportional gain and an integral gain, respectively;
• supplying power to the motor according to the control signal;
• and
• adjusting the gain of each control action to a first value where the motor is in the steady operational state thereof, and to a second value different from the first value where the motor is in the hold state thereof.

A circuit for controlling operation of a brushless direct-current motor having an output shaft for transmitting torque, the motor rotating at a given rotational speed in a steady operational state thereof, and stopping rotation while being energized in a hold state thereof,

• the circuit comprising:
• means for supplying power to the motor according to a control signal;
• means for acquiring a measured rotational position of the motor shaft;
• means for acquiring a targeted rotational position of the motor shaft;
• means for calculating a difference between the measured and targeted rotational positions of the motor shaft;
• a PID controller to generate the control signal based on the calculated difference through a combination of control actions, including at least a proportional action and an integral action employing a proportional gain and an integral gain, respectively;
• and
• a gain adjuster connected to the controller to adjust the gain of each control action to a first value where the motor is in the steady operational state thereof, and to a second value different from the first value where the motor is in the hold state thereof.