Motor control system, motor control device, brushless motor, and motor control method

A motor control device, comprising:

• a first connection to a host controller for receiving a PWM command signal over a first signal transmission line, the PWM command signal includes a plurality of pulse periods having different pulse-period durations from one another, and has a duty factor, that is a ratio of a pulse width to the pulse-period duration, modulated by a command signal, and to control a motor to rotate according to the command signal restored from the PWM command signal received;
• a PWM demodulating section for demodulating the PWM command signal and restoring the command signal;
• a rotation control section for generating a drive signal of the motor according to the command signal;
• a power drive section for generating a drive voltage to energize and drive a winding of the motor based on the drive signal;
• an information signal generating section for generating an information signal to be sent to an outside;
• a PWM modulating section for generating a PWM information signal having the duty factor modulated by the information signal;
• and
• a second connection to the host controller for transmitting the PWM information signal over a second signal transmission line in physical proximity to the first signal transmission line,
• wherein the PWM modulating section generates and outputs the PWM information signal in synchronization with the pulse-period durations of the PWM command signal such that a first magnetic field radiated from the first transmission line and a second magnetic field radiated from the second transmission line cancel each other out.

A motor control method for controlling a motor, the method comprising:

• transmitting from the host controller to the motor control device a PWM command signal over a first signal transmission line, the PWM command signal including a plurality of pulse periods having different pulse-period durations from one another, and having each of which a duty factor, that is a ratio of a pulse width to pulse-period duration, modulated by the command signal;
• restoring the command signal from the PWM command signal received in the motor control device, making the motor rotate based on the command signal restored;
• generating an information signal to be transmitted to an outside;
• generating a PWM information signal having a duty factor modulated by the information signal in synchronization with the pulse-period duration of the PWM command signal;
• transmitting the PWM information signal over a second signal transmission line in physical proximity to the first signal transmission line;
• and
• outputting the generated PWM information signal from the motor control device to the host controller, such that a first magnetic field radiated from the first transmission line and a second magnetic field radiated from the second transmission line cancel each other out.