Brushless DC motor is a typical mechatronics product, which is composed of motor body and driver. Brushless motor refers to the motor without brush and commutator (or collector ring), also known as commutator less motor.

The stator winding of motor is mostly made into three-phase symmetrical star connection, which is very similar to three-phase asynchronous motor. The rotor of the motor is attached with a magnetized permanent magnet. In order to detect the polarity of the rotor, a position sensor is installed in the motor. The driver is composed of power electronic devices and integrated circuits. Its functions are: to receive the start, stop and brake signals of the motor to control the start, stop and brake of the motor; to receive the position sensor signals and positive and negative signals to control the turn-on and turn off of each power tube of the inverter bridge to generate continuous torque; to receive the position sensor signals and positive and negative signals to control the turn-on and turn off of each power tube of the inverter bridge; Receive speed command and speed feedback signal, used to control and adjust speed; provide protection and display, etc.

Because the controller provides different current direction of DC, to achieve the alternating change of coil current direction in the motor. There is no brush or commutator between the rotor and stator of brushless motor.