Brushless DC motor is composed of motor body and driver, which is a typical mechatronics product. The stator windings of the motor are mostly made of three-phase symmetric star connection, which is very similar to three-phase asynchronous motor.A magnetized permanent magnet is attached to the rotor of the motor. 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, etc. Its functions are: to accept the start, stop and brake signals of the motor to control the start, stop and brake of the motor; It receives position sensor signals and positive and negative rotation signals, which are used to control on and off of each power tube of the inverter bridge and generate continuous torque.Accept speed instruction and speed feedback signal, used to control and adjust the speed; Provide protection, display, and so on.