The servo motor can control the speed, the position accuracy is very accurate, and the voltage signal can be converted into torque and speed to drive the control object. The rotor speed of the servo motor is controlled by the input signal and can respond quickly. In the automatic control system, it is used as an executive element, and has the characteristics of small electromechanical time constant and high linearity, which can convert the received electrical signal into the motor shaft. angular displacement or angular velocity output. It is divided into two categories: DC and AC servo motors. Its main feature is that when the signal voltage is zero, there is no rotation phenomenon, and the speed decreases uniformly with the increase of torque.