The servo motor can make the speed and position control accuracy become very accurate, and can convert the voltage signal into torque and speed to drive the control object. The speed of the servo motor rotor is controlled by the input signal and can react quickly. In automatic control systems, servo motors can be used as actuators. Servo motor has the characteristics of small electromechanical time constant and high linearity, and it can convert the received electrical signal into angular displacement or angular velocity output on the motor shaft. It can be divided into two categories: DC and AC servo motors. Its main feature is that there is no autorotation when the signal voltage is zero, and the speed decreases at a uniform speed with the increase of torque.