Servo motor is an engine that controls the operation of mechanical components in a servo system. It is an auxiliary motor indirect transmission device. The servo motor can control the speed, the position accuracy is very accurate, can convert the voltage signal into the torque and the speed to drive the control object. Servo motor rotor speed is controlled by the input signal, and can respond quickly, in the automatic control system, as an executive component, and has a small electromechanical time constant, high linearity, starting voltage and other characteristics, the received electrical signal can be converted into the motor shaft angular displacement or angular speed output. It can be divided into dc servo motors and ac servo motors. Its main characteristics are that when the signal voltage is zero, there is no rotation phenomenon, and the speed decreases with the increase of torque.

Servo motors are widely used in various control systems, which can convert the input voltage signal into the mechanical output of the motor shaft and drag the controlled components to achieve the purpose of control.

There are dc and ac servo motors; The earliest servo motor is a general dc motor, in the control of the accuracy is not high, the use of the general dc motor to do the servo motor. The current dc servo motor is a low-power dc motor in structure, and its excitation is mostly controlled by armature and magnetic field, but usually armature control.

The classification of rotating motor, dc servo motor in the mechanical characteristics can meet the requirements of the control system, but because of the existence of commutator, there are many shortcomings: commutator and brush between easy to produce sparks, interference driver work, can not be used in the case of flammable gas; There is friction between the brush and commutator, resulting in a large dead zone.

The structure is complex and maintenance is difficult.

Ac servo motor is essentially a two-phase asynchronous motor, and there are mainly three control methods: amplitude control, phase control and amplitude control.

In general, the servo motor requires the motor speed to be controlled by the voltage signal; The rotational speed can change continuously with the change of voltage signal. The response of the motor should be fast, the volume should be small, the control power should be small. Servo motors are mainly used in various motion control systems, especially the servo system.