Servo system, also known as servo system, is a feedback control system used to accurately follow or reproduce a process. Servo system is an automatic control system that enables the output controlled quantities such as the position, orientation and state of the object to follow the arbitrary change of the input target (or given value). Its main task is to amplify, transform and regulate the power according to the requirements of the control command, so as to make the torque, speed and position control of the driving device very flexible and convenient. In many cases, servo system specifically refers to the feedback control system of mechanical displacement or displacement speed and acceleration. Its function is to make the output mechanical displacement (or rotation angle) accurately track the input displacement (or rotation angle). Its structure is not different from other forms of feedback control system in principle. Servo system was initially used in national defense and military industry, such as artillery control, automatic piloting of ships and aircraft, missile launch, etc. later, it was gradually extended to many departments of the national economy, such as automatic machine tools, wireless tracking control, etc.