There is no principle difference between the structure and composition of servo system and other forms of feedback control system. 

Mechatronics servo control system structure, various types, but from the perspective of automatic control theory, servo control system generally includes the controller, the controlled object, the execution of the link, detection link, comparison link and other five parts. 

Comparison link: Comparison link is the link that compares the input instruction signal with the feedback signal of the system to obtain the deviation signal between the output and input, usually by a special circuit or computer to achieve. 

Controller: controller is usually a computer or PID control circuit, its main task is to compare the output of the deviation signal transformation processing, in order to control the executive components according to the requirements of the action. 

Execution link: The function of execution link is to convert various forms of input energy into mechanical energy to drive the controlled object to work according to the requirements of control signal.  Mechatronics system in the executive components generally refers to a variety of motor or hydraulic, pneumatic servo mechanism. 

Controlled object: the number of mechanical parameters including displacement, speed, acceleration, force, and torque is controlled object. 

Detection link: Detection link refers to the device that can measure the output and convert it into the dimension required by the comparison link, generally including sensors and conversion circuits. 

Servo control system was initially used in ship autopilot, gun control and commanding instrument, and then gradually extended to many fields, especially automatic lathe, antenna position control, missile and spacecraft guidance.