servo system can be divided into Open-loop, semi-closed loop, closed-loop control system. Closed-loop control system with feedback from the position detection section, an enlarged portion of the deviation, the operative part and charged objects.

Servo system performance requirements
Servo system must have good controllability, high stability and strong adaptability and other basic properties. brief Explaination, good controllability means when signal disappeared it can immediately stopped; high stability is the torque increases with speed and uniform decline; adaptable means quick, sensitive, good quality sound state.

Servo System Type
Usually divided by the type of servo-driven machines, there are three types,electric, hydraulic or electric - hydraulic. If the servo system divided by function points, It's metering servo and power servo system; analog servo and power servo system; position servo and acceleration servo systems.
Electric servo system based on the electrical signal can be divided into DC and AC and DC servo systems. AC servo system have two categories. AC induction motor AC servo systems have servo systems and synchronous motor servo system.