You can shift the position of the servo motors via two correction inputs, ie. to build up a control loop. This compensates all interference which influences the firing process.

Adopting ac servo motor as the driving device, can the dc servo motor and a high precision, high performance as the half closed loop or closed loop control system.

A kind of the pulse control mode, the drive and motor closed loop, but not to the numerical control system, the feedback device, in a sense, can open loop control called the servo control.