Generally the entire numerical control system is composed of three parts, namely control system, servo system and position measurement system. According to machining process control systems for interpolation operation, a control instruction to the servo drive system; Servo drive system will enlarge control instruction, servo motor drive mechanical movement as required; Position or velocity measurement system to detect mechanical movement, and feedback to the control system, to adjust control instruction. The organic combination of the three parts of the full closed loop control of CNC system. And control system is mainly composed of bus, CPU, power supply, storage, operation panel and the display screen, a control unit, the programmable logic controller control unit and data input/output interface, etc. The latest generation of numerical control system includes a communication unit, it can complete CNC, PLC high external and internal data communication network connection. Servo drive system mainly includes the servo drive and motor. A long grating position measurement system is mainly the incremental displacement or circular grating encoder.