Study On Field Bus Technology With High Speed And High Precision Multi-channel CNC System

High-speed and high-precision control is the development trend of CNC technology. With the developing of CNC system technology, the analog quantity or pulsed quantity interface of traditional CNC system has been difficult to meet the requirements of high speed, high precision and multi-channel; however, this problem was solved well by the field bus and the field bus digital communication is the inevitable development tendency of the CNC technology. The Ethernet technology is maturity, openness, fast communication speed, strong compatibility and low cost, which meets the requirements of CNC system well, and the emergence of FPGA technology simplifies the process of design, reduce the cost, improve the reliability of the system and it can realize the hardware circuit design. So applying the Ethernet technology and FPGA technology to the high speed and high precision multi-channel CNC field bus is an important research content of high-standard CNC system, this paper carried out the following research on this theme.The demand of the high-speed and high-precision multi-channel CNC system for field bus, the characteristics of the field bus and its domestic and foreign research situation was analyzed.Around how to realize real time high-speed and high-precision multi-channel CNC system’s synchronization and reliability requirements, the CNC system field bus communication scheme based on FPGA, the physical topology structure of CNC system field bus and the hardware structure of CNC system communication module were designed based on the combination of the industrial Ethernet technology and FPGA technology.According to SOPC technology, the Nios II embedded processor of CNC system field bus was designed and the initialization and data communication of field bus based on FPGA was researched. A realized method of IEEE1588protocol based on FPGA and a adjustable frequency real-time clock were designed aiming at the deficiency of the industrial Ethernet synchronization. A hybrid task communication mode was put forward to solve the real-time scheduling problem of time critical and non time critical task in field bus, which prevented data delay due to the data blockage. After the research of the reliability technology of CNC system field bus, the hardware redundancy mechanism and error control method were proposed to prevent data transfer process from being error, which improved the reliability of data transmission.Based on FPGA technology, a CNC system field bus was designed and developed which has realized the real-time communication between CNC system controller servo drives and I/O terminal, and the synchronization, real-time and reliability of the CNC system field bus have been verified and analyzed which achieved the requirements of high-speed, high-accuracy and multi-channel CNC system.