Research On EtherCAT Master Based On FPGA In High Speed And High Precision Multi-channel CNC System

The ever-changing computer and microelectronics technology allows many fields experienced a change of baptism,CNC technology as a crucial role in the manufacturing caught up with the trend of the era,breaking the pattern of the original toward the open,networking,intelligence.Traditional communication interface of CNC system has weak real-time,complex field configuration,tough firmware upgrades,those become difficult obstacle to restrict the development of high-speed high-precision multi-channel gradually.At present,Ethernet technology in the field of industry cut a striking figure,more and more CNC system communication interface is with Ethernet technology.EtherCAT(Ethernet for Control Automation Technology)industrial real-time Ethernet by the German Beckhoff not only implemented Ethernet technology to the I/O level,but also has a high transmission rate,high synchronization,low latency,multi-topology and other good features.To solve the problem of numerical control system communication interface,the paper propose to design a real-time Ethernet EtherCAT master based on FPGA.To consult the history of fieldbus combined with the development of numerical control system and to point out the limitation of traditional numerical control system communication interface,we need new demands.This paper.studies the technical background and international standard of real-time Ethernet fieldbus in recent years,and expounds the technical advantages of EtherCAT in the field of automatic processing and numerical control by comparing the mainstream real-time Ethernet solution.The paper deeply study the protocol principle of EtherCAT technology,including topology,addressing mode,distributed clock synchronization principle and application layer protocol making the theoretical basis for implementing EtherCAT master station.As the kernel the hardware circuit with FPGA is designed and introduce selection of each function module with schematic diagram in order to providing a dependable platform.FPGA is the implemented platform of EtherCAT master.Protocol stack and network card drives in the Nios Ⅱ software core.Other modules use VHDL to implement.Implementations which based on can be more accurately captured timestamp feature;use PI controller principle to establish clock synchronization algorithm and build a clock frequency compensation module to optimize the stable master clock oscillator.The hardware structure of the dual network port is used to realize the redundancy of the master station,the reliability of the system is improved,the processing flow of salve under the abnormal control is given.Finally,to build a system test platform,including EtherCAT FPGA master controller,Delta digital AC servo drive ASDA-A2-E750W and motor ECMA-C10807RS.The experimental results show that the EtherCAT communication system dominated by the master station designed in this paper has good real-time,synchronization and stability.