EtherCAT从站设计及精确时钟同步技术研究

EtherCAT Slave Design and Precise Clock Synchronization Research

中文关键词:  EtherCAT  时钟同步  高速性  实时性  并行传输  分布时钟

英文关键词:EtherCAT  clock synchronization  high speed  real-time  parallel transmission  distribute clock

中文摘要:

      EtheCAT是一种具有高速性和高实时性的以太网现场总线，是运动控制及工业机器人不可或缺的高速通信手段。为解决对多自由度机器人协调控制等构成的分布系统的同步问题，基于EtherCAT网络拓扑结构，重点分析了DC（distributed clock,分布时钟）同步机制、算法及主从系统间的通信时序，深入研究了主站网卡驱动延时、从站物理位置和数据帧循环周期等几个关键因素对同步性能准确度和精度的影响。通过设计实时驱动网卡程序、完善从站的物理顺序、缩短数据帧的循环周期使之得以改善，并在搭建的ET1100与STM32F407并行传输数据的EtherCAT从站平台上测试，实验结果证明EtherCAT同步误差能够达到小于15 ns的精度，足以满足高速同步实时需求。

英文摘要:

      EtheCAT is a kind of high speed and high real-time Ethernet fieldbus，and indispensable for high-speed communications of motion control and industrial robots.To solve the problem of complicated distribution system such as signal synchronization of multi degree of freedom robot coordinated control，based on the topology structure of EtherCAT，the mechanism of the EtherCAT clock synchronization，the distribution clock algorithm and implementation，the communication timing between the master and slave system，are analyzed.The effect of several key factors such as the main network adapter driver delay，the physical location and data frame cycle on the accuracy and precision of synchronization performance is further researched.It is improved by adding real-time driver card program，changing the slave station physical order，shortening the cycle of data frame.In order to simulate and analyze the synchronization error，EtherCAT slave is built by ET1100 transmitting data in parallel with STM32F407.The experimental results show that the accuracy of EtherCAT synchronization error can reach less than 15 ns，which is enough to meet the high-speed synchronous real-time requirements.