EtherCAT时钟同步技术研究

Research on EtherCAT Clock Synchronization Technology

摘要:

EtherCAT是一种实时工业以太网协议；基于EtherCAT实时性强的特点,重点研究了EtherCAT分布时钟机制,并提出了在嵌入式设备上基于实时操作系统μC/OS II完成主站设计的方案；通过分析传输延时补偿、初始偏移补偿、动态漂移补偿等时钟同步过程,完成了对主站系统时钟同步技术的设计；基于环形冗余结构搭建了一主三从的EtherCAT测试系统,并通过计算机、示波器等设备采集得到从站间产生SYNC0信号的时间差值数据；最后,根据SYNC0周期为1 ms的数据,分析得到系统时钟误差维持在55 ns以内的同步性能,为时钟同步技术的理论研究提供了数据支持。

Abstract:

EtherCAT is a real-time industrial Ethernet protocols. Based on the EtherCAT characteristic of strong real-time, paper focuses on the distributed clock mechanism and proposes the proposal of master systm design based on real-time operation system μC/OS II on embedded devices. According to analysis of the clock synchronization process which includes the propagation delay compensation, the initial offset compensation and the dynamic drift compensation, the design of clock synchronization technology is completed in master system. The EtherCAT test system consists of a master and three slaves based on redundant ring structure. Using an oscilloscope and computer, the time difference of generating SYNC0 between slaves are gathered. Finally, it analyzes the clock synchronization performance of the system based on the data of SYNC0 period of 1 ms and gets the accuracy within 55 ns. These data provide support for the theory of clock synchronization.