基于EPL的分布式时钟同步方法

Distributed Clock Synchronization Method Based on EPL

工业以太网协议Ethernet POWERLINK(EPI)分布式站点的时钟同步方法并不能在实时运行过程中保持很高的同步精度,无法满足特定环境下的控制要求;研究了工业以太网协议EPL的两种时钟同步机制,通过数理计算分析了时钟同步误差产生的原因,针对误差较大的缺点,提出了减小误差的方法;通过迭代计算消除了主从站同步报文往返的路径延迟,并设计基于现场可编程门阵列(FPGA)的集线器(Hub)用于EPL菊花链网络拓扑结构,有效地克服了时钟同步报文往返传输延时不一致的缺点,测试结果表明新方法明显优于协议自身的时钟同步方法,对于实现基于EPI的高精度分布式时钟同步网络具有重要意义。

The clock synchronization methods for distributed nodes provided by Ethernet POWERLINK does not maintain very high synchronization accuracy during runtime, which can not meet the requirements in some specific control environments. Two methods of clock synchronization for EPL have been studied. After some numerical analysis of the cause for the clock synchronization deterioration, a method of reducing them is proposed, that is eliminate the time delay of the packets between the main node and the slave nodes by numerical itera tion. A hub based on FPGA has also been designed in the daisy--chain topology of EPL, which overcomes the shortage of inconsistence introduced by the packets back and forth. Test results show that the new method is way better than those introduced by EPL, which makes a siganificant improvement for the realization of high accuracy distributed clock synchronization network based on EPL.