Research On Clock Synchronizationtechnology For High Speed Industrial Ethernet

With the increasing requirement of industrial control automation, the traditional fieldbus technologies have not been able to meet the needs of industry. Subsequently, the industrial Ethernet technolog y began to be used in industrial control automation. It is based on Ethernet. Although the industrial Ethernet technology enhance the speed of data transmission, but it cannot accurately predict the time of data arriving and enable equipments to complete complex tasks synchronously. These are mainly because of the Ethernet CSMA/CD access mode and the characteristic of asynchronous. To solve these problems, many companies proposed real-time Ethernet technologies. In 2003, Beckhoff Automation developed the Ether CAT technology. Ether CAT is one of the best real-time industrial Ethernet protocols. With reference to the precision clock synchronization mechanism of IEEE1588, clock synchronization accuracy of Ether CAT can be controlled within 1us between slaves.This paper focuses on the Ether CAT clock synchronization technology and implements it. Based on the technology, equipments work synchronously. This paper studies the Ether CAT clock synchronization mechanism- the distributed clock. 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. By modifying the EEPROM profile and designing the interrupt handler, slave achieves the function of clock synchronization.In addition, this paper designs a platform to test the accuracy of clock synchronization. The platform is based on oscilloscope and computer. Using the testing platform, the analysis of clock synchronization factors and the test of system performance are completed. According to the analysis of the influence factors which include the accuracy of system delay function and the accuracy of timer, paper gives the optimal implementation. In the case of fixed SYNC0 cycle time, the paper completed tests of transmission reliability and clock synchronization accuracy. For different cycle times, the performance of the system clock synchronization is also tested.