On Clock Synchronization For Redundant Industrial Ethernet

Nowadays, the structure of industrial systems are usually distributed.Under this structure, since the cooperation of different productionprocesses heavily depends on the communication between devices, wemust keep the network working even a certain extent failure occurs.Network redundancy is often used to achieve this goal; The distributedstructure also brings lots of independent clocks. To get the same timebase for the whole system, we should synchronize all the clocks. To thatend, it is critical to study the redundancy and clock synchronization ofindustrial ethernet.Based on the comparison between different methods of networkredundancy and clock synchronization, we found that IEEE1588andMRP is a reasonable choice to achieve network redundancy and clocksynchronization respectively. Since protocols are just descriptions of theworking mechanism, it needs much consideration of how to realize thembefore applying them into real project. What’s more, the synchronizationsystem recover too slowly when the topology of the network changes. Sothat’s why this paper research the realization of these two protocols. Byseveral optimization methods in realization and the optimization in thecombination of network redundancy and clock synchronization, thispaper proposes a method that can recover faster and synchronizes moreaccurate.The corresponding works are listed as follows:1. Quantifiable method to bound parameters is proposed. Based onthe analysis of effects that the key parameters in design have on theperformance, this paper proposes the calculation method of parameters’ bound under given performance index, setting the base of appropriateconfiguration of parameters for redundancy and synchronization system;2. A method to get time value based on compensation is proposed.Based on the analysis of rule of clock deviation, this paper proposes amethod using compensation to get accurate time value;3. Clock synchronization fast recovery algorithm under MRPprotocol is proposed. Based on the analysis of characteristics of thesystem using both IEEE1588and MRP protocol, this paper optimizes theprocess of master-slave relationship building and reduce the time neededto recover the synchronization when topology change occurs;4. The simulation model, hardware platform and protocol code areestablished. Simulation model of IEEE1588is established. This paperalso designs the hardware platform and realizes it. The code of theprotocol is written. Using these experiment platforms, we have verifiedthe effectiveness of all the methods we propose.