Research On Clock Synchronization Of Wireless Sensor Nodes In EtherCAT Data Acquisition System

EtherCAT (Ethernet Controller Technology) data acquisition system is widelyused in the field of industrial control, data acquisition and system testing for its higheraccuracy in clock synchronization. But the EtherCAT slave stations cannot be wireconnected to the system in all applications. If wireless sensors were adopted, it isdifficult to synchronize them using the Distributed Clock synchronization system. Tosolve the problem, in this paper, we propose a scheme which achieves the clocksynchronization between the WSN (Wireless Sensor Network) and EtherCAT slavestations by adopting the EtherCAT slave stations’ clock as the reference clock. Throughinstalling a wireless data acquisition card on the EtherCAT slave stations, datacollection and clock synchronization will be achieved between a conventionalEtherCAT system and the Wireless Sensor Network.The method of wireless sensor clock synchronization was studied mainly in thispaper. First, brief introduction to wireless sensor networks was made. Second, a surveyof the exiting synchronization methods was made and categorizations were given.Meantime some typical wireless sensor clock synchronization algorithm were analyzedThen we analyzed the PBS (Pairwise Broadcast Synchronization) and proposed alow-power consumption clock synchronization method—IPBS (Improved PairwiseBroadcast Synchronization). Finally, we present a thorough analysis of thecommunication process between two USRPs (Universal Software Radio Peripheral) onwhich we implement several related synchronization methods and our scheme. Theresults of experiments show that IPBS solved the problem effectively that the clocksynchronization between the nodes outside the common communication range of thetwo communization nodes and decreased the number of information exchange forclock synchronization, reducing network overheads and saving wireless sensor powerconsumptions network. The paper’s work provides a valid reference for the relatedresearch and implementation of wireless clock synchronization based on the EtherCATdata acquisition system and lays a solid foundation for the further USRPcommunication experiment.