Research And Implementation Of OPC UA Publish Subscribe Method For WIA-PA Networks

With the continuous integration of industrial systems and the Internet,the interconnection between the underlying network and the upper-layer facilities in the industrial Internet network system becomes more and more important.OPC Unified Architecture(OPC UA)is a data exchange standard for industrial communication,which is regarded as the foundation for realizing information interoperability of industrial Internet.OPC UA publish/subscribe model can solves the problems of tight coupling of communication objects and server performance bottlenecks in the current Client/Server model,and meets the communication needs of scenarios such as the Internet of Things and Machine to Machine.Wireless Networks for Industrial Automation-Process Automation(WIA-PA)is one of the three major industrial wireless standards,which has the characteristics of low energy consumption,high real-time performance,and flexible networking.Publish/subscribe model is one of the core transmission modes of WIA-PA,the integration of the OPC UA publish/subscribe model and the WIA-PA publish/subscribe model not only makes use of OPC UA's information description capabilities,but also provides a safe and efficient means of communication for WIA-PA to access the industrial Internet.However,there are few studies on the OPC UA publish/subscribe model,and there is no research on its combination with WIA-PA.Therefore,this thesis optimizes and improves the existing OPC UA publish/subscribe method,and proposes an OPC UA publish/subscribe method for WIA-PA networks.The main work includes:1.Based on the WIA-PA network communication requirements,an OPC UA publish/subscribe communication scheme for WIA-PA was proposed through the investigation and analysis of OPC UA publish/subscribe technology.2.A WIA-PA & OPC UA joint publish/subscribe method was proposed.To solve the data mapping problem between WIA-PA and OPC UA,a WIA-PA virtualization method for OPC UA Pub/Sub data source is designed.The WIA-PA/OPC UA joint publish/subscribe transmission mechanism is designed to solve the coupling problem of the two transmission processes,and the corresponding configuration mechanism is also designed.The proposed method can ensure the OPC UA publish/subscribe communication efficiency for WIA-PA and easy to deploy.3.The aforementioned method is implemented,including OPC UA publish/subscribe communication unit and WIA-PA gateway communication unit.The OPC UA publisher or subscriber is virtualized as a WIA-PA application layer device to implement the WIAPA/OPC UA joint publish/subscribe transmission mechanism and related configuration mechanism.4.Based on the WIA-PA devices,open62541 OPC UA SDK and related software platforms,a test system was built to conduct experimental verification of the designed OPC UA publish/subscribe method for WIA-PA networks.The test results show that the proposed method can realize OPC UA publish/subscribe communication for WIA-PA devices.The proposed method does not change the core protocol of WIA-PA and OPC UA,which is conducive to actual deployment.Meanwhile,from the data refresh frequency,communication success rate,and subscriber message processing time aspects,the proposed method is able to meet most industrial applications needs.Hence,the research work of this thesis has a high reference value for deploying industrial wireless networks with OPC UA publish/subscribe mode.