Research And Implementation Of OPC UA Server System For Data Access Standardization Of Dispenser

With "Industry 4.0","Smart Manufacturing" and other strategic plans put forward one after another,industrial control systems have begun to transform towards informatization and intelligence.The enterprise management has paid more and more attention to data from the device.However,in the industrial site,there are a variety of devices,most of these devices have different suppliers,and their bus protocols and interface access methods are different,which will cause the formation of "information islands" between the devices,poor compatibility,difficult to achieve interconnection and interoperability between devices,which seriously affects the enterprise management to achieve intelligent and unified management to all devices.OPC UA can solve the problems of interoperability of data,compatibility of platforms,and openness of technology in industrial control systems,which is very helpful to realize information sharing and management between different devices and different systems in industrial control sites and automation fields.In this paper,we research and implement a set of OPC UA Server system for dispensing machine and test it.The main contents are as follows.1.Analyze the key technologies of OPC UA.Firstly,the application software of early monitoring system is analyzed to communicate and interact with devices by developing drivers using the protocols supported by devices,and the characteristics of two commonly used protocols Modbus and Profibus are summarized to draw out that OPC technology is the solution to realize data integration and sharing of multi-source heterogeneous systems.Then the characteristics of classic OPC,OPC XML-DA,and OPC UA technologies are analyzed,and it is concluded that OPC UA is the better solution to achieve interconnection and intelligent management of various devices and systems.Finally,OPC UA specification,implementation mechanism,information modeling,address space,nodes and references and other key technologies are analyzed to lay the foundation for the development of OPC UA server.2.Build the OPC UA information model of dispensing machine.By analyzing the dispensing process and dispenser system,we construct the OPC UA information model of the dispenser and complete the mapping of the characteristic parameters in the dispenser and the OPC UA nodes.3.Design and implement OPC UA Server system.The OPC UA Server architecture is summarized according to the OPC UA architecture and OPC UA implementation mechanism,and the middle layer OPC UA SDK is implemented in modules,mainly including the creation of data structure,address space management module,communication configuration and connection module,and data access module.Each module encapsulates API functions and implements the basic functions of the server according to the definition of each service in the OPC UA specification.Among them,the address space management module mainly implements the functions of browsing the address space and adding and deleting nodes and references,the communication configuration and connection module implements the functions of establishing communication connections between OPC UA server and clients,and the data access module implements the functions of reading and writing node attributes.4.Develop OPC UA server system for dispenser controller.Firstly,the dispenser specific OPC UA information model is built in the opcua-modeler modeling tool according to the information model of the dispenser already built and the XML file is generated.Then the XML file of the customized information model is converted into source code and the dispenser-oriented OPC UA Server system is built in the Linux system.Finally,the source code is loaded into the OPC UA Server system for reprocessing,which mainly includes three aspects: firstly,coupling the address space constructed by the custom dispenser information model with the original address space of the OPC UA Server system;secondly,concrete implementation of the method node in the dispenser information model;thirdly,adding data sources to the variable node in the dispenser information model.5.Test the OPC UA subsystem of the dispenser controller.It mainly includes communication connection test,browsing address space test,test of method nodes,reading and writing attributes of variable nodes test,in addition to cross-platform test to verify the cross-platform nature of OPC UA.