Design And Implementation Of Data Acquisition System Based On OPC UA Protocol

With the rise of intelligent manufacturing and the Internet of things in the industrial field,it has become a mainstream trend to obtain equipment production data through the OPC UA protocol and analyze production data to improve production efficiency.In this paper,a data acquisition system based on OPC UA protocol is designed to solve the problem that some devices in the market cannot provide OPC UA protocol services due to early delivery.The research content of this paper mainly includes the following parts:(1)The core part of the system design and the protocol conversion of device data is completed through protocol converter.In order to complete the conversion of device data protocol and solve the problem of complex link in the process of protocol conversion,the protocol converter is divided into address space,data requester,protocol resolver and driver load by modular design.In the design of address space,the hierarchical relationship between nodes is saved in XML tree structure to improve the efficiency of node retrieval,and the reference class provided by OPC UA SDK is used to construct the address space in OPC UA protocol.In the design of the data requester,the data requester can complete the collection of device data according to the user's requirements by formulating the data request information specification.At the same time,the driver loader is designed based on the factory design pattern to make the data requester compatible with most drivers and scalable.In the design of the protocol parser,in order to enable the parser to parse the data according to the user's needs,the protocol information specification is developed,and the node management class is designed to operate the device node in the address space flexibly.In order to complete the datainteraction between the data requester and the protocol parser,as well as to make the data requester compatible with different types of device driver design and drive development templates,the drive development template was used to regulate the development process of device driver,and to complete the drive development of robot,PLC and lathe.(2)To store historical data and hot spot data for other applications,establish a database in MySQL according to node classification and store historical data according to device category,this can improve the efficiency of historical data query,and cache the recently collected and converted data into memory through Redis cache database,which improves the efficiency of client request.The main thread needs to complete the functions of protocol transformation,historical data storage,hot spot data storage,log and alarm in the system,but the main thread of execution efficiency is very low and protocol conversion delay is bigger,in order to solve this problem,RabbitMQ messaging middleware is adopted to decouple the historical storage,the storage of hot data and other functions from protocol transformation,which improves the execution efficiency of the main thread of the system and the throughput of the system,moreover,RabbitMQ is adopted to expand the interface of the system.In order to solve the problem that configuration files in the system are chaotic and easy to be lost or deleted by mistake,ZooKeeper distributed collaborative framework is adopted as the configuration center of the whole system to store and manage configuration information in the whole system,which improves the stability of the system.(3)The interactive software is designed to realize the operation of the protocol converter and to solve the problem that the system needs more configuration information and the configuration process is more complex.At the same time,in order to simplify the configuration process of device node hierarchy configuration,data requester configuration and protocol parser,the wizard function is designed in the software by combining the window control technology in Winform and factory design mode.In order to solve the security problem of the system,encryption method was adopted according to the OPC UA specification to complete the system security settings in the software.Meanwhile,in the interactive software,the view historical data,access hot data and other functions was designed.Finally,the interactive software was tested by OPC UA clientAfter completing the design of the data acquisition system based on OPC UA protocol,the system was verified by using virtual debugging technology combined with processing process flow and polishing process flow,the experimental results showed that the data acquisition system based on OPC UA protocol presented in this paper conforms to the design objectives,and has the advantages of convenient interaction,accurate conversion and strong expansibility.