Research And Application Of OPC UA Information Model Based On Knowledge Graph

In the context of digital transformation in the manufacturing industry globally,the interconnection and intercommunication problem of heterogeneous data needs to be solved urgently.As a new industrial data transmission specification,OPC UA(Unified Architecture)can help to realize the unified transmission of heterogeneous device data.However,OPC UA information model,as the basis of OPC UA communication,needs to be constructed manually,which requires professional knowledge and is time-consuming and labor-intensive.At the same time,there are still a large number of devices that do not support OPC UA in existing factories.The way to achieve OPC UA transformation by replacing new devices will bring large costs.To solve the above problems,this thesis proposes an automated construction method of OPC UA information model based on knowledge graph technology,and designs a three-tier architecture which can realize OPC UA data acquisition through edge gateways.The above research results can help to speed up the transformation and reduce the cost.In order to verify the effectiveness of the proposed method and architecture,this thesis has built a testbed and transformed the data acquisition system using OPC UA technology.Finally,the information model of each device in the testbed has been constructed automatically and the unified acquisition of heterogeneous device data has been realized.The specific work are as follows:1.An automated OPC UA information model construction method based on knowledge graph is designed and realized.The existing relational database was selected as the datasource to match the needs of data acquisition system.By analyzing the similarity of database schema,knowledge graph and OPC UA,a set of mapping rules are designed.To generate information model conforming to OPC UA specifications,UA-ModelCompiler is used,which ensures quality of the model,reduces the requirements for professional knowledge and reduces the workload.2.An industrial data acquisition system architecture based on edge gateway is designed.The system is divided into three parts:field device layer,network access layer and enterprise network layer.This thesis focus on the functions and components of edge gateway in network access layer.Also,the information exchange method between the components is introduced.With the help of this architecture,traditional devices don't need to be replaced.By adding edge gateways,upper-level applications can realize unified acquisition of heterogeneous data and the cost of transformation can be reduced.3.By extracting common processing units in discrete manufacturing industries,a discrete manufacturing testbed has been built.The testbed can achieve assembly,marking and visual inspection.Based on the designed construction method and system architecture,OPC UA information model of each device in the testbed has been constructed automatically.Also,a unified data acquisition system based on OPC UA has been implemented which verified the feasibility and effectiveness of the work in this thesis.