Web-Based Digital Twin
The data for the Data View originates from different sources . On the one hand the digital twin has its own database system , which can be one of the databases the utilized framework Django supports , for example : PostgreSQL , MariaDB , MySQL , Oracle or SQLite . On the other hand , external databases , also from the cloud , can be integrated via HTTP . Fig . 8 shows exemplary data on the operation history of the laser plotter .
Furthermore , the Data View links the OPC UA information model of the laser plotter to the web service . Fig . 9 shows a section of the data node structure created using the FreeOpcUa 1 library . The JavaScript library jsTree 2 was used to display the data [ 10 ] of the OPC UA Server . In addition to the system information structured according to use cases , the control variables of the laser plotter are also represented .
For the basic representation of geometric models there are some JavaScript libraries . However , the import of standardized CAD exchange formats such as STEP are not supported as the preferred option . Babylon . js was identified as an alternative which supports the file formats . glTF , . glb , . obj and . stl . The CAD models are represented by vector graphics on the web pages and can be viewed in the Internet browser from different perspectives . The calculations are performed on the computing resources of the client and thus determine the performance . Fig . 10 shows an example of the implemented CAD user interface using the plot and laser unit .
Fig . 9 : OPC UA data structure of the laser plotter integrated into the web-based digital twin ( ns – namespace , i – Identifier ).
The live view combines the up-to-date data and the 3D geometry models . The representation of the
1 https :// github . com / FreeOpcUa / freeopcua
2 https :// www . jstree . com /
Fig . 10 : Visualization of 3D geometry of a laser plotter component .
- 12 - March 2021