# Scene Equipment Saving and Loading Method for Digital Twin Workshop
###### Abstract  
The digital twin workshop contains a vast quantity of heterogeneous data from multiple sources, such as the historical state of workshop equipment, which is essential for analyzing implicit problems and bottlenecks in manufacturing tasks. Nevertheless, the current unidirectional and irreversible time flow of the digital twin workshop makes it difficult to optimize workshop productivity using historical data. This paper proposes a scene equipment saving and loading method for the digital twin workshop to address this issue. The initial steps involve defining a workshop information model which represents multiple pieces of workshop equipment in the virtual space and the content of the data it covers. This model stores data for each object type on the workshop using distinct data structures; a workshop element data saving and loading method is proposed, which can save the historical scene equipment data of the digital twin workshop and load the saved data into the digital twin software; finally, a case study is conducted to determine the data compatibility, the saving and loading efficiency, and the system's ability to save and load actual workshop scenes. The results demonstrate that this method can efficiently save and load scene equipment data on the workshop, enabling workshop administrators to identify problems and bottlenecks in historical manufacturing tasks and then take steps to increase workshop productivity.  
digital twin; data management; historical data; information model; system framework +
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to model digital twin objects [4]. In addition to this, related data modeling work has been carried out at the level of manufacturing tasks [5], individual equipment [6], and tools [7]. Modeling the data on the workshop and abstracting it into different categories based on the characteristics and commonalities of the data can reveal opportunities to optimize the management of the data and improve the efficiency of the manufacturing tasks in the workshop. However, modeling and analyzing a broader range of objects in the workshop is challenging, and at this stage, there are still many studies that focus only on individual equipment or components for DT modeling. In addition, most of the DT in the studies are non-retrogressive in the time dimension, which is an obstacle when it comes to analyzing the implicit problem of workshop history.  
In this paper, we propose a scene equipment saving and loading method for the DT workshop. The saving task is the process of writing the object information data from the DT workshop system to the local disk as an archive file, while the loading task corresponds to the process of loading the data information contained within the archive to the workshop software. This method makes it possible to save historical data for workshop equipment objects locally and return to historical time nodes when analyzing workshop manufacturing bottlenecks. A 3D historical time state scene is provided to the workshop administrator, helping them analyze the manufacturing process from a more detailed perspective.  
The rest of this paper is structured as follows: Section 2 presents a literature review on building information models and using data for production process optimization in the DT workshop; Section 3 defines the DT workshop information model using a five-layer framework, proposes a workshop scene equipment saving and loading model and presents the principles and details of the workshop information saving/loading process; Section 4 introduces the case study test objects, system configuration and test methodology; Section 5 presents the results and a discussion of the case study's testing of data compatibility, saving and loading efficiency as well as virtual workshop scene saving and loading capability; finally, conclusions and future works are drawn in Section 6.