# Digital-Twin-Based Monitoring System for Slab Production Process
## 3 The Proposed System  
### System Structure  
A DT refers to the virtual representation of entities created using digital technologies while maintaining a one-to-one relationship with their corresponding physical objects [PERSON] et al. (2019). DTs offer a comprehensive and visual model, enabling users to gain precise insights into the status of monitored objects. This facilitates better understanding and monitoring of physical entities in the real world. Consequently, this paper proposes a DT-based monitoring system for the slab production process. The system comprises two modules: the defect detection module and the production management module. The defect detection module utilizes a neural network to obtain defect type and positional coordinate information from images. The production management module facilitates data management of slab production output and utilizes objective factors, namely temperature and humidity, to predict the probability of defect occurrence. Figure 1 illustrates the overall structure of the monitoring system. The digital twin is a virtual replica of a physical object, establishing a bidirectional mapping relationship between the physical entity and its digital model. Following the closed-loop structure of ISO 23247, the system monitors the slab production process through DT-driven implementation [PERSON] et al. (2019). The system encompasses two spaces: the physical space and the virtual space. In this system, the physical layer refers to the collection of entity models present in the production scene during the slab production process, including the slab entity, scanning and imaging devices, and sensing detection devices. Scanning and imaging devices are used to capture images of slabs for subsequent defect identification and classification. Sensors and detection devices primarily collect dynamic environmental data during the production process. To facilitate user monitoring and observation, the virtual space must be kept in real-time synchronization with the physical space and reflect its relevant characteristics. The virtual space includes the data layer, model layer, application layer, and service layer, each with distinct functionalities outlined below. 1. Data layer: This layer manages collected temperature, humidity, weight, and image data, forming a historical record for user observation at any time. 2. Processing of data layer: The data obtained from the data layer are processed, with temperature, humidity, and weight data used for calculating production output and predicting the probability of defect occurrence. Image data are employed for identifying the presence of defects and obtaining classification information. 3. Model layer: This layer is responsible for creating a virtual model of the slab and simultaneously displaying the position, size, and classification of defects within the model. 4. Application layer: Acting as a bridge between the server and model layers, this layer facilitates virtual visual monitoring of slabs and production state monitoring. UNITY 3D stands out as a robust and versatile game development engine, offering seamless integration capabilities for a diverse range of data sources [40]. This includes the incorporation of real-time sensor inputs, process parameters, and environmental conditions. Serving as a pivotal layer within the monitoring system, it facilitates the creation of an all-encompassing digital representation of the slab production process. 5. Server layer: The server layer is situated upstream of the application layer, providing an intuitive display of the application layer on various terminal devices. By encapsulating the management system constructed in the application layer into different terminal devices, personnel can actively participate in the direct monitoring and management of the slab production process using PC, phone, pad, Web, and VR clients. Figure 1: Monitoring system structure.