## 3 Intelligent Production Line System Architecture Based on Digital Twin  
This study examines an intelligent manufacturing line for automobile wheel hubs and presents the development of a digital twin system. It encompasses a physical production line layer, a data layer, a digital twin production line layer, and an application service layer, all organized through a hierarchical design methodology. The integration of the Industrial Internet of Things (IIoT) with digital twin technology establishes a novel framework that enables three-dimensional (3D) visual monitoring. The implementation of this system is expected to enhance production efficiency, reduce costs, and improve quality control, as evidenced by successful applications of digital twin technology in automotive manufacturing. Figure 4 illustrates the architecture of the intelligent production line system, which utilizes digital twin technology to integrate functions across the various layers:  
Figure 3: Digital twin mapping in automotive wheel hub production. (1) Physical production line layer: This layer serves as the foundation of the digital twin production line system and is responsible for critical tasks such as 3D model construction and the collection of production data. It consists of two main modules: 1 The physical equipment module, which integrates industrial robot execution units, CNC machining centers, tool units, sorting units, grinding units, testing units, storage units, a total control unit, and other core equipment, along with personnel and the production line environment, collectively constituting the physical entity of the production line. 2 The data perception module, which includes sensors, programmable logic controllers (PLCs), industrial computers, motion controllers, and network infrastructure, is responsible for transmitting commands and collecting data to facilitate real-time communication and efficient data acquisition. (2) Data layer: The data layer plays a central role in the digital twin production line system, ensuring efficient connectivity and stable operation among its components. Its primary function is to facilitate interconnectivity within the system by coordinating data collection, transmission, integration, and analysis, while simultaneously driving the system's operations. The data layer consolidates real-time data from the physical production line, data generated by the digital twin, and information from the application service system. Comprehensive integration and thorough analysis of these data are crucial for the efficient  
Figure 4: Architecture diagram of automobile wheel hub intelligent production line system based on digital twin. functioning of the digital twin. The data layer is essential for uploading and storing data from the physical entity layer onto the server, subsequently distributing it to the digital twin production line layer, thereby enriching the twin model with valuable information. Additionally, it addresses the big data requirements of the application service layer and enhances capabilities for data visualization, status monitoring, and fault diagnosis. (3) Digital twin production line layer: The digital twin production line layer facilitates the precise digital mapping of the physical production line, encompassing a comprehensive digital twin model that includes geometric models, assembly constraints, visual materials, behavioral and logical properties, and data interfaces. Within the framework of digital twin technology, the physical production line layer employs logical scripts and real-time data to drive a model that accurately emulates actual processing actions, signal transmission, and control logic. This model serves as a foundation for 3D visual monitoring [35].