# Research on a Real-Time Control System for Discrete Factories Based on Digital Twin Technology
## 1 Introduction  
The real economy, dominated by the manufacturing industry, determines a country's economic strength and economic health level [1]. China, despite having developed into a machinery manufacturer of a certain quantity, still has some way to go when compared with some machinery manufacturers of quality and efficiency in the world [2]. Therefore, the Industry 4.0 concept and the Made in China 2025 strategy are highly respected in the transformation and upgrading of the manufacturing industry. Through a Baidu online search, there are two different production methods in the modern manufacturing industry: discrete manufacturing and process manufacturing. Discrete manufacturing is suitable for producing products which are composed of multiple independent components, such as automobiles, electronic products, mechanical equipment, etc. In discrete manufacturing, products are decomposed into multiple parts or components, produced at different processing locations separately, and ultimately assembled into a complete product. Process manufacturing is process-oriented and is suitable for industries with continuous production processes and relatively fixed product forms, such as chemical, refining, steel, and food and beverage enterprises. In process manufacturing, raw materials are transformed into final products through a series of continuous production steps and chemical or physical changes. Most discrete manufacturing enterprises apply multi-product and small-batch production methods, meaning that the control system of discrete enterprises is usuallymuch more complex than that of process-oriented manufacturing enterprises. Mechanical gears are widely used as mechanical components, and gear manufacturing enterprises are most typical discrete manufacturing enterprises and can serve as the representatives of discrete manufacturing enterprises. Gear factories are the main departments for each gear manufacturing enterprise, and many gear factories are presently striving to promote intelligent manufacturing to improve efficiency and reduce costs. Digital twin technology is currently one of the most reliable ways for gear factories to achieve intelligent manufacturing. Meanwhile, a gear factory is willing to try to use digital twin technology to establish a real-time control system. The gear factory is specialized in manufacturing the intermediate shaft dual gear of a new energy vehicle gearbox, and has currently implemented the digital management of barcodes and QR codes. Now, it wants to transform and upgrade to intelligent manufacturing, but it does not know where to start. Therefore, the research on the real-time control system of discrete factories not only conforms to the Industry 4.0 concept and the Made in China 2025 strategy, but can also meet the needs of transforming and upgrading discrete factories. As the production mode of the manufacturing industry gradually develops towards complex, integrated, and composite directions, various process data have increased dramatically. Meanwhile, the digital equipment has also been introduced to the manufacturing site, with huge amounts of data reflecting the status of production. Product manufacturing and process control will gradually enter the stage of digital management. In the research regarding digital factories at the present stage, [PERSON] et al. discussed the various existing architecture definitions of digital twins, and elaborated on the three major characteristics of intelligent digital twins as follows: synchronization with the real world, active data acquisition ability, and integration with artificial intelligence, proposing a collaborative simulation development method for agent-based digital twin systems [3]. [PERSON] et al. systematically reviewed the thematic analysis of digital twin technology over the past decade and summarized the characteristics and future research areas of digital twin systems. When describing the characteristics of digital twins, a summary analysis was conducted concerning the conceptual state and key terms [4]. [PERSON] et al.