[Abstract]: This paper focuses on the application of typical DCS (Distributed Control System)/FCS (Fieldbus Control System) in our steelmaking process. It mainly introduces the two major industrial control systems, DCS and FCS, from the perspective of overall production network configuration, and provides a schematic network configuration in the steelmaking plant. Infi90 is one of the most widely used DCS systems, while the Siemens series is a typical FCS system. Through network configuration in the steelmaking process, this paper compares and analyzes the distributed control system and the fieldbus control system. [Keywords]: Steelmaking process, Distributed Control System (DCS), Token Ring Network, INFI90, Fieldbus Control System (FCS), Siemens S7, PROFIBUS-DP (Decentralized Periphery) 1. Foreword Meishan Steel Plant successfully commenced full-scale continuous casting in April 1999, setting a precedent for similar enterprises in the history of the global metallurgical industry (only Meishan Steel Plant and Nucor in the United States have achieved this feat). As one of Baosteel's three major carbon steel production bases, Meishan can now produce over 30 steel grades in 6 major categories, and has developed high-value-added steel grades such as cold-rolled steel, welded cylinder steel, pipeline steel, and container steel. Among these, automotive beam steel, welded cylinder steel, and container steel have become Meishan brands. The effective operating rate and hourly output of its continuous casting machines have also achieved the highest ranking in the country. Before 2003, the entire steelmaking process used Bailey's Infi90 as the control system. In 2002, the steel plant added SIEMENS to its continuous casting process. The No. 2 continuous casting machine, controlled by a PLC, went into operation in February 2003. Designed for a casting speed of 2.4 m/m, it incorporates the world's most advanced control technology and will play a leading role in this year's production plan. The steelmaking process is shown in Figure 1: Figure 1 Steelmaking Process Flow Diagram 2. DCS, INFI90, and Steel Plant Production Network Configuration Diagram The DCS distributed control system is a centralized management and distributed control system based on microprocessors. Functionally, it is layered into field control level, process unit control level, workshop operation management level, and plant-wide optimization and scheduling management level, thus forming different divisions of labor and related functional departments in production, enabling the production line and service line to achieve seamless integration. The IEEE 802.4 token bus and IEEE 802.5 token ring communication protocols are the most widely used in DCS systems. The working principle of a token ring network is that a unique "token" short frame continuously flows through the loop in a closed loop, searching for a station that needs to send information. Only by intercepting the token can a station send information. Moreover, as long as one station sends information, there are no more idle tokens flowing in the loop, thus allowing for efficient operation under heavy load. After interception, the token's unique identifier is converted into an identifier for the information frame. After one loop, it will inevitably return to the sending source station, check the returned data, and diagnose whether the transmission was successful. The token is then released, and the search continues. INFI90, a typical DCS system developed by Bailey, has been widely used since the 1970s, becoming a mainstream representative of process industrial automation control at the time. It improves equipment availability through the dispersion of personnel, location, function, hazard, equipment, and operation. The continuous casting loop of the steel plant has 22 (12 + 9 + APMS) stations distributed throughout; each station has 1-3 controllers (MFPs) forming the process unit control level; HMIs realize workshop operations, etc., all of which are based on the DCS function definition to form a complete production network. The NIS/NPM system transmits data between stations using a token protocol, and the 19 downstream controllers form a CONTROLWAY communication network. Sub-modules have their own extension buses, and the management layer relies on TCP/IP for monitoring. Therefore, the numerous independent protocols at each layer are a major drawback of the DCS. This system has been fully utilized in the continuous improvement of the steel plant, and its network configuration diagram is shown in Figure 2. 3. FCS, Siemens S7, and Steel Production Network Configuration Diagram Fieldbus is a real-time control communication network that interconnects the lowest-level field controllers and field intelligent instruments in automation, following all or part of the communication protocols of the ISO OSI Open Systems Interconnection Reference Model. The FCS field control system transforms individual, distributed measurement and control devices into network nodes, forming a network system and control system that jointly completes the automatic control tasks. Therefore, fieldbus is both a communication network and an automatic control system. The steel plant uses Siemens PROFIBUS-DP, a typical bus type, as its production network. Its data transmission type is RS485, supporting communication rates from 9.6K to 12M and repeater expansion functionality. It supports communication based on fiber optic transmission media; it also supports point-to-point, bus, and ring fiber optic networks. The controller can be configured for dual-machine hot standby and redundant communication modes for applications with high reliability requirements. The controller or master controller is based on a general-purpose industrial PC and Windows NT hardware and software platform. The bus interface generally uses a PCI bus PROFIBUS network card (such as CP1613). The steel plant uses only a 1.5MDP communication rate, fiber optic transmission media repeater expansion, dual-machine hot standby, and bus links to form a production network, as shown in Figure 3. PROFIBUS-DP is mainly used for high-speed data transmission in industrial automation systems to realize adjustment and control functions. It is a high-speed, low-cost communication used for communication between equipment-level control systems and distributed I/O. CP443-1 communicates using the TCP/IP protocol and connects to EWS engineering stations, servers, etc. CP443-5 connects to VVVF, ET200 and other industrial control products using the PROFIBUS protocol. Its network is simple and easy to maintain. Since the input and output modules ET200 are in the form of bus transmission, they are installed at the field nodes, saving a lot of signal cables. This is the biggest advantage of PROFIBUS over DCS. The No. 2 continuous casting main system of the steel plant uses 6 PLC processors and dual server hot standby. Among them, VVVF has two buses for information communication with PLC and dedicated machine reading and downloading of frequency conversion parameters. 4. DCS/FCS Comparison (1) Openness and Interoperability Openness FCS will break the monopoly of large DCS manufacturers and bring equal competition opportunities to small and medium-sized enterprises. Interoperability enables the "plug-and-play" function of control products, allowing industrial control products from different manufacturers to be interchangeable and replaceable. (2) Decentralization: Thorough decentralization means that the system has high reliability and flexibility, the system is easy to reorganize and expand, and easy to maintain. (3) Low cost: To measure the overall cost of a control system, one should not only consider its construction cost, but also the total investment in the entire life cycle of system installation, commissioning, and especially operation and maintenance. Compared with DCS, FCS's open architecture and OEM technology will greatly shorten the development cycle and reduce development costs. The thoroughly decentralized distributed structure will change the 1-to-1 analog signal transmission mode to the 1-to-N digital signal transmission mode, saving a large number of A/D and D/A conversion devices in the analog signal transmission process. Network protocol transmission replaces the installation cost of a large number of signal lines and wiring. Reliable performance reduces maintenance costs. Therefore, overall, the cost of FCS is much lower than that of DCS. From a maintenance perspective, FCS is convenient for production with its unified protocol, mutual compatibility, reasonable reliability, and cost-effectiveness. From a cost perspective, it is the reason for FCS to replace DCS. 5. Conclusion It can be said that openness, decentralization, and low cost are the epoch-making transformative factors in traditional automatic control systems. Their depth and breadth will surpass any previous revolution, inevitably ushering in a new era of automatic control. Due to the need to adapt to the decentralized, networked, and intelligent development trend of industrial control systems, TCP/IP Ethernet will undoubtedly be the best choice for truly realizing openness in future integrated industrial system control, including production networks (including between field control levels, process unit control levels, workshop operation management levels, and plant-wide optimization and scheduling management levels), office networks, and the World Wide Web.