Abstract: This paper mainly introduces the use of PROFIBUS fieldbus technology to build an enterprise control network, realize data acquisition and remote monitoring; and uses OPC interface technology to achieve seamless connection between the bus control network and management information network, thereby improving the enterprise's overall automation level and management level. Keywords: PROFIBUS bus, OPC specification, control network, integrated automation, monitoring system 0. Introduction Fieldbus technology is a network communication technology for various field automation devices and their control systems that developed rapidly in the 1990s. It is a data communication system for various field instruments (including transmitters, actuators, recorders, single-loop controllers, programmable logic controllers, process analyzers, etc.) and computer-based control systems. PROFIBUS fieldbus is an international standard for networking a certain number of area and unit-level devices, mainly used for factory automation workshop-level monitoring and field device-level data communication and control. It can realize distributed digital control and field communication networks from the field device level to the workshop level monitoring, providing a feasible solution for realizing factory integrated automation and intelligent field devices. Integrated automation is the development direction of modern industrial automation. In a complete enterprise network architecture, the fieldbus control network model should involve the data transmission process from the bottom-level field device network to the upper-level information network. The network is the foundation of enterprise integrated automation. In the entire enterprise network architecture, the fieldbus occupies a fundamental position; therefore, constructing a complete fieldbus control network model is of great significance. This model extends to the highest level of the control field, namely the management decision-making level. Therefore, it requires close integration of the control network and the information network to ensure correct data transmission and forwarding from the bottom-level field devices to the top-level production management. The OPC specification is based on OLE/DCOM technology, and OLE/DCOM supports network protocols such as TCP/IP. Therefore, various subsystems can be physically separated and distributed across different nodes in the network. The OPC standard ensures that automation systems and business systems can share information and interoperate through the factory. Therefore, using OPC interface technology can achieve seamless connection between the control network and the management information network. 1. System Design Requirements and Tasks To align with international standards and meet the enterprise's informatization and modernization requirements. A Guangdong alkali plant plans to build a comprehensive information network system for enterprise management and production process monitoring. Utilizing advanced technology, the system will achieve network interconnection, creating a network system suitable for modern office and industrial process control. Simultaneously, it will be interconnected with a wide area network (WAN) to achieve full information sharing and secure information transmission mechanisms. The system will centrally monitor nearly 856 test points and alarm points (temperature, pressure, liquid level, etc.) across six production workshops in the plant area from a central control room. Real-time data from field equipment will be published to the company website, accessible to users via a browser, enabling the sharing of various information data. The control network is required to have high real-time performance, reliability, data integrity, and availability. Each control substation should be able to perform safe and reliable monitoring and control of field-level industrial equipment, featuring a user-friendly interface that dynamically displays the process flow, simple parameter settings, and functions such as historical and real-time trend curve queries, alarms, and automatic report printing. 2. System Design The data acquisition and remote monitoring system utilizes an S7-300 series CPU315-2DP programmable controller, PROFIBUS-DP communication modules, and extended I/O modules interconnected via a PROFIBUS fieldbus. The integrated cabling of the data acquisition and monitoring system at each control substation is based on the PROFIBUS-DP framework. In the six workshops, 14 S-300 PLCs and I/O expansion modules are used to connect to sensors in the industrial field, depending on the input points. The control substations transmit real-time data acquired by the PLCs to the main monitoring computer in the main control room via the PROFIBUS bus for display. In line with the requirements of resource information sharing, a comprehensive enterprise management and production process monitoring information network system is built using PROFIBUS bus and Internet technology, achieving tight integration between the control network and the information network. The control network interconnects with the information network through real-time databases and OPC interface technology, establishing a comprehensive real-time information database for the enterprise, providing a basis for optimized control and scheduling decisions. The data acquisition and remote monitoring system of an alkali plant in Guangdong mainly consists of subsystems such as distributed I/O data acquisition, main station monitoring, remote monitoring, company intranet, process control, and integrated network cabling. The system structure and configuration are shown below: [align=center] Figure 1. System Block Diagram[/align] 2.1 Data Acquisition and Monitoring System Based on the characteristics of the data acquisition and remote monitoring system of a certain alkali plant in Guangdong, Siemens' fully integrated automation products are used. The data acquisition system is composed of S7-300 series CPU315-2DP, PROFIBUS-DP communication modules, and SIMATIC ET200M expansion I/O modules, and is integrated through the PROFIBUS bus. After considering various factors, this solution has a high performance-price ratio. In traditional factory automation, input/output devices are connected to a centralized rack. When equipment is changed or the system is expanded, it leads to a large amount of wiring work, high cost, and low flexibility. The system uses SIMATIC ET200 distributed I/O to connect components through an open and standardized fieldbus system, which is the best solution to these problems. The human-machine interface (HMI) of the control substation adopts Siemens' fully integrated PROTOOL configuration software, developing a user-friendly and aesthetically pleasing interface that can dynamically display the process flow and simplify parameter settings. It also includes functions such as historical and real-time trend curve query, alarms, and automatic report printing. Field-level execution equipment is centrally controlled by PLCs and programmed using adaptive, fuzzy, and intelligent PID control algorithms, ensuring safe and reliable control and achieving optimized control of unit-level equipment to meet various control requirements of field devices. [align=center] Figure 2. Field PROTOOL HMI[/align] 2.2 Central Real-Time Monitoring Layer (Dispatch Center) The main control room uses WINCC as the upper-level monitoring software. WINCC is a neutral system for solving visualization and control tasks in production and process automation. This software is characterized by its ease of use, convenient configuration, reliable performance, and comprehensive functions; it has numerous communication interfaces, allowing communication with various intelligent devices. Based on Siemens' fully integrated automation technology, WINCC can communicate with SIMATIC S7 devices using various protocols through the SIMATIC S7 protocol set. WINCC handles data management, factory data acquisition, alarms, trends, data logging, and Chinese reports within the system. Operators gain a detailed understanding of the entire plant's production operations and monitor field equipment in real time through the terminal, achieving full plant automation control. The WINCC configuration software displays the real-time operating status of each device according to system requirements and features a user-friendly interface. Some human-machine interfaces are shown below: [align=center] Figure 3. Central WINCC Human-Machine Interface[/align] 3. Connection between Control Network and Information Network Traditional real-time monitoring systems, as infrastructure supporting modern industrial production and social life, have been widely used and developed. However, in the past, even with the best technology and talent, good real-time monitoring systems could be developed, but due to a lack of openness and overly tight connections between components, the systems became overly complex. This made system updates, expansions, and upgrades extremely difficult. Another major problem in the development of traditional real-time monitoring systems was the duplication of software development; software could not be reused, resources could not be shared, resulting in a significant waste of human and material resources. Now, the OPC standard has become the default solution for system interconnection in the industrial sector, ensuring that automated systems and commercial systems can share information and interoperate through the factory. The OPC specification is based on OLE/COM technology. Furthermore, OLE/COM's extended remote OLE automation and DCOM technologies support multiple network protocols such as TCP/IP. Therefore, OPC clients and servers can be physically separated and distributed across different nodes on the network. The client/server relationship diagram below illustrates the application of OPC in a SCADA system. Enterprise informatization and office automation are mainly achieved through Internet and Web technologies, publishing information online and browsing it through web pages to achieve resource sharing. There are two main ways to update web pages: one is through ActiveX technology, and the other is through dynamic page technology. ActiveX technology achieves dynamic updates and interaction with online information by downloading ActiveX controls. It offers more flexible information representation and interaction methods and has rich development tool support, but it has higher performance requirements for the client machine. Dynamic page technology is implemented through CGI, ASP programming, or embedding various scripting languages. Currently, ASP web page technology is more popular. To achieve the sharing of information resources on the control network, Java scripts can be embedded in web pages to access real-time data from the OPC server, dynamically refreshing the data on the web page; accessing the real-time database and viewing historical trend charts on the web page are also possible. The WINCC server serves as both a central monitoring platform and an OPC server within the system. It allows data exchange with other applications that have OPC client interfaces. Web servers (WEB, email servers) communicate with the OPC server (WINCC server) via the OPC communication interface program, enabling the display of real-time data on the company's webpage. Viewing real-time data via a webpage is shown in Figure 4. [align=center]Figure 4. Webpage Browsing via Information Network[/align] By combining the control network and the information network, a unified distributed database can be established, ensuring the integrity and interoperability of all data. Real-time communication between field equipment and the information network allows users to understand production status anytime, anywhere through a standard graphical interface within the information network. The tight integration of the control network and the information network also facilitates remote monitoring, diagnosis, and maintenance functions. This provides a hardware platform for establishing a complete, efficient, practical, and convenient ERP management system and comprehensive production control, truly achieving full integration and automation of office and process control. 4. Conclusion This system has a large amount of data acquisition, many control substations, and high system reliability. It has basically built a network system suitable for modern office and industrial process control through PROFIBUS bus and OPC interface technology, realizing informatization, office automation and resource sharing. It can operate reliably and safely, and basically meets the design requirements. References 1. Yang Xianhui. Fieldbus Technology and Its Application. Beijing: Tsinghua University Press, 1999 2. Jamahl. An Internet-Based Real-Time Control Engineering Laboratory. IEEE, 1999 3. Zhang Hang et al. Application of Distributed Control System Based on Fieldbus in Water Plant Automation. Electrical Engineering Technology, 2001, (9) 4. Qiu Gongwei. Programmable Controller Network Communication and Application. Tsinghua University Press, 2000, (4). 5. Song Tingxi. Fieldbus and Modern Control Management Networks. Electrical Era, 2001, (10) 6. Tang Jiyang. Fieldbus PROFIBUS Technology and Bus Bridge Products. Electrical Era, 2001, (11) 7. The OPC Data Access Custom Specification 2.0A, OPC Foundation 1997. Design and Implementation of Industrial Networks Based on PROFIBUS Bus Technology