Abstract: This paper introduces the necessity of fieldbus integration technology and the development of fieldbus control system (FCS) integration technology. The design and implementation of FCS integration technology based on Profibus-DP are illustrated with examples, and several integration schemes based on Profibus-DP fieldbus control systems are presented. Several issues that should be considered in fieldbus integration are also discussed. Keywords: Fieldbus control system; Integration; Profibus-DP; PLC; Ethernet 1 Introduction: Fieldbus has become a hot topic in the field of automatic control due to its unique advantages. Building a comprehensive automation system based on the underlying fieldbus control network to achieve integrated enterprise management and control is a goal that enterprises strive to achieve. As the underlying network of an enterprise, fieldbus technology should serve the enterprise's goals to complete information integration. Fieldbus control system integration technology has gradually developed and progressed based on this goal. It is an integrated solution that uses a single system or automation platform to accomplish all functions that previously required multiple systems to work together, greatly simplifying the system structure and reducing a large number of interface components. Application integration technology overcomes the boundaries between the host computer and field industrial control devices, and between centralized and decentralized systems. PROFIBUS fieldbus technology is an open, digital, multi-point communication underlying control network. Using the fieldbus as a link, it can transform individual, distributed measurement and control devices into network nodes, forming information sharing between underlying intelligent field devices and higher-level system systems, meeting the development requirements of distributed, flattened, and intelligent industrial control systems. PROFIBUS accounts for a significant proportion of fieldbus applications and has important advantages, consistently holding a pioneering position in the field. Due to the wide applicability of PROFIBUS (it is suitable for both discrete processing in industrial automation and continuous and batch processing in process automation), as well as its maturity, advancement, and landmark status, this article uses PROFIBUS as a representative of fieldbus to introduce the integration technology of fieldbus control systems. 2. Development of Fieldbus Control System Integration Technology 2.1 The Emergence of Fieldbus Control Systems Fieldbus is a product of the integration of three different fields: process control technology, intelligent instrumentation technology, and computer network technology. It brings automatic control systems and equipment into the information network, becoming the underlying layer of the enterprise information network, thus providing a feasible foundation for realizing enterprise information integration and comprehensive enterprise automation. Fieldbus has led to a transformation of the traditional control system structure, forming a new type of network-integrated fully distributed control system—the Fieldbus Control System (FCS). 2.2 The Development of Fieldbus Control System Integration Technology Due to the continuity and inheritance of technological development, and driven by R&D investment and market interests in different systems, the emergence of fieldbus control systems will not cause other systems (such as DCS, PLC, etc.) to disappear quickly, resulting in a situation of multiple system integrations. Currently, multiple fieldbuses still coexist in the world, and the standardization of fieldbuses is diversified. Therefore, it is necessary to develop integration technologies between multiple fieldbuses. Now the Internet and Intranet (enterprise internal information network) are connecting computers and communication devices around the world into a global data network, which has generated much more powerful functions than isolated networks. With the emergence of the field control network Infranet composed of various fieldbus intelligent units, the devices on the control network are also connected to the Internet, and a new generation of enterprise information network structure has also emerged. How to achieve seamless connection between the control network and the enterprise information network is the focus of enterprise information network development in the near future. The information integration technology of fieldbus control system is generated under such trend. Due to the development and competition of various fieldbus technologies, the penetration and application of various mainstream computer technologies in the field of industrial control, and the continuity and inheritance of automation technology development, the research and development of integration technology in fieldbus control system will face the situation of multi-bus integration, multi-system integration, and multi-technology integration [3]. 3 Integration of Profibus-DP fieldbus control system Combined with the fieldbus control system of the "Intelligent Control Network Technology Laboratory of Beijing Union University", this paper explains how to realize the integration technology of Profibus-DP fieldbus control system to achieve the integration of Infranet, Intranet and Internet to form a measurement, control and management integration. 3.1 Network Architecture The controlled field devices include two three-container level control systems, two belt conveyors, and three vertical electric furnaces. The three-container level control system is a dual-input, dual-output system that controls the opening of the pump valves to bring the liquid levels in the three containers to the set values. The belt conveyors' transmission speed is changed by controlling the frequency of the frequency converter. The vertical electric furnaces are dual-input, dual-output temperature field control objects, with their temperature controlled by adjusting the duty cycle. Because there are many controlled objects and they are widely distributed, the monitoring system must be thoroughly decentralized and distributed. The entire system consists of a three-layer network: the bottom layer is the field device layer, the middle layer is the monitoring layer, and the top layer is the information management layer. The field device layer is based on the PROFIBUS-DP bus, interconnecting field devices and integrating a PLC system into the distributed control network Infranet. The monitoring layer is located in a ring-shaped industrial Ethernet network, acquiring data from the field devices to perform various control, operating parameter monitoring, alarm, and trend analysis functions, as well as control configuration design. It connects fieldbus segments to Ethernet segments via a dedicated fieldbus converter, making system configuration more flexible. The information management layer connects to the campus LAN and the Internet to achieve a remote monitoring system in a distributed network environment. Why use Ethernet? Because fieldbus is designed specifically for communication between industrial field-level devices. It only solves the information integration problem of the lower-level automation system and is not suitable for transmitting large amounts of data, nor is it easy to integrate with the management layer. Ethernet, on the other hand, was originally designed for office networks for data processing, and industrial Ethernet can achieve very high communication speeds. Utilizing the advantages of Ethernet, combined with PLC controllers and fieldbus, a fully distributed and open distributed control system can be constructed. 3.2 Hardware and Software Configuration: Field Layer: Considering the wide distribution of equipment and the need for parallel operation of various processes and devices, three Profibus-DP buses are used to form the entire lower-level control network to control the production process of each controlled object in real time. Each bus contains a PLC master station and several DP slave stations, and the three buses operate independently without affecting each other. In this example, a Siemens SIMATIC S7 series PLC is used as the Profibus master station. Three PLCs are connected to Ethernet via a switch. Field devices such as smart sensors, actuators, and frequency converters act as slave stations, using the Profibus-DP protocol to communicate with the PLCs via the field devices, Profibus-DP communication modules, and expansion I/O modules. If more controlled objects need to be added, the PLC station (or other master stations) can be expanded on the Ethernet network to form several new buses, without affecting the existing PLC station and buses. (1) 1# Profibus-DP bus controls two three-container level devices: PLC S7-300 (CPU model CPU 314C-2 DP) is the master station, CP 343-1 communication card realizes the connection between PLC and Ethernet, four level sensors and four electromagnetic pumps of the two three-container devices are slave stations, interconnected through Profibus-DP bus and communicate with PLC master station; (2) 2# Profibus-DP bus controls two belt conveyors: PLC S7-400 (CPU model CPU 414-3 DP) is the master station, CP443-1 communication card realizes the interconnection between PLC and Ethernet, ET200M IM 153-1 is the DP remote slave station, communicates with PLC master station through Profibus-DP bus, ET200M slave station has three I/O modules, and the four frequency converters of the two belt conveyors communicate with the I/O modules of ET200M station respectively; (3) Three vertical electric furnaces are controlled by Profibus-DP bus: PLC S7-400 (CPU model CPU 412-2 DP) serves as the master station, CP443-1 communication card realizes the interconnection between PLC and Ethernet, and ET200S IM151-1 serves as the DP remote slave station, communicating with the PLC master station through Profibus-DP bus. The ET200S slave station is equipped with a power supply module and four I/O modules. The six RTD power supplies and six temperature sensors of the three vertical electric furnaces communicate with the I/O modules of the ET200S station respectively. Monitoring layer: It consists of multiple computers, multiple engineering stations and monitoring stations, which can be added according to actual needs without affecting each other. Each station communicates with each PLC station through Ethernet. The engineering station is equipped with Step7 control software, which is the supporting software for Siemens SIMATIC S7 series PLCs and is responsible for the hardware configuration, software programming, parameter setting, etc. of the system. To establish communication between the upper-level computer stations and the lower-level PLC stations, Step7 software is needed to assign IP addresses to each CP module for Ethernet communication. The monitoring station is equipped with WinCC monitoring software compatible with Siemens PLCs, enabling system software configuration, including data acquisition, data recording, data management, alarms, trend analysis, and report printing. Operators can access detailed information about the operation of each device through their terminals, achieving real-time monitoring and automatic control of field equipment. The information layer consists of a campus LAN connected to the Internet, comprised of high-performance computers, workstations, and PCs. Through client and server connections, a distributed database management system is established, integrating general and real-time databases to achieve data sharing and maintain data integrity, interoperability, and consistency. Remote monitoring can be achieved by installing monitoring software on workstations within the LAN. Internet connectivity enables information integration between internal management and remote network points. This control system, incorporating Ethernet technology, achieves network integration, information transmission, remote control, and monitoring, and can be expanded with additional monitoring and PLC stations as needed. By combining this with Internet technology, a comprehensive information network system for enterprise management, production, and process monitoring can be built, achieving tight integration of the control network and information network. This allows information from field devices to be accessed on the enterprise intranet and even the extranet without requiring on-site observation. This control system example completes the integration of a Profibus-DP fieldbus-based control system, truly realizing an integrated Intranet/Infranet/Internet measurement, control, and management network system, achieving informatization, office automation, and resource sharing. The entire control system is built to simulate factory equipment, has operated for an extended period with excellent results, and is a suitable network system for modern office and industrial process control. This control system utilizes only a few integration technologies based on actual needs, but there are many other integration schemes that can be implemented based on the Profibus-DP fieldbus control system; the appropriate scheme should be selectively applied according to the specific needs of the project. Several commonly used solutions are presented below: integration of Profibus-DP with other buses, such as CAN bus and LONWORKS bus; integration of FCS with PLC and DCS; integration with Ethernet to achieve interconnection between the field control network (Infranet) and the enterprise's internal information network (Intranet); and integration with technologies such as OPC (OLE for Process Control) and DDE (Dynamic Data Exchange) to achieve data and information sharing. 4. Conclusion The Profibus-DP fieldbus control system integration technology uses the Profibus-DP bus as the underlying control network, integrating the advantages of the Profibus-DP bus and other related technologies to achieve interconnection with the upper-level enterprise network. This allows for timely exchange of field production and control information within the enterprise network, and even the publication of relevant information on the enterprise's external network, providing greater information sharing. Relevant personnel can easily understand the enterprise's production status, which is beneficial for management decision-making. It also enables remote monitoring, diagnosis, and maintenance of production objects, saving significant manpower and resources. It is particularly suitable for large enterprises, bringing substantial economic benefits. However, the following issues must be considered when implementing integration technology based on fieldbus control systems: 1. Whether the project is suitable for using fieldbus; 2. Network performance, such as system real-time performance and reliability; 3. Network structure, such as network topology type and maximum segment length; 4. Whether there are successful application precedents; 5. Market factors, etc. References: [1] Yang Xianhui et al. Fieldbus Technology and Its Applications [M]. Tsinghua University Press, 1999 [2] Lei Lin. Fieldbus Control Network Technology [M]. Electronic Industry Press, 2004 [3] Richard H Caro. Ethernet will transform fieldbus [J]. Hydrocarbon Processing, 2000, 79 (6): 7-9 [4] Feng Dawei, Yang Xianhui. Development of Fieldbus Technology from the Perspective of Information Integration [J]. Metallurgical Automation, 2001, 6 (5): 22-27 [5] Teng Bin, Wang Cheng. Interconnection of Ethernet and Fieldbus [J]. Microcomputer Information, 2004 (10): 41-42 [6] A. Flammini, P. Ferrari, E. Sisinni. Sensor interfaces: from fieldbus to Ethernet and Internet [J]. Sensors and Actuactor, 2002 (101): 194-202