Abstract: With the rapid development of fieldbus, Ethernet will also become the development direction of network control systems. Ethernet, with its digital, interoperable, and open characteristics, has received increasing attention and importance. This paper analyzes and solves the key problems of using Ethernet in industrial control networks, and designs and constructs an industrial process control system based on Ethernet. Keywords: Ethernet; industrial process; control system; fieldbus 1 Introduction Due to the different technical characteristics and design features of different fieldbuses, transparent information exchange between products based on different fieldbuses cannot be achieved. Theoretically, different fieldbus products can be connected through network interconnection devices and gateways to achieve mutual information exchange between them. However, this undoubtedly increases the complexity of information transmission. Moreover, since different fieldbus networks have their own proprietary technical specifications in error checking and configuration, information is often lost when transmitted between different buses. Ethernet technology can easily overcome these problems. 2 Control Network System Scheme Industrial Ethernet is a local area network technology that applies Ethernet to industrial control and management. Based on the characteristics of Ethernet and the requirements of existing industrial control networks, the following design scheme is proposed: A dedicated industrial Ethernet control network. Employing proprietary technologies different from ordinary Ethernet, this system uses an Ethernet structure to implement all the control functions of a fieldbus, achieving seamless integration of office automation and industrial automation. For example, it uses specialized Ethernet hub technology, with the hub acting as the network arbiter; field instruments are connected to dedicated Ethernet entry addresses, and data is transmitted using completely separate lines, creating a dedicated network. The structural block diagram and topology diagram are shown in Figure 1. [align=center] Figure 1 Industrial Ethernet Control System Structure Diagram[/align] Ethernet control system integrated with other control networks. Ethernet is gradually developing towards the field device level and is integrating with other network forms as much as possible. Currently, sensors and transmitters based on Ethernet + TCP/IP can directly become network nodes, and their control parameters and control status can be directly transmitted and shared within the enterprise information network, thus avoiding the integration difficulties of FCS due to multiple protocols. However, Ethernet and TCP/IP protocols were not originally designed for the control field. Compared with mature automation solutions, they still have many issues that need to be studied and resolved in terms of architecture, protocol rules, physical media, data, software, and usage environment. Therefore, other control forms retain their respective advantages and complement each other, which is currently the most common application scheme for Ethernet in the control field. Its structural block diagram is as follows. [align=center] Figure 2 Ethernet/FCS Network Structure[/align] Industrial Ethernet, used in combination with other control networks, provides modern industrial enterprises with a wide range of choices, making better use of existing industrial networks, reducing enterprise investment, and lowering costs. Before the widespread application of ideal industrial Ethernet, this hybrid mode is the development direction for some time to come. 3 Control Network Construction 3.1 Hardware Structure of Control Network System As can be seen from the above analysis, the existing fieldbus cannot be completely replaced by industrial Ethernet at present, but we must not ignore the huge potential of the latter. In view of the current situation of China's industrial development, combining fieldbus with industrial Ethernet is more practical. Therefore, this paper proposes a network control system that integrates multiple fieldbuses, PLCs, and FCSs onto a single Ethernet network, using Ethernet, database, OPC, and object-oriented technologies, and enables remote monitoring via the Internet. The control system comprises various field instruments, embedded controllers, PLCs, industrial computers, workstations, database servers, gateway devices, and switched Ethernet connections, and can be divided into a process monitoring layer and an industrial field device layer. The process monitoring layer network serves as the system's backbone, connecting engineering workstations, operator workstations, database servers, and manufacturing execution system equipment. In the industrial field device layer, PLCs with Ethernet interfaces are directly connected to the switched hub, and embedded controllers can access the control network via their built-in Ethernet interfaces. Field monitoring workstations handle industrial monitoring configuration, equipment configuration monitoring, and network management. Remote monitoring workstations can utilize programming to remotely retrieve real-time data and modify parameters, achieving remote monitoring functionality. Intelligent instruments and advanced control technologies can be integrated into a real-time database platform and connected to the enterprise information network and ERP system, providing real-time production data and maximizing enterprise management and production scheduling capabilities. The control network system is characterized by its communication being based on the Ethernet + TCP/IP protocol, integrating various fieldbuses through a gateway. When the host computer sends a query or control command to a field device, it first sends the corresponding information to the gateway via Ethernet and TCP/IP protocols. The gateway then forwards the information to the corresponding field device or smart instrument according to the fieldbus protocol. Furthermore, the OPC (OLE for Process Control) interface specification is used to exchange data with the application in real time. Conversely, when a field smart instrument sends information to the host computer, the gateway acts as a proxy to forward the information to the corresponding host computer. Considering the harsh field environment, when operators and engineers cannot or do not need to be on-site, remote access and control can be achieved via the Internet. 3.2 Software Structure of the Control Network System Considering the complex environment of industrial sites, all field and remote computers in this system are industrial control computers running Windows 2000/NT. This provides secure, reliable, and simple TCP/IP network configuration, supports client/server mechanisms and object-oriented programming, and is capable of handling Ethernet control systems. The task of this system is to integrate real-time information data from the field into a real-time database. Based on this real-time database and operating system platform, configuration software and other application software run on the field industrial control computer. The software design follows the OPC interface specification, so that the upper-level software does not depend on specific devices. Simultaneously, remote workstations monitor the entire system's operation via the Internet or Ethernet. [align=center]Figure 3 Control System Software Functional Module Diagram[/align] The entire system is centered around the real-time database and mainly consists of a database system, a communication system, and a monitoring and configuration system. The database includes a real-time database and a historical database. The real-time database, acting as the system server, is stored separately on an industrial control computer and can store real-time time-series data obtained from various instrument and equipment system interfaces, accessible to remote clients. The real-time database achieves the integration and sharing of process and management data. The monitoring and configuration software is designed in three main modules: an initialization module, a data processing program module, and a multi-threaded event processing module. The initialization module performs functions such as reading the configured system configuration file and initializing the system configuration hardware, reading configuration variable records from the configuration database to create the real-time database, and reading flowchart configuration files to create graphical display screens. After system initialization, the data communication program will be invoked to communicate with the lower-level machine, and a multi-threaded task processing program will be started to realize graphical display, refresh, alarm, historical data storage, real-time report printing, etc. 4. Application of Key Ethernet Technologies in the System To promote the application of Ethernet in the field of industrial control, the Industrial Ethernet Association (IEA) was established internationally, and it collaborates with institutions such as the ARC Advisory Group/ARM Research Center and Gartner Group in the United States to conduct research on key industrial Ethernet technologies. To ensure stable operation in uninterrupted industrial applications, Synergetic Micro Systems (USA) and Hirschman (Germany) have specifically developed and produced DIN rail transceiver series, hub series, and switch series. These are mounted on standard DIN wires and have redundant power supplies; the connectors adopt a robust DB-9 structure. The price of industrial Ethernet communication interface chips developed by NET Silicon (USA) has dropped to $10-15 per chip. Currently, the key technologies for using Ethernet in the field of industrial control are as follows: 1. Real-time communication. Ethernet was initially designed for office automation and did not consider some issues in industrial control. It uses Carrier Sense Multiple Access with Collision Detection (CSMA/CD) to resolve contention at the communication medium layer. This mechanism leads to non-determinism because after a series of collisions, messages may be lost, and communication between nodes cannot be guaranteed, making it difficult to ensure the deterministic and real-time communication required by the control system. However, with the development and widespread application of Internet technology, the following technologies can enhance communication determinism and real-time performance to a certain extent: Using full-duplex port switching; Using high-speed Ethernet; Using switching technology; Furthermore, to improve real-time performance, the Ethernet protocol can be modified and QoS functions can be added to the network. For example, existing Ethernet protocols RETHER (Real-Time Ethernet) and RTCC (Real-Time Communication Control) are novel transmission mechanisms that do not change existing hardware. 2. Bus Power Supply. "Bus power supply" or "bus-fed power" means that the cables connected to field devices not only transmit data signals but also provide power to the field devices. Bus power supply reduces network cabling, lowers installation complexity and cost, and improves network and system maintainability. It is particularly important in harsh and hazardous environments. Since Ethernet was primarily used for commercial computer communication, most devices or workstations already had their own power supplies, eliminating the need for bus power supply; therefore, the transmission medium was only used for information transmission. Bus power supply for field devices can be achieved using the following methods: In-Band method (power transmission via pins 1, 2, 3, and 6). This involves appropriately modifying the physical layer specifications based on the current Ethernet standard, modulating the Manchester signal of Ethernet onto a DC or low-frequency AC power supply, and then separating these two signals at the field device end. [align=center]Figure 4 In-Band Power Supply[/align] While this method achieves consistency with the "bus power supply" method used in traditional DCS and fieldbuses such as FF and Profibus, enabling "one line for two uses" and saving on-site wiring, it differs from traditional Ethernet in the form of signals transmitted over the physical medium. Therefore, this modified Ethernet device can no longer directly interconnect with traditional Ethernet devices, requiring additional adapters to connect (such as a computer's Ethernet card). Furthermore, bus power supply should include overload protection and redundant power supply functions to ensure that in the event of a circuit failure, redundant circuits can automatically switch to another power source to power the terminal device. The author's innovation: This paper applies Ethernet, currently the most widely used local area network technology, to industrial control networks, proposing an Ethernet-based industrial process control system. Furthermore, the use of Ethernet TCP/IP enables openness and low cost. References: [1] Feng Dongqin, Jin Jianxiang, Chu Jian. Analysis of Industrial Ethernet and Real-time Ethernet Protocol. PLC&FA 2005.1:6～7 [2] Zhao Jie, Zhang Fan. Industrial Ethernet Technology and Development [J]. Instrument and Meter User, 2004, 11:1～2 [3] Sui Yunfeng, Liu Yibo, Xie Yi, Zhou Jianhong. Problems and Solutions of TCP in Cable Television Networks [J]. Microcomputer Information, 4-3:141-143 [4] Su Shaoxing et al. 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