Ethernet technology supports almost all network protocols, so it is widely used in data information networks. It has the advantages of high transmission speed, low power consumption, easy installation, good compatibility, high openness and support equipment. In recent years, with the development of network technology and the increasingly high requirements for network performance in the field of industrial control, Ethernet is gradually entering the field of industrial control, forming a new type of Ethernet control network technology. The openness of Industrial Ethernet provides an unparalleled advantage in the seamless integration of industrial control networks and enterprise information networks.
Ethernet has the advantages of high transmission speed, low power consumption, easy installation and good compatibility. It is widely used in commercial systems because it supports almost all popular network protocols. In recent years, with the development of network technology, Ethernet has entered the control field and formed a new type of Ethernet control network technology. This is mainly due to the development of industrial automation systems to distributed and intelligent control. Open and transparent communication protocols are inevitable requirements.
Ethernet technology is introduced into the field of industrial control, and its technical advantages are very obvious: 1Ethernet is a fully open, all-digital network. Devices of different vendors can be easily interconnected according to network protocols. 2 Ethernet can realize industrial control network and enterprise information network. Seamlessly connect, form a fully open network with enterprise-level management and control integration, as shown in Figure 2; 3 software and hardware are low-cost, because Ethernet technology is very mature, hardware and software supporting Ethernet are highly valued and widely supported by manufacturers. There are a variety of software development environments and hardware devices for users to choose; 4 high communication rate, with the expansion of enterprise information systems and the increasing complexity, the demand for information is also increasing, and sometimes even audio and video data are needed. Transmission, Ethernet Ethernet communication rate of 10M, 100M Fast Ethernet has begun to be widely used, Gigabit Ethernet technology has gradually matured, 10G Ethernet is also being researched, and its rate is much faster than the current field bus. 5 The potential for sustainable development is great. In this era of rapid information change, the survival and development of enterprises will depend to a large extent on a fast and effective communication management network. The development of information technology and communication technology will be more rapid and mature. This ensures that Ethernet technology continues to evolve.
Ethernet enters the field of industrial control, and there are also some problems. The main ones are: 1 Real-time problem: The medium access control method of CSMA/CD used by Ethernet is essentially non-real-time. A plurality of nodes hang on a bus to compete for the bus, waiting for the bus to be idle. This approach is difficult to meet the real-time requirements of the industrial control field. This is also the technical bottleneck of Ethernet technology entering the industrial control field; 2 Adaptability and reliability to the industrial environment: Ethernet is designed according to the office environment, and it is required to make the anti-jamming capability and design conform to the requirements of the industrial site. 3 Applicable to the application layer protocol of industrial automation control. The data structure defined by the application layer protocol defined in the information network is not suitable for real-time communication between field devices in the industrial process control field. Therefore, it is also necessary to define a uniform application layer specification. 4 Intrinsic safety and network security: Industrial Ethernet must be considered intrinsically safe if it is used in a flammable and explosive workplace. In addition, Industrial Ethernet, due to the use of the TCP/IP protocol, may be subject to network security threats including viruses, hackers, and illegal operations. 5QOS (Quality of Service) problem: With the advancement of technology, the signal under the control of the factory is not limited to pure digital and analog, but includes Audio and low-resolution Video signals. The network should be able to meet different user needs. And different content to ensure timely real-time requirements.
With the continuous development of network technology, the above problems have been solved completely or partially. 1 In recent years, the fast switching Ethernet technology has emerged. Full-duplex communication can completely avoid collisions in CSMA/CD, and the priority mechanism can be easily realized to ensure the maximum utilization of network bandwidth and the best real-time. performance. It completely avoids possible inefficiencies such as CSMA/CD, master-slave, token, etc. 2Special anti-jamming measures for network equipment manufacturers in different industrial environments make it more in line with industrial requirements; 3 users in application layer protocols TCP/IP protocol stacks can be added or removed as needed, and network protocols that are more industrially compliant are required. 4 Device manufacturers provide devices that adapt to industrial environments, using sealed, rugged, vibration-resistant Ethernet devices. The connector is used to solve the intrinsic security problem; the security management of the network is enhanced by various security mechanisms such as user password, data encryption, firewall, etc., but the solution to the industrial automation control network security problem needs to be studied carefully; 5 with the network speed Improvements and further improvements to the network protocol, QOS issues have also been resolved.
Industrial Ethernet control systems have significant advantages over other control systems and can be used in a variety of industrial control applications. With the further development of integrated circuits, industrial Ethernet and embedded Internet technologies, the era of Ethernet-based industrial control networks will soon come, and become the most open industrial control network architecture. This new type of network system echoes the development of fieldbus in Ethernet, and is a revolution in the traditional industrial control network, which will surely bring a new world to the field of industrial control. However, in some areas such as automotive control systems, CNC machine tools, etc., due to its harsh working conditions, real-time, and high reliability requirements, it is not suitable for industrial Ethernet. From the current trend, there is no doubt that Industrial Ethernet has entered the field control level. But at least for now, it is difficult to completely replace the fieldbus as a single standard for real-time control communication. The existing fieldbus will continue to exist for a long period of time, and the most likely scenario is to develop a hybrid control system with multiple networks coexisting.
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