In the past, the biggest obstacle for Ethernet to enter the fieldbus system was the uncertainty of Ethernet, because Ethernet uses CSMA/CD medium access control protocol in the data link layer. This protocol is highly efficient in the case of light load, but in the case of heavy load, because the protocol will pause for a random time and retry transmission after a conflict. This affects the real-time performance of the data. This is intolerable for the industrial control network with very strict real-time requirements, and the equipment used by Ethernet, including connectors, hubs, switches and cables, are designed for office applications and do not meet the requirements of the harsh environment of the industrial site. In addition, Ethernet has poor anti-interference performance, does not have essential safety performance, and cannot supply power to field instruments. However, with the development of technology, 100M Ethernet has become the mainstream, ten gigabit Ethernet has also been put into actual operation, and the development of switched Ethernet technology has fundamentally solved the problem of large randomness of transmission time caused by Ethernet collision. And Ethernet equipment manufacturers are also developing equipment that meets the requirements of the industrial field to meet the requirements. At the same time, it has the following characteristics:
1, Ethernet is the most widely used computer network technology, by a wide range of technical support. Almost all programming languages support Ethernet application development, such as Java, Visual C++, Visual Basic, etc. These programming languages are widely used and highly valued by software developers, so they have good prospects for development. Therefore, if Ethernet is used as fieldbus, it can ensure that a variety of development tools and development environments can be selected.
2. Low cost. Because Ethernet is the most widely used, it is highly valued and widely supported by hardware development and manufacturers. There are a variety of hardware products for users to choose from, and because of the wide application, hardware price is relatively low. At present, the price of Ethernet network adapter is only one-tenth of that of Profibus, FF and other fieldbuses, and with the development of integrated circuit technology, its price will further decrease [34].
3. High communication rate. At present, 100M fast Ethernet has been widely used, 1000M Ethernet technology is gradually mature, 10 gigabit Ethernet has been put into use, its rate is much faster than the current fieldbus. Ethernet can meet the higher requirements for bandwidth.
4. Rich software and hardware resources. Because Ethernet has been used for many years, people have a lot of experience in the design and application of Ethernet, and are very familiar with its technology. A large amount of software resources and design experience can significantly reduce the development and training costs of the system, which can significantly reduce the overall cost of the system, and greatly speed up the development and promotion of the system.
5. Great potential for sustainable development. Due to the wide application of Ethernet, its development has been widely valued and a lot of technical investment. And, in this era of information change, the survival and development of enterprises to a large extent depends on a fast and effective communication management network, the development of information technology and communication technology will be more rapid, more mature, thus ensuring that the Ethernet technology continues to develop forward.
Therefore, if the industrial control field uses Ethernet as a communication network platform between field devices, fieldbus technology can be avoided from the development of computer network technology outside the mainstream, so that fieldbus technology and other network technology to promote each other, common development, and ensure the sustainable development of technology, in terms of technology upgrade without separate research investment. In the future, industrial control network is bound to develop to industrial interconnection.
