Fieldbus Development Trend

Fieldbus is the international development formed in the late 1980s and early 1990s for fieldbus technology process automation, manufacturing automation, building automation and other fields of field intelligent equipment interconnection communication network. It serves as the basis of the digital communication network of the factory, communicating between the production process site and control equipment and its connection with higher control management levels. It is not only a grassroots network, but also an open, new type of fully distributed control system. This comprehensive technology with intelligent sensing, control, computer, digital communication and other technologies as the main content, has received worldwide attention, become a hot spot in the development of automation technology, and will lead to profound changes in the structure of automation systems and equipment. Many strong and influential companies in the world have successively carried out the development of fieldbus technology and products to different degrees. The working environment of fieldbus devices is at the bottom of the process equipment, and as the basic communication network at the factory equipment level, it requires the characteristics of simple protocol, strong fault tolerance, good security and low cost: it has certain time certainty and high real-time requirements, and also has the characteristics of stable network load, mostly short frame transmission and frequent information exchange. Due to the above characteristics, the fieldbus system has the characteristics of different upper layer high-speed data communication networks from network structure to communication technology.

Generally, the fieldbus system is called the fifth generation control system, also called FCS - Fieldbus Control System. People generally call the pneumatic signal control system PCS before the 50s the first generation, the electric analog signal control system such as 4-20mA the second generation, the digital computer centralized control system the third generation, and the distributed control system DCS since the mid 70s the fourth generation. As a new generation control system, FCS, a field bus control system, on the one hand, breaks through the limitation of DCS system using communication special network and adopts the solution based on openness and standardization to overcome the defects caused by closed system; on the other hand, the centralized and decentralized system structure of DCS is combined into a new fully distributed structure, and the control function is completely decentralized to the site. It can be said that openness, decentralization and digital communication are the most significant features of fieldbus system.

The development of fieldbus technology should be reflected in two aspects: one is the continued development and improvement of low-speed fieldbus field; the other is the development of high-speed fieldbus technology.

At present, the fieldbus products are mainly low-speed bus products, which are applied in the field of low operation rate and the performance requirement of the network is not very high. From the application status, both FF and Profibus, or some other fieldbuses, can better realize the process control with slower rate requirement. Therefore, it is difficult for anyone to unify the whole world market in the field of control with lower rate requirement. One of the key technologies of fieldbus is interoperability, and it is the wish of all users to realize the unification of fieldbus technology. How to develop and unify the fieldbus technology in the future is an issue of great concern to all manufacturers and users.

High-speed fieldbus is mainly applied to interconnection within the control network, connecting control computers, PLCs and other devices with higher intelligence and faster processing speed, as well as realizing the connection between low-speed fieldbus bridges, which is necessary to fully realize the fully decentralized control structure of the system. This area is still relatively weak. Therefore, the design and development of high-speed fieldbus will be a very competitive field, which will also be an important opportunity for fieldbus technology to realize unification. And what kind of network technology is chosen as the overall framework of high-speed fieldbus will be its primary content.

The development of fieldbus technology has become the focus of industrial automation field, the international fieldbus research and development, so that the measurement and control system has broken the confinement of the long-term closed system and embarked on the journey of open development, which is an excellent opportunity and a serious challenge for the development of fieldbus control system in China. The network of automation system is a major trend of development, and the fieldbus technology is profoundly influenced by the computer network technology. Some new network technologies with significant influence will be further integrated into the fieldbus technology, and these promising fieldbus technologies are: hardware and software technology for intelligent instrument and network device development; configuration resistance, including network topology, network equipment, network segment interconnection, etc.; network management technology, including network management software, network data operation and transmission; human-machine interface, network management software, network data management and network management technology. operation and transmission; human-machine interface, software technology; fieldbus system integration technology.

 As the current automation technology has developed from stand-alone control to factory automation FA and to system automation. Factory automation information network can be divided into the following three levels of structure: factory management level, workshop monitoring level, and field device level, while fieldbus is the communication network between devices at the bottom of the factory. Here, we will first introduce Ethernet, which refers to industrial Ethernet. Industrial Ethernet is an industrial network protocol derived from the field of office automation, which mainly refers to the IEEE802.3 protocol according to the custom, and if the TCP/IP protocol family is further adopted, "Ethernet + TCP/IP" is used to express its technical characteristics It is mainly suitable for information management and information processing systems, and has been a great success in the IT industry. There are many successful cases of industrial Ethernet in the field of information integration at factory management level and shop floor monitoring level, and there are also many applications at the equipment level without strict requirements for real-time. Due to the wide variety of fieldbuses and different standards, many people hope that Ethernet technology can intervene in the lower level of equipment and widely replace the existing fieldbus technology, and Schneider is an active advocate and practitioner of this idea, and a number of industrial-grade products have been launched and applied. However, for the time being, Ethernet is not really able to solve the problems of real-time and determinism, and most field layers still prefer fieldbus technology. Due to the limitation of technology and the competition of interests among manufacturers, such a status quo of multiple industrial bus technologies co-existing and Ethernet technology penetrating will be maintained for some time. Users can choose the required solution according to the technical requirements and the actual situation.

The rise of fieldbus technology has opened up a new world of factory floor network. It will promote the rapid development of enterprise network and bring new benefits to enterprises, thus it will be widely used and promote the development of automation-related industries.