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Introduction to Fieldbus and Industrial Ethernet

As traditional manufacturing companies are accelerating the process of intelligent manufacturing transformation, the Industrial Internet is rapidly emerging around the world. In the technical framework of the Industrial Internet, accessing different devices, systems and products through various communication methods to collect massive data is an important part of it. This article will focus on two communication methods for industrial bottom equipment: fieldbus and industrial Ethernet. Let’s follow the editor of Feichang Technology to take a look!

Understanding Fieldbus

Looking back at the development history of fieldbus, it can be seen that fieldbus appeared roughly from the late 1980s to the early 1990s. During this period, with the increasing production scale, there was a demand for interconnection of factory equipment (the interconnection demand at this stage mainly positioned For remote I/O data transmission, and data exchange of different equipment inside the production line), people hope to realize the operation control of multi-point information by comprehensively grasping multi-point operating parameters and information. However, the computer system at this time had the defect of a closed system. The products of each manufacturer were self-contained, and the devices of different manufacturers could not be interconnected. Due to the limitations of the technology at that time, the network system that wanted to achieve a wider range of information sharing, There are many difficulties.

In the actual development process, many famous fieldbus technologies have emerged, such as Foundation Fieldbus FF, HAPT fieldbus, CAN fieldbus, LONWORKS fieldbus, Devicenet fieldbus, INTERBUS fieldbus, PROFIBUS fieldbus, WorldFIP fieldbus , CC-Link field bus, etc. These field buses have their own characteristics and form a specific range of applications. However, there are too many types of fieldbus, and the communication protocols used are completely different, so the standard of fieldbus has not been unified so far. Finally, a fieldbus standard of IEC61158 with various fieldbuses has been formed. There are quite a lot of them on the Internet. The data will not be expanded here.

I have searched for many versions of the definition of fieldbus, but whether it is Baidu Encyclopedia or the definition of fieldbus given by the IEC standard of the International Electrotechnical Commission, it is still difficult for beginners to understand. It wasn’t until I saw a popular interpretation about fieldbus recently that I felt suddenly enlightened. To share with you: Fieldbus is a real-time control communication network that interconnects the lowest level of automation field controllers and field intelligent instrumentation equipment. It follows all or part of the communication protocol of the ISO/OSI Open System Interconnection Reference Model.

Beginners can understand fieldbus from two aspects: First, according to the hierarchical structure of factory automation information network (factory management level, workshop monitoring level, field device level), it can be known that fieldbus is located at the bottom of production control and network organization, which is the bottom layer of the factory. A communication network between devices. The advantage of applying fieldbus technology at the bottom of the factory is that it can realize the transparent communication of the vertical integration of factory information, that is, the data access from the management layer to the bottom layer of automation.

Second, the field bus is based on the seven-layer model of ISO/OSI, and can be less than seven layers. It should be pointed out that in practical applications, the ISO model is only a reference. Different types of fieldbus protocol stacks are quite different. Usually, the seven-layer model of ISO/OSI is simplified to achieve lower communication delay and faster communication. Speed, more conducive to the realization of the real-time characteristics of the field bus.

Remarks: The Open System Interconnect reference model (OSI for short) is an open system interconnection reference model jointly developed by the International Organization for Standardization (ISO) and the Consultative Committee for International Telegraph and Telephone (CCITT), which provides A framework of functional structures. It is from low to high: physical layer, data link layer, network layer, transport layer, session layer, presentation layer and application layer.

Walk into Industrial Ethernet

In view of the fact that the standard of the field bus is still based on the compromise of various field bus standards, and in a certain sense, the multi-standard means that there is no standard. People began to look for a new way out of industrial communication, and at this time Ethernet technology came into people’s eyes. Due to its simple technology, good openness, and low price, Ethernet technology has a very high market share in office and business. Some manufacturers (for example, Schneider proposed a solution based on Ethernet + TCP/IP) proposed to introduce Ethernet technology into the bottom layer of factory equipment, and industrial Ethernet came into being.

However, Ethernet is the most common communication protocol standard in computer local area networks. It was originally designed for office automation applications, and did not take into account the needs of industrial field environments, such as high temperature, low temperature, and dust-proof lamps. Therefore, Ethernet cannot be used directly. at the industrial site. Think tank encyclopedia believes that industrial Ethernet refers to the application of Ethernet related components and technologies in the automation control and process control of industrial environments. Industrial Ethernet adopts TCP/IP protocol, which is compatible with IEEE 802.3 standard, but will add their own unique protocols in the application layer. From a definition point of view, industrial Ethernet is also a kind of fieldbus, just like various protocols of fieldbus.

Just as Ethernet is suitable for information management and information processing systems, industrial Ethernet is also widely used in information integration fields such as factory management and workshop monitoring. The biggest advantage of industrial Ethernet is that it can meet the requirements of all levels of the control system, so that the enterprise’s information network and control network can be unified; Ethernet is easy to realize network integration, fast speed, extensive development technology, wide range of hardware upgrades, and low price , easy to get the support of many manufacturers.

However, Ethernet is a random network with the characteristics of communication uncertainty, which made industrial Ethernet once labeled as “unsuitable for high-speed real-time data communication”. For this reason, major companies in the world have turned to study the deterministic and real-time problems of communication based on Ethernet, and have made some achievements. At present, the more influential real-time industrial Ethernets include: Siemens’ PROFINET, Beckhoff’s EtherCAT, B&R’s Powerlink, Yokogawa’s VNET/IP, Toshiba’s TCnet, Schneider’s Modbus-IDA, Zhejiang University’s SUPCON’s EPA etc.

Generally speaking, the network communication of the industrial scene has experienced the development process from the field bus to the industrial Ethernet, and then to the real-time industrial Ethernet. According to the latest survey data from the Swedish network expert HMS, the number of fieldbus safety nodes accounted for 48% of the entire market in 2016, a large drop from the 58% market share in 2015, while the industrial Ethernet The market share rose from 38% to 46%. According to industry analysts, the development of strategies such as the Industrial Internet and Industry 4.0 has promoted the interconnection of more and more industrial equipment, but the industrial network communication market is still fragmented.