As we all know, in enterprise information systems, Ethernet has become the standard network, and industrial real-time control is an extension of traditional Ethernet, helping users build more open and integrated industrial automation and information networks.
Industrial Ethernet technology is a combination of standard Ethernet and general industrial protocols. First of all, it meets the real-time requirements of industrial automation, from high-precision time synchronization (±100ns), distributed servo control, discrete control, process control to safety systems, etc. And it supports on-site and remote monitoring, diagnosis and configuration; of course, industrial Ethernet products can also use other standard Ethernet services such as HTTP, SNMP. This means that industrial automation and enterprise information systems are more directly integrated. For example, without additional programming, relevant personnel can easily configure, diagnose and monitor plant equipment through a web browser. In addition, industrial Ethernet also makes regulations in terms of EMC and installation protection levels to ensure the strict industrial environment adaptability of Ethernet products.
(1) Determinism and real-time communication of industrial Ethernet
Industrial Ethernet network is different from ordinary data networks. Its biggest feature is that the signal transmission must be fast enough and the determinism of the signal must be met. Real-time control often requires accurate and timing refreshing of the data of certain variables. Traditional Ethernet technology is difficult to meet the real-time requirements of the control system for accurate timing communication, and has been regarded as a "non-deterministic" network. However, the development of fast Ethernet and switched Ethernet technology has brought new opportunities to solve the non-deterministic problem of Ethernet, making this application possible.
(2) The stability and reliability of industrial Ethernet
The traditional Ethernet was not designed for industrial applications, and did not consider the adaptability needs of the industrial field environment. Since the mechanical, climate, and dust conditions at the industrial site are very harsh, higher requirements are placed on the industrial reliability of the equipment. In the factory environment, industrial Ethernet must have good reliability, recover-ability and maintainability.
(3) Security of industrial Ethernet
The network security of industrial systems is another security issue that must be considered for industrial Ethernet applications. Industrial Ethernet can integrate the traditional three-layer network system of the enterprise, namely the information management layer, the process monitoring layer, and the field equipment layer, so that the data transmission rate is faster, the real-time performance is higher, and it can be seamlessly integrated with the Internet. It can realize the sharing of data and improve the operational efficiency of the factory. But at the same time, a series of network security issues have been introduced. Industrial networks may be subject to network security threats including virus infection, illegal intrusion by hackers, and illegal operations. In general, a gateway or firewall can be used to isolate the industrial network from the external network, and the security management of the network can also be strengthened through multiple security mechanisms such as authority control and data encryption.
(4) The power supply issue of industria Ethernet
Bus power supply (or bus feed) means that the cables connected to the field devices not only transmit data signals, but also provide working power to the field devices. The following methods can be adopted for power supply of field devices:
On the basis of the current Ethernet standard, appropriately modify the technical specifications of the physical layer, modulate the Manchester signal of the industrial Ethernet to a DC or low-frequency AC power supply, and then separate the two signals at the field device side.
Do not change the current physical layer structure, but provide power for field devices through idle cables in the connection cables.