H25E-F1-SS-10 BEI
At the beginning of the development of soft PLC mostly PC_BASE as the hardware platform, and later on the one hand PC_BASE limited into the trough, the cost and reliability are difficult to improve, only slowly joined ARM, 51, AVR and other support, and has been emphasizing the development of modular structure, so that the migration becomes easy.
At present, PLC is usually divided into several different grades according to the number of points and price, while according to the internal implementation technology is divided into hard PLC, soft compiler PLC, soft interpretation PLC three kinds, according to the structure is divided into back plate, modular, distributed several. Among them, large and medium-sized PLC is to add many functions of DCS and PC in the function, so that it can annexe some DCS market, such as now many self-owned power plants and no longer use DCS and use PLC to complete. On the other hand, it should be noted that PLC has developed many special PLC, including CNC special, vehicle, equipment special, security, building and so on.
At the same time, DCS has also developed many products downward, so that it can replace a part of the PLC products, such as the Zhejiang central control, Zhejiang Dazhong from a series of products to do relatively small, only a few loops, with a display screen, can meet some single-loop control needs.
From the current point of view, PLC and DCS must blend with each other, in ten years we will not be the controller to choose DCS or PLC and worry, because they are actually the same, now most manufacturers have recognized this (most mainstream manufacturers in the new system will be the two into one), It is just that most users do not change their habits because the manufacturer’s propaganda is not in place.
1.2. Fieldbus and FCS
Shortly after the emergence of soft PLC, a new wave of technology hit the waist of industrial control, which is the fieldbus. At the same time, the concept of FCS (fully distributed control system based on fieldbus) was derived based on fieldbus. At the beginning, I was also a supporter and developer of FCS, and I believed that FCS with lower and lower chip capabilities was the future control system. However, in the actual development and application process, we find that the cost of full decentralization not only increases, but also becomes difficult to maintain, because all nodes rely on the network, and the reliability of the network becomes a bottleneck. Such a long network cable, any short circuit or open circuit will have fatal damage, if the use of redundant networks and systems, it will lead to significant cost. And the decentralized logic will cause major errors in the entire system because of the failure of an intermediate node, of course, if the user has a deep understanding of the concept of distributed control, of course, there is no big problem, but in fact, it is increasingly strong and unrealistic for the user engineer to understand such a complex topology structure and consider such a complex field structure.
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