Discussion on the method of designing new industri

2022-09-26
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"Discussion on the method of designing new industrial control system" after reading

Mr. Yang Changkun is an old expert in PLC and has participated in many large-scale projects in the country. This article is a little thought of Mr. Yang Changkun after reading the article. After reading Mr. Li Mingze's paper "Discussion on the method of designing new industrial control system", it has some enlightenment. It is true that most of the articles published in "electromechanical integration technology at home and abroad" are application-oriented, and few people put forward unique ideas or innovative concepts. The recently published "EPA based control system" and Mr. Li Mingze's paper have indeed brought a trace of spring breeze. I hope to see more such articles, and I suggest that the journal can open a technical forum for heated discussion and contention, Because only through academic discussion and contention can we deepen people and promote the development of technology. I hope this forum can bloom bright flowers and bear fruitful results. After reading Mr. Li Mingze's paper (hereinafter referred to as the article), I have the following immature views, supplier 9) to adopt standard database management experimental data discussion, please correct any improper points. The central idea of this article is to discuss the single board embedded CPU, which is currently developing rapidly and is mainly used in consumer appliances, and configure the corresponding I/O, as well as develop configuration, programming and diagnosis software, so as to make it a powerful and connected control device. The idea is novel and quite ingenious. Embedded devices allow a variety of structures, which are highly flexible, can be cut and combined by themselves, and can design their own CPU. They have the advantages of low power consumption, high integration, low price, high reliability, and do not have to rely on PC. But the disadvantage is that it is generally only equipped with specific applications, which can not be used in general, lack of openness, and usually cannot be connected. The target material of this article is optimized for strength and toughness, entitled "Discussion on the scheme of designing a new industrial control system", but from the analysis of the structure diagram given in the article, it seems to be limited to one device of the control system or one site of the distributed system. Because modern control system is generally a three-tier structure (field layer, control layer and management layer, which may also be related, FCS system may be simplified to a two-tier structure). With the development of informatization, informatization promotes automation. The vertical seamless integration of information between the control layer and the management layer, that is, the integration of management and control (horizontal integration, that is, the flattening of the architecture is not discussed in this paper) is the inevitable trend of development, so it can greatly improve the competitiveness of enterprises from many aspects. The three-tier structure must have middle tier application software. The middle tier application software includes a batch of leading enterprise libraries in the optical film industry for real-time data convergence. Relational database, historical database, data publishing, data mining, model calculation, process simulation, formulation design and processing, process optimization, parameter detection and deviation analysis, etc. These middle tier software can provide decision-making for the control layer downward and valuable data for the management layer upward. Therefore, the author believes that what Li proposed is a control device that can cover a considerable range of application fields (it can not be considered as the most widely used), which is not a system, but may also be a bottom-up design method, that is, this device is the basis of a new industrial control system, which can be upward connected to the human-machine interface, and then connected to the IT world. The article puts forward that the hardware should have the following characteristics: 32-bit microprocessor without mechanical heat dissipation, 4 to 256MB memory capacity, 5 to 30MB flash electronic disk, 1 to 2 built-in Ethernet drives, USB interface, and the price is 300 to 2000 yuan. It points out that this product is readily available in the market. There are some immature views on the software configured for the above hardware, which are for reference only. (1) Fieldbus is a one-way analog signal transmission that replaces the parallel one-way traditional analog signal transmission with the serial, bidirectional and multi-channel digital communication of field devices. Only one communication cable is needed to connect the scattered field devices and realize the full digital communication network from the field level to the management level. The industry generally believes that this is a profound revolution in the control system. In the future, the control system may develop to the fieldbus control system (which is absolutely in line with the national standard FCS). Fieldbus is based on the international standard of the 7-layer open communication reference model of ISO/OSI 7498. Its characteristics are that each layer is independent and interrelated, and the tasks of each layer are clear. This can not only improve the transmission efficiency, but also avoid data errors. The article puts forward that "the programming ability of IEC61131-3 is allocated to each network (Fieldbus) terminal equipment, that is, to realize field control", which seems to be embodied in the above design principles. The class I master station (to realize control) and class II master station (to realize programming, configuration and diagnosis) of PROFIBUS are a better solution, and it seems unnecessary to design and develop a new fieldbus service protocol standard based on the above views. (2) In the big paragraph "2. Network and Fieldbus", this paper lists some shortcomings of fieldbus, which has been widely used at present, and believes that the current fieldbus is in an uncertain state. However, the author believes that most of the current fieldbus is quite mature in technology, and there are millions of successfully applied nodes, which are deeply welcomed by users. The article also points out that "the incompatibility of Fieldbus products is due to the refinement of the physical layer to the application layer, etc.". The fact is that the root cause of incompatibility is that different fieldbuses are developed by different multinational companies or groups, and the technologies are different. For example, different data access technologies have nothing to do with the so-called refinement. The article emphasizes that "specific fieldbus can only be used in specific application fields", which is indeed the case. But the world is colorful, and no fieldbus can cover all application fields. Even now the hot ether is not a panacea. For example, PROFIBUS is applicable to the manufacturing industry dominated by discrete control, FF is applicable to the process industry dominated by continuous control, AS-I and seriplex are applicable to simple systems composed of on-off control, SERCOS is applicable to motion control systems, etc. At present, there are too many kinds of fieldbus, which makes users at a loss, but the market is the touchstone. Finally, a few fieldbuses that can withstand the test can be screened out. As for the article, it is worried that the existing fieldbus "physical layer and hardware cannot be integrated with the mainstream 8-bit and I6 bit embedded computer chips". This problem does exist. It is suggested to develop a fieldbus interface suitable for embedded system and connect it as a slave to the fieldbus network. In a word, it's the same sentence: it seems unnecessary to develop new fieldbus service standards. (3) This paper proposes that "when Ethernet is used for real-time control, real-time control is applied through TCP/IP

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