Development trend of automatic control technology

The development trend of automatic control technology in water industry

1 the intellectualization, decentralization and networking of control system

one of the development trends in the field of industrial automation is the intellectualization, decentralization and networking of control system, and the rise of fieldbus is the symbol of this development trend

1.1 the rise of Fieldbus

for more than half a century, the process control system in the field of industrial automation has gone through four generations of process control systems, including base instrument control system, electric unit combined analog instrument control system, centralized digital control system and distributed control. The factors that affect surface treatment are the selection of surface treatment materials, quality and process management system (DCS), At present, the mainstream level of water industry automation in China is in the stage of DCS system based on PLC. It should be noted here that DCs is not only the name of a process control system, but also sometimes refers to a complete and integrated distributed control system product sold by manufacturers. This kind of DCS system is relatively closed. At present, most DCS systems of water industry automation are integrated by users, so it is relatively open

compared with some early control systems, DCS system has made great progress in function and performance. On this basis, it can realize optimization and decentralized control at device level and workshop level, but it is still an analog-to-digital hybrid system. The detection, feedback, operation instruction and other signal transmission from site to PLC or computer still rely on a large number of one-to-one wiring. This signal transmission relationship is called signal transmission rather than data communication, which makes it difficult to realize the information exchange between instruments. Therefore, it calls for the emergence of instruments and systems with communication function and full digitalization of transmission signals, so as to transition from distributed control to complete decentralized control. Driven by this demand, since the mid-1980s, the on-site general Jinan assay product R & D department line came into being, And continuously rise through fierce market competition

fieldbus is a fully digital, real-time, bidirectional, multi node digital communication system applied in the production field. Fieldbus technology puts the special CPU into the traditional measurement and control instruments, so that they have the ability of digital calculation and communication, that is, the so-called "intelligence"; Twisted pair cables and coaxial cables that can be simply connected are used as links to connect multiple field level measurement and control instruments connected to the bus as network nodes, and data transmission and information exchange between field measurement and control instruments and between field measurement and control instruments and remote monitoring computers are realized according to open and standardized communication protocols, forming a variety of control systems that meet the actual needs, that is, the so-called "Networking"; Because these nodes are intelligent communicable products, the control information (such as real-time measurement data) it needs can be obtained directly from another node on the same layer without accessing to PLC or computer. In the environment of fieldbus control system (FCS), with its computing and communication capabilities, many complex calculations can be carried out on the site, Form a complete control system that is truly scattered on the site, and improve the autonomy and reliability of the system

fcs has become one of the development trends because it has changed the structure of the traditional control system, formed a new network integrated fully distributed system, adopted all digital communication, and has the characteristics of openness, full distribution, interoperability and adaptability to the field environment. It has formed an all digital communication network from measurement and control equipment to monitoring computers, which conforms to the development requirements of the control network

1.2 current situation and standardization of Fieldbus

at present, there are more than 60 kinds of Fieldbus at home and abroad. Due to the potential and huge market prospect of this new technology, driven by commercial interests, it has led to the great war of formulating international standards for Fieldbus in recent years. Under the call of unified international standards for market and technological development, the revised IEC 61158.3 ~ 6 standard was finally adopted on January 4, 2000. The standard includes eight types of Fieldbus subsets, which are: ① Foundation Fieldbus FF (the original Technical Specification IEC 611 has been completed on the basis of prefabrication 58); ②Control Net； ③Profibus； ④P—Net； ⑤FF HSE； ⑥Swift Net； ⑦Word FIP； ⑧Intferbus。 Among these 8 kinds of fieldbus, ④ and ⑥ are special Fieldbus for limited fields; ② ③, ⑦ and ⑧ are developed from PLC based control systems, which are essentially based on remote i/o bus technology. They usually do not have the power supply to field equipment through the bus and intrinsic safety performance; ① ⑤ is developed from the traditional DCS control system, with bus power supply and intrinsic safety functions; ① ⑧ belongs to field device level bus, ② and ⑤ belong to monitoring level fieldbus; ③ ⑦ includes two levels of fieldbus

the above eight types of Fieldbus adopt completely different communication protocols. For example, PROFIBUS adopts token ring and master/slave mode; Ffhse is CSMA electromechanical/cd mode; WordFIP is a bus arbitration method. Therefore, it is almost impossible for these eight fieldbuses to be compatible and interoperable. Facing this situation of multi bus coexistence, system integration will face more complex tasks, and system integration technology will also have great development

1.3 the new trend of Fieldbus - Industrial Ethernet

the long-term standard dispute has actually slowed the development of fieldbus. In order to speed up the development of the new generation system, people began to seek a new way out. A new trend is to turn from Fieldbus to Ethernet, using Ethernet as the main transmission of the high-speed fieldbus framework. Ethernet is the most widely used network technology in computers. It has been used in the IT field for many years and has been supported by a wide range of hardware and software development technologies. More importantly, enabling Ethernet as a high-speed fieldbus framework can integrate fieldbus technology with the mainstream technology of computer network technology. In order to promote the application of Ethernet in the industrial field, the industrial Ethernet association has been established internationally to carry out research on the key technologies of industrial Ethernet. In addition, the development equipment suppliers association (ODVA) has released a global standard for the use of Ethernet in factory sites - the Ethernet/ip standard. This standard enables users to use available Ethernet physical media and components, that is, interoperable Ethernet products provided by multiple suppliers, while using an open industrial application layer. With the development of network technology, the problems of network determinability, environmental adaptability, including bus power supply and intrinsic security, which Ethernet has to face in the industrial field will be solved quickly

2 management and control integration

industrial automation