Application of the hottest distributed control sys

The application of distributed control system in industrial control field

Abstract: through reviewing the development of distributed control system in recent 30 years, this paper expounds its outstanding technical characteristics and introduces its future development direction

key words: distributed control system data communication technology basic regulator computer integrated manufacturing technology (CIMS)

preface

total distributed control systems (hereinafter referred to as DCS) is also known as distributed computer control systems. It is a new computer control system with microprocessor as the core and adopting data communication technology and graphic display technology. The system can complete the functions of direct digital control, sequence control, batch control, data acquisition and processing, multivariable decoupling control and optimal control. In the advanced distributed control system, it also includes the command, scheduling and management functions of flake graphite production of about 3000 yuan per ton

1 production of distributed control system

the process control system composed of conventional analog regulating instruments has low cost, high reliability and easy maintenance and operation. However, with the development of production, the limitations of analog instruments become more and more obvious, such as analog instruments are difficult to realize multivariable decoupling control and other complex control laws; The control accuracy is not high; With the expansion of production scale and the increasingly complex process, there are more and more instrument control systems, and the instrument panel in the control room is getting larger and larger, which makes it difficult to realize centralized operation and display; It is difficult to realize communication between various systems; When the production process requirements change, it is often necessary to change the regulating instrument. The computer control system can overcome the above defects of analog regulating instruments, and the computer control system can realize complex control laws; Each subsystem can realize communication, centralized operation and display, and the control accuracy is relatively high

in computer centralized control, a computer controls dozens or even hundreds of circuits. Once the computer fails, the work of the whole system will be affected, and the reliability of the system is relatively low. Of course, in order to improve the reliability of the system, the dual machine operation mode can be adopted, but the cost will increase. The development of industry in the 1970s made the production process more complex and expanded, especially the petrochemical industry. With the expansion and complexity of production scale, accidents continue to occur, while centralized control will interrupt production when accidents occur. Therefore, the development of production urgently requires a highly reliable computer control system

on the basis of summarizing the advantages and disadvantages of analog regulating instruments and computer centralized control, a distributed control system has been developed and formed. The distributed control system is distributed in the production site with multiple microcomputer processors to measure and control the process, which realizes the decentralization of function and geography, and avoids the danger caused by the high concentration of measurement and control and the limitation of single control function of conventional instruments; The application of data communication technology, CRT display technology and other external equipment can facilitate centralized operation, display and alarm, and overcome the characteristics of too decentralized conventional instrument control and difficult human-machine connection. The major breakthroughs in microelectronics and computer technology in the 1970s provided microprocessors and various semiconductor chips with small volume, strong functions, high reliability and low price for the distributed control system, which laid a material foundation for the development of distributed control system and the continuous change of market demand

distributed control system can be regarded as the combination of computer technology, communication technology, graphic display technology and control technology

2Development of distributed control systems abroad

in the early 1970s, the United States, Japan, Europe and other countries began to develop distributed control systems. In 1975, the United States and Japan successively developed tdc-2000, tosdic, CENTUM, UNITROL, micrex and other systems

according to the technical characteristics, its development can be divided into three stages:

a. the late 1970s - the start-up period

tdc-2000 of Honeywell company in the United States is more famous; Spectrum of Foxboro company and network-90 of Bailey company; CENTUM of Yokogawa, Japan; Tosdic of Toshiba; TELEPERM m of Siemens, Germany; Control P of hartman&braum, etc. The products of this period have obvious technical limitations. Most microprocessors use 8-bit CPU

B. junior high school development period in the 1980s

in the 1980s, with the enhancement of microprocessor computing power, the improvement of VLSI integration and the continuous decline of cost, the development of process control has taken on a new look, enabling the unimaginable functions in the past to be realized. On the basis of the original, the reliability of the second generation products of the distributed control system has been further improved and its functions have been further expanded. Multifunctional process control stations, enhanced operation stations and optical fiber communication technology have been added. The representative products are TDC-3000 of Honeywell company in the United States; MAX-1 of leads&northrup; MOD300 of Taylor company; WDPF of westing house; CENTUM a, B, C, etc. of Yokogawa, Japan. This generation of products is characterized by 16 bit CPU, standardized and modular design, flexible expansion, perfect functions and friendly user interface

c. the third generation of distributed control system in the late 1980s mature period combines process control, supervisory control, management and scheduling organically, strengthens the intermittent control function, and adopts expert system and map communication standards. Its representative products are tdc-3000/lcn of Honeywell company in the United States; Foxboro i/a series; INFI-90 of Bailey company; WDPF - Ⅱ Ⅲ of Westinghouse company; CENTUM XL of Yokogawa company in Japan, etc. This generation of products is characterized by the use of 32-bit CPU and ASIC, which makes the control function stronger, smaller and more reliable. Its communication system realizes open communication

3 application of distributed control system in China

distributed control system (DCS), as a new generation of industrial automation process control and management equipment, has been widely used in petrochemical, metallurgical, electric power and other industrial fields, although it has only a history of more than 20 years. China began to introduce distributed control equipment in the early 1980s, and then began the application of distributed control system in China's industrial control field

the newly-built large and medium-sized petrochemical equipment in the petrochemical industry adopts distributed control system (DCS). The first DCS of petrochemical enterprises is the spectrum system of Foxboro company introduced by the refinery of Shanghai Gaoqiao Petrochemical Company in 1982, which is used for the production control of atmospheric and vacuum distillation units

in the metallurgical industry, the application of distributed control system (DCS) is concentrated in new enterprises such as Baosteel and the expanded branches of Shougang, Angang, WISCO, Chongqing Iron and Steel Co., Ltd. and Masteel. The first set of distributed control system for the emergence of a large number of new materials in the metallurgical system is the network-90 system of Bailey company of the United States purchased by Shougang company for its sintering plant automatic control system

the first distributed control system (DCS) of the power system is the PROCONTROL-P system of BBC company of Switzerland adopted by Liaoning Chaoyang Power Plant in 1985, which is used to transform the sequence control system and burner management system of 200MW units. At present, the application of distributed control system (DCS) in thermal power plants mainly includes five aspects: analog control, data acquisition and processing, boiler furnace safety monitoring, sequence control, turbine digital electro-hydraulic control, etc

at the same time, from the late 1980s to the early 1990s, the state organized powerful scientific research forces to jointly tackle key problems, and successively developed our own distributed control system. The representative products emerging in this period include DJK-7500 (Chongqing Institute of Automation), hs-dcs-1000 (the sixth Institute of the Ministry of Electronics), star-2000 (a relay Co., Ltd.), dcs-100 (Department of automation, Tsinghua University), djk-2000 (Shanghai Institute of Automation), youli-2000 (Petrochemical Corporation, the second Academy of the Ministry of space), etc. The star-2000 distributed control system developed by a relay Co., Ltd. has been applied in the production process control of dozens of power plants, such as the analog regulation system of 200MW units in Harbin third power plant and the fire protection system of 300MW units in Shijiazhuang Yangluo, since the first application system (power plant boiler fire protection MHB Ⅲ/b) was put into operation in Henan Xinxiang Power Plant in 1989. On this basis, its second-generation product star-3000 has been more widely used in the industrial field in recent years, and has made great progress in technology

4 the development direction of distributed control system in the future

the development direction of distributed control system is that the basic regulator develops towards less loop or single loop; In addition to PID and other algorithms, the basic regulator will gradually adopt more effective new algorithms to make it have new functions (such as gain adaptive function); Use optical fiber instead of high-speed data channel, and unify communication procedures; Strive to use modern control theory flexibly to get a more general control algorithm

5 conclusion

the essence of distributed control system (DCS) is a new control technology that integrates centralized monitoring, operation, management and on-site front-end decentralized control of the production process by using computer technology. Its emergence is a milestone in industrial control. The development of industrial process control has gradually developed from single machine monitoring, direct digital control to distributed control. It will also progress from distributed control to computer integrated system with broader application prospects. The solutions exhibited include low smoke halogen-free flame retardant materials and high temperature oil-resistant and heat-resistant materials. The achievements of computer integrated manufacturing (CIMS) technology in recent years are enough to prove this

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