The development course
Control system actually began to use since the 1940 s, the early field JiDeShi instrument and later relay control system of the predecessor. Represented by PLC and DCS, * * * * from 70 since the beginning of application, in metallurgy, electric power, petroleum, chemical industry, light industry and so on obtains the rapid development in industrial process control. * * * * beginning from 90, has been the fieldbus control system, control system based on PC, etc., will be briefly introduced all kinds of common control system, and analyze the evolution process and the development direction of the control system.
In the mid - 70 - s, because of the enlarged equipment, process flow continuity requirement is high, the increase in the number of process parameters to control, and strict requirements according to operation concentration, etc., which has universal electric unit combination instrument cannot be completely meet the requirements. In this case, through market research industry manufacturers, determine the development of DCS products should be with analog feedback control is given priority to, complementary with amount of sequence control and analog switch on-off mixed batch control, they can cover oil refining, petrochemical, chemical, metallurgical, power, light industry and municipal engineering, etc. Most of the industry.
Around 1975, in the original use of small and medium scale integrated circuit and the formation of a direct digital controller (DDC), on the basis of automatic control and computer technology, developed a displayed in a centralized operation and decentralized control for the characteristics of distributed control system (DCS). Due to the computer is not popular, so the development of DCS should emphasize don't understand the user can use a computer DCS; At the same time, the development of DCS should also be emphasized to provide customers with the entire system. In addition, the development of DCS central control room should be done with conventional instrument with the same technical conditions, to ensure the reliability and security.
In after nearly 30 years, DCS and complete sets of equipment form a complete set first, and then gradually expand to the process plant modification, meanwhile, is also divided into two categories, large DCS and small and medium-sized DCS products, to make it more competitive price performance ratio. DCS products although not many breakthroughs in principle, but as a result of technological progress, the change of external environment change and the demand, there were three generations of DCS products. 1975 to the early 80 s is the first generation product, the mid - 80 - s to the early 90 s is the second generation product, in the mid 90 s to the early 21st century is the third generation product.
Control station
DCS system, the control station as A complete computer, its main I/O devices to the scene of the input, output, processing equipment, as well as the process input/output (PI/O), including signal transformation and signal conditioning, A/D, D/A conversion. Control station is the basis of the DCS, its reliability and safety is most important, crash and control failure phenomenon is absolutely not allowed, and redundancy, power-fail protection and anti-interference, constitute the explosion protection system, etc, should be very effective and reliable, to meet user requirements.
About DCS control station system software, including real time operating systems, programming languages, and build system, database system, since the diagnosis system and so on, it's just perfect degree. The second generation of DCS control station started a process oriented language and high-level language; The third generation of DCS control station system software can complete the quad state and online modify the control strategy. In order to complete the control strategy for sequence control and batch control programming, all sorts of DCS control station takes a different approach.
DCS operation station
DCS operation station has the function of operators, engineers, communication function and high-level language function, such as engineer functions including system configuration, system maintenance, system has the function of general (Utility), and the system configuration, operating tag, trend record, history data management, configuration, control station configuration general appearance, process unit or regional configuration, etc.
The actual DCS operation station is a typical application of computer, it differs from the control station, has a wealth of man-machine interface and peripheral devices. In the aspect of man-machine interface, and gradually transition to the GUI graphical user interface for the platform and USES the mouse, configuration production flow chart and the control circuit diagram and the menu, Windows, etc., make the friendly man-machine interface. The third generation of DCS operation station is on a personal computer (PC) and the Windows operating system popularization and commercialization of gm monitoring graphics software has born on the basis of. DDE and OPC interface technology, Ethernet interface connected to the network management. DCS system configuration, operating station configuration, control station configuration has the corresponding software, engineering design personnel to provide man-machine interface for DCS users. Some DCS using general monitoring graphics software, or with such software as the core, for secondary development.
Control system
Control system
Data communication and network
Because data communication standards involved in network structure, communication medium (channel), communication protocol, IEEE802.4 token bus transmission mode and IEEE802.5 token ring network transmission mode of communication protocols in the DCS system is the most widely used, whether can become the future of the DCS communication standard, it remains to be seen.
Development issues
Existing problems in the DCS, mainly in three aspects:
1, namely system open questions;
2, with the sensor, transducer and actuator wiring problem;
3, the price is more expensive problems [1].
These problems in the third generation of DCS has started to be solved. In the 21st century, a new generation of DCS should satisfy the customers' needs.
On the DCS application industry distribution, such as the modification of DCS products, is to keep its status in the industry.