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mentionedFirst of all, the skeleton of DCS system network, it is the basis of the DCS and the core. Due to network for DCS, reliability and real-time performance of the whole system scalable, plays a decisive role, therefore all the manufacturers in this aspect has carried on the elaborate design. For DCS system network, it must meet the requirements of real-time, namely the complete transmission of information within a certain time limit. Here \"ok\" the time limit, is to point to in no matter what circumstances, information can be found within the time limit, and the time limit is according to the real-time requirement of the control process. Measure system, therefore, the rate of network performance index is not the networkDCSDCS, known as the number of bits per second (BPS), but the system real-time performance of the network, can be in a much longer time to ensure the transmission of the information needed to complete. System network must also is very reliable, in any case, the network communication cannot interrupt, so most of DCS adopts double bus, ring, or double star network topology. In order to meet the requirements of system expansion, the system can access the maximum number of nodes on the network should be several times greater than the actual use of the number of nodes. So, on the one hand, can add a new node at any time, on the other hand can also make the system run in a lighter network communication load condition, in order to ensure the real-time and reliability of the system. In the process of system operation, the Internet and various nodes in the net is possible at any time, especially the operator station, in this way, network reconfiguration often, and this kind of operation is absolutely should not affect the normal operation of the system, therefore, system network should have a strong online refactorings. Second, it is a completely to the I/O processing and realization of direct digital control (DDC) function of the network nodes. Usually to set the scene in a set of DCS I/O control station, to share the I/O and control function of the whole system. This can avoid the failure of the whole system due to a site failure, improve system reliability, also can make the site to share the data acquisition and control functions, to improve the performance of the whole system. DCS operator station is to handle all related to the operation of Human Machine Interface (HMI - Human Machine Interface or operator Interface) function of the network nodes.Engineer station is offline on DCS configuration, configuration and online system of supervision, control, maintenance of network nodes, its main function is to provide the DCS configuration, configuration software tools (that is, the configuration software), and DCS run online real-time monitoring the DCS operation of each node on the network,make the system engineer can engineer timely adjust system configuration and some parameters setting, make the DCS under the best working status at any time. Unlike the centralized control system, all the DCS requires system configuration function, can say, no system configuration function of the system can't call it the DCS.DCS since 1975, has experienced the developing course of more than 30 years. In this more than 30 years, although DCS happens on the system architecture of major changes, but after continuous development and improvement of its function and performance have been great improved. In general, the DCS is toward a more open, more standardized, more the direction of the transition.As a computer control system in the field of production process automation, the traditional DCS is only a narrow concept. If thought DCS was production process automation system, it will lead to the wrong conclusion, because now the meaning of computer control system has been greatly expanded, it includes not only the past DCS contained in the various content, also down deep into the field of each measurement devices, actuators, up to the production management, all aspects of enterprise management. In the traditional sense of the DCS now only refers to this part of the automation control of the production process, and the concept of industrial automation system, should be the location of a comprehensive solution to enterprises, the total solution. Only from this point of view put forward problems and solve problems, to make the computer automation really play its proper role.DCSDCSDCS has the following features:1. High reliability. Due to dispersion in the function of DCS control system implemented on the computer, the system structure of fault tolerance design, so the failure will not result in system of a computer is the loss of their other functions. In addition, due to the system based on the task of each computer is single, can according to need to realizethe function of use with a specific structure and special computer software, so that every computer in the system reliability is also improved.2. Open. DCS with open, standardized, modular and seriation design, computer using LAN communication of the system, and realize the information transmission, when need to change or expand the system function, new computer can be easily connected to the system communication network or unloaded from the network, almost does not affect other the work of a computer system.Form ofIs the abbreviation of Distributed Control System DCS (Distributed Control System), in the domestic industry is called Distributed Control System.It is a composed of process Control and process monitoring by the Computer system of multilevel Communication network as the link, a combination of Computer (Computer), Communication (Communication), display (CRT) and Control (Control) and so on 4 c technology, its basic idea is decentralized Control, centralized operation and decentralized management, flexible configuration, easy configuration.The development historyThe first stageFrom 1975 to 1980, the technical features of DCS control system in this period is characterized by:DCSDCS1) controlled by microprocessor based unit, realize the decentralized control, there are all kinds of algorithms, through configuration loop control independently, has the self-diagnosis function2) used for CRT monitors the operation of the station and unit separation process, realize the centralized monitoring, centralized operation3) USES the advanced redundant communication systemThe second stage1980-1985. During this period and distributing control system of the technical features are:1) the figures of the microprocessor to improve, improve the resolution of the CRT display2) strengthen the modular system3) to strengthen the information management system, and strengthen the function of communicationThe third stageAfter 1985, into the third generation of distribution system, its technical features are:1) using open systems management2) using 32-bit microprocessor operation station3) adopting multi-user real-time multitasking operating systemSince the ninety s, the computer technology by leaps and bounds, more new technology has been applied into DCS. PLC is a kind of developed electronic devices to control the sequence logic, it is mainly used to replace is not flexible and heavy relay logic. Field bus technology in the mid - ninety - s after developing very rapidly, so much so that some people have made a prediction: based on field bus control system of FCS will replace DCS as protagonist.Features introducedDCS is a Distributed Control System (Distributed Control System), the domestic general practice known as Distributed Control System. It is a composed of process Control and process monitoring by the Computer system of multilevel Communication network as the link, a combination of Computer (Computer), Communication (Communication), display (CRT) and Control (Control) and so on 4 c technology, its basic idea is decentralized Control, centralized operation and decentralized management, flexible configuration, the configuration is convenient, DCS characteristics are as follows.High reliabilityDue to dispersion in the function of DCS control system implemented on the computer, the system structure of fault tolerance design, so the failure will not result in system of a computer is the loss of their other functions. In addition, due to the system based on the task of each computer is single, can according to need to realize the function of use with a specific structure and special computer software, so that every computer in the system reliability is also improved.openDCS with open, standardization, modularization and serialization design, computer using LAN communication of the system, and realize the information transmission, when need to change or expand the system function, new computer can be easily connected to the system communication network or unloaded from the network, almost does not affect other the work of a computer system.flexibilityBy configuration software application process according to different objects of software and hardware configuration, the measurement and control signal and connection relationship between each other, from the control algorithms library to choose suitable control law, and from the basic graphics graphics library calls for a variety of monitoring and alarm screen, and conveniently constitute the necessary control system.Easy to maintainSpecial function of a single small or micro computer, has the characteristics of maintenance is simple, convenient, when a local or a computer failure, can be in online without affecting the operation of the whole system change, rapid troubleshooting. coordinationSend a variety of data through the communication network between each workstation, the system information sharing, coordination, to complete the overall function and the optimization of control system.To control the function is all readyControl algorithm is rich, continuous control, sequence control and batch control into an organic whole, can realize cascade, feedforward decoupling, adaptive and predictive control, and other advanced control, and can easily add the special control algorithm is required. DCS structure mode is very flexible and can be managed by a dedicated computer, operator station and engineer station, record stand, field control station and data acquisition station, etc, can also be used by the general servers, industrial control computer and programmable controller. At the bottom of the process control level by general decentralized field control station, data acquisition station on-site data acquisition and control, and production level monitoring computer via data communication network. Production monitoring level focus on data from the process control level for operation management, such as all kinds of optimization, statistics, fault diagnosis and display alarm, etc. With the development of computer technology, the DCS can be in accordance with the needs and higher performance of computer equipment connection through the network to realize centralized management of the more advanced features, such as planning and scheduling, inventory management, energy management, etc.structureStructurally, divided into DCS including process level, operation level and management level. Process level is mainly composed of process control station, the I/O unit and field instrument, is the main implement part of the system control function. Operation level including: operator station and engineer station, to complete the operation of the system and configuration. Management level mainly refers to the plant management information system (MIS), as an application of DCS higher level at present domestic paper industry application to this layer of the system is less.DCS control program: DCS control decision making is done by process control station, so the control program is performed by the process control station.The composition of the process control station:DCS process control station is a complete computer system, mainly by the power, the CPU (central processing unit), the network interface and I/OI/O: control systems need to build a signal input and output channels, this is I/O. DCS I/O in general is modular, an I/O module has one or more I/O channel, used to connect the sensors and actuators (regulator).I/O unit: usually, a process control station is a few frame, each frame can put a certain number of modules. CPU's frame is called CPU units, the same process in only one CPU units, other only used to put the I/O module rack is I/O unit.Application at home and abroadDistributed control systemInstrumentation in 1975, the largest U.S. companies Honeyw ell was first introduced to the world its comprehensive TDC - 2000 Distributed Control system (Toal Distributed Control - 2000), the system of the published, immediately cause the industrial Control industry highly, is called \"the most inspiring events\". Companies around the world have also follow suit, launched one after another and distributing system, process control into the distribution system in the new period.During this period have yokogawa's CEN TUM, MO SË Taylor instrument companies in the United States; DCÉ, bobby fischer company; N - 90-400, pele company, foxboro company Cpect Telepermm rum and Germany's Siemens.With the rapid development of computer, especially the micro computer and network technology, combined with the manufacturer's fierce competition, the DCS soon from the first generation of development in the 70 s to 70 s at the beginning of the third generation of DCS. Although before the distribution system of technical level is very high, but there was one of the major ills is: companies launched dozens of different types of systems, almost all the company's patented product, each company in order to protect their own interests, is the patent network are used, this is for the factory, the whole enterprise management problems.With the development of computer and network development makes the control manufacturers more commercial computer technology, in the late 80 s many companies to launch a new generation of distribution system, its main characteristic is the new system of local network with MA P agreement; Reference intelligent transmitter and field bus structure; In the control software of PLC is introduced in sequence control and batch control, make DCS also has the function of PLC.Countries well-known to the early 90 s of the DCS are: 3000, Bailey IN F I - 90, Ro semoun RS - 3 t, W est Hoo se WDPF, L eeds & Non th rup's MAX - 1000, Foxbo Ro IöA S, yokogawa CEN TUM. Mentioned here are large of DCS, the manufacturers in order to meet the needs of the market also has developed A lot of small and medium-sized DCS system such as S - 9000, MAX - 2, LXL, A 2 PACS, and so on.Process industry CIMSProcess industry CIMS is a complex integrated automation system, the processing of object is the enterprise of all production activities, DCS, as a kind of effective tool and means of implementation, do important basis in the process industry CIMS production data acquisition, control and real-time dynamic monitoring, and other functions. Compared with the management computer, DCS can provide more reliable production process data, optimization decisions are made by the CIMS system is more reliable. Look from the function, production automation of process industry CIMS system, dynamic monitor system and on-line quality control can be implemented by DCS. Look from the hierarchical structure of the process industrial CIMS, DCS main task for process control and process optimization, some production scheduling and management also can be finished in DCS.The main manufacturersDCS main manufacturers in China are: Shanghai xinhua, nanjing automation group co., LTD., hangzhou optimal stability and control of zhejiang, hollysys, via, zhejiang province, since the instrument co, luneng control, guodian wisdom deep, Shanghai Chinese, Shanghai focus, since in chint, etc.Abroad: Westinghouse, Emerson, FOXBORO, ABB, Siemens, honeywell, yokogawa, rockwell, yamatake honeywell, FISHER - ROSEMOUNT company, etc.。