1、中文 6790字 DCS principle and PLC foundation DCS principle Distributed Control System (DCS) carries on the centralism monitor, the operation, the management and the disperser control which is one kind of new control technology using the computer technology to the production process. DCS is base on the
2、computer technology, the signal processing technology, the survey control technology, the correspondence network technology, the CRT technology, the graphical display technology and the man-machine connection technology mutually seeps the development to produce. DCS both is different with the disper
3、sible measuring appliance control, and different with Yuji Chinese type computer control system, but overcomes the two flaw to concentrate the two superiority, it has concentrated function and so on step less control, batch control, logic sequential control, data acquisition. Basic component of DCS
4、The logic structure of the system needs realizing by the physics structure. We can sum up their physics structure as the structure of the type of a gleam of past three simply . first line refers to its skeleton computer network, the three means that join three kinds of different kinds of nodes in th
5、e network: Face on-the-spot I/O which is accused of the course scene to control and stand； Facing the attenbants operators station； Facing DCS supervise the administrative staffs engineer standing. I/O controls the station live An on-the-spot I / O is controlled and stood to finish dealing with and
6、realizing the network node of digital control DDC (Direct Digital Control ) directly to on-the-spot I/O of course, there are three main functions: 1, which carried on digitization of various kinds of on-the-spot course amount (such as the flow , pressure ), and the quantity after digitizing is store
7、d in the memory , form one keep the same with on-the-spot course amountly, can one-one is it video in real time according to actual running situation with newer on-the-spot course quantity to change in real timing； 2, the real-time data gathering our station are sent to operators station , standing
8、and other engineers live through the network FO control the station, in order to realize the supervision and control of the whole system, at the same time it is stood the message issued by operators standing , engineer that can also receive , in order to realize that establishes artificial control o
9、r parameter to our station of the scene. 3, calculation and closing ring controlling , in order to control etc. IN realizing the part and automaticallying control in our station , return circuit , algorithm whose some classical algorithm generally, can remove theatrical makeup and costume non-standa
10、rd algorithm , complicated algorithm. Operators station The operator of DCS deals with all functions of man-machine interface (MMI-Man Machine Interface ) related to operating and operating at station, embody in and offer the man-machine interface for operating attendants mainly, enable operators to
11、 understand on-the-spot operation state , to present value of various kinds of operation parameters , and have unusual situations to take place etc. In time through operators station, and can control and regulate the craft course through the input equipment , so as to ensure the security of the prod
12、uction process , reliable , high-efficient , high quality. It is colored CRT that operators main man-machine interface equipment of the station outputs the respect in the computer, which control the equipment for industry keyboard and cursor in importing in computer (such as the mouse, orbit ball).
13、The content outputted on CRT includes mainly: 1, the simulation flow chart of the production process (namely by imitating production device and production line that the figure expresses), which wins a bid of real-time status with all key data ,to control parameter and equipment； 2, the warning windo
14、w: By arranging the time order way (namely the most emerging alarm ranks the top of the window ) and listing the unusual situation appearing in production processes , if number value restricts . Reporting to the police should include time , unusual state and value , confirming by operator and unusua
15、l brief illustration to tabulate already of the unusual data to unusually appear ； 3, the real-time trend shows: With curve say come out change recently, producting process of data, so that the operator understands its development and change to some extent, and can help to analyse the running situat
16、ion of the production process .which Can generally show the trend curves of 4-8 data in the same system of coordinates , so can compare with all relevant data ,to make the analysis on on-the-spot situation very more clearly. The engineer stands It is disposed to DCS off-line that the engineer stands
17、, configuration and network node supervised , controlled , maintained online. Its main function is to finish the systematic configuration , dispose the work, and monitor the each nodal running situation when real when the line is operated, make system engineer can stand in time adjusting system disp
18、osing and some settlement of systematic parameter through engineer, to make the system in the best working state at any time. Systematic network It is all some isolated nodes that on-the-spot I/O is controlled and stands , stands at operators station and engineer, to finish ones own work each. If no
19、ne of unified coordination can not form the intact system, the systematic network offers the foundation for coordinating , which becomes the core of the whole system. 1, Network characteristic Different from some network that general office automation adopts, the communication network that DCS adopt
20、s was used for the control and management of have the industrial production process, so, it should possess the characteristics of the following : Real-time character is good, respond fast dynamically Meet the abominable on-the-spot environment of industry Dependability is high Opening is good 2, Net
21、work structure Early LAN with better real-time character of often adopt IEEE802.4 making brand total network or IEEE802.5 to make the card surround the network alone etc. of information management network of DCS control system. But no matter domestic or abroad, which uses most is IEEE802.3 CSMA/CD Ethernet at present. Ethernet enters
