外文翻译自动控制基础Word格式文档下载.docx

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1.1. 

Outline

Thisdeviceistemperaturecontrolexperimentaldeviceoftemperature,lever,pressure,thatarethemostcommoncontrolsubjectforwatertreatmentplants,chemicalfactoriesandpowerplants.

Attheexperimentofautomaticcontrol,itisveryimportanttokeepthebalanceofsystem.Automaticcontrolsystemiscomposedofcontrolsubjectsandtokeepcontroldevice.Especiallyprocesscontrolhasmanycontrolsubjectstokeepself-balance,sotheexperimentalresultsisconductedwithbalancecondition.

Thisexperimentaldeviceexperimentsabouttherelationofinputsignalandoutputsignaltokeepthebalance（Systemcharacteristics）atthecascadeexperimentandfixedcommandcontrol,alsoexperimentsondynamiccharacteristic（Balanceconditionwithouttimevariation）,staticcharacteristic（Balanceconditionconsideratingtimevariation）.

Andyourecordthechangeofcontrolamountwhichwasinputhandlingamountorestablishmentofcharacteristicexperiment.Thesetypicalresponsecanbethoughtstepresponse.Youexperimentoptimumcontrolexperiment,fixingP.I.Dconstantofcontroldevice

relatingthisstepresponse.

2. 

Processcontrol

Processcontrolkeepsthebalanceofthesystem,automaticallycorrectingtowarddeviation,andcompareseveryvariabletooperatingtowarddeviation,andcompareseveryvariabletooperationconditionofindustrialprocessofflux,temperature,surface,pressure,etcwiththeestablishedgoal.

ProcesscontrolisdecidedintoclosedloopandOpenloopcontrol.

3. 

Kindsofautomaticcontrol

Controliscomposedofdetection（measurement）,comparison,judgment,operationandmanualcontrolisdonebyman’shandandautomaticcontrolisdonebymeasureoradjusterorothermachinery.

Atpresent,automaticcontrolistakenatthemanyplants.Moreover,wecannotthinkplantcontrolwithoutautomaticcontrol.

Kindsofautomaticcontrolisdecidedlikebelow.

AutomaticcontrolOpenloopcontrolFeedforwardcontrol

Sequentialcontrol

ClosedloopcontrolFeedbackcontrol

3-1.Feedbackcontrol

Feedbackcontroldetects（measure）compares,judges,operates,automatically.Anditmeasurestheresultseverymoment,andcorrectsautomaticallyifthereisanydifferentialbetweenthedesiredvalue（setvalue）.

Feedbackcontrolisoneofthemainprocesscontrol.

Thisisthecontrolthatdetecting（measuring）theresults（Controlamount:

tankwaterlever）withdifferentialtransmitter,andcomparingthevaluewiththesetwaterleverandcorrectthedeviation（Openingoperationflowcontrolofthecontrolvalue）

Liketheabove,feedbackcontrolautomaticallydoesthemovementofmeasurement（detection）comparisoncalculationmodernfication.Feedbacksystemhastheelementofdoingthesefunctions.

Atthediagram3-1blocklinediagramitistheclosedloopandittransmittedthecorrectingsignaloftheoppositiontowardtheprocessflow.

Diagram3—1Blocklinediagramoffeedbackcontrolcorollary

Blocklinediagram:

Indicatingtheconstructingelementofcontrolsysteminblock,andconnectingthelineexpressingthesignalflow.

Signal:

Theamountbeingusedfortransmittheinformation

3-2.Feedforwardcontrol

Feedforwardcontrolisthecontrolmethoddoingnecessarycorrectmovementbeforetheinfluenceappearstothecontrolsystem,whendisturbanceentersintothecontrolsystem.

Atfeedbackcontrol,itstartscorrectmovementtoerasethedeviationaftertheinfluencebydisturbanceappears,soincaseofsuddenchangeofdisturbanceorsetvalue,thencontroldisorderstransientlyandarisesmanyproblems.

Feedforwardcontrolbreaksdownthisweakpoint.

Atfeedforwardcontrol,resultsofthecontrollerisnotdonefeedbackandbecomesopen-loopcontrol,notbeingclose-loopcontrol.Accordingly,incaseoffeedbackcontrol,therelationbetweencauseandeffectofdisturbanceandtheresultsofcontrolmustbeunderstoodwell.Thatis,relationofinfluencetothecontrolamounttowardloadchange,andoperatingamountneededtocompensateitshouldbeclear.

Butitisgenerallydifficult.Inmanycasesitisdifficultthatallthedisturbanceisdetected,andtogettheperfectprocessmodelinactualprocess.

Moreoveritisdifficulttoavoidconstantdeviation,soitisusedcombinedwithfeedbackcontrol.

3-3Sequencecontrol

Sequencecontrolprocessesthefixedprocessinadvancestepbystep.Thissequencecontrolisusedinneonsigns,vendingmachines,orelectricwashingmachines.Ontheotherhand,itisneededintheproducingprocessatchemicalfactory,automobilefactory,conveyer,automaticwarehouseasautomation.

3.4 

Classificationofcontrolmethods

Productionmethodbycontinuousprocessisemployed,whenscaleofprocessindustrygetsbiggerandlar