冷库温度控制系统的设计 外文翻译.docx
- 文档编号:23660508
- 上传时间:2023-05-19
- 格式:DOCX
- 页数:17
- 大小:33.04KB
冷库温度控制系统的设计 外文翻译.docx
《冷库温度控制系统的设计 外文翻译.docx》由会员分享,可在线阅读,更多相关《冷库温度控制系统的设计 外文翻译.docx(17页珍藏版)》请在冰豆网上搜索。
冷库温度控制系统的设计外文翻译
大连交通大学信息工程学院
毕业设计(论文)外文翻译
学生姓名1111专业班级自动化0111班
指导教师1111职称 11111
所在单位电气工程系
教研室主任
完成日期1111年4月13日
DateAcquisition
Dateacquisitionsystemsareusedtoacquireprocessoperatingdataandstoreitonsecondarystoragedevicesforlateranalysis.Manyofthedataacquisitionsystemsacquirethisdataatveryhighspeedsandverylittlecomputertimeislefttocarryoutanynecessary,ordesirable,datamanipulationsorreduction.Allthedataarestoredonsecondarystoragedevicesandmanipulatedsubsequentlytoderivethevariablesofinterest.Itisveryoftennecessarytodesignspecialpurposedataacquisitionsystemsandinterfacestoacquirethehighspeedprocessdata.Thisspecialpurposedesigncanbeanexpensiveproposition.
Powerfulmini-andmainframecomputersareusedtocombinethedataacquisitionwithotherfunctionssuchascomparisonsbetweentheactualoutputandthedesirableoutputvalues,andtothendecideonthecontrolactionwhichmustbetakentoensurethattheoutputvariablesliewithinpre-setlimits.Thecomputingpowerrequiredwilldependuponthetypeofprocesscontrolsystemimplemented.Softwarerequirementsforcarryingoutproportional,ratioorthreetermcontrolofprocessvariablesarerelativelytrivial,andmicrocomputerscanbeusedtoimplementsuchprocesscontrolsystems.Itwouldnotbepossibletousemanyofthecurrentlyavailablemicrocomputersfortheimplementationofhighspeedadaptivecontrolsystemswhichrequiretheuseofsuitableprocessmodelsandconsiderableon-linemanipulationofdata.
Microcomputerbaseddataloggersareusedtocarryoutintermediatefunctionssuchasdataacquisitionatcomparativelylowspeeds,simplemathematicalmanipulationsofrawdataandsomeformsofdatareduction.Thefirstgenerationofdataloggers,withoutanyprogrammablecomputingfacilities,wereusedsimplyforslowspeeddataacquisitionfromuptoonehundredchannels.Alltheacquireddatacouldbepunchedoutonpapertapeorprintedforsubsequentanalysis.Suchhardwireddataloggersarebeingreplacedbythenewgenerationofdataloggerswhichincorporatemicrocomputersandcanbeprogrammedbytheuser.Theyofferanextremelygoodmethodofcollectingtheprocessdata,usingstandardizedinterfaces,andsubsequentlyperformingthenecessarymanipulationstoprovidetheinformationofinteresttotheprocessoperator.Thedataacquiredcanbeanalyzedtoestablishcorrelations,ifany,betweenprocessvariablesandtodevelopmathematicalmodelsnecessaryforadaptiveandoptimalprocesscontrol.
Thedataacquisitionfunctioncarriedoutbydataloggersvariesfromoneloggingsystemtoanother.Simpledataloggingsystemsacquiredatafromafewchannelswhilecomplexsystemscanreceivedatafromhundreds,oreventhousands,ofinputchannelsdistributedaroundoneormoreprocesses.Therudimentarydataloggersscanselectnumberofchannels,connectedtosensorsortransducers,inasequentialmannerandthedataarerecordedindigitalformat.Adataloggercanbededicatedinthesensethatitcanonlycollectdatafromparticulartypesofsensorsandtransducers.Itisbesttouseanon-dedicateddataloggersinceanytransducerorsensorcanbeconnectedtotheuseofappropriatesignalconditioningmodules.
Microcomputercontrolleddataacquisitionfacilitatesthescanningofalargenumberofsensors.Thescanningratedependsuponthesignaldynamicswhichmeansthatsomechannelsmustbescannedatveryhighspeedsinordertoavoidaliasingerrorswhilehereisverylittlelossofinformationbyscanningothercannelsatslowerspeeds.Insomedataloggingapplicationsthefasterchannelsrequiresamplingatspeedsofupto100timespersecondwhileslowchannelscanbesampledonceeveryfiveminutes.Theconventionalhardwired,non-programmabledataloggerssampleallthechannelsinasequentialmannerandthesamplingfrequencyofallthechannelsmustbethesame.Thisprocedureresultsintheaccumulationofverylargeamountsofdata,someofwhichisunnecessary,andalsoslowsdowntheoveralleffectivesamplingfrequency.Microcomputerbaseddataloggerscanbeusedtoscansomefastchannelsatahigherfrequencythanotherslowspeedchannels.
Thevastmajorityoftheuserprogrammabledataloggerscanbeusedtoscanupto1000analogand1000digitalinputchannels.Asmallnumberofdataloggers,withahigherdegreeofsophistication,aresuitableforacquiringdatafromupto15,000analoganddigitalchannels.ThedatafromdigitalchannelscanbeintheformofTransistor-TransistorLogicorcontactclosuresignals.Analogdatamustbeconvertedintodigitalformatbeforeitisrecordedandrequirestheuseofsuitableanalogtodigitalconverters(ADC).ThecharacteristicsoftheADCwilldefinetheresolutionthatcanbeachievedandtherateatwhichthevariouschannelscanbesampled.AnincreaseinthenumberofbitsusedintheADCimprovestheresolutioncapability.SuccessiveapproximationADC’sarefasterthanintegratingADC’s.Manymicrocomputercontrolleddataloggersincludeafacilitytoprogramthechannelscanningrates.Typicalscanningratesvaryfrom2channelspersecondto10,000channelspersecond.
Mostdataloggershavearesolutioncapabilityof±0.001%orbetter.Itisalsopossibletoachievearesolutionof1micro-volt.Theresolutioncapability,inabsoluteterms,alsodependsupontherangeofinputsignals,Standardinputsignalrangesare0-1-volt,0-50voltand0-100volt.Thelowestmeasurablesignalvariesform1uvoltto50uvolt.Ahigherdegreeofrecordingaccuracycanbeachievedbyusingmoduleswhichacceptdatainsmall,selectablerages.Analternativeistheautorangingfacilityavailableonsomedataloggers.
Theaccuracywithwhichthedataareacquiredandloggedontheappropriatestoragedeviceisextremelyimportant.Itisthereforenecessarythatthedataacquisitionmoduleshouldbeabletorejectcommonmodenoiseandcommonmodevoltage.Typicalcommonmodenoiserejectioncapabilitieslieintherange110dBto150dB.Adecibel(dB)isatermwhichdefinestheratioofthepowerlevelsoftwosignals.ThusifthereferenceandactualsignalshavepowerlevelsofNrandNarespectively,theywillhavearatioofndecibels,where
n=10Log10(Na/Nr)
Protectionagainstmaximumcommonmodevoltagesof200to500voltisavailableontypicalmicrocomputerbaseddataloggers.
Thevoltageinputtoanindividualdataloggerchannelismeasured,scaledandlinearisedbeforeanyfurtherdatamanipulationsorcomparisonsarecarriedout.
Inmanysituations,itbecomesnecessarytoalterthefrequencyatwhichparticularchannelsaresampleddependinguponthevaluesofdatasignalsreceivedfromaparticularinputsensor.Thusachannelmightnormalbesampledonceevery10minutes.If,however,thesensorsignalsapproachthealarmlimit,thenitisobviouslydesirabletosamplethatchannelonceeveryminuteorevenfastersothattheoperatorscanbeinformed,therebyavoidinganycatastrophes.Microcomputercontrolledintelligentdataloggersmaybeprogrammedtoalterthesamplingfrequenciesdependinguponthevaluesofprocesssignals.Otherdataloggersincludeself-scanningmoduleswhichcaninitiatesampling.
Theconventionalhardwireddataloggers,withoutanyprogrammingfacilities,simplyrecordtheinstantaneousvaluesoftransduceroutputsataregularsamplinginterval.Thisrawdataoftenmeansverylittletothetypicaluser.Tobemeaningful,thisdatamustbelinearisedandscaled,usingacalibrationcurve,inordertodeterminetherealvalueofthevariableinappropriateengineeringunits.Priortotheavailabilityofprogrammabledataloggers,thisfunctionwasusuallycarriedoutintheoff-linemodeonamini-ormainframecomputer.Therawdatavalueshadtobepunchedoutonpapertape,inbinaryoroctalcode,tobeinputsubsequentlytothecomputerusedforanalysispurposesandconvertedtotheengineeringunits.Papertapepunchesareslowspeedmechanicaldeviceswhichreducethespeedatwhichchannelscanbescanned.Analternativewastoprintouttherawdatavalueswhichfurtherreducedthedatascanningrate.Itwasnotpossibletocarryoutanylimitcomparisonsorprovideanyalarminformation.Everysinglevalueacquiredbythedataloggerhadtoberecordedeventhoughitmightnitserveanyusefulpurposeduringsubsequentanalysis;manydatavaluesonlyneedrecordingwhentheylieoutsidethepre-setlowandhighlimits.
1.ABSTRACT
ThefeaturesofthedataacquisitionandcontrolsystemsoftheNASALangleyResearchCentersJetNoiseLaboratoryarepresented.TheJetNoiseLaboratoryisafacilitythatsimulatesrealisticmixedowturbofanjetenginenozzleexhaustsystemsinsimulatedight.Thesystemscapableofacquiringdataforacompletetake-o_assessmentofnoiseandnozzleperformance.Thispaperdescribesthedevelopmentofanintegratedsystemtocontrolandmeasurethebehaviorofmodeljetnozzlesfeaturingdualindependenthighpressurecombustingairstreamswithwindtunnelow.Theacquisitionandcontrolsystemiscapableofsimultaneousmeasurementofforces,moments,staticanddynamicmodelpressuresandtemperatures,andjetnoise.Thedesignconceptsforthecoordinationofthecontrolcomputersandmultipledataacquisitioncomputersandinstrumentsarediscussed.Thecontrolsystemdesignandimplementationareexplained,describingthefeatures,equipment,andtheexperiencesofusingaprimarilyPersonalComputerbasedsystem.Areasforfuturedevelopmentareexamined.
2.INTRODUCTION
Theproblemofjetnoisehasbeenstudiedformanyyears.Sincesoundfromjetsisgeneratedbyavarietyof
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 冷库温度控制系统的设计 外文翻译 冷库 温度 控制系统 设计 外文 翻译