英文原文Auto-testingsystemforfanperformancebasedonvirtualinstrumentationtechnologyAbstract:Inaccordancewiththepresentstatusofmeasurementoffanperformancewithburdensomeinlabors,lowinaccuracyandbackwardintestingmethod,auto-testingsystemforfanperformancebasedonVirtualInstruments(VI)technologywasdeveloped.Thesystemintegratedsensortechnology,computertechnologyandmeasurementtechnology.Asaresult,thesystemcannotonlyautomaticallyacquire,processtestingdataandexpressthefinalresultsinsuitableformsbutalsocontrolandadjustdifferentworkingloads.Thewholesystemisfriendlyininterface,easyinoperationandcompleteinfunctions.Theexperimentresultsshowedthatthestabilityoftheexperimentprocessincreased,thereadingerrorwasavoidedandthemeasurementaccuracyandexperimentefficiencywereimproved.Thesystemhasbeenwidelyappliedtomanyfanproductionfactoriesandresearchinstitutes.Keywords:fan；performancetesting；auto-testing；virtualinstrumentation；dataprocessing1IntroductionTheparametersoffan:flux,pressure,powerandeficiencynotonlydecideworkingperformancebutalsoarethebasisofselectingandusingblowerforpeople.Becauseoftheblowertheorybeingnotperfect,performancetestingisthemainmethodofacquiringtheseparameters.Moreover,thetestingisimportantfortestingproductsanddesigningnewproducts.InChina,traditionalfanperformancetestingisalwaysdonemanuallyorbysinglechipwhichhasmanyshortagesincludinglowerprecision,heavylaborintensity,unfriendlyuser-interface,andsoon.Therefore,accordingtothedemandsofmoderntimesexperimenttechnique,anautomatictestandanalysissystemforfanperformancebasedonvirtualinstrumentationtoolLabWindows/CVIwasdesignedinthispaper.Combinedsensortechnology,computertechnologyandtestingtechnique,thevirtualinstrumentation(VI)technologymakesthemostuseofintelligenceofcomputertothoroughlybreakdownthemodethatthetraditionalinstrumentsaredefinedbythemanufacturers,howevertheuserscannotchange.WithVI,usersareprovidedaspacetoexerttheircapacityandimaginationadequately.Itistheuser,notthemanufacturer,whocandesigntheirown.instrumentsystemattheirpleasureaccordingtopersonalneed.Inthevirtualinstrumentsystem,thehardwareonlyprovidesasolutiontotheinputandoutputofsignals,howeverthesoftwareisthekeytothewholesystem.Anyusermaymodifythesoftwaretochange,increaseordecreasethefunctionsandscalesoftheinstrumentsystem.Asaresult,thesystemcannotonlyautomaticallyacquire,processtestingdataandexpressthefinalresultsinsuitableformsbutalsocontrolandadjustdifferentworkingloads.Thewholesystemisfriendlyininterface,easyinoperationandcompleteinfunctions.Theexperimentresultshaveshownthatthestabilityoftheexperimentprocesshasincreased,thereadingerrorwasavoidedandthemeasurementaccuracyandexperimentefficiencywereimproved.Thesystemhasbeenwidelyappliedtomanyfanproductionfactoriesandresearchinstitutes.2HardwaredesignofthesystemHardwareofthissystem,whichisthebasisofsignalacquisition,conversion,enhanceandprocessing,consistsoffan,motors,windpipe,sensors,computer,dataacquisitionboard,frequencyconversiongovernor,etc.TheblockdiagramofsystemstructureisshowninFig.1.Amongthosecomponents,computerandplug-inDAQboardplayanimportantroleinthesystem.WiththehighperformanceDAQboard,notonlydataacquisition,A/Dconversionbutalsofrequencycontrol,stepmotorcontroletcarerealized.Consideredofthetechnicalindexessuchassamplingfrequency,accuracy,A/D&D/Aconversionrate,resolution,theDAQboardPCI-6024EfromNationalInstruments(U.S.A),withwhich200ks/s,12-bitperformanceon16single-endedanaloginputscanbegotupto,isselected.The6024Efeaturesdigitaltriggeringcapacity,aswellastwo24-bit,20MHzcounter/times；and8digitalI/Olines.Two12-bitanalogoutputsarealsofeaturedbythe6024E.Thefanparameters:flux,staticpressure,torqueandrotationspeedaremeasuredbycorrespondingsensorsincludingdifferentialpressuretransmitter(BC69type,accuracyisFS),staticpressuretransmitter(JYBtype,accuracyis1%FS),andtorque&rotatespeedsensor(AKC-205type,accuracyis0.3%FS).Thesensoroutputsareallstandardcurrentsignalwith420mA.TomeettheDAQboardinputsignaltypeandrange,05Vvoltagesignalsareachievedfrom420mAcurrentsignalsbyaninterfaceboardwhichisusedforsignaltransformation.Throughtheanalogoutputchannelon6024E,05Vvoltagesignalwhichiscorrespondingon050HzofACfrequency,aresentouttocontrolfrequencyconverter(FR-A540-1.5K-CHtype,MITSUDISHI,Japan).Then,thefanspeedchangeswithvariablevoltage.Theregulatingunitofworkingstatus,whichisdesignedbytheauthors,istherotatingbafflestructurecomposedofroundbaffle,shaftcoupling,creepergearandstepmotoretc.(SeetheFig.2).Thiskindofstructurecannotonlyrealizetheauto-controlbutalsoissmallandflexible.ThreedigitalI/Oportonthe6024Eareusedtosendoutthree-phasepulsetocontroltherotationangleofstepmotor.Thestepmotordrivestheroundbafflethroughthecreepergeartorevolveinsidethewind-pipe,resultinginthechangeofaperturegapbetweentheroundbaffleandwind-pipe,therebyalteringthefluxofairflowinsidethewind-pipe,namelythealterationofworkingstatusisrealized.Thecreepergearcanpreventthepositionofroundbafflechangingwhentheairflowistoostrong.Toinsurethemeasurementaccuracy,severalanti-interferencemeansareadoptedsuchasdifferentialinputsofsignalstoeliminatethecommonmodeinterference,goodearthofsignallineandinstruments,digitalfilteringtechnologyinsoftware.3Softwaredesignofthesystem3.1DataprocessingDataprocessinginthissystemincludesthreeaspects:processingacquiredsignalstoweedoutvariousdisturbingsignals；usinghydrodynamicsformulastocalculateperformanceparametersoffans；fittingperformanceparametersbasedonleastsquaremethodtodrawperformancecurvesoffans.3.1.1CalculationofperformanceparametersRefertothenationalstandardGB1236-85,Aerodynamicsperformancetestprocedureofventilator,theventilatorperformancetestingofthedischargeoutletisachieved.Thefanperformanceparametersarecalculatedasfollowso:whereistheapertureofrestrictionorifice；istheflowcoefficient；isthegasexpansioncoefficient；isthegasdensityoffanoutlet；Fitthetorquebetweenmotorandfan；nistherotationspeedofmotor；pstisthestaticpressure；Pdisthekineticpressure；Aistheareaofwindpipe；visthespeedoftheairflow；istheavailableoutput.3.1.2PerformancecurvefittingTherearemanycurvefittingmethodssuchasexponentialfitting,orthogonalpolynomialfitting.Theleastsquaremethodisadoptedtofitperformanceparametersbecausethecharacteristiccurveoffanismostlyparabola.Whatiscalledleastsquaremethodisstatisticallyprocessingtheobservedvaluesfromexperimentstomakedesiredvalueofobservationequaltoitstheoreticalvalueandrectifytheobservedvalue.UsingthefunctionPolynomialthatisintheadvancedanalysislibraryofLabWindows/CVI,theperformancecurvefittingwascompleted.TheformatoffunctionPolynomialisasfollows:Polynomial(doublex,doubley,intn,intorder,doublez,doublecoef,double*mse)Thepurposeofthisfunctionistofindthecoefficientsthatbestrepresentthepolynomialfitofthedatapoints(x,y)usingtheleastsquaresmethod.PolyFitobtainstheitselementoftheoutputarrayandmeansquarederror(mse)usingthefollowingformula:Withthisfunctiontheflux-wholepressurecurve,flux-staticpressurecurve,andflux-efficiencycurvecanbeachieved.3.2StructureofthesoftwareThesoftwareisdevelopedbyLabWindows/CVIwhichisanintegratedANSICenvironmentforengineersandscientistscreatingvirtualinstrumentationapplications.WithintegratedI/Olibraries,analysisroutines,anduserinterfacetools,LabWindows/CVIdeliverseverythingyouneedforbuildingadvancedtestandmeasurementsystems.Basedonmodulardesignmethodofprogram,8modulesaredesignedinthissystem:(1)Basicparameterssetting:usercankeyinthefantypeandenvironmentalparametersincludingatmospherictemperature,humidityandpressureinthismodule.(2)Dataacquisitionandcontrolparameterssetting:inthismodule,thesamplingchannel,controlchannel,samplingrate,signalinput/outputlimitetc(3)Maincontrolstation:thismoduleisthemaininterfaceforoperators.Thevisualizedcontrols,suchaspowerswitch,testingstartswitch,operatingmodeselectingslide,fanspeedselectingslide,andreal-timenumeric&waveformdisplayofsignals,aredeliveredinthefrontpanelforuseroperatingthissystemconveniently.(4)Dataprocess