外文翻译--一种用 CCD 检测活塞环漏光度的新方法.doc

翻译材料学生姓名学系专班号部机电工程系业机械工程自动化级二零一一年四月ANewDetectionMethodofLightLeakageDegreeofPistonRingsBasedonCCDLILin,WANGZhong,SUNYanStateKeyLaboratoryofPrecisionMeasuringTechnologyandInstrumentsofTianjinUniversityTianjinUniversityTianjin,ChinaAbstractIncomparisontothetraditionalmanualmeasurementofthelightleakagedegreeofpistonrings.AnewdetectionII.PRINCIPLESOFCCDDETECTIONmethodoflightsealdegreeLSDbasedonCCDimagesensorsispresented.ThefeaturesofCCDaredeeplyanalyzedinthispaper.ThesimilaritiesanddifferencesbetweentheareaarrayCCDimagingplanandthelinearCCDscanningplanarediscussedinthedetectionofLSDofapistonring.Finally,itispointedoutthattheareaarrayCCDwhichcouldcollectsingleimageisusedinthelightleakagemeasurementapproachandthedataoflightleakagearematchedaroundacircle.Thehighlyreliabilityofthisapproach,fordeterminingwhetherthelightleakageofpistonringsisqualified,hasbeenprovedbytherepetitiveexperiments.Whatsmore,themostpracticalapplicationofthisworkisitprovidesasolidfoundationforthenoncontactonlinedetectionoflightleakageofpistonrings.KeywordspistonringlightleakagelinearCCDAreaArrayCCDsmearI.INTRODUCTIONApistonringisoneofthekeypartsofanengine.Thereisnodirectcontactbetweenapistonringandthecylinderwallinanengine.Apistonringisusedastheintermediatemediumforreciprocatingmotion.Inanidealstate,itmustbenogapbetweentheringandthecylinderwall.However,becauseofthemanufactureandinstallationcrafts,thegapsgenerateinevitablywhentheringisassembled.Oneimportanteffectisthatitmayleadtogasblowbyandoilleakagefinally,ithasabadinfluenceontheguaranteeofoptimumefficiency1.LightleakageisusedbetweenpistonringsandthecylinderwallforanevaluationonairtightnessinChina.Theleakagedegreeofpistonringisdefinedasfollowsofapistonringputintoaringgauge,withthespecificrequirementsoflight,theabilityofpreventinglightraypassingthroughofouterringofpistonring2.Therefore,referringtothatprovisions,Peoplecanknowwhetherthepistonringisuptostandardbydetectingthelightleakage.Atpresent,artificialvisualmeasurementiswidespreadusedfordetectionoflightleakage.Butunfortunately,thismethodcausesseriousdamagetoeyesightwhenobservinglowlightgapforalongtime.Moreover,italsobringsinsubjectivefactorsandmakestestresultsinaccurate.Lastly,pistonringsaremassproducts,whichneedtobedetectedonebyone.Inthispaper,amethodbasedonthechargecoupleddeviceisproposedindetectingthelightleakageofpistonrings.A.TraditionaldetectionmethodandstandardonairtightnessThetraditionapproachdependsonrotatingpistonringartificiallyandevaluatingthelightleakageofwholecirclearcandtheirdisposition,afterputtingthepistonringintoringgauge.Besides,lightsourcemustbeusedfrombelowtothejointsurfacebetweentheouterringofpistonringandtheinnercircleoftheringgauge3.Theprovisionsonparametersoflightleakageforthepistonrings,whosediametersareatmost200mmintheinternalcombustionengines,areasfollowsTheaccuracyofarclengthmeasurementislessthanorequaltothearcofcentralangleof2°Thecentralangleofcontinuousarcoflightleakagecannotbelargerthan25°Thecentralangleofdiscontinuousarcoflightleakagecannotbelargerthan45°PunctuateleakageoflightisnotincludedThecentralangleofdisleakyarclengtharoundendgapislargerthanorequalto15°4.B.FundamentalsandstructureofCCDlightleakagedetectionCCDcamerapistonlightsourceFigure1.SchematicofLightleakagemeasuringAsFigure1shows,apistonringisfixedintotheringgaugewhichapproximatelyhasthesamediameterascylinder.Then,puttheringgaugeonaprecisionelectricdisplacementrotarytable,whichrotatewithringgaugeatsomeangularspeed.ACncmachinetoolsandbasicmanufacturingequipmentsofNationalimportantsubjectsofscienceandtechnologyProjectnumber2009ZX04014092.9781424437092/10/25.00©2010IEEEVmaxf2halogentungstenlampisusedfortheverticalbacklightilluminationfrombelowtothefayingsurfacewhichisconsistofouterringofpistonringandtheinnercircleofringgauge.AnareaCCDcameraisselectedtoreplacethehumaneyeforthedetectionandsignalcollection.Certainly,wemustmakesurethatthecenteroflightsource,thegapoflightleakageandcentralcameralensareinonestraightlinethroughadjustingdevices,forfurthestreceivinginformationofleakageoflight.Andthen,acquiredimagesaresenttothecomputerbyanimageacquisitioncard.Wecandrawaconclusionthatwhetherthepistonringisuptothestandardthroughimageprocessingmethods,ofwhichincludeshootingdynamicallywithaCCDcameraalongthegapofthewholecircleandcombiningdataoflightleakage.C.ChracteristicsanalysisoflightleakageAccordingtothestatesofleakypistonring,thereareafewtypesasfollowslightleakageofwideangleandlargegap,lightleakageofshallow,lightleakageofwideangleandtinygap,lightleakageofinterruptedandlightleakageofpunctiform.Fromtheirownleakageofpistonrings,theplacesoflightleakagehavenothingincommonwitheachother.ItseasyforCCDtoreceivelightleakageofwideangleandlargegap.However,itsalittledifficulttodeterminefortheweakgap.Thus,thekeypointofthequestionishowtoemergefurthestallarclengthofleakage,whichshouldbethat,andevenrecognizespotgapoflightleakage.Nationalstandardaskforthebrightnessbehindringgaugeabovesurrounding400lx500lx,sothatitcanprotecttestfromstraylight.Sodetectioniscarriedinthedarkroom.Practically,wearelookingforaCCDcamerasuittothelowilluminationlevel.III.THESELECTIONOFCCDIMAGESENSORSACCDimagesensor,withasetofphotoelectricconversion,selfscanning,highsensitivity,largerangeofspectralresponse,largedynamicrangeandlowcost,iswidelyusedinthefieldofindustrialinspectionandhasanexcellentperformance.ItcanbedividedintoareaarrayCCDandlineararrayCCD.Bothprinciplesaredifferent,theformer,ofwhichequipmentisrelativelysimple,isbasedonimagingmethod,whichhasahigherspeedtoobtainstwodimensionalimageinformationwithoutscancontrolcircuits,drivemechanismandsoon4.Thelattermustbeinamovementscanmodeifinwantoftwodimensionalimage,whichbasedonscanningprinciple.LinearCCDtogetherwithopticallensescanbeusedindetectingbigtargetsize,andthefieldisnotrestrictedtoonearealikeareaarrayCCD.However,lineardevicesaremorecomplexmoreover,theyrequireprecisecontrolofdivetransmission.Therefore,linearCCDsadaptabilityisnotsostrongenough6.Inaddition,Scannedimageissolikelytobeaffectedbyscanningvelocityormechanicaltransmissionerrorsthatitcanreduceaccuracyandultimatelyaffectthemeasurementaccuracy.Soitrequestsforseverelyconstantvelocity.Secondly,lightsourceishighlyrequiredbyLinearCCD.LinearCCDsensorshaveextremelyfastscanningspeedcurrently.Forexample,linefrequencyofsomeofthemcaneasilybe18KHZandevenreachto52KHZ,whileaveryshortintegrationtimeoflightisrequired.Thatsbecauseinthemostcases,wecanenhanceilluminationtogethighlylinefrequencyandatthesametimekeepsensitivitynotdecline.Forthisdetectionoflightleakageofpistonring,darkroomenvironmentisnotallowedtofillinlight.ComparedtoalinearCCDsensor,areaarrayCCDisasuperpositionofmultilineinformation.Notonlyitssystemantijammingcapabilitygreatlyimproved,butalsoitssignaltonoiseratioisobviouslybetterthanthatoflineararray.Moreover,theadjustmentofareaarrayimagingismoreconvenientandsimplethanlinearscanning.Forinstance,whenthemeasuredsizeoftheobjectchanges,wehopethatmagnificationofimagesystemcandynamicallychange,sothatlargerobjectsdonotexceedthescopeofmeasurementandsmallerobjectscanaccountforenoughpixels.AreaarrayCCDcandothisconvenientlywhenlinearCCDismoredifficultbecausescanningspeedandratiocoefficientneedtobeadjusted7.Sincetheleakybeamenergyalmostradiateverticallyanddiametersofpistonringsrangefrom80mmto126mmandthefieldofanareaarraycameraislimitedthatcantphotographastateofwholering,aslightleakageofdirectionconsidered,finally,wechooseareaarrayCCDcameraasanreceiverforcontinuouslycollectingimagesalongawholeringgapdynamically.Andthen,wewillgetlightleakageofapistonringwithimageprocessinganddatacombination.A.ThesmearissueofareaarrayCCDIfanareaarrayCCDdynamicshootingisusedindetection,theissueofsmearhastobeconsidered.SmearphenomenonreferstotheCCDchip,whenhighbrightnesslightsourceorthelargecontrastisrealinimageplane,formingawhitestripephenomenonthroughouttheentireimageplane.Eachpixelthatdonotmovedintostorageareawillstillbesubjecttotheroleoflightoutsideandcontinuetoaccumulatecharge.Thus,smearphenomenonappeared.WhenusingaframetransferCCDtoacquireimages,theimagesmearcannotchangethefacts.Smearinimageexistallthetimebecauseitistheresultofnormaloperationofthedetector.Smearpollutionlevelisproportionaltoframetransfertime.Innormalcircumstance,theimagepollutionofsmearisrelativelysmall,usuallyinsignificant.Butforhighcontrastimageorwhenscientificmeasurementapplicationsneedtorelyonpixeldensity,smearcomestobeaproblem8.Therefore,theamountofimagesmearshouldbecontrolledforaclearimage.9haspointedoutthattheamountofresidualimagemotionshouldbeonethirdofCCDpixelsizeinordertoensuresufficientdynamicresolution.However,theamountofresidualimagemotionischosenwithinonepixelsizepractically.Thatistosay,withintimeofexposuret,smearcanbeignored.LVt1VHLa3LshiftamountofimagemotionatperfieldintegrationtimeofCCDcameratperfieldintegrationtimeselectedinthisexperiment.AfterusingVC6.0compileenvironment,processedimagesasshowninFigure3.VVHfmaxspeedofimagemotionofCCDtargetsurfacespeedofameasuredobjectworkingdistancethelargestfocallengthofopticalsystemaapixelsizeEXPERIMENTANDANALYSISIV.A.ImageprocessthresholdsegmentationreversecolorIncomprehensiveconsiderationofrepeatability,costandcomplexity,MVVS142FCareaarrayCCDcameraofMicrovisionDigitalImageTechnologyCo.Ltd.wasusedinthetests,whichhadglobalshutterandframeexposure.AndthetypeofcoupledindustriallenswasM214mp,ofwhichfocallengthwas16mm,pixelsizewas6.45umandworkingdistancewas85mm.Therangefieldofviewwas55mmaround.Inaddition,Thespeedrequirementwasthatthetestoflightleakageofringsshouldbecompletedin3secondsnotincludingloadingandsorting.Measurementaccuracyofarclengthrequirednolargerthan2°centralanglecorrespondingofleakyarc.Accordingtotheformulaofconservativeestimates,exposuretimewaslessthan400usifnonsmearofpistonringwasneeded.However,byadjustingtheelectronicshutter,3msexposuretimenotonlymettherequirementsofsensitivity,butalsoproducedsmearof0.36°withthe126mmdiameterofthering.Atthismoment,smearphenomenoncanbeignored.Figure2aretwocollectedimagesoflightleakage,whicharethesamearcoflightleakageofpistonring.Theleftisastaticpicture,whiletheotherimageiscapturedat120°/sangularvelocityofturntable.medianfilterthinningFigure3.originalimagepreprocessingB.CalculationsofpistonleakyparametersTheparametersdetectionofleakypistonringsincludeleakydegreesinarangeof30°withthegapasthemidpoint,acontinuousaccumulationleakydegreeofthewholeringandabiggestcontinuousleakydegree.Wecanfindthecoordinatesoftwoendsoflightleakyarcbyextractingleakypointscoordinates,justasFigure4shows.Figure4.geometrymethodofanglecalculationFigure2.lightleakageimageofpistonringatstaticanddynamicAccordingtotheformulatocalculatedegreesoflightleakage.Pistonringsof126mmdiameterwereintervalcaptured2024picturesalongacircle,andthensingleimageshouldbepretreatmentbecauseofthenoiseandinterference.Whenwehadcuteachpieceofoverlappinginformationoflightleakage,itmeantthatwecouldgetarcinformationoflightleakagebyextractingtheleakypointcoordinates.Wepickedup18°perpartandthencombinateddataofeverypartthatwehadThelightleakageofthewholecircumferenceshallbethesumofallreadingresults.Androundingresultsisallowedwhenspotlightleakageistoosmalltoconsiderbeforethesum.Thefollowingtableisanoutcomeofmeasurementsofonesameringrepeatedfor10times.