翻譯材料學(xué)生姓名：學(xué)系專班號(hào)：部：機(jī)電工程系業(yè)：機(jī)械工程自動(dòng)化級(jí)：二零一一年四月ANewDetectionMethodofLightLeakageDegreeofPistonRingsBasedonCCDLILin,WANGZhong,SUNYanStateKeyLaboratoryofPrecisionMeasuringTechnologyandInstrumentsofTianjinUniversityTianjinUniversityTianjin,ChinaAbstractIncomparisontothetraditionalmanualmeasurementofthelightleakagedegreeofpistonrings.AnewdetectionII.PRINCIPLESOFCCDDETECTIONmethodoflightsealdegree(LSD)basedonCCDimagesensorsispresented.ThefeaturesofCCDaredeeplyanalyzedinthispaper.ThesimilaritiesanddifferencesbetweentheareaarrayCCDimagingplanandthelinearCCDscanningplanarediscussedinthedetectionofLSDofapistonring.Finally,itispointedoutthattheareaarrayCCDwhichcouldcollectsingleimageisusedinthelightleakagemeasurementapproachandthedataoflightleakagearematchedaroundacircle.Thehighlyreliabilityofthisapproach,fordeterminingwhetherthelightleakageofpistonringsisqualified,hasbeenprovedbytherepetitiveexperiments.Whatsmore,themostpracticalapplicationofthisworkisitprovidesasolidfoundationforthenon-contactonlinedetectionoflightleakageofpistonrings.Keywords-pistonring；lightleakage；linearCCD；AreaArrayCCD；smearI.INTRODUCTIONApistonringisoneofthekeypartsofanengine.Thereisnodirectcontactbetweenapistonringandthecylinderwallinanengine.Apistonringisusedastheintermediatemediumforreciprocatingmotion.Inanidealstate,itmustbeno-gapbetweentheringandthecylinderwall.However,becauseofthemanufactureandinstallationcrafts,thegapsgenerateinevitablywhentheringisassembled.Oneimportanteffectisthatitmayleadtogasblowbyandoilleakage；finally,ithasabadinfluenceontheguaranteeofoptimumefficiency1.LightleakageisusedbetweenpistonringsandthecylinderwallforanevaluationonairtightnessinChina.Theleakagedegreeofpistonringisdefinedasfollows:“ofapistonringputintoaringgauge,withthespecificrequirementsoflight,theabilityofpreventinglightraypassingthroughofouterringofpistonring”2.Therefore,referringtothatprovisions,Peoplecanknowwhetherthepistonringisuptostandardbydetectingthelightleakage.Atpresent,artificialvisualmeasurementiswidespreadusedfordetectionoflightleakage.Butunfortunately,thismethodcausesseriousdamagetoeyesightwhenobservinglowlightgapforalongtime.Moreover,italsobringsinsubjectivefactorsandmakestestresultsinaccurate.Lastly,pistonringsaremassproducts,whichneedtobedetectedonebyone.Inthispaper,amethodbasedonthechargecoupleddeviceisproposedindetectingthelightleakageofpistonrings.A.TraditionaldetectionmethodandstandardonairtightnessThetraditionapproachdependsonrotatingpistonringartificiallyandevaluatingthelightleakageofwholecirclearcandtheirdisposition,afterputtingthepistonringintoringgauge.Besides,lightsourcemustbeusedfrombelowtothejointsurfacebetweentheouterringofpistonringandtheinnercircleoftheringgauge3.Theprovisionsonparametersoflightleakageforthepistonrings,whosediametersareatmost200mmintheinternalcombustionengines,areasfollows:Theaccuracyofarclengthmeasurementislessthanorequaltothearcofcentralangleof2；Thecentralangleofcontinuousarcoflightleakagecannotbelargerthan25；Thecentralangleofdiscontinuousarcoflightleakagecannotbelargerthan45；Punctuateleakageoflightisnotincluded；Thecentralangleofdisleakyarclengtharoundendgapislargerthanorequalto154.B.FundamentalsandstructureofCCDlightleakagedetectionCCDcamerapistonlightsourceFigure1.SchematicofLightleakagemeasuringAsFigure1shows,apistonringisfixedintotheringgaugewhichapproximatelyhasthesamediameterascylinder.Then,puttheringgaugeonaprecisionelectricdisplacementrotarytable,whichrotatewithringgaugeatsomeangularspeed.A“Cncmachinetoolsandbasicmanufacturingequipments”ofNationalimportantsubjectsofscienceandtechnologyProjectnumber:2009ZX04014-092.978-1-4244-3709-2/10/$25.002010IEEEVmaxf(2)halogentungstenlampisusedfortheverticalbacklightilluminationfrombelowtothefayingsurfacewhichisconsistofouterringofpistonringandtheinnercircleofringgauge.AnareaCCDcameraisselectedtoreplacethehumaneyeforthedetectionandsignalcollection.Certainly,wemustmakesurethatthecenteroflightsource,thegapoflightleakageandcentralcameralensareinonestraightlinethroughadjustingdevices,forfurthestreceivinginformationofleakageoflight.Andthen,acquiredimagesaresenttothecomputerbyanimageacquisitioncard.Wecandrawaconclusionthatwhetherthepistonringisuptothestandardthroughimageprocessingmethods,ofwhichincludeshootingdynamicallywithaCCDcameraalongthegapofthewholecircleandcombiningdataoflightleakage.C.ChracteristicsanalysisoflightleakageAccordingtothestatesofleakypistonring,thereareafewtypesasfollows:lightleakageofwide-angleandlargegap,lightleakageofshallow,lightleakageofwide-angleandtinygap,lightleakageofinterruptedandlightleakageofpunctiform.Fromtheirownleakageofpistonrings,theplacesoflightleakagehavenothingincommonwitheachother.ItseasyforCCDtoreceivelightleakageofwide-angleandlargegap.However,itsalittledifficulttodeterminefortheweakgap.Thus,thekeypointofthequestionishowtoemergefurthestallarclengthofleakage,whichshouldbethat,andevenrecognizespotgapoflightleakage.Nationalstandardaskforthebrightnessbehindringgaugeabovesurrounding400lx500lx,sothatitcanprotecttestfromstraylight.Sodetectioniscarriedinthedarkroom.Practically,wearelookingforaCCDcamerasuittothelowilluminationlevel.III.THESELECTIONOFCCDIMAGESENSORSACCDimagesensor,withasetofphotoelectricconversion,self-scanning,highsensitivity,largerangeofspectralresponse,largedynamicrangeandlowcost,iswidelyusedinthefieldofindustrialinspectionandhasanexcellentperformance.ItcanbedividedintoareaarrayCCDandlineararrayCCD.Bothprinciplesaredifferent,theformer,ofwhichequipmentisrelativelysimple,isbasedonimagingmethod,whichhasahigherspeedtoobtainstwo-dimensionalimageinformationwithoutscancontrolcircuits,drivemechanismandsoon4.Thelattermustbeinamovementscanmodeifinwantoftwo-dimensionalimage,whichbasedonscanningprinciple.LinearCCDtogetherwithopticallensescanbeusedindetectingbigtargetsize,andthefieldisnotrestrictedtoonearealikeareaarrayCCD.However,lineardevicesaremorecomplex；moreover,theyrequireprecisecontrolofdivetransmission.Therefore,linearCCDsadaptabilityisnotsostrongenough6.Inaddition,Scannedimageissolikelytobeaffectedbyscanningvelocityormechanicaltransmissionerrorsthatitcanreduceaccuracyandultimatelyaffectthemeasurementaccuracy.Soitrequestsforseverelyconstantvelocity.Secondly,lightsourceishighlyrequiredbyLinearCCD.LinearCCDsensorshaveextremelyfastscanningspeedcurrently.Forexample,linefrequencyofsomeofthemcaneasilybe18KHZandevenreachto52KHZ,whileaveryshortintegrationtimeoflightisrequired.Thatsbecauseinthemostcases,wecanenhanceilluminationtogethighlylinefrequencyandatthesametimekeepsensitivitynotdecline.Forthisdetectionoflightleakageofpistonring,darkroomenvironmentisnotallowedtofill-inlight.ComparedtoalinearCCDsensor,areaarrayCCDisasuperpositionofmulti-lineinformation.Notonlyitssystemantijammingcapabilitygreatlyimproved,butalsoitssignal-to-noiseratioisobviouslybetterthanthatoflineararray.Moreover,theadjustmentofarea-arrayimagingismoreconvenientandsimplethanlinearscanning.Forinstance,whenthemeasuredsizeoftheobjectchanges,wehopethatmagnificationofimagesystemcandynamicallychange,sothatlargerobjectsdonotexceedthescopeofmeasurementandsmallerobjectscanaccountforenoughpixels.AreaarrayCCDcandothisconvenientlywhenlinearCCDismoredifficultbecausescanningspeedandratiocoefficientneedtobeadjusted7.Sincetheleakybeamenergyalmostradiateverticallyanddiametersofpistonringsrangefrom80mmto126mmandthefieldofanareaarraycameraislimitedthatcantphotographastateofwholering,aslightleakageofdirectionconsidered,finally,wechooseareaarrayCCDcameraasanreceiverforcontinuouslycollectingimagesalongawholeringgapdynamically.Andthen,wewillgetlightleakageofapistonringwithimageprocessinganddatacombination.A.ThesmearissueofareaarrayCCDIfanareaarrayCCDdynamicshootingisusedindetection,theissueofsmearhastobeconsidered.SmearphenomenonreferstotheCCDchip,whenhigh-brightnesslightsourceorthelargecontrastisrealinimageplane,formingawhitestripephenomenonthroughouttheentireimageplane.Eachpixelthatdonotmovedintostorageareawillstillbesubjecttotheroleoflightoutsideandcontinuetoaccumulatecharge.Thus,smearphenomenonappeared.Whenusingaframe-transferCCDtoacquireimages,theimagesmearcannotchangethefacts.Smearinimageexistallthetimebecauseitistheresultofnormaloperationofthedetector.Smearpollutionlevelisproportionaltoframetransfertime.Innormalcircumstance,theimagepollutionofsmearisrelativelysmall,usuallyinsignificant.Butforhigh-contrastimageorwhenscientificmeasurementapplicationsneedtorelyonpixeldensity,smearcomestobeaproblem8.Therefore,theamountofimagesmearshouldbecontrolledforaclearimage.9haspointedoutthattheamountofresidualimagemotionshouldbeonethirdofCCDpixelsizeinordertoensuresufficientdynamicresolution.However,theamountofresidualimagemotionischosenwithinonepixelsizepractically.Thatistosay,withintimeofexposuret,smearcanbeignored.LVt(1)VHLa(3)LshiftamountofimagemotionatperfieldintegrationtimeofCCDcameratperfieldintegrationtimeselectedinthisexperiment.AfterusingVC+6.0compileenvironment,processedimagesasshowninFigure3.VVHfmaxspeedofimagemotionofCCDtargetsurfacespeedofameasuredobjectworkingdistancethelargestfocallengthofopticalsystemaapixelsizeEXPERIMENTANDANALYSISIV.A.ImageprocessthresholdsegmentationreversecolorIncomprehensiveconsiderationofrepeatability,costandcomplexity,MV-VS-142FCareaarrayCCDcameraofMicrovisionDigitalImageTechnologyCo.Ltd.wasusedinthetests,whichhadglobalshutterandframeexposure.AndthetypeofcoupledindustriallenswasM214-mp,ofwhichfocallengthwas16mm,pixelsizewas6.45umandworkingdistancewas85mm.Therangefieldofviewwas55mmaround.Inaddition,Thespeedrequirementwasthatthetestoflightleakageofringsshouldbecompletedin3seconds(notincludingloadingandsorting).Measurementaccuracyofarclengthrequirednolargerthan2centralanglecorrespondingofleakyarc.Accordingtotheformulaofconservativeestimates,exposuretimewaslessthan400usifnon-smearofpistonringwasneeded.However,byadjustingtheelectronicshutter,3msexposuretimenotonlymettherequirementsofsensitivity,butalsoproducedsmearof0.36withthe126mmdiameterofthering.Atthismoment,smearphenomenoncanbeignored.Figure2aretwocollectedimagesoflightleakage,whicharethesamearcoflightleakageofpistonring.Theleftisastaticpicture,whiletheotherimageiscapturedat120/sa