外文翻译--三坐标测量机.doc

英文原文CoordinateMeasuringMachiningOn-linediagnosticsintheMobileSpatialcoordinateMeasuringSystem(MScMS)FiorenzoFranceschini,MaurizioGaletto,DomenicoMaisano,LucaMastrogiacomoPolitecnicodiTorino,DipartimentodiSistemidiProduzioneedEconomiadellAzienda(DISPEA),CorsoDucadegliAbruzzi24,10129-Torino,ItalyKeywords:MobilemeasuringsystemCoordinatemetrologyDimensionalmeasurementsLarge-scalemetrologyWireless-sensor-networksLocalizationalgorithmsOn-linediagnosticsAbstract:MobileSpatialcoordinateMeasuringSystem(MScMS)isawireless-sensor-networkbasedsystemdevelopedattheindustrialmetrologyandqualityengineeringlaboratoryofDISPEAPolitecnicodiTorino.Ithasbeendesignedtoperformsimpleandrapidindoordimensionalmeasurementsoflarge-sizevolumes(large-scalemetrology).Itismadeupofthreebasicparts:a“constellation”ofwirelessdevices(Crickets),amobileprobe,andaPCtostoreandelaboratedata.Cricketsandmobileprobeutilizeultrasound(US)transceiversinordertoevaluatemutualdistances.Thesystemmakesitpossibletocalculatethepositionintermsofspatialcoordinatesoftheobjectpoints“touched”bytheprobe.Acquireddataarethenavailablefordifferenttypesofelaboration(determinationofdistances,curvesorsurfacesofmeasuredobjects).Inordertoprotectthesystemagainstcausesoferrorsuchas,forexample,USsignaldiffractionandreflection,externaluncontrolledUSsources(keyjingling,neonblinking,etc.),orsoftwarenon-acceptablesolutions,MScMSimplementssomestatisticaltestsforon-linediagnostics.Threeofthemaredeeplyanalyzedinthispaper:“energymodel-baseddiagnostics”,“distancemodel-baseddiagnostics”,and“sensorphysicaldiagnostics”.Foreachmeasurement,ifallthesetestsaresatisfiedatonce,themeasuredresultmaybeconsideredacceptablewithaspecificconfidencecoefficient.Otherwise,themeasurementisrejected.AfterageneraldescriptionoftheMScMS,thepaperfocusesonthedescriptionofthesethreeonlinediagnostictools.Somepreliminaryresultsachievedbythesystemprototypearealsopresentedanddiscussed.1.IntroductionInmanyindustrialfields(forexample,automotiveandaerospace)dimensionalmeasurementsoflarge-sizeobjectsshouldbeeasilyandrapidlytaken15.Nowadays,theproblemcanbehandledusingmanymetrologicalsystems,basedondifferenttechnologies(optical,mechanical,electromagnetic,etc.).Thesesystemsaremoreorlessadequate,dependingonmeasuringconditions,usersexperienceandskill,cost,accuracy,portability,etc.Ingeneralformeasuringmediumlarge-sizeobjects,portablesystemscanbepreferredtofixedones.Transferringthemeasuringsystemtothemeasuredobjectplaceisoftenmorepracticalthanthevice-versa1.ThispaperanalyzestheMobileSpatialcoordinateMeasuringSystem(MScMS),whichhasbeendevelopedattheindustrialmetrologyandqualityengineeringlaboratoryofDISPEAPolitecnicodiTorino6.MScMSisawireless-sensor-networkbasedsystem,designedtoperformdimensionalmeasurementsofmediumlarge-sizeobjects(forexample,longeronsofrailwayvehicles,airplanewings,fuselages,etc.).Theseobjectscanhardlybemeasuredbytraditionalcoordinatemeasurementsystems,suchas,forexample,CoordinateMeasurementMachines(CMMs)becauseoftheirlimitedworkingvolume7,1.MScMSworkingprincipleisverysimilartothatofwell-knownNAVSTARGPS(NAVigationSatelliteTimingAndRangingGlobalPositioningSystem)8.ThemaindifferenceisthatMScMSisbasedonultrasound(US)technologytoevaluatespatialdistances,insteadofradiofrequency(RF).MScMSiseasilyadaptabletodifferentmeasuringenvironmentsanddoesnotrequirecomplexproceduresforinstallation,start-uporcalibration6.Theaimofthispaperistodescribetheon-linediagnosticstoolsimplementedinthesysteminordertocontinuouslymonitormeasurementreliability.2.Theconceptof“reliabilityofameasurement”IfwerefertothefieldofCMMs,theconceptof“on-linemetrologicalperformanceverification”isstrictlyrelatedtothenotionof“on-lineself-diagnostics”5,9.Inasamesense,thisapproachis“complementary”tothatofuncertaintyevaluation1015.Ingeneral,theon-linemeasurementverificationisaguaranteeforthepreservationofameasurementsystemcharacteristics(includingaccuracy,repeatability,andreproducibility)16,17.Theeffectofameasuringsystemdegradationistheproductionof“non-reliablemeasurements”.Ingeneral,wecandefinetheconceptof“reliabilityofameasurement”asfollows.3.MScMStechnologicalandoperatingfeaturesMScMSprototypeismadeupofthreemaincomponents(seeFig.1)6:-aconstellation(network)ofwirelessdevices(Crickets),opportunelyarrangedaroundtheworkingarea；-ameasuringprobe,communicatingviaultrasoundtransceivers(US)withconstellationdevicesinordertoobtainthecoordinatesofthetouchedpoints；-acomputingandcontrollingsystem(PC),receivingandprocessingdatasentbythemobileprobe,inordertoevaluateobjectsgeometricalfeatures.Themeasuringprobeisamobilesystemhostingtwowirelessdevices,atiptotouchthesurfacepointsofthemeasuredobjectsandatriggertoactivatedataacquisition(seeFig.2)6.Giventhegeometricalcharacteristicsofthemobileprobe,thetipcoordinatescanbeunivocallydeterminedbymeansofthespatialcoordinatesofthetwoprobeCrickets6.4.MScMSdiagnosticsystemFig.5.Anexampleof2Dmassspringsystem.Threereferencenodes(_x1,_x2,_x3)withknownpositionarelinkedbyspringstothepointtobelocalized(_xP).BeingbaseduponUStechnology,MScMSissensibletomanyinfluencingfactors.USsignalsmaybediffractedandreflectedbyobstaclesinterposedbetweentwodevices,externaluncontrolledeventscanbecomeundesirableUSwavesourcesandevenpositioningalgorithmscanleadtonon-acceptablesolutions.Theseandotherpotentialcausesofaccidentalmeasurementerrorsmustbetakenundercontroltoassureproperlevelsofaccuracy.Withtheaimofprotectingthesystem,MScMSimplementsaseriesofstatisticaltestsforon-linediagnostics.Threeofthemareanalyzedinthefollowingsections:-“energymodel-baseddiagnostics”；-“distancemodel-baseddiagnostics”；-“sensorphysicaldiagnostics”.5.ConclusionMScMSisaninnovativewirelessmeasuringsystemcomplementartoCMMs.AprototypeofthissystemhasbeendevelopedattheindustrialmetrologyandqualityengineeringlaboratoryofDISPEAPolitecnicodiTorino.Itisportable,nottoomuchexpensive,andsuitableforlarge-scalemetrology(uneasyonconventionalCMMs).Someinnovativeaspectsofthesystemconcernitson-linediagnosticstools.Whendealingwithmeasurementsystems,theimportanceofagooddiagnosticsofproducedmeasuresiscrucialforapplicationsinwhicherrorscanleadtoseriousconsequences.Thediagnosticstoolsdescribedinthispaper,allbasedontheconceptof“reliabilityofameasurement”,enableMScMSusertorejectmeasurementswhichdonotsatisfyaseriesofstatisticalacceptancetestswithagivenconfidencecoefficient.Foreachmeasurement,ifallthesetestsaresatisfiedatonce,themeasuredresultisconsideredacceptable.Otherwise,themeasurementisrejected.Afterrejection,theoperatorisaskedtoredothemeasurement,changingtheorientation/positioningoftheprobeor,ifitisnecessary,beaconsarrangementinthesystemnetwork.Insamecases,thesystemmightforcetorepeatameasurementtoomanytimes,causinganexcessiveextensionofthemeasurementduration.Thisproblemcanbeovercomebychangingtheconfigurationoftheconstellation.Futurework,aswellasimprovingthepoweroftheexistingtools,willbeaimedtoenrichMScMScontrolsystembyimplementingadditionaltoolsabletosteertheoperatorduringmeasurement.Forexample,suggestingthepositionoftheprobeinthemeasuringvolume,orproposingpossibleextensionsofthenetworkofbeacons,orautomaticallyfilteringand/orcorrectingcorruptedmeasurements.6.ThreecoordinatesmeasuringinstrumentprofileThreedollarsandnameismechanicalmeasuringthreecoordinatesanessentialtool.Tri-ordinatemeasuringmachine,itistopointtoinonehexahedralspacecanbehave,withinthescopeofgeometry,lengthandcircumferentialindexing,etc,andtheinstrumentmeasurementcapabilitiesthreecoordinatesmeasuringinstrumentorcalledthreecoordinatesquantitybed.Tri-ordinatemeasuringinstrumentcanbedefinedasahascanmakethreedirectionofdetectors,canbeinthreemutuallyperpendicularguiderailtomove,theprobecontactornon-contactsignalmeanssuchasthethreeshafttransmitsystem(asdisplacementmeasurementbyopticalrulerdataprocessororcomputercalculation,etcallpointcoordinatestheneededparts(X,Y,Z)andvariousfunctionmeasurementinstrument.Tri-ordinatemeasuringinstrumentmeasurementfunctionshouldincludesizeaccuracy,positioningaccuracy,geometryprecisionandcontourprecision,etc.Afewdecadesago,threecoordinatesmeasuringinstrumentindustryisonlyfewpeopleknow.Sincethe1960s,becauseelectronic,computerandsensortechnologydevelopment,thethreecoordinatesfunctionsandapplicationofmeasuringapparatus,alsoimprovedmany,makethemanufacturingindustrycanachievehighquality,highefficiencyandmultifunctionaletcmeasurementrequirements.Soqualitymanagementdepartmentcantosizeofworkpiecegeometryandoutline,suchasrapidandaccuratemeasuringreach.ReferFrommechanicalspeaking,coordinatemeasuringmachine(threeyuan)advantagesare:1thekey-,andtechnologicalprogresscoordinatemeasuringmachinefortheadvancementofscienceandtechnology,makeacoordinatemeasuringmachinepractical,andhavemanydifferentmeasurementfunction.Thekeytechnologicalpro