液压泵外文报告加翻译

ExperimentsforderivedfactorswithapplicationtohydraulicgearpumpsC.J.Sexton,S.M.LewisandC.P.PleaseUniversityofSouthampton,UK[ReceivedJune1999.RevisedOctober2000]Summary.Forexperimentsonmechanicalproductscomposedofseveralcomponents,suchasahydraulicgearpump,conventionalmethodsofdesigningandimplementingfactorialexperimentscanbeimpracticalbecauseoftheprohibitivecostsofobtainingcertaincomponentswithfactorssettoprespecifiedvalues.Afurtherdifficultyisthatoftensomeofthefactorsthatarebelievedtoinfluencetheproduct'sperformancearenotfeaturesofasinglecomponentbutarederivedasfunctionsofthedimensionsofseveralcomponentsarisingfromtheproduct'sassembly.Experi-mentsareproposedwhichuseasampleofmeasuredcomponentstoexploretheinfluenceofsuchderivedfactors.Analgorithmicmethodforobtainingefficientdesignsispresentedandappliedtofindingplansforstudiesonthegearpump.Anexperimentonthepumpisdescribedwhichinvolvedbothconventionalandderivedfactors.Thisexperimentledtonewknowledgeonhowtoimprovetheengineeringdesignofthepumpand,inparticular,onhowtoimproveitsrobustnesstothevaryingpressuresthatareexperiencedinoperation.Keywords:Algorithm;Components;Factorialexperiment;Mechanicalengineering;Optimaldesign;Qualityimprovement;Robustness1.IntroductionThedesignofaconventionalfactorialexperimentspecifiesthelevelsofeachfactorandhowtheyshouldbecombinedtoformruns.Whentheobjectiveoftheexperimentistoinvestigateandimprovetheperformanceofaproductassembledfromseveralseparatecomponents,e.g.amechanicalorelectricaldevice,twomethodsofobtainingtherequiredcombinationsoffactorlevelstorealizethedesignarecommonlyused.Oneapproachistomanufactureone-offcomponentstohavethefactorvaluesthatarerequiredfortheexperiment.Alternatively,samplesofthevariouscomponentscanbetakenfromproductionand,throughmeasur-ingthefeaturesofinterest,componentsfoundwiththerequiredproperties.Typically,therequiredfactorlevelsareat,ornear,theextremesofthefactorrangesobtainedinproduction,solargesamplesofcomponentsmustbemeasuredtofindsufficientfortheexperiment.Forsomeproducts,thecostsoftheseapproachesareprohibitive.AnexampleisthehydraulicgearpumpshowninFig.1，wheremachiningtheindividualgearteethonthedriveanddrivengearstoprecisespecifications,ormeasuringtheirprofiles,isslowandcostly.Afurtherdifficultywithmechanicalproductsisthatoftenacomponentcannotbeusedinmorethanoneexperimentalproduct,e.g.whenrunningandtestingtheproductproducescomponentwear,asinthegearpump.Forsuchsituations,weproposeanapproachwhichtakesamuchsmallerrandomsampleofcomponentsfromproduction,measurestheirrelevantfeaturesandassemblesthemtoAddressforcorrespondence:C.J.Sexton,DepartmentofMathematics,UniversityofSouthampton,Highfield,Southampton,S0171BJ,UK.E-mail:[e-mail]○C2001RoyalStatisticalSociety0035-9254/01/50155formasetofprototypesfortestingthatgivesasmuchinformationaspossibleonthefactorialeffectsofinterest.Thusfullcontrolissacrificedoverthevaluestakenbyafactor,butsomeControlisretainedoverwhichfactorvaluesarecombinedintheexperiment.Suchfactorscanberegardedassemicontrolled;seealsoHarville(1974).Anaddedcomplicationformanymechanicalproductsisthatthemeaningfulfactorsarenotthemeasuredfeaturesofthecomponentsbutfactorsderivedfromthem,suchasadistancebetweentwocomponents,orotherfunctionsofseveralvariablesthatrelateinengineeringtermstotheproduct'sperformance.Wepresentanalgorithmicmethodofobtainingefficientdesignsforexperimentsinvolvingderivedfactors.InSection2thehydraulicgearpumpisdescribed,andSection3definesthedesignproblem.AnalgorithmforgeneratingdesignswhenallthefactorsarederivedisgiveninSection4;thisalgorithmhasbeenusedtofindadesignforapilotstudyonthepump.Section5considersanexperimentwheresomefactorscanbefullycontrolledandotherscannot.Anextensionofthealgorithmisusedtoobtainadesignforthisexperiment.InSection6theanalysisofthedatafromtheexperimentisoutlined,togetherwiththenewknowledgegainedonhowtoimprovetheengineeringdesignofthepump.2.ThehydraulicgearpumpHydraulicgearpumpsareusedinawidevarietyofmachines,e.g.agriculturalandconstructionvehiclesandaeroplanes,toprovideflexiblepowerfromtheenginetoliftinggearorancillaryequipment.Thepumpunderinvestigationhereformspartofthepowersteeringmechanismofanagriculturaltractor.AsshowninFig.1，itconsistsofadrivegearandadrivengearwhichsitintwobearingblocks,floatingwithinahousing,withaflangeplateononesideandacoverontheothertopresstheblocksontothegears.Asthedriveshaftturns,thegearteethmeshanddrawhydraulicfluidthroughthepump.However,atendencyforsomeofthefluidtoleakbackaroundtheinternalcomponentscanleadtoareductionintheefficiencyofthepump.Toimprovetheengineeringdesignbyreducingsuchleakage,themanufacturerwishedtoinvestigatetheinfluenceofthemanygeometricalaspectsofthecomponentsonpumpleakage,definedasthedifferencebetweenthetheoreticalandactualflowratesoffluidthroughthepump.Becauseoftheveryhighpressuresthatareexperiencedbythehydraulicfluid,thedesignmustaccommodatetheflexingofcomponentswhichwouldotherwisecreatesubstantialgapsbetweencomponentsandresultinhighleakage.Withinthepump,theflexingispartlycontrolledbyacar