英文版汽车资料.docx
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英文版汽车资料
英文版汽车资料
Designconsiderationsforanautomotivemagnetorheologicalbrake
KeremKarakoca,EdwardJ.Park,a,andAfzalSulemana
aDepartmentofMechanicalEngineering,UniversityofVictoria,P.O.Box3055,STNCSC,Victoria,BC,CanadaV8W3P6
Received10October2007;
accepted22February2008.
Availableonline11April2008.
Abstract
Inthispaper,designconsiderationsforbuildinganautomotivemagnetorheological(MR)brake
arediscussed.TheproposedbrakeconsistsofmultiplerotatingdisksimmersedinaMRfluidandanenclosedelectromagnet.Whencurrentisappliedtotheelectromagnet,theMRfluidsolidifiesasitsyieldstressvariesasafunctionofthemagneticfieldapplied.Thiscontrollableyieldstressproducesshearfrictionontherotatingdisks,generatingthebrakingtorque.Inthiswork,practicaldesigncriteriasuchasmaterialselection,sealing,workingsurfacearea,viscoustorquegeneration,appliedcurrentdensity,andMRfluidselectionareconsideredtoselectabasicautomotiveMR
brakeconfiguration.Then,afiniteelementanalysisisperformedtoanalyzetheresultingmagneticcircuitandheatdistributionwithintheMRbrakeconfiguration.Thisisfollowedbyamultidisciplinarydesignoptimization(MDO)proceduretoobtainoptimaldesignparametersthatcangeneratethemaximumbrakingtorqueinthebrake.AprototypeMRbrakeisthenbuiltandtestedandtheexperimentalresultsshowagoodcorrelationwiththefiniteelementsimulationpredictions.However,thebrakingtorquegeneratedisstillfarlessthanthatofaconventionalhydraulicbrake,whichindicatesthataradicalchangeinthebasicbrakeconfigurationisrequiredtobuildafeasibleautomotiveMRbrake.
Keywords:
Mechatronicdesign;Magnetorheologicalfluid;Automotivebrake;Magneticcircuit;
Finiteelementanalysis;Multidisciplinarydesignoptimization;Brake-by-wireArticleOutline
1.
Introduction
2.
AnalyticalmodelingofMRbrake
3.
DesignofMRbrake
3.1.Magneticcircuitdesign
3.2.Materialselection
3.2.1.Magneticproperties
3.2.2.Structuralandthermalproperties
3.3.Sealing
3.4.Workingsurfacearea
3.5.Viscoustorquegeneration
3.6.Appliedcurrentdensity
3.7.MRfluidselection
4.
FiniteelementmodelingoftheMRBrake
5.
Designoptimization
6.
Overviewofexperimentalsetup
7.
Experimentalresults
7.1.Discussions
8.
Conclusion
References
1.Introduction
Theautomotiveindustryhasdemonstratedacommitmenttobuildsafer,cheaperandbetterperformingvehicles.Forexample,therecentlyintroduced“drivebywire”technologyhasbeenshowntoimprovetheexistingmechanicalsystemsinautomobiles.Inotherwords,thetraditionalmechanicalsystemsarebeingreplacedbyimprovedelectromechanicalsystemsthatareabletodothesametasksfaster,morereliablyandmoreaccurately.
Inthispaper,anelectromechanicalbrake(EMB)prototypesuitablefor“brake-by-wire”
applicationsispresented.Theproposedbrakeisamagnetorheologicalbrake(MRB)thatpotentiallyhassomeperformanceadvantagesoverconventionalhydraulicbrake(CHB)systems.ACHBsysteminvolvesthebrakepedal,hydraulicfluid,transferlinesandbrakeactuators(e.g.diskordrumbrakes).Whenthedriverpressesonthebrakepedal,themastercylinderprovidesthepressureinthebrakeactuatorsthatsqueezethebrakepadsontotherotors,generatingtheusefulfrictionforces(thusthebrakingtorque)tostopavehicle.However,theCHBhasanumberlimitations,including:
(i)delayedresponsetime(200–300ms)duetopressurebuildupinthe
hydrauliclines,(ii)bulkysizeandheavyweightduetoitsauxiliaryhydrauliccomponentssuchasthemastercylinder,(iii)brakepadwearduetoitsfrictionalbrakingmechanism,and(iv)lowbrakingperformanceinhighspeedandhightemperaturesituations.
TheMRBisapureelectronicallycontrolledactuatorandasaresult,ithasthepotentialtofurtherreducebrakingtime(thus,brakingdistance),aswellaseasierintegrationofexistingandnewadvancedcontrolfeaturessuchasanti-lockbrakingsystem(ABS),vehiclestabilitycontrol(VSC),electronicparkingbrake(EPB),adaptivecruisecontrol(ACC),aswellason-boarddiagnosticfeatures.Furthermore,reducednumberofcomponents,simplifiedwiringandbetterlayoutarealladditionalbenefits.Intheautomotiveindustry,companiessuchasDelphiCorp.andContinental
AutomotiveSystemshavebeenactivelyinvolvedinthedevelopmentofcommerciallyavailableEMBsasnextgenerationbrake-by-wiretechnology.Theseareaimedatpassengervehicleswithconventionalpowertrains,aswellasvehicleswithadvancedpowersources,likehybridelectric,fuelcellandadvancedbatteryelectricpropulsion(e.g.42Vplatform).Forexample,Delphihasrecentlyproposedaswitchedreluctance(SR)motor[1]asonepossibleactuationtechnologyforEMBapplications.AnothertypeofpassengervehicleEMBsthatanumberresearchgroupsandcompanieshavebeendevelopingiseddycurrentbrakes(ECBs),e.g.[2].WhileanECBisacompletelycontactlessbrakethatisperfectlysuitedforbrakingathighvehiclespeeds(asitsbrakingtorqueisproportionaltothesquareofthewheelspeed),however,itcannotgenerateenoughbrakingtorqueatlowvehiclespeeds.
AbasicconfigurationofaMRBwasproposedbyParketal.[3]forautomotiveapplications.As
showninFig.1,inthisconfiguration,arotatingdisk(3)isenclosedbyastaticcasing(5),andthegap(7)betweenthediskandcasingisfilledwiththeMRfluid.Acoilwinding(6)isembeddedontheperimeterofthecasingandwhenelectricalcurrentisappliedtoit,magneticfieldsaregenerated,andtheMRfluidinthegapbecomessolid-likeinstantaneously.TheshearfrictionbetweentherotatingdiskandthesolidifiedMRfluidprovidestherequiredbrakingtorque.
Full-sizeimage(49K)
Fig.1.Cross-sectionofbasicautomotiveMRBdesign[3].
ViewWithinArticle
TheliteraturepresentsanumberofMRfluid-basedbrakedesigns,e.g.[3],[4],[5],[6],[7]and[8].In[4]and[5],CarlsonofLordCorporationproposedandpatentedgeneralpurposeMRBactuators,whichsubsequentlybecamecommerciallyavailable[6].In[7],anMRBdesignwasproposedforexerciseequipment(e.g.asawaytoprovidevariableresistancetoexercisebikes).Morerecently,anMRBwasdesignedandprototypedforahapticapplicationaswell[8].Inthiswork,usingtheBinghamplasticmodelfordefiningtheMRfluidbehavior,itsbrakingtorquegenerationcapacitywasinvestigatedusinganelectromagneticfiniteelementanalysis.Ourpreviouswork[3]E.J.Park,D.Stoikov,L.FalcaodaLuzandA.Suleman,Aperformanceevaluationofanautomotive
magnetorheologicalbrakedesignwithaslidingmodecontroller,Mechatronics16(2006),pp.405–416.Article|PDF(547K)|ViewRecordinScopus|CitedByinScopus(21)[3]wasafeasibilitystudybasedonaconceptualMRBdesignthatincludedbothelectromagneticfiniteelementandheattransferanalysis,followedbyasimulatedbrake-by-wirecontrol(wheelslipcontrol)ofasimplifiedtwo-diskMRBdesign.
Now,thecurrentpaperisafollowupstudytoourpreviouswork[3].HeretheMRBdesignthatwasproposedin[3]isfurtherimprovedaccordingtoadditionalpracticaldesigncriteriaandconstraints(e.g.beabletofitintoastandard13”wheel),andmorein-depthelectromagneticfinite
elementanalysis.ThenewMRBdesign,whichhasanoptimizedmagneticcircuittoincreaseitsbrakingtorquecapacity,isthenprototypedforexperimentalverification.
2.AnalyticalmodelingofMRbrake
TheidealizedcharacteristicsoftheMRfluidcanbedescribedeffectivelybyusingtheBingham
[10],[11]and[12].Accordingtothismodel,thetotalshearstressτisplasticmodel[9],
(1)whereτHistheyieldstressduetoappliedmagneticfield,μpisthe
no-fieldplasticviscosityofthefluidandistheshearrate.Thebrakingtorqueforthegeometry
showninFig.1canbedefinedasfollows:
(2)whereAistheworkingsurfacearea
(thedomainwherethefluidisactivatedbyappliedmagneticfieldintensity),zandjaretheouterandinnerradiiofthedisk,Nisthenumberofdisksusedintheenclosureandristheradialdistancefromthecentreofthedisk.
AssumingtheMRfluidgapinFig.1tobeverysmall(e.g.1mm),theshearratecanbeobtainedby
(3)assuminglinearfluidvelocitydistributionacrossthegapandnoslipconditions.InEq.(3),wistheangularvelocityofthediskandhisthethicknessoftheMRfluidgap.Inaddition,theyieldstress,τH,canbeapproximatedintermsofthemagneticfieldintensityappliedspecificallyontotheMRfluid,HMRF,andtheMRfluiddependentconstantparameters,kandβ,i.e.
BysubstitutingEqs.(3)and(4),thebrakingtorqueequationinEq.
(2)canbe(4)
rewrittenas
(5)Then,Eq.(5)canbedividedintothe
followingtwopartsaftertheintegration
(6)
(7)whereTHisthetorquegeneratedduetotheappliedmagneticfield
andTμisthetorquegeneratedduetotheviscosityofthefluid.Finally,thetotalbrakingtorqueisTb=Tμ+TH.Fromthedesignpointofview,theparametersthatcanbevariedtoincreasethebrakingtorquegenerationcapacityare:
thenumberofdisks(i.e.N),thedimensionsandconfigurationofthemagneticcircuit(i.e.rz,rj,andotherstructuraldesignparametersshowninFig.3),andHMRFthatisdirectlyrelatedtotheappliedcurrentdensityintheelectromagnetandmaterialsusedinthemagneticcircuit.
3.DesignofMRbrake
Inthispaper,theproposedMRBwasdesignedconsideringthedesignparametersaddressedintheprevioussection.Inaddition,someofthekeypractica