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