专家主轴设计系统英文翻译.docx

专家主轴设计系统英文翻译.docx

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专家主轴设计系统英文翻译

英文翻译

英文原文

Expertspindledesignsystem

Abstrac

Thispaperpresentsanexpertspindledesignsystemstrategywhichisbasedontheefficientutilizationofpastdesignexperience,thelawsofmachinedesign,dynamicsandmetalcuttingmechanics.Theconfigurationofthespindleisdecidedfromthespecificationsoftheworkpiecematerial,desiredcuttingconditions,andmostcommontoolsusedonthemachinetool.Thespindledrivemechanism,drivemotor,bearingtypes,andspindleshaftdimensionsareselectedbasedonthetargetapplications.Thepaperprovidesasetoffuzzydesignrules,whichleadtoaninteractiveandautomaticdesignofspindledriveconfigurations.Thestructuraldynamicsofthespindleareautomaticallyoptimizedbydistributingthebearingsalongthespindleshaft.TheproposedstrategyistoiterativelypredicttheFrequencyResponseFunction（FRF）ofthespindleatthetooltipusingtheFiniteElementMethod（FEM）basedontheTimoshenkobeamtheory.ThepredictedFRFofthespindleisintegratedtothechattervibrationstabilitylaw,whichindicateswhetherthedesignwouldleadtochattervibrationfreecuttingoperationatthedesiredspeedanddepthofcutfordifferentflutesofcutters.ThearrangementofbearingsisoptimizedusingtheSequentialQuadraticProgramming（SQP）method.

Keywords:

Spindledesign;Expertsystem;Chattervibration;Finiteelementmethod;Optimization

1.Introduction

Thespindleisthemainmechanicalcomponentinmachiningcenters.Thespindleshaftrotatesatdifferentspeedsandholdsacutter,whichmachinesamaterialattachedtothemachinetooltable.Thestaticanddynamicstiffnessofthespindledirectlyaffectthemachiningproductivityandfinishqualityoftheworkpieces.Thestructuralpropertiesofthespindledependonthedimensionsoftheshaft,motor,toolholder,bearings,andthedesignconfigurationoftheoverallspindleassembly.

Thisresearchconsidersspindlecomponentselectionandconfigurationusingtheproposedexpertsystembasedonthedigitalknowledgebase.Theexpertsystemwithfuzzylogicisimplementedastheselectionsystem.

Eskiciogluetal.[1]developedarule-basedalgorithmfortheselectionofspindlebearingarrangementusingPRO-LOG,whichisaprogramminglanguageforexpertsystems.Thebearingarrangementsaredeterminedbythecuttingoperationtype,andtherequiredcuttingforceandlifeofbearings.WongandAtkinson[2]demonstratedaknowledgecellapproachfordiversedesigns.Theydividedtheknowledgecellintofourparts;theFunction,Selection,Graphics,andLogiccells.

Fordesignoptimizationofspindles,Yang[3]conductedstaticstiffnesstooptimizeabearingspanusingtwobearings,anddescribedthemethodsusedtosolvethemulti-bearingspans’optimizationmethod.Tayloretal.[4]developedaprogramwhichoptimizesthespindleshaftdiameterstominimizethestaticdeflectionwithaconstrainedshaftmass.TheDownhillSimplexMethodisusedtofindtheoptimum

value.LeeandChoi[5]conductedanoptimizationdesigninwhichtheyminimizedtheweightoftherotor-bearingsystemwiththeaugmentedLagrangemultipliermethod.Chenetal.[6]andNatarajandAshrafiuon[7]demonstratedtheoptimizationresultstominimizetheforcestransmittedbythebearingstothesupports.WangandChang[8]simulatedaspindle-bearingsystemwithafiniteelementmodeland

dependingonthemachiningapplication.Inaddition,mostofthemoptimizedesignparameters,suchasshaftdiameter,bearingspan,andbearingpreload,tominimizethestaticdeflection.Thispaperconsidersmorethantwobearingsinthespindlemodelandtakesintoaccountthechatterstabilitythatistotallyrelatedtothedynamicpropertiesofthespindle.

TheoverallexpertspindledesignsystemisoutlinedinFig.1.Thedesignofthespindlewithoptimizedbearingspacingisautomatedusingtherequirementssetbythemachiningapplication,expertspindledesignrules,cuttingmechanics,structuraldynamicsandchatterstabilityofmillingprocess.

2.Expertsystemforspindledesign

Theexpertsystemforspindledesignisintroducedheretofacilitatethedesignprocessusingpastexperienceandknowledge.

TheexpertsystemcombinedwiththefuzzylogicisusedastheselectionsystemofcomponentsforthespindledesigninordertohandleuncertaintiesinthedesignprocessasillustratedinFig.2.Therequiredinputdataforthespindledesign,suchasthecuttingtorqueandpower,arecomputedusingthelawsofcuttingmechanics,asdescribedin[11].Theinputdataisenteredintothefuzzyinferencesystem,whichisestablishedbydesignexperts,andisfuzzifiedusingmembershipfunctions.TheMamdanimethodisusedastheinferencesystem.Thefuzzifiedvaluesareappliedtothefuzzyrulesandaggregatedusingthemaximummethod.Theresultoftheaggregationisdefuzzifiedusingthecentroidmethod,

andadefuzzifiednumberisobtained.Thesimpledefuzzifiednumberisappliedtotheselectionrulefor

thespindlecomponents.Anexternaldatabase,whichincludesmaterialcuttingcoefficients,isconnectedtothefuzzyinferencesystem,whichuserscanaccess.Thesupervisingengineer,whoispermittedtomaintainthisexpertsystem,canmodifythemembershipfunctionanddatabasewhenthetendencyofthefuzzyterms,suchas‘high’,‘middle’,and‘low’changesasthetechnologyevolves.Inthisarticle,transmissionandlubricationtypesaredeterminedusingtheexpertsystemwithfuzzylogic

3.Optimizationofbearinglocations

Inordertoapplytheoptimizationtothespindledesign,objectiveanddesignvariablesareestablished.Chattervibrationisanimportantissueformachinetoolssinceitmayleadtospindle,cutterandpartdamages.

Therearesignificantnumberofparametersinatypicalspindledesignprocess,suchasthedimensionsofthespindleshaft,housing,andcollars.However,themosteffectivedesignparametersneedtobeselectedtooptimizethespindledesigninpractice.Therearenumerousconstraintsonthegeometricdesignofspindleparts,anddesigndimensionswhichareusuallycoupledwitheachother.Forexample,ifthediameterofthespindleshaftchanges,theborediameterofthehousingalsohastobechanged,wheremoreparametersneedtobetakenintoaccountwhichmayleadtoaconvergenceprobleminoptimizationalgorithm.Sincetheobjectivefunctionishighlynon-linear,theSequentialQuadraticProgramming（SQP）methodisusedintheoptimizationofthespindledesign.

4.Applicationoftheexpertspindledesignsystem

Theproposedsystemisdemonstratedagainstacommerciallyexistingmachinetool（MoriSeikiSH-403）asshowninFig.14forcomparison.ThemainspindlespecificationsofSH-403areshownin[17].Thespindlehasamotorizedtransmissionwithoil–airtypelubricationwithfourbearingsatthefrontandoneattherear.Themaximumspindlespeedis20,000rpmandthepowerandtorquepropertiesofthespindlemotoraresetfromthedatashownin[17].ItisassumedthattheuserwishestousethemachinepredominantlyincuttingaircraftpartsmadefromAl7075-T6withafour-flutedendmillwithadesired

depthofcutof3mmand15,000rpmspindlespeed.ThemostcommoncuttingconditionsarelistedinTable4.

Inordertoselectthetransmissiontypefromeitherthedirectcouplingtypeorthemotorizedtype,‘SpindleSpeed’,‘HighDynamicStiffnessvs.LowBalancingVibration’,‘LowThermalEffectvs.SmallNoise’,and‘LowReplacementOperationCostvs.LowReplacementPartsCost’needtobeinput.Thespindlespeedisautomaticallysetfromthemaximummotorspeed.Inthiscase,thenumbersareassumedfromtheconceptsofthemachinewrittenintheSH-403catalog[17].Thefuzzyweightnumbersareset

as‘3’,‘8’,and‘4’,respectively.Similarly,thefuzzyweightofthelubricationsystemisset.

Table5showstheresultsofthespindlecomponents’selection.TheExpertSpindleDesignSystemselectedthepropertransmissionandlubricationtype.

Table6showsthelistofagreementsbetweentheactualdesignandthedesignthatusesthisexpertsystem.Theresultsattainedviatheexpertsystemmatchthoseoftheactualdesigninallfivecases.Therefore,theproperspindlecomponentscanbeselectedwiththeproposedexpertsystem,thatis,therulebaseandthemembershipfunctionsofthissystemaredefinedproperly.

5.Conclusions

ThispaperpresentsanExpertSpindleDesignsystemformachinetoolengineers.Itproposesanalternativemethodtothepresentdesignpractice,whichisbasedonthepastexperienceofindividualdesigners,whileattemptingtoeliminatecostlytrialsbyusingthelawsofmachinedesign,solidmechanics,andmetalcuttingdynamicsinanintegratedfashion.

Thedesignconfigurationsandmembershipfunctionsarestoredinaknowledgebaseusingsetsofdesignrulesbasedonthepastexperienceandlawsofcuttingmechanics.Fuzzylogicisusedasaninferenceengineintheproposedexpertsystem.Thefuzzylogiccandealwithdesignuncertaintiessuchashigh,mediumandlowspeedsorlarge/smalltorquerequiredfromthespindleswheretheexactnumericalvalues

aredifficulttosetrigidlybythedesigners.Themembershipfunctionscanbeupdatedbythedesignersastheruleschangeduetotechnologicaladvancesinindustry.Theexpertsystemleadstoautomaticgenerationofspindleconfigurationwhichincludesdriveshaft,motortypeandsize,transmissionmechanismbetweenthemotorandshaft,andtoolholderstyle.

Whiletheconfigurationandsub-componentsofthespindlearebasedonthetorque,power,andspeed

requirementsfromthemachinetool,theexactlocationsofthebearingsmustbedeterminedbasedonthechattervibrationstabilityofthespin