外文翻译数字模拟冲击试验机的多液压缸电动液压的系统和控制器设计.docx
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外文翻译数字模拟冲击试验机的多液压缸电动液压的系统和控制器设计
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英文原文
NUMERICALMODELINGOFMULTICYLINDERELECTRO-HYDRAULICSYSTEMANDCONTROLLERDESIGNFORSHOCKTESTMACHINE
Abstract:
Ahighfidelitydynamicmodelofahigh-energyhydraulically-actuatedshocktestmachineforheavyweightdevicesispresentedtosatisfythenewly-builtshockresistancestandardandsimulatetheactua1underwaterexplosionenvironmentsinlaboratoryaswel1asincreasethetestingcapabilityofshocktestmachine.Inordertoproducetherequirednegativeshockpulseinthegiventimeduration.fourhydraulicactuatorsareutilized.Themodelisthenusedtoformulateanadvancedfeedforwardcontrollerforthesystemtoproducetherequirednegativewaveformandtoaddressthemotionsynchronizationofthefourcylinders.Themode1providesasafeandeasilycontrollablewaytoperforma“virtua1testing”beforestartingpotentiallydestructivetestsonspecimenandtopredictperformanceofthesystem.Simulationresultshavedemonstratedtheeffectivenessofthecontroller.
Keywords:
ShocktestmachineNegativeshockpulseActuatorredundancyFeedforwardcontrollerVirtua1testing
0INTRODUCTION
Theeffectsofunderwaterexplosions(UNDEX)onshiphullsandequipmenthavebeenstudiedsincethel800sLU.Non-contactunderwaterexplosionsagainstsurfaceships,i.e.bymines,ormissilesmaycauseextensiveequipmentdamageandrendershipsinoperativeeventhoughhulldamageisnotcritica1.Thusshocktestmustbecarriedoutoneverycriticaldeviceorequipmentonsubmarineandsurfaceshiptoconfirmthatitwillstillfunction.orinsevercaseswillsurvive,aftertheoccurrenceoftheshockconditionswhichitcanbeexpectedtoencounterduringitsservice.Themosteffectiveanddirectwaytocheckouttheanti—shockcapabilityofdevicesistotestthemonavesselsubjectedtounderwaterexplosion.Testsconductedusingliveexplosiveshaveinherentlimitationsincludingenvironmentalimpact,significantcost,measuringresultsinthefieldandavailablequantityoftests.Atpresent,thecommonlyusedmethodtoassesswarshipequipment’sshockresistancecapabilityistoconducttestonashocktestmachineinacontrollableway.
TheUNDEXenvironmentisverycomplex.composedofa“kick”fromtheincidentshockwavefollowedbytheeffectsofcavitations,bubblepulse,andstructuralwhipping.Thebubblepulseoscillatesatafrequencyveryclosetothefirstbendingmodeoftheship.ItwillbeevenmoredestructivethantheincidentpressurewavewhenthebubblemigratesnearenoughtotheshiptoexcitethismodeHowever,thetraditionalshockmachines.1ikelightweightshockmachine(LWSM)andmediumweightshockmachine(MWSM),cannotsimulateshockenvironmentforthebubblepulsesinducedbyUNDEX.andtheshockenvironmentsimulatedbytraditionalmachinesislargelydifferentfromtheactualUNDEXphysicalenvironment.AccordingtothenewlydesignspecificationsOfMIL.S.90lD.theinputforshocktestshouldbeshockresponsespectra(SRS1,insteadofasingletime.history.accelerationwaveformsuchashalf-sine.triangularsawtoothpulse.Besides.theshockinputinthedesignspecificationsOfBV043/85isadoubletransientshockpulse.i.e.apositiveaccelerationpulseanegativeone.IntheorytheSRScanbetransformedintotimedomainanditisequivalenttoadouble.waveforil1.Therefore.shockmachinesthatwillbebuiltshouldadapttotherequirementofthelatestshockcriteriontosimulatetheactualUNDEXenvironmentasmuchaspossible.
Theaimofshocktestingistoimpartprecisereplicationsofhigh.energytransientshockpulseintotestspecimens.Thetestspecimensarevaluableandunique,andneedtobetestedtoexactshocklevelswithspecificenterspectra:
toomuchcandamagethespecimen,toolittleleavesquestionsaboutthespecimenrobustness.Owingtothetestseverity,itisthenessentialthatthetestshouldbecontrollable.Classiccontrolmethods,suchaspoleplacement.havebeeninvestigatedforshockcontrol,butwithlimitedsuccess.Themainreasonisthatthedurationofshocktestisveryshort.bythetimethesystemcandetectanerrorbetweencommandsandtheactualoutputs.itisalreadytoolatetorespondadequately.
Thispaperformulatesahighfidelitynumericaldynamicmodelforadampingsystem.whichisapartofthewholeshockmachineusedtoproducetherequirednegativeshockpulseinthetestingprocess.Componentsofthesystemmodelareusedtoformelateanadvancedfeedforwardcontroller.Theactuatorredundancyissueisalsoconsideredduringthecontrollerdesign.Themodelandcontrollerprovideasafeandeasilycontrollablewaytoperforma’virtualtesting”beforestartingpotentiallydestructivetestsonthespecimenandtopredicttheperformanceofthesystem.Furtherore.inordertosolvetheuncertaintyproblemofthetestspecimendynamicsforfeedforwardinversemodelcontrol,anewinitialtuningtechniqueisproposedforourspecialcases.
Theorganizationofthispa1)erisasfollows:
Insectionl,adescriptionofthedampingsystemanditsdynamicmodelispresented.Variousfeaturesofthemodelarediscussed,includingthesettlementofactuatorsredundant.Insection2.thecontrolstrategiesareproposed.Thesimulationresultsarepresentedinsection3.Finally,theconclusionsectionfollows.
1PROBLEMFORMULATIONANDDYNAMICMODEL
ThestructureofthedampingsystemisshowninFig.1anditsfunctionistoproducetherequirednegativeshockpulseduringshocktestingprocess.Thedurationoftheshockwavetransientsisunder0.1s.withdesiredaccelerationsupto25~50gformegiventestspecimenalltheseparameterscanbeadjustedaccordingtodifferenttestingconditions.Thetestingcapacityofmeshockmachineisunder5000kg(includingfixture).Thetestspecimenisfixedonmeteststandmovingverticallyatmegivenspeed,whichisproducedbytheshocksysteminmepositiveshockpulsegeneratingprocess.Whenthemaximumspeedisachieved,the
dampingsystembeginstoforceittostopinthegiventime
Themaindifficultyindesigningthedampingsystemliesinthatthesystemshouldproducetherequiredforcesinthegiventimetosaristhewaveformrequirement.Forthispurpose,fourcomplexandsophisticatedhydraulicactuatorsaredesignedtoexertthedampingforces.Theactuatorsareconnectedwiththeteststandthroughsphericalhingesandthefourram-typecylindersarearrangedinasymmetricalmanner.DetailsofthecontactingpointsbetweenteststandandcylinderscanbeseeninFig.2.Thepointsontheteststandthatcontactthecylindersvarywiththerotationoftheteststand.Itsmotiondependsontherotationangleand.Inrealitytherotationangleisverysmall,thismotioncanbeignoredandwejustfocusontheverticaldisplace.MendandtherotationalongtherollaxisrandthepitchaxisP.Eachcylinderiscontrolledbyfourthree.stageservovalves.Thehightransientenergyissuppliedbyaseriesofaccumulators(seeFig.3)
1.1Systemmodeling
Inwhatfollowing.mathematicalmodelofthecomponentsinthenegativepulsesystemwillbebuiltindetail.
1.1.1Testspecimen
Fig.1showstheforcesactingonthehydrauliccylindersandFig.4isthetopviewofthesystemtoindicatethelocationofthespecimen.Sphericalcontactsurfacesareassumedbetweenthecylindersandtheteststand.Theteststand(includingtestspecimen)canrotatefreelyaroundtherollaxisrandthepitchaxisP.Therol1axisrisdefinedtobeperpendiculartothe1ineconnectingcylinder1andcylinder2andthepitchaxisPisdefinedtobeparalleltothelineconnectingcylinder1andcylinder2.AccordingtoNewton’ssecondlawandthetheoremofangularmomenturn,thefollowingequationscanbeobtainedtorepresentthemotionofthespecimen.
wherem:
ms+mt,msandmtrepresentmassofthetestspecimenandtheteststand,respectively.representsthereactionforceactingoncylinder(i=1,2,3,4);gisthegravitationalconstant;Iiand12arethemomentam1forwithrespecttotherotationalaxisrandP;jandJvrepresenttherotationalmomentofinertiaoftheloadabouttheaxisrandaxisp;8rand8,aretherotationangleabouttheaxisrandaxispFIandFIrepresentthefrictionforcebetweentheteststandandcylindersalongthedirectionoftheaxis,andaxisp;aandbrepresentoff-centerdistancesofthespecimenwithrespecttotheteststandcenterO1;02isthegravitycenterofthetestspecimen.
1.1.2Hydrauliccylinders
ConsidertheforcesFA(1,2,3,4)actingonthecylinders,theequationsofmotionforthecylinderscanbeexpressedasfollows
wherepirepresentsthepressureinthechamberofcylinderIand4representstheeffectivepistonarea;mrepresentsthepistonmassofcylinder.Firepresentsthefrictionforce;lrepresentstheviscousdampingcoefficient.
Thecontactingeffectbetweentheteststandardthecylindercanbeassumedtobeequivalenttoamassspring-dampersystemwithstiffnessanddampingratio,andthenthecontactingeffectcanbemodeledbythefollowingequation
whererepresentstherelativedisplacementofthecontactpointbetweentheteststandandthecylinders.
1.1.3Cylinderpressure
Thepressureineachcylinderiscontrolledbyservovalves.Considerthecompressibilityofthefluidinthecylindersaswellastheleakages,thepressuredifferentialequationsgoverningthedynamicsoftheactuatorcanbeexpressedasfollows
where(x)=a+v,and(x)representsthetotalactuatorvolumeandisdefinedtobethefluidvolumeeofthehosesfromthevalveprostatecylinderi.frepresentstheloadflowofcylinderi.representsspoolvalveareagradient.Krepresentstheeffectivebulkmodulus.Cmrepresentsthecoefficientofleakage.Cdrepresentsdischargecoefficient.Psrepresentsthes