液压挖掘机的半自动控制系统 外文翻译.docx
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液压挖掘机的半自动控制系统 外文翻译.docx
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液压挖掘机的半自动控制系统外文翻译
液压挖掘机的半自动控制系统外文翻译
Semi-automaticcontrolsystemforhydraulicshovel
Abstract
Asemi-automaticcontrolsystemforahydraulicshovelhasbeendeveloped.Usingthissystem,unskilledoperatorscanoperateahydraulicshoveleasilyandaccurately.Amathematicalcontrolmodelofahydraulicshovelwithacontrollerwasconstructedandacontrolalgorithmwasdevelopedbysimulation.Thisalgorithmwasappliedtoahydraulicshovelanditseffectivenesswasevaluated.Highcontrolaccuracyandhigh-stabilityperformancewereachievedbyfeedbackplusfeedforwardcontrol,nonlinearcompensation,statefeedbackandgainschedulingaccordingtotheattitude.Keywords:
Constructionmachinery;Hydraulicshovel;Feedforward;Statefeedback;Operation
1.Introduction
Ahydraulicshovelisaconstructionmachinerythatcanberegardedasalargearticulatedrobot.
Diggingandloadingoperationsusingthismachinerequireahighlevelofskill,andcauseconsiderablefatigueeveninskilledoperators.Ontheotherhand,operatorsgrowolder,andthenumberofskilledoperatorshasthusdecreased.Thesituationcalls
5x.Thereasonsforhydraulicshovels,whichcanbeoperatedeasilybyanypersonw1–
whyhydraulicshovelrequiresahighlevelofskillareasfollows.1.Morethantwoleversmustbeoperatedsimultaneouslyandadjustedwellinsuchoperations.
2.Thedirectionofleveroperationsisdifferentfromthatofashovel’sattachmentmovement.
Forexample,inlevelcrowdingbyahydraulicshovel,wemustoperatethreelevers?
arm,boom,
bucket.simultaneouslytomovethetopofabucketalongalevelsurface?
Fig.1..In
thiscase,theleveroperationindicatesthedirectionoftheactuator,butthisdirectiondiffersfromtheworkingdirection.Ifanoperatoruseonlyoneleverandotherfreedomsareoperatedautomatically,theoperationbecomesveryeasily.Wecallthissystemasemi-automaticcontrolsystem.Whenwedevelopthissemi-automaticcontrolsystem,thesetwotechnicalproblemsmustbesolved.
1.Wemustuseordinarycontrolvalvesforautomaticcontrol.
2.Wemustcompensatedynamiccharacteristicsofahydraulicshoveltoimprovetheprecisionofcontrol.
Fig.1.Levelcrowdingofanexcavatorandframemodelofanexcavator.
Wehavedevelopedacontrolalgorithmtosolvethesetechnicalproblemsandconfirmtheeffectofthiscontrolalgorithmbyexperimentswithactualhydraulicshovels.Usingthiscontrolalgorithm,wehavecompletedasemi-automaticcontrolsystemforhydraulicshovels.Wethenreporttheseitems.
2.Hydraulicshovelmodel
Tostudycontrolalgorithms,wehavetoanalyzenumericalmodelsofahydraulicshovel.Thehydraulicshovel,whoseboom,arm,andbucketjointsarehydraulicallydriven,ismodeledasshowninFig.2.Thedetailsofthemodelaredescribedinthefollowing.
Fig.2.Modelofhydraulicshovel.
2.1.Dynamicmodel[6]
Supposingthateachattachmentisasolidbody,fromLagrange’sequationsofmotion,
thefollowing
expressionsareobtained:
其中
Ksm1g;andgsgravitationalacceleration.33g3
θiisthejointangle,τiisthesupplytorque,liistheattachmentlength,lgiisthe
distancebetweengithefulcrumandthecenterofgravity,miisthemassofthe
attachment,Iiisthemomentofinertiaaround(thecenterofgravitysubscriptsis1–3;
meanboomarm,andbucket,respectively.)
2.2.Hydraulicmodel
Eachjointisdrivenbyahydrauliccylinderwhoseflowiscontrolledbyaspoolvalve,
asshowninFig.
3.Wecanassumethefollowing:
1.Theopenareaofavalveisproportionaltothespooldisplacement.2.Thereisnooilleak.
3.Nopressuredropoccurswhenoilflowsthroughpiping.4.Theeffectivesectionalareaofthecylinderisthesameonboththeheadandtherod
sides.Inthisproblem,foreachjoint,wehavethefollowingequationfromthepressure
flowcharacteristicsofthecylinder:
when,
where,Aiseffectivecross-sectionalareaofcylinder;hiscylinderlength;Xisspool
displacement;Psissupplypressure;Piscylinderhead-sidepressure;Piscylinder
rod-sidepressure;Visoilvolumeinthecylinderandpiping;Bisspoolwidth;γsoil
density;Ksbulkmodulusofoil;andcsflowcoefficient.
2.3.Linkrelations
InthemodelshowninFig.1,therelationbetweenthecylinderlengthchangerateand
theattachmentrotationalangularvelocityisgivenasfollows:
(1)leg
(2).arm
(3).bucket
当时,
Fig.3.Modelofhydrauliccylinderandvalve.
2.4.Torquerelations
FromthelinkrelationsofSection2.3,thesupplytorquetisgivenasfollows,takingcylinderfrictionIintoconsideration:
Where,CciistheviscousfrictioncoefficientandFiiskineticfrictionalforceofacylinder.
2.5.Responsecharacteristicsofthespool
Spoolactionhasagreateffectoncontrolcharacteristics.Thus,weareassumingthatthespoolhasthefollowingfirst-orderlagagainstthereferenceinput.
Where,XXisthereferenceinputofspooldisplacementandTisatimeconstant.3.Anglecontrolsystem
AsshowninFig.4,theangleuisbasicallycontrolledtofollowthereferenceangleubypositionfeedback.Inordertoobtainmoreaccuratecontrol,nonlinearcompensationandstatefeedbackareaddedtothepositionfeedback.Wewilldiscussdetailsofthesealgorithmsasfollows.
Fig.4.Blockdiagramofcontrolsystem
3.1.Nonlinearcompensation
Intheordinaryautomaticcontrolsystems,newcontroldevicessuchasservovalvesareused.Inour
semi-automaticsystem,inordertorealizethecoexistenceofmanualandautomaticoperations,wemustusethemaincontrolvalves,whichareusedinmanualoperation.Inthesevalves,therelationbetweenspooldisplacementandopenareaisnonlinear.Then,inautomaticoperation,usingthisrelation,thespooldisplacementisinverselycalculatedfromtherequiredopenarea,andthenonlinearityiscompensated
Fig.5.Nonlinearcompensation.
3.2.Statefeedback
BasedonthemodeldiscussedinSection2,ifthedynamiccharacteristicsforboomanglecontrolarelinearizedinthevicinityofacertainstandardcondition?
spool
displacementX,cylinderdifferential10pressureP,andboomangleu.,theclosed-looptransferfunctioncanbeexpressedby
where,Kispositionfeedbackgain;
Thissystemhasacomparativelysmallcoefficient,sotheresponseisoscillatory.Forinstance,ifinourlargeSK-16hydraulicshovel,X10is0,thecoefficientsaregivenasas2.7=10y2,,a1=6.010,a2=1.210.Addingtheaccelerationfeedbackof
gainKa,tothistheupperloopinFig.a
4.,theclosedlooptransferfunctionisgivenas
Addingthisfactor,thecoefficientofs2becomeslarger,thus,thesystembecomesstable.Inthisway,accelerationfeedbackiseffectiveinimprovingtheresponsecharacteristics.However,itisgenerallydifficulttodetectaccelerationaccurately.Toovercomethisdifficulty,cylinderforcefeedbackwasappliedinsteadofaccelerationfeedbackthelowerloopinFig.4..Inthiscase,cylinderforceiscalculatedfromdetectedcylinderpressureandfilteredinitslower-frequencyportion[7.8].Thisiscalledpressurefeedback.4.ServocontrolsystemWhenonejointismanuallyoperatedandanotherjointiscontrolledautomaticallytofollowthemanualoperation,aservocontrolsystemmustberequired.Forexample,asshowninFig.6,inthelevelcrowdingcontrol,theboomiscontrolledtokeepthearmandheightZ(calculatedfrom81and82)tor.Inordertoobtainmoreaccuratecontrol,thefollowingcontrolactionsareintroduced.
4.1.Feedforwardcontrol
CalculatingZfromFig.1,weobtain
DifferentiatingbothsidesofEq.(8).withrespecttotime,wehavethefollowing
relation,
Thefirsttermoftheright-handsidecanbetakenastheexpression(feedbackportion)toconvertZ?
to,andthesecondtermoftheright-handsideistheexpression
(feedforwardportion)tocalculatehowmuchushouldbechangedwhenuischangedmanually.Actually,u?
isdeterminedusingthedifferencevalueofDu.Tooptimize
thefeedforwardrate,feedforwardgainKistunned.ffTheremaybeamethodtodetectandusethearmoperating-leverconditioniangle.insteadofarmangularvelocity,sincethearmisdrivenatanangularvelocitynearlyproportionaltothislevercondition.
4.2.AdaptiÕegainschedulingaccordingtotheattitude
Inarticulatedmachineslikehydraulicshovels,dynamiccharacteristicsaregreatlysusceptibletotheattitude.Therefore,itisdifficulttocontrolthemachinestablyatallattitudeswithconstantgain.Tosolvethisproblem,theadaptivegainschedulingaccordingtotheattitudeismultipliedinthefeedbackloopFig.6..AsshowninFig.7,theadaptivegain(KZorKu).ischaracterizedasafunctionoftwovariables,andZ.
meanshowthearmisextended,andZmeanstheheightofthebucket.
5.Simulationresults
ThelevelcrowdingcontrolwassimulatedbyapplyingthecontrolalgorithmdescribedinSection4tothehydraulicshovelmodeldiscussedinSection2.Inthesimulation,ourlargeSK-16hydraulicshovelwasemployed..Fig.8showsoneoftheresults.Fivesecondsafterthecontrolstarted,load
disturbance
Fig.6.Blockdiagramofcontrolsystem(Z).
Fig.7.Gainschedulingaccordingtotheattitude.
wasappliedstepwise.Fig.9showstheuseoffeedforwardcontrolcanreducecontrolerror.
6.Semi-automaticcontrolsystem
Basedonthesimulation,asemi-automaticcontrolsystemwasmanufacturedfortrial,andappliedtotheSK-16shovel.Performancewasthenascertainedbyfieldtests.Thissectionwilldiscusstheconfigurationandfunctionsofthecontrolsystem.6.1.Configuration
Asillust
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