1、AutomationinConstruction102001.477486rlocaterautconSemi-automaticcontrolsystemforhydraulicshovelHirokazuAraya),MasayukiKagoshimaMechanicalEngineeringResearchLaboratory,KobeSteel,Ltd.,Nishi-ku,KobeHyogo6512271,JapanAccepted27June2000AbstractAsemi-automaticcontrolsystemforahydraulicshovelhasbeendevelo

2、ped.Usingthissystem,unskilledoperatorscanoperateahydraulicshoveleasilyandaccurately.Amathematicalcontrolmodelofahydraulicshovelwithacontrollerwasconstructedandacontrolalgorithmwasdevelopedbysimulation.Thisalgorithmwasappliedtoahydraulicshovelanditseffectivenesswasevaluated.Highcontrolaccuracyandhigh

3、-stabilityperformancewereachievedbyfeedbackplusfeedforwardcontrol,nonlinearcompensation,statefeedbackandgainschedulingaccordingtotheattitude.q2001ElsevierScienceB.V.Allrightsreserved.Keywords:Constructionmachinery;Hydraulicshovel;Feedforward;Statefeedback;Operation1.IntroductionAhydraulicshovelisaco

4、nstructionmachinerythatcanberegardedasalargearticulatedrobot.Diggingandloadingoperationsusingthismachinerequireahighlevelofskill,andcauseconsiderablefatigueeveninskilledoperators.Ontheotherhand,operatorsgrowolder,andthenumberofskilledoperatorshasthusdecreased.Thesituationcallsforhydraulicshovels,whi

5、chcanbeoperatedeasilybyanypersonw15x.Thereasonswhyhydraulicshovelrequiresahighlevelofskillareasfollows.1.Morethantwoleversmustbeoperatedsimulta-neouslyandadjustedwellinsuchoperations.2.Thedirectionofleveroperationsisdifferentfromthatofashovelsattachmentmovement.Forexample,inlevelcrowdingbyahydraulic

6、shovel,wemustoperatethreeleversarm,boom,bucket.simultaneouslytomovethetopofabucketalongalevelsurfaceFig.1.Inthiscase,theleveroperationindicatesthedirectionoftheactuator,butthisdirectiondiffersfromtheworkingdirection.Ifanoperatoruseonlyoneleverandotherfree-domsareoperatedautomatically,theoperationbe-

7、comesveryeasily.Wecallthissystemasemi-auto-maticcontrolsystem.Whenwedevelopthissemi-automaticcontrolsystem,thesetwotechnicalproblemsmustbesolved.1.Wemustuseordinarycontrolvalvesforauto-maticcontrol.2.Wemustcompensatedynamiccharacteristicsofahydraulicshoveltoimprovetheprecisionofcontrol.Corresponding

8、author.E-mailaddress:arayahrknedo.go.jpH.Araya.0926-5805r01r$-seefrontmatterq2001ElsevierScienceB.V.Allrightsreserved.PII:S0926-580500.00083-2478H.Araya,M.KagoshimarAutomationinConstruction10(2001)477486Wehavedevelopedacontrolalgorithmtosolvethesetechnicalproblemsandconfirmtheeffectofthiscontrolalgo

9、rithmbyexperimentswithactualhydraulicshovels.Usingthiscontrolalgorithm,wehavecompletedasemi-automaticcontrolsystemforhydraulicshovels.Wethenreporttheseitems.2.HydraulicshovelmodelTostudycontrolalgorithms,wehavetoanalyzenumericalmodelsofahydraulicshovel.Thehy-draulicshovel,whoseboom,arm,andbucketjoin

10、tsarehydraulicallydriven,ismodeledasshowninFig.2.Thedetailsofthemodelaredescribedinthefollowing.2.1.Dynamicmodel6Supposingthateachattachmentisasolidbody,fromLagrangesequationsofmotion,thefollowingexpressionsareobtained:Fig.1.Levelcrowdingofanexcavatorandframemodelofanexcavator.¨lqJ12cosu1yu2.u&

11、#168;2qJ13cosu1yu3.u¨3qJ12sinu1yu2.u22qJ13sinu1yu3.u32yK1sinu1st1J11u¨1qJ22u¨2qJ23cosu2yu3.u¨3yJ12sinu1yu2.u12qJ23sinu2yu3.u32yK2sinu2st2J12cosu1yu2.u¨1qJ23cosu2yu3.u¨2qJ33u¨3yJ13sinu1yu3.u12qJ23sinu2yu3.u32yK3sinu3st3J13cosu1yu3.u1.2where,J11sm112J12sg1qm2qm311qI1

12、;m2111g2qm3111g3;J13sm3111g3;J22sm212g2q22m312qI2;J23sm3121g3;J33sm31g3qI3;K1sm11g1qm211qm311.g;K2sm21g2qm313.g;K3sm31g3g;andgsgravitationalacceleration.uiisthejointangle,tiisthesupplytorque,1iistheattachmentlength,1giisthedistancebetweenthefulcrumandthecenterofgravity,miisthemassoftheattachment,Iii

13、sthemomentofinertiaaroundthecenterofgravitysubscriptsis13,meanboom,arm,andbucket,respectively.2.2.HydraulicmodelEachjointisdrivenbyahydrauliccylinderwhoseflowiscontrolledbyaspoolvalve,asshowninFig.3.Wecanassumethefollowing:1.Theopenareaofavalveisproportionaltothespooldisplacement.2.Thereisnooilleak.

14、3.Nopressuredropoccurswhenoilflowsthroughpiping.H.Araya,M.KagoshimarAutomationinConstruction10(2001)477486479Fig.2.Modelofhydraulicshovel.4.Theeffectivesectionalareaofthecylinderisthesameonboththeheadandtherodsides.Inthisproblem,foreachjoint,wehavethefollowingequationfromthepressureflowcharacter-ist

15、icsofthecylinder:VisK0iXiPsiysgnXiP1iyiPAih2.K1iwhen,mentrotationalangularvelocityisgivenasfollows:1.boomf1u1.s1h1u11sinu1qb1.K0iscBiP1isP1iyP2isy2.armf2u1,u2.swhere,Aiseffectivecross-sectionalareaofcylin-der;hiscylinderlength;Xisspooldisplacement;Psissupplypressure;P1iscylinderhead-sidepres-sure;P2

16、iscylinderrod-sidepressure;Visoilvol-umeinthecylinderandpiping;Bisspoolwidth;gsoildensity;Ksbulkmodulusofoil;andcsflowcoefficient.2.3.LinkrelationsInthemodelshowninFig.1,therelationbe-tweenthecylinderlengthchangerateandtheattach-3.bucket21q1q211cos,u1qb1.2h2yu1usy2222sinu2yu1qb2qa2.222q22q22222cosu2

17、yu1qb2qa2.,when33s33s33s33Y3h3333u3yu2qg3ya3qu2.f3u2,u3.ssy.2Yu3yu233q33q23333u3yu2qg3ya3qu2.3.480H.Araya,M.KagoshimarAutomationinConstruction10(2001)477486Fig.3.Modelofhydrauliccylinderandvalve.2.4.TorquerelationsFromthelinkrelationsofSection2.3,thesupplytorquetiisgivenasfollows,takingcylinderfrict

18、ionintoconsideration:t1syf1u1.P11A1qf2u1,u2.P12A2qf3u2,u3.P13A3yCc1f1u1.u1qsgnu1.F1/f1u1.4.t2syf2u1,u2.P12A2y½Cc2f2u1,u2.u2yu1/qsgnu2yu1/F25f2u1,u2.t3syf3u2,u3.P13A3y½Cc3f3u2,u3.u3yu2/qsgnu3yu2/F35f3u2,u3.Where,CciistheviscousfrictioncoefficientandFiiskineticfrictionalforceofacylinder.2.5.

19、ResponsecharacteristicsofthespoolSpoolactionhasagreateffectoncontrolcharac-teristics.Thus,weareassumingthatthespoolhasthefollowingfirst-orderlagagainstthereferenceinput.XXis1T.spiSq1Xi.5Where,XXplacementandiisthereferenceinputofspooldis-Tspiisatimeconstant.3.AnglecontrolsystemAsshowninFig.4,theangle

20、uisbasicallycontrolledtofollowthereferenceangleugbyposi-tionfeedback.Inordertoobtainmoreaccuratecontrol,nonlinearcompensationandstatefeedbackareaddedtothepositionfeedback.Wewilldiscussdetailsofthesealgorithmsasfollows.3.1.NonlinearcompensationIntheordinaryautomaticcontrolsystems,newcontroldevicessuc

21、hasservovalvesareused.Inoursemi-automaticsystem,inordertorealizethecoexis-tenceofmanualandautomaticoperations,wemustusethemaincontrolvalves,whichareusedinmanualoperation.Inthesevalves,therelationbe-tweenspooldisplacementandopenareaisnonlinear.Then,inautomaticoperation,usingthisrelation,thespooldispl

22、acementisinverselycalculatedfromtherequiredopenarea,andthenonlinearityiscompen-satedFig.5.Fig.4.Blockdiagramofcontrolsystemu.H.Araya,M.KagoshimarAutomationinConstruction10(2001)477486481Fig.5.Nonlinearcompensation.3.2.StatefeedbackBasedonthemodeldiscussedinSection2,ifthedynamiccharacteristicsforboom

23、anglecontrolarelinearizedinthevicinityofacertainstandardcondi-tionspooldisplacementXpressureP10,cylinderdifferential110,andboomangleu10.,theclosed-looptransferfunctioncanbeexpressedbyu1sKpa2s3qa6.1s2qa0sqKug1pwhere,Kpispositionfeedbackgain;anda10.A1Cf1u10.0sf1uK01qc1s11102A1Ps1yP110.asXX10ÄJ11q

24、J12cosu2qJcosuXX132qu3.412A1f1u10.Ps1yP110.qCc1f1u10.V1A1KK01Ps1yP110VXXXa1ÄJ11qJ12cosu2qJ13cosu2qu3.42sA1f1u10.KK01s1.110Thissystemhasacomparativelysmallcoefficienta1,sotheresponseisoscillatory.Forinstance,ifinourlargeSK-16hydraulicshovel,X10is0,thecoefficientsaregivenasa2=10y6,a.0s2.7=10y,aAd

25、dingtheacceleration1s6.0feedbackof2s1.2=10y3gainKa,tothistheupperloopinFig.4.,theclosedlooptransferfunctionisgivenasuKp1saur1.7.2s3qa1qKa.s2qa0sqKpAddingthisfactor,thecoefficientofs2becomeslarger,thus,thesystembecomesstable.Inthisway,accelerationfeedbackiseffectiveinimprovingtheresponsecharacteristi

26、cs.However,itisgenerallydifficulttodetectacceler-ationaccurately.Toovercomethisdifficulty,cylin-derforcefeedbackwasappliedinsteadofaccelera-tionfeedbackthelowerloopinFig.4.Inthiscase,cylinderforceiscalculatedfromdetectedcylinderpressureandfilteredinitslower-frequencyportionw7,8x.Thisiscalledpressure

27、feedback.4.ServocontrolsystemWhenonejointismanuallyoperatedandanotherjointiscontrolledautomaticallytofollowthemanualoperation,aservocontrolsystemmustberequired.Forexample,asshowninFig.6,inthelevelcrowd-ingcontrol,theboomiscontrolledtokeepthearmendheightZcalculatedfromuInordertoobtainmoreaccurate1and

28、u2.torefer-enceZr.control,thefollowingcontrolactionsareintroduced.482H.Araya,M.KagoshimarAutomationinConstruction10(2001)477486Fig.6.BlockdiagramofcontrolsystemZ.4.1.FeedforwardcontrolCalculatingZfromFig.1,weobtainZs11cosu1q12cosu2.4.2.AdaptiÕegainschedulingaccordingtotheatti-tude8.Differentiat

29、ingbothsidesofEq.8.withrespecttotime,wehavethefollowingrelation,1syuZ11sinu1y12sinu211sinu12.u9.Thefirsttermoftheright-handsidecanbetakentoastheexpressionfeedbackportion.toconvertZ1,andthesecondtermoftheright-handsideistheuexpressionfeedforwardportion.tocalculatehowmuchu1shouldbechangedwhenu2ischang

30、edmanually.2isdeterminedusingthedifferenceActually,uvalueofDu2.Tooptimizethefeedforwardrate,feedforwardgainKffistunned.Theremaybeamethodtodetectandusethearmoperating-leverconditioni.e.angle.insteadofarmangularvelocity,sincethearmisdrivenatanangu-larvelocitynearlyproportionaltothislevercondi-tion.Ina

31、rticulatedmachineslikehydraulicshovels,dynamiccharacteristicsaregreatlysusceptibletotheattitude.Therefore,itisdifficulttocontrolthema-chinestablyatallattitudeswithconstantgain.Tosolvethisproblem,theadaptivegainschedulingaccordingtotheattitudeismultipliedinthefeedbackloopFig.6.AsshowninFig.7,theadapt

32、ivegainKZorKu.ischaracterizedasafunctionoftwoXXandZ.u2meanshowthearmisvariables,u2extended,andZmeanstheheightofthebucket.5.SimulationresultsThelevelcrowdingcontrolwassimulatedbyapplyingthecontrolalgorithmdescribedinSection4tothehydraulicshovelmodeldiscussedinSection2.Inthesimulation,ourlargeSK-16hyd

33、raulicshovelwasemployed.Fig.8showsoneoftheresults.Fivesecondsafterthecontrolstarted,loaddisturbanceH.Araya,M.KagoshimarAutomationinConstruction10(2001)477486483Fig.7.Gainschedulingaccordingtotheattitude.wasappliedstepwise.Fig.9showstheuseoffeed-forwardcontrolcanreducecontrolerror.6.Semi-automaticcon

34、trolsystemBasedonthesimulation,asemi-automaticcontrolsystemwasmanufacturedfortrial,andappliedtotheSK-16shovel.Performancewasthenascertainedbyfieldtests.Thissectionwilldiscusstheconfigurationandfunctionsofthecontrolsystem.6.1.ConfigurationAsillustratedinFig.10,thecontrolsystemcon-sistsofacontroller,s

35、ensors,manmachineinterface,andhydrauliccontrolsystem.Thecontrollerisbasedona16-bitmicrocomputerwhichreceivesangleinputsignalsoftheboom,arm,andbucketfromthesensor;determinestheconditionofeachcontrollever;selectscontrolmodesandcalculatesactuatingvariables;andoutputstheresultsfromtheamplifieraselectric

36、alsignals.Thehy-Fig.8.Simulationresultoflevelcrowding.drauliccontrolsystemgenerateshydraulicpressureproportionaltotheelectricalsignalsfromtheelectro-magneticproportional-reducingvalve,positionsthespoolofthemaincontrolvalve,andcontrolstheflowratetothehydrauliccylinder.Inordertorealizehigh-speed,high-

37、accuracycon-trol,anumericdataprocessorisemployedfortheFig.9.EffectoffeedforwardcontroloncontrolerrorofZ.484H.Araya,M.KagoshimarAutomationinConstruction10(2001)477486Fig.10.Schemaofcontrolsystem.controller,andahigh-resolutionmagneticencoderisusedforthesensor.Inadditiontothese,apressuretransducerisins

38、talledineachcylindertoachievepressurefeedback.Themeasureddataarestoreduptothememory,andcanbetakenoutfromthecommunicationport.6.2.ControlfunctionsThiscontrolsystemhasthreecontrolmodes,whichareautomaticallyswitchedinaccordancewithleveroperationandselectorswitches.Thesefunc-tionsarethefollowing1.Levelc

39、rowdingmode:duringthemanualarmpushingoperationwiththelevelcrowdingswitch,thesystemautomaticallycontrolstheboomandholdsthearmendmovementlevel.Inthiscase,therefer-encepositionistheheightofthearmendfromthegroundwhenthearmleverbegantobeoperated.Operationoftheboomlevercaninterruptautomaticcontroltemporar

40、ily,becausepriorityisgiventoman-ualoperation.2.Horizontalbucketliftingmode:duringthemanualboomraisingoperationwiththehorizontalbucketliftingswitch,thesystemautomaticallycon-trolsthebucket.Keepingthebucketangleequaltothatatthebeginningofoperationpreventsmaterialspillagefromthebucket.3.Manualoperation

41、mode:whenneitherthelevelcrowdingswitchnorthehorizontalbucketlift-ingswitchareselected,theboom,arm,andbucketarecontrolledbymanualoperationonly.TheprogramrealizingthesefunctionsisprimarilywritteninClanguage,andhaswell-structuredmod-uletoimprovemaintainability.7.ResultsandanalysisoffieldtestWeputthefie

42、ldtestwiththesystem.Wecon-firmedthatthesystemworkedcorrectlyandtheeffectsofthecontrolalgorithmdescribedinChaps.3and4wereascertainedasfollows.7.1.AutomaticcontroltestsofindiÕidualattach-mentsForeachattachmentoftheboom,arm,andbucket,thereferenceanglewaschanged"58stepwisefromtheinitialvalue,a

43、ndtheresponsesweremeasured;thus,theeffectsofthecontrolalgorithmdescribedinChap.3wereascertained.H.Araya,M.KagoshimarAutomationinConstruction10(2001)477486485Fig.11.Effectofnonlinearcompensationonboomangle.7.1.1.EffectofnonlinearcompensationFig.11showsthetestresultsofboomlowering.Becausedeadzonesexis

44、tintheelectro-hydraulicsystems,steady-stateerrorremainswhensimplepo-sitionfeedbackwithoutcompensationisappliedOFFinthefigure.AdditionofnonlinearcompensationONinthefigure.canreducethiserror.7.1.2.EffectofstatefeedbackcontrolForthearmandbucket,stableresponsecanbeobtainedbypositionfeedbackonly,butaddin

45、gac-celerationorpressurefeedbackcanimprovefast-re-sponsecapability.Asregardstheboom,withonlythepositionfeedback,theresponsebecomesoscilla-tory.Addingaccelerationorpressurefeedbackmadetheresponsestablewithoutimpairingfast-responsecapability.Asanexample,Fig.12showsthetestresultswhenpressurefeedbackcom

46、pensationwasappliedduringboomlowering.7.2.LeÕelcrowdingcontroltestControltestswereconductedundervariouscon-trolandoperatingconditionstoobservethecontrolFig.12.Effectofpressurefeedbackcontrolonboomangle.Fig.13.EffectoffeedforwardcontroloncontrolerrorofZ.characteristics,andatthesametimetodetermin

47、etheoptimalcontrolparameterssuchasthecontrolgainsshowninFig..EffectsoffeedforwardcontrolInthecaseofpositionfeedbackonly,increasinggainKptodecreaseerrorDZcausesoscillationduetothetimedelayinthesystem,asshownbyAOFFBinFig.13.Thatis,Kpcannotbeincreased.Apply-ingthefeedforwardofthearmlevervaluedes

48、cribedinSection4.1candecreaseerrorwithoutincreasingKpasshownbyAONBinthefigure.7.2.2.EffectsofcompensationinattitudeLevelcrowdingisapttobecomeoscillatoryattheraisedpositionorwhencrowdingisalmostcom-pleted.ThisoscillationcanbepreventedbychanginggainKpaccordingtotheattitude,ashasbeendiscussedinSection4

49、.2.TheeffectisshowninFig.14.Thisshowstheresultwhenthelevelcrowdingwasdoneataround2maboveground.Comparedtothecasewithoutthecompensation,denotedbyOFFinthefigure,theONcasewiththecompensationprovidesstableresponse.Fig.14.EffectofadaptivegaincontroloncontrolerrorofZ.486H.Araya,M.KagoshimarAutomationinConstruction10(2001)4774867.2.3.EffectsofcontrolinterÕalTheeffectsofcontrolintervaloncontrolperfor-mancewereinvestigated.Theresultsare:1.whenthecontrolintervalissettomorethan100ms,oscillationbecomesgreateratattitudeswithlargemomentsofinertia;and2.whenthecontr