水平变幅控制系统英文论文翻译.docx

水平变幅控制系统英文论文翻译.docx

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水平变幅控制系统英文论文翻译

Levelluffingcontrolsystemforcrawlercranes

Abstract

Alevelluffingcontrolsystemforcrawlercraneshasbeendeveloped.Byusingthissystem,anoperatorcansafelykeepsuspendedloadslevelatelevatedspotsoronsiteswherevisualoperationisimpossible.Thissystemconsistsofamicrocomputer-basedcontroller,sensors（boomangle,ropelength,boomleverpressure,enginespeed）andhydraulicactuators.Thecontrolalgorithmisthecombinationoffeedbackandfeedforwardcontrol.Nonlinearcompensationandgainschedulingbyenginespeedarealsoadded.Theeffectofthisalgorithmwasverifiedbynumericalsimulationsandexperimentaltests.Wecouldkeepthesuspendedloadlevelintheaccuracywithin0.15mbyonlyboomoperation.Andthesystemhasbeenputtopracticaluse.

Keywords:

Crawlercrane;Feedforward;Nonlinearcompensation;Controller;Operation

1.Introduction

Fig.1.Crawlercrane.

Atsuchconstructionsitesashighapartmentbuildingandtheelevatedroad,etc.,theimprovementoftheworkefficiencyisdesiredtoshortentheconstructionterm.

So,easyoperationisrequestedforacrawlercrane（Fig.1）whichisoftenusedatsuchconstructionsites[1and2].

Whenoperatingacrawlercrane,theoperatormustdealwithalargeamountoflevelmovementsofsuspendedloads,whichrequiresahighlevelofskill.Itisespeciallydifficulttokeeptheloadataconstantheightbyrelyingonvisualsensingandbymanipulatingtwoleverssimultaneously:

aboomraising/lowingleverandahoistinglever.Wecallthisoperationlevelluffing.Atelevatedspotsoronsiteswherevisualoperationisimpossible,thedifficultygreatlyincreases（Fig.2）.Furthermore,thesimultaneousmanipulationoftwoleversmakesitimpossibletoperformaswingingoperationatthesametime.

Tosolvethisproblem,amicrocomputer-basedcontrollerwasdeveloped,whichpermitslevelluffingandextendingofsuspendedloadswithasingleboomraising/loweringlever.

Whenweconsidertheautomationproblemoftheconstructionmachinery,manyresearchhavebeendoneforhydraulicshovels[3,4,5,6and7],butthereisalmostnoresearchoncrawlercranesnotcountingourresearch[8and9].

Inthispaper,thecontrolalgorithmandthesystemcomponentsofthiscontrolleraredescribedaswellastheresultsofsimulationsandexperimentaltestsperformedwiththiscontroller.

2.Controlalgorithm

Inthiscontrolsystem,thehoistingdrummustbecontrolledsoastokeepaloadataconstantheightwhentheboomisdrivenmanuallytotransferaload.However,severaldifficultiesmayariseinthiscontrolsystemasfollows.

1.Theresponseofacranetendstobeoscillatorybecauseofthelowrigidityofthecranestructure.Therefore,thefeedbackgaincannotbehigh.

2.Theactuatorparthasnonlinearcharacteristics.

3.Thecharacteristicsofthecontrolledobjectvariesaccordingtochangesintheenginespeedandintheweightofaload.

4.Thetimedelayofthesensorsandactuatorscauseslargecontrolerroratthebeginningoflevelluffingcontrol.

Tocopewithitem1,feedforwardplusfeedbackcontrolisapplied.Usingthismethod,thecontrolerrorcanbereducedwithouthighfeedbackgain.Inotherwords,levelluffingisapproximatelyachievedwithfeedforwardcontrol.Theremainingcontrolerrorcanthenbereducedwithfeedbackcontrol.

Tocopewithitem2,nonlinearcompensationhasbeenadopted.

Tocopewithitem3,thecontrolparametershavebeenmodifiedaccordingtotheenginespeed.

Tocopewithitem4,accelerationoftheboomatthebeginningoflevelluffingcontrolisregulated.Forthispurpose,theboomisdrivenbythestartpatternwhichthecontrollergenerates.Thenthefeedforwardcontrolvalueisincreasedinaccordancewiththestartpattern.

TheblockdiagramofthecontrolsystemisshowninFig.3.Detailsofeachcontrolalgorithmaredescribedbelow.

2.1.Feedbackcontrol

InFig.4,whenraisingaboomfrom

to

keepingthesuspendedloadheightconstant,thedesiredvalueofropetravel

isgivenasfollows:

（1）

where,

:

boomlength[m],

:

boomangle[rad],

:

initialvalueofboomangle[rad].

Thecontrolerroroftheheightofaloadisobtainedasfollows:

=

-

（2）

where,

:

controlerroroftheheightofaload,

:

realropetravel.

Thefeedbackcontrolvalue

iscalculatedby

asfollows:

=

（3）

where,

:

proportionalfeedbackgain,

:

integralfeedbackgain.

2.2.Feedforwardcontrol

DifferentiatingbothsidesofEq.

（1）withrespecttotime,Eq.（4）isobtained:

（4）

ThefeedforwardcontrolvalueisobtainedbyEq.（4）,becausetheoutputtothehoistingdrumcontrolsthespeedoftheropetravel.

Inthiscontrolsystem,theboomoperatingleverconditionwhichisobtainedbydetectionoftheboompilothydraulicpressureisusedinsteadoftheboomangularvelocity,sincetheboomisdrivenatanangularvelocitynearlydirectlyproportionaltothelevercondition.Thereasonforusingtheleverconditionisasfollows:

1.Actuallytheboomangularvelocityisdeterminedbyusingthedifferencevalueoftheboomangledetectedbythesensor.Takingintoconsiderationtheresolvingpoweroftheboomanglesensor,thevalueobtainedbythemethodmentionedaboveisnotaccurateenough.

2.Becauseofthetimedelayoftheanglesensorandactuators,thecontrolerroratthebeginningoflevelluffingcontrolcannotbereducedwhentheboomangularvelocityisdetectedbytheanglesensor.

Thefeedforwardcontrolvalueshouldreflecttheboomlengthandthenumberofpartsofthelineforhoistreeving.Sothefeedforwardgainiscalculatedasfollows:

（5）

where,

:

numberofthepartsofthelineofthehoistreeving,

:

thestandardlengthoftheboom[m],

:

theoptimalfeedforwardgainofthestandardboom,C:

controlgain.

2.3.Nonlinearcompensation

Withthecraneasthecontrolledobject,thehoistingdrumisdrivenbytwohydraulicpumpsandregulatedbythecontrolvalve.Nonlinearrelationbetweenspooldisplacementandopenareaofthecontrolvalveisusuallymadeforincreasedcontrolperformanceduringmanualoperation.Thiscausesthenonlinearrelationbetweentheoutputtothehoistingdrumandtherotationspeedofthehoistingdrum.Fig.5showsthisrelationexperimentallyobtained.Thereissaturationofspeed（themaximumspeedofthefirstspeed）relatedtothecapacityofthefirsthydraulicpump（

inFig.5）.Adeadbandappearsuntilflowfromthesecondpump（thesecondspeed）isadded.Thewidthofthedeadbandvariesaccordingtotheenginespeed.Adeadbandexistsalsointhevicinityofthezeropoint（

inFig.5）.Thisdeadbandiscausedbytherelationspooldisplacementandopenareaofthecontrolvalve.

Thewidthsofthetwodeadbandsaresogreatthattheyhaveasignificanteffectonthecontrolperformance.Therefore,thisnonlinearitymustbecompensated.TherelationbetweenthecontrolvaluebeforethecompensationandthatafterthecompensationareshowninFig.6.Inthiscase,

ismodifiedaccordingtotheenginespeeddetectedbythetachometer.

2.4.Regulationofaccelerationoftheboom

Inordertoreduceboththeswingofaloadandthecontrolerroratthebeginningofthelevelluffingcontrol,accelerationoftheboomisregulatedforafixedperiodafterthestartofthelevelluffing.Thecontrollergeneratesthestartpattern（seeFig.7）fortheperiod.Theelectromagneticproportionalreducingvalveoftheboomisdrivenbythestartpatternandtheaccelerationoftheboomisregulated.Aftertheperiodisended,thesolenoid-operatedreducingvalveoftheboomisfullyopenandtheboomisoperatedmanually.Theboompilotlineofthehydraulicsystemisavailableforthismethod（seeFig.13）.

Thefeedforwardcontrolvalueisincreasedinaccordancewiththestartpattern.

2.5.Modificationofthecontrolparametersaccordingtotheenginespeed

Thefollowingcontrolparametersaremodifiedaccordingtotheenginespeed:

1.feedbackgain—inordertopreventanoscillatorycharacterofresponse,theenginespeedbecomesfaster,thecoefficient

mustbesmaller.

2.feedforwardgain—thismodificationcompensatesfortheslightimbalancebetweentheboomspeedandthehoistingspeed.

3.nonlinearcompensation—thiscorrespondstothechangeofwidthofthedeadbandaccordingtotheenginespeed.

4.startpattern—theenginespeedbecomesfaster,theaccelerationmustbelower.

3.Numericalsimulationresults

ThenumericalsimulationmodeloflevelluffingcontrolwasconstructedandisshowninFig.8.Themodelsimulatestheeffectoffeedforwardplusfeedbackcontrolduringthelevelluffingcontrol.ThedynamiccharacteristicsoftheboomandtheboomanglesensorareconsideredandlinearizedtosecondordersystemsasinFig.8.Andtheirparameterswereexperimentallydetermined.

Fig.9showsoneoftheresultswithonlyfeedbackcontrol.Fig.9a,bshowstheresultswithonlyproportionalcontrol;（b）showsanexampleofhighfeedbackgain;（c）showsaresultwithproportionalandintegralcontrol.In（c）,steady-stateerrorisreducedtobecomparedwiththatof（a）;butthecontrolerroratthebeginningstillremainsandtheresponseisoscillatory.

Fig.10showstheresultswithfeedforwardplusfeedbackcontrol;（a）showsthecasewhentheboomleverconditionforthefeedforwardcalculationhasbeenusedinsteadoftheboomangularvelocity.Theactualoutputtotheboomisusedasthelevercondition（thedottedlineinfig.8）.in（a）,boththebeginningcontrolerrorandthesteady-stateerrorarereduced;（b）showsthecadewhenthedifferenceofthedetectedboomanglehasbeenusedastheboomangularvelocity.Thecontrolperformanceof（b）isworsethan（a）.

Consideri