液压挖掘机.docx
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液压挖掘机.docx
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液压挖掘机
JournalofZhejiangUniversity-SCIENCEA(AppliedPhysics&Engineering)ISSN1673-565X(Print);ISSN1862-1775(Online)
E-mail:
jzus@
Quantitativemeasuresforassessmentofthehydraulicexcavatordiggingefficiency*
DragoslavJANOSEVIC†1,RosenMITREV2,BobanANDJELKOVIC1,PlamenPETROV2
(1FacultyofMechanicalEngineering,UniversityofNis,Nis18000,Serbia)(2FacultyofMechanicalEngineering,TechnicalUniversityofSofia,Sofia,Bulgaria)
†E-mail:
janos@masfak.ni.ac.rs
ReceivedNov.18,2011;RevisionacceptedMar.27,2012;CrosscheckedNov.1,2012
Abstract:
Inthispaper,quantitativemeasuresfortheassessmentofthehydraulicexcavatordiggingefficiencyareproposedanddeveloped.Thefollowingfactorsareconsidered:
(a)boundarydiggingforcesallowedforbythestabilityofanexcavator,(b)boundarydiggingforcesenabledbythedrivingmechanismsoftheexcavator,(c)factorstakingintoconsiderationthediggingpositionintheworkingrangeofanexcavator,and(d)signanddirectionofpotentialdiggingresistiveforce.Acorrecteddiggingforceisdefinedandamathematicalmodelofkinematicchainanddrivemechanismsofafive-memberexcavatorconfigurationwasdevelopedcomprising:
anundercarriage,arotationalplatformandanattachmentwithboom,stick,andbucket.Onthebasisofthemathematicalmodeloftheexcavator,softwarewasdevelopedforcomputationanddetailedanalysisofthediggingforcesintheentireworkspaceoftheexcavator.Byusingthedevelopedsoftware,theanalysisofboundarydiggingforcesisconductedandthecorrecteddiggingforceisdeterminedfortwomodelsofhydraulicexcavatorsofthesamemass(around17000kg)withidenticalkinematicchainparametersbutwithdifferentparametersofmanipulatordrivingmechanisms.Theresultsoftheanaly-sisshowthattheproposedsetofquantitativemeasurescanbeusedforassessmentofthediggingefficiencyofexistingexcava-tormodelsandtoserveasanoptimizationcriterioninthesynthesisofmanipulatordrivingmechanismsofnewexcavatormodels.
Keywords:
Hydraulicexcavators,Diggingefficiency,Quantitativemeasures
doi:
10.1631/jzus.A1100318Documentcode:
ACLCnumber:
TV53
1Introduction
Thehydraulicexcavatorsarepopularmultifunc-tionalconstructionandminingmachines.Themainfunctionofthehydraulicexcavatorsofalltypesandsizesisthecyclicdiggingandtransferofsoil.ThisfunctionisachievedbyuseofanopenkinematicchainconsistingofundercarriageL1,anupperstruc-tureL2andafrontattachmentwithboomL3,stickL4andworktoolL5(Fig.1).Fordiggingoperationsbelowthegroundlevel,thetowardoneselftechnol-ogy(inrelationtotheexcavatoroperator)isem-ployedandabackhoeattachmentisused(Fig.1a).
*Project(No.035049)partlysupportedbytheMinistryofEducationandScienceoftheRepublicofSerbia
©ZhejiangUniversityandSpringer-VerlagBerlinHeidelberg2012
Fordiggingoperationsabovethegroundleveltheawayfromoneselftechnologyandashovelattach-mentareused(Fig.1b).
Duringdiggingoperations,theoccurringdig-gingresistiveforceactingagainstthemanipulatortoolisovercomebydiggingforces.Thediggingforcesofanexcavatorareexertedbythekinematicchainoftheexcavator,whichispoweredbythefol-lowingdrivingmechanisms:
(1)hydraulicmotorsformotionofswingandtravellingbodies;
(2)doubleactinghydrauliccylindersforpoweringofthema-nipulatorlinks.
Foranoptimaldesignofthefrontmanipulatoranddrivingmechanisms,itisnecessarytoperformadetailedanalysisofthediggingforcesandthediggingresistiveforcesintheentireworkspaceoftheexcava-tor.Theconductedanalyticalandexperimental
researchthatpointsouttheimportanceofknowledgeaboutthediggingresistiveforcesfordevelopmentandanalysisofhydraulicexcavatorsisrelatedto:
(1)analyticalmodelingandexperimentaldeterminationofthevalueandthechangeinthediggingresistiveforceduringtheexcavationprocess(MaciejewskiandJarzebowski,2002;Maciejewskietal.,2003;Yangetal.,2008);
(2)developmentofmathematicalmodelsforkinematicanddynamicanalysisofexca-vators(Budnyetal.,2003;Towarek,2003;HallandMcAree,2005;Guetal.,2007);(3)developmentofcontrolsystemsforautomationofthediggingproc-ess(Ploneckietal.,1998;Haetal.,2000;ChangandLee,2002;LeeandChang,2002;Floresetal.,2007;Linetal.,2008);and,(4)definitionofquantitativemeasuresforanalysisandassessmentofexcavatordiggingefficiencyintheworkspace.
L
L3
2
L4
L5
L1
(a)
L3
L2
L4
L5
L1
(b)
Fig.1Hydraulicexcavatorswithbackhoe(a)andshovelattachment(b)
Asindicatedbythemanufacturer,stickandbucketdiggingforcesareimportantparametersoftheexcavator.Theyaredefinedbyappropriatestan-dards(ISO6015,2006;SAEJ1179,2008)asoneofthecharacteristicsoftheexcavatordiggingfunction.Forroboticmanipulators,quantitativemeasuresofworkspaceattributesaredefined,whichincludesstructurallengthindexandmanipulabilitymeasure
(Craig,2005).Someofthesemeasurescanbeusedfortheassessmentofthedynamicperformanceofshovels(Lipsett,2009).Inmanycases,theabovementionedmeasuresarenotsufficientforassessmentofdiggingpossibilitiesandefficiencyoftheexcava-torintheworkspace.
Inthispaper,asetofquantitativemeasuresforassessmentofthehydraulicexcavatordiggingeffi-ciencyisproposedanddeveloped.
Foracomprehensiveanalysisofvaluesanddi-rectionsofdiggingforcesinaspecificpositionofthefrontmanipulator,ahodographofboundarydiggingforcesatthetopofthebuckettoothisdefined.Ithasaformofapolygonwhosesidesarecomposedbyvectorsofboundaryforcesexertedbythemanipula-tordrivingmechanismsandvectorsofboundaryforcesallowedbythestabilityoftheexcavator.Theratioofthecomputeddiggingforceandthepotentialdiggingforceisdefinedasameasureofthediggingefficiency.Thecomputeddiggingforceisdeter-minedbyamathematicalmodeloftheexcavator.Computationsareperformedforagivenpositionandorientationofthemanipulatorandpressuresinthehydrauliccylindersofdrivingmechanisms.Thepo-tentialdiggingforcerepresentstheminimumvalueofboundarydiggingforces(Dudczak,1977).
Ahodographoftheeffectivediggingforcesisdefinedasapartofthehodographoftheboundarydiggingforces,forwhichthedotproductofthedig-gingvelocityanddiggingforcevectorispositive.Theratiooftheareaandrangeoftheeffectivedig-gingforceshodographisacceptedasacriterionforexcavatordiggingefficiency,whereastheareaoftheeffectivehodographrepresentsthemeanvalueofthealloweddiggingforces.Therangeofthehodographoftheeffectivediggingforcesreflectsthedegreeofcompatibilityofmanipulatoractuatorparameters,excavatorweightdistribution,anddiggingforcedis-tribution(Budny,1989).
Acorrecteddiggingforceissetasameasureofdiggingefficiencyintheentireworkspace.Thefol-lowingconsiderationsaretakenintoaccount:
bound-arydiggingforcesallowedbythestabilityofanex-cavator;boundaryforcesexertedbythedrivingmechanismsofanexcavator;andfactorswhichre-latetothediggingpositionofthemanipulatorintheworkspaceaswellasthesignanddirectionofthepotentialdiggingresistanceaction(Janosevic,1997).
Inthispaper,mathematicalmodelsoftheexca-vatorkinematicchain,drivingmechanismsandboundarydiggingforcesareproposedanddeveloped.
2Mathematicalmodelingofexcavator
AsideviewoftheexcavatorisshowninFig.2.Themathematicalmodeloftheexcavatorconsistsofthemathematicalmodeloftheexcavatorkine-maticchainandthatofthemanipulatordrivingmechanisms.
2.1Modeloftheexcavatorkinematicchain
Theexcavatorrepresentsafive-linkopenkine-maticchainwhichconsistsofthetravellingbodyL1,theswingbody(rotationalplatform)L2andthethree-linkfrontmanipulatorconsistingofaboomL3,astickL4,andabucketL5(Fig.2).
Thelinksofthefrontattachmentkinematicchainareconnectedbykinematicpairsofthefifthclass–rotationaljointswitha1DOFwithdifferentorientationsinthespace.Thekinematicchainofthefrontmanipulatorwhichisapartoftheexcavatormodelisplanar.ThecentersofthemanipulatorjointsOi(i=3,4,5)arepenetrationpointsofjointaxisthroughtheplaneofsymmetryofmanipulatorchain
torisconsideredasanopenkinematicchainwithalastlink(bucket)thatissubjectedtothediggingre-sistiveforceW(Janosevic,1997).
Todescribemathematicallythekinematicmodeloftheexcavator,thefollowingcoordinatesystemshavebeenassigned:
(1)GlobalreferenceframeOXYZwithunitvectorsi,j,kalongthecoordinateaxesOX,OY,andOZ,respectively.Thesupportbaseliesinthehori-zontalplaneOXZandtheverticalaxisOYcoincideswiththeaxisoftherotationaljointbetweentheun-dercarriageandupperstructureO2.
(2)BodyfixedcoordinatesystemsOixiyizi(i=1,
2,3,4,5),whichareconnectedtoeachlinkLiofthekinematicchain.ThecoordinatesystemsbeginningOiissituatedinthecenterofjointbywhichthechainmemberLiisconnectedtothepreviousmemberLi−1.ThebucketisconnectedtoacoordinatesystemwhoseaxisO5x5passesthroughthecenterofthejointO5andthetopofthecuttingedgeofthebucketOw.
Inthecaseofthestationaryundercarriage,thecoordinatesystemO1x1y1z1coincideswiththeglobalcoordinatesystem.
ThegeometryofthekinematicchainlinksLiisdefinedinitslocalcoordinate
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