八足蜘蛛机器人文献翻译Word文档格式.docx

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学位论文

RoboticsandAutonomousSystems

Volume59,Issue2,February2011,Pages142–150

1Efficientforcedistributionandlegpostureforabio-inspiredspiderrobot

∙R.Vidoni, 

∙A.Gasparetto 

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doi:

10.1016/j.robot.2010.10.001

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1.1Abstract

Leggedwalkingandclimbingrobotshaverecentlyachievedimportantresultsanddevelopments,buttheystillneedfurtherimprovementandstudy.Asdemonstratedbyrecentworks,bio-mimesiscanleadtoimportanttechnicalsolutionsinordertoachieveefficientsystemsabletoclimb,walk,flyorswim（Saunderset 

al.,2006[36],Ayers,2001 

[25],SafakandAdams,2002 

[26]）.Inthispaper,takingintoaccounttheanatomyandtheadhesiveandlocomotioncapabilitiesofthespider（i.e.,aneight-leggedsystem）,wepresentontheonehandastudyofthefootforceandtorquedistributionindifferentoperativeandslopeconditionsand,ontheotherhand,apostureevaluationbycomparingdifferentlegconfigurationsinordertominimizethetorqueeffortrequirements.

1.1.1.1Researchhighlights

►Weaddressedtheforceandtorquedistributionforaneight-leggedspiderrobot.►Weconsideredtheanatomyandtheadhesiveandlocomotioncapabilitiesofthespider.►Thestaticproblemissolvedinalltheworkingconditions.►Weevaluateddifferentbio-mimeticposturesfromaminimumeffortpointofview.►TheC-shapepostureallowsaloweffortandatorquediminutionalongthelegjoints.

1.2Keywords

∙Climbingspiderrobot;

∙Leggedmechanism;

∙Bio-mimesis;

∙Forcedistribution;

∙Adhesion

1.31.Introduction

Mostofthevehiclesthatwearefamiliarwithusewheelsfortheirlocomotion.Theycanachievehighspeedandrelativelysmallcontrolcomplexitybut,evenwithcomplexsuspensionsystems,theypresentalotoflimitationsinirregularandroughterrains（e.g.,hazardousenvironmentsandunevenground）.Withleggedsystems,mostofthedifficultiescanbeovercomethankstotheflexibilityandgroundadaptation.Indeed,theopportunitytochoosebetweendifferentavailablesolutionsandtoadaptandcontrolthepositionofthecenterofmassofthesystemallowsavoidingslippageandoverturnsduetoterrainirregularities.Thecoststhathavetobepaidarelowerspeedoflocomotionandhighercomplexityofthecontrolwithrespecttowheeledsystems.However,bio-inspiredlocomotioncontrollersbasedoncentralpatterngenerators（CPGs;

see 

[1]）,i.e.,neuralcircuitscapableofproducingcoordinatedpatternsofhigh-dimensionalrhythmicoutputsignalswhilereceivingonlysimpleinputsignals,andonreflexivecontrollers,i.e.,Crusecontrolforthecoordinationofthelegs 

[2] 

and 

[3],arelookingtofillthegap.

Moreover,duetothefactthatthelegsareindependentlycontrolled,leggedsystemshavealargenumberofdegreesoffreedom（DOFs）tobecoordinatedinordertocontroltheposition,balancetheforces（e.g.,load,externalforces）andconsumeaslittleenergyaspossible.Sincethetaskoffindinganoptimalforceallocationshouldbedoneinrealtime,fastalgorithmsandcontrolfunctionshavetobeused,asalsowhenabodyforcecommandsolutionisnotachievableandanewplanhastobeformulated.

Leggedrobotshaveabodyandanumberofarticulatedlegsthatstartfromit.Eachofthesekinematicchainscanbeviewedasamanipulatorthatactslikealimbandcontributestotheoverallpositionandequilibriumofthestructure.

Inordertoevaluateandcreateaneffectiveleggedrobot,theideaistodrawinspirationfromnature.Innature,differentleggedsystemsabletowalkandclimbdifferentsurfaceswithalowenergeticconsumptionandhighautonomycanbefound.Indeed,safeattachmenttoandeasydetachmentfromsmoothsubstratesisamajorfeatureofadiverserangeofanimalspecies.Attachmentwithoutusingfluids,so-calleddryadhesion,isexploitedbygeckosand 

Evarchaarcuata 

spidersbymeansoffibrillarelements 

[4], 

[5], 

[6] 

[7].

Theadhesionforceseemstoberelatedtotheapproachinganglebetweentheattachingelementsandthesurface:

themaximumadhesionconditionisreachedwhentheangleisaround30°

;

aslidingconditionoccurswhentheangleissmaller,anddetachmentoccurswhentheangleisbigger 

[8] 

[9].

Inthisworkourattentionisfocusedonabio-mimeticspiderrobot.

Startingfromthekinematicmodelandsimulator（Fig. 

1）,whicharetheresultofapreviousbiologicalandkinematicstudy 

[10] 

[11],thestaticandquasi-staticproblemsappliedtothespidereight-leggedsystemindifferentslopeconditionsaresolved.

Fig. 

1. 

Kinematicmodelofthespiderrobot.Eachlegiscomposedofthreelinksandthreejoints（oneuniversalandtworevolutepairs;

[11]）.

Figureoptions

InSection 

2,theanalysisofthedifferenttheoriesandapproachesrelatedtotheforceandtorquefootdistributionthatcanbefoundinliterature 

[12], 

[13], 

[14], 

[15], 

[16], 

[17], 

[18], 

[19], 

[20], 

[21], 

[22],[23] 

[24] 

arereviewed.

3,thetheoryoftheoptimalforcedistributionispresentedandextendedinordertosearchforaneffectiveresultforthespidersysteminallworkingconditions（i.e.,flat,verticalandinvertedsurfaces）.

4 

ananalysisoftheoverallamountoftorquethathastobeappliedformaintainingdifferentconfigurationsandacomparisonbetweendifferentbio-mimeticposturesandconditionsforthelegsismade.

Finally,concludingremarksandfutureworkdirectionsarepresentedinSection 

5.

2.Leggedrobots:

theforcedistributionproblem（FDP）

Thecomplexityoflightleggedrobots,suchassix-leggedandfour-leggedrobots,isduetothedifferentkinematicchains（i.e.,legs）thatduringthelocomotionhavetodeveloptwodifferentactions:

thosethatareinarestedconditionhavetosupportandshiftthebodywhilebalancingtheforces;

thelegsinflighthavetoreachthefuturesupportposition.

Moreover,duetotheexistenceoffouractuatedjointsineachleg,asin 

[11],theoctopodmodelhasaredundantactuationleadingtomoreactivejointsthanthenumberofrobotdegreesoffreedom.Therefore,therearefewerforcemomentbalanceequationsthanunknowndesignvariables,andthemathematicalsolutionoftheseequationsisnotunique,duetothepresenceofanon-squaredmatrix.Lookingattherealworld,therearesomephysicalconstraintsthathavetobetakenintoaccount（i.e.,thecontactnature,friction,adhesion,torquelimits）andthatcanberepresentedonlythroughinequalitiesduetothenatureofthecontact.

Aneffectiveapproachistheonebasedonthedistributionofforcesthattrytosolvetheso-called 

forcedistributionproblem 

（FDP;

see,e.g., 

[13]）.Eachlegthattouchesandsupportsthebodyappliesacertainforce（fd）onthesupportpointthatisbalancedbymeansofan（equalandopposite）reactionforce（fr）ofthesubstrate. 

fd 

isthedistributedforcebecauseitrepresentsthedistributedcomponentoftheexternalforcesandmomentsappliedonthatleg.Hence,eachlegcanbeconsideredasamanipulatoranchoredtothebodythathastobeabletogenerateonthetipofthelastlimboftheleg（i.e.,theend-effector）an 

forceinordertocreateastaticequilibrium.Thegeometryofthestructureandthepositionofthelegsproducethedistributionofforcesandmomentsonthelegs.Sincethemathematicalsolutionisnotuniqueandthephysicalconstraintsareonlyinequalities,theFDPinvolvestheoptimizationoftheforceforthelegs.Then,theFDPcanbeformulatedasanonlinearconstrainedprogrammingproblemundernonlinearequalityandinequalityconstraints.

Intheliterature,severalapproachesandalgorithmshavebeenproposedforsolvingandfindingtheoptimalsolutionoftheFDPforleggedrobots.Therearefourmainmethodsthatcanbestudiedandevaluatedforarealimplementationofthecontrol.

1.

Linear-programming（LP）method 

[14].

2.

Compact-dualLP（CDLP）method 

[16].

3.

Quadraticprogramming（QP）method 

[21].

4.

Analyticalmethod 

[22].

Incomparisonwiththeexistingliterature,severaloriginalfeaturesofthisworkcanberemarkedupon.

Thespiderisaneight-leggedsystem,whereasusuallysix-leggedandfour-leggedrobotsarestudied.NoapplicationsoftheFDPproblemforaneight-leggedsystemhavebeenfoundintheliterature.Asaconsequence,atleastfourlegsareincontactwiththesubstrateinthesupportphasecondition（i.e.,fourlegsincontactandfourlegsinflight）andthehypothesisadoptedforsix-leggedrobotsinordertoreducethecomplexityofthesystem 

[22] 

cannotbeapplied.

Moreover,thespiderroboticsystemmustbeabletowalkandclimbondifferentslopeconditionsuptotheinvertedcondition;

hence,theadhesivecapabilitieshavetobetakenintoaccount.

Finally,inthemodelpresentedinthiswork,eachspiderleghasfourDOFswhileintheliteraturethenumberofDOFsoftheeight-leggedrobotsisusuallythreeorless 

[25], 

[26] 

[27].

Thus,thepresentstudyismoregeneralwithrespecttoalltheotherstudiesdealingwithleggedsystems.Inparticular,notonlythefrictionforcebutalsotheadhesionforceshavetobetakenintoaccountinordertosimulateandcontrolthesystemintheclimbingphases.

Theartificialattachingsystemsdevelopeduntilnow 

[28], 

[29], 

[30] 

[31] 

donotreachtheadhesivecapabilitiesoftherealones,andusuallydegradethemselveswithuse;

asaconsequence,inordertoevaluateandsimulateanefficientmodel,thebiologicalcharacteristicsandadhesivecapabilitiesofthespiderE.arcuata 

[7] 

willbeu