DOC

Mechanical design and implementation of a new biomimetic robot fish

By Theresa Ellis,2014-12-15 02:48
7 views 0
Mechanical design and implementation of a new biomimetic robot fish

    Mechanical design and implementation of a

    new biomimetic robot fish

    mGHTECHN010GYIERSfVo1.13No.4fDec.2007343

    Mechanicaldesignandimplementationofanewbiomimeticrobotfish?

    WangLong(王龙),CaoZhiqiang,TanMin,WangShuo~

    (LaboratoryofComplexSystemsandIntelligenceScience,InstituteofAutomation, ChineseAcademyofSciences,Beijing100080,P.R.China)

    Abstract

    Amechanicaldesignmethodofrobotfishisintroducedinthispaper.Basedonthismethod.anau.

    tonomous3.Dimension(3D)locomotionrobotfishwithtwopectoralfinsandacaudalfinisdeveloped.

    I1}lepectoralfinmechanismhas3degreesoffreedom(3

    DOFs),whichenablestherobotfishtorealize

    yawingandpitchingmotionsbycontrollingtwopectoralfins.Andthecaudalfinmechanismisdesigned

    basedonfishbodywaveCHIVefitting.Theforwardvelocitycanbeadjustedbychangingthecaudalmech

    anism'soscillatingfrequency.Finallyaphysicalimplementationoftherobotfishandexperimentalresults

    alegiven.

    Keywords:biomimetic,fishbodywave,mechanism,robotfish,pectoral,caudal 0Introduction

    Manydesignconceptsofrobotsoriginatefromthe

    imitationofcreaturesinnature,becausenatureselection

    hasenduedcreatureswithexcellentadaptabilitytoliving

    environment.Oneofthetypicalexamplesisthestudyof

propulsionoffishtoimprovetheperformanc,eofunderwa

    tervehicles.Unliketheconventionalmarinevehicles poweredbyrotary.

    propeller.fishesrelyonthemovelnent

    offinsandtailstoprovideforwardthrnst.Scientificex

    perimentsonrealfishshowthatthispropellingstrategy mayyieldmoreefficientpropulsionandlowernoisethan thatofconventionalpropellerl.Motivatedbythisobsm'

    vation,manyresearcheshavebeenconductedtodesign robotfishwhichmayprovidemorecluesfordeveloping smallunderwatervehicleswithhighspeedandsuperior maneuverability.

    1]hepioneeringeffortsondevelopingrobotfishcan betracedtotheworkofTriantafvlloueta1.onRoblHa in1994.Equippedwiththeflexibleposteriorbodyand aflappingfoil(tailfin)thatexploitsexternalfluidforces toproducethrust,RoboTunaenjoysmanyadvantagesin

    cludingincreasedenergysavingsandlongermissiondura

    tion.Afterthissuccessfulexample,manyrobotfishes havebeendevelopedfordifferentpurposes.Tovalidate theroleofpectoralfinsoffish,KatodevelopedtheBlack. bassRobotin1995l,whichwasequippedwiththepee. toralfinslikeapparatus.Experimentalresultsrevealed thatthecombinationoffeatheringmotionandlead.1agno. tionofapairofpectoralfinscoulddominatethemotionof movingtbnvard,movingbackward,hoveringandturning. In2003,Guoeta1.presentedanewprototypeof313 underwaterfish.1ikemicrorobot.Sucharobothadtwoin. dependentlycontrolledtailfins,abodypostureadjuster, andabuoyancyadjuster.Torealizeswimmingmotionwith

3degreesoffreedom(DOF),aJ1ionicconductingpoly

    merfilm(ICPF)actuatorwasutilizedastheservoactua. tor.In2004,Koichidesignedaprototypefishrobot.Its bodylengthwasabout6001"11/11andithadatailwiththree iointsmotivatedbytwoservomotorswithanoriginallink mechanisml.Yudevelopedaradiocontrolled.four-link

    biomimeticrobelicfish,whichusedaflexibleposterior b0dyandanoscillatingfoilasthepropeller.rn1eswim

    ruingspeedoftheroboticfishwasadjustedbymodulating joint'soscillatingfrequency,anditsorientationwascon

    trolledbydifferentoint'sdeflections.

    Itshouldbenotedthatalloftheaboveresearchesfo. CUSonthedesignofbodyandcaudalfinpropulsion (BCF)orpectoralfinpropulsion(MPF).However,fish mayexhibitmorethanoneswimmingmode.eitheratdif- ferenttimeoratdifferentspeed.Medianandpairedfins areroutinelyusedinconjunctiontoprovidethrustwith varyingcontributionsfromeach,achievingsmoothtmjec

    tories.Moreover,manyfishtypicallyutilizeMPFmodes forforaging,asthesemodesoffergreatermaneuverability, theabilitytoswitchtoBCFmodesathigherspeedand highaccelerationl.Inthispaper,wedeveloparobot fishwhichconsistsofacaudalfintopropeltherobotfish. twopectoralfinstoenabletherobotfishtopitchandyaw. Severalsensorsareembeddedtoprovidetheenvironmental informationsuchastemperature,pressure,graphicinfor

    marion.andobstacles.

    bytheNa,!on~Nat,~ScienceFoundationofChina(No.50475179)andtheNationalHighTex

    :hnolo~,ResearchandDevelopmentn

ofChina(1o.ul^Allz225,.

    Towhomcorrespondenceshouldbeaddressed.Emai1:swang@compsys.ia.ac.cn ReceivedonJuly14.2OO6

344GH?HNo]lGYIESlV01.13N0.4lDec.200r7

    1Oeagn0fpectoralmechanismandits

    worle~analysis

    I1lemotionpatternofpectoralfinhasbeenofinter- eatformanyresearchers[].

    AccordingtoRefs.[12

    14],thelocomotionofpectoralfinmaybeclassifiedas therowingmodeandflappingmode.1heformerismore efficientatlowerspee~,whereastheliftbasedflapping

    ITlodeismoreefficien,

    tathighersPeed.Blakeconcluded

    thatrowingmotionincludestwostrokes:powerstrokeand recovelystroke.Duringpowerstroke.pectoralfin

    nlovesbackwardathighattackangletogeneratethrust whilepectoralfinfeatherstoreduceresistanceandnloves forwardduringrecoverystroke.Webbdividedthecycleof flappingmotionintothreephases:abduction,adduction andrefractory.Generallyspeaking,thefinmovesaway fi'omthebodyanddownwardsduringabduction.Itisthen broughtbacktothebodysurface(adductionphase),and thefinisorientatedtoitsoriginalpositionbyrotationof theleadingeaseinrefractionphase.WeatneatandWau【一

    erplottedthefintiDtracefromthelateralviewinrelation tothebodyofthefish.Thepectoralfintiptracesafig

    ure-8paththatisnearlyperpendiculartothebodyaxis anddirectionofmotion.

    Accordingtotherowingandflappingmodesandthe fintiptrace,eachpectoralfinneedsatleast2DOF.In otherwords.thereare4DOFfortwopectoralfins.How

    ever.3DOFisenoughbecausethefeatheringmotionsof twopectoralfinsmaybeuniform.Fig.1Vesapectoral

    finmechanism.

    rag.1Thepectoralmechanism

    Physicaldimensionofpectoralfinmainlyincludes planarconfigurationandaiffoilsection.Planarconfigura

    tionisclassifiedastriangularwing,trapezoidalwing,el

    liptical1g,etc.1heellipticalwingischosenasplanar configurationofpectoralfinsinceellipticalwingisgood notonlyatsmallattackanglebutalsoatbigattackangle. Airfoilsectionmaybesortedintolowspeedaerofoiland highspeedaerofoil.Becausethepectoralfinsaremainly usedtosteerswimmingdirectionofrobotfish,lowspeed aerofoilisselectedasthesectionofpectoralfin.Fig.2 showstheshapeofpectoralfinwhoseairfoilsectionis NACA23012(roundheadandtiptail).Theaspectratio ofpectfin:

    =2.1,wherespanlength

    Z=100mmandwingareaS=4704turn2.

    (a)HanarconOguratlon(b)Airfoilsection

    Fig.2Shapeofpectoralfinanditsairfoilsection Inordertocontrolthemotionsofpectoralfins.iti8 necessarytoanalyzetheworkspaceofpectoralfins.Be. causetherightandleftpectoralfinshavethesamemech. anism,hereonlytheworkspaceofrightpectoralfinis studied.Themechanismofrightpectoralfinistreatedas twolinkshingedtheachother.asshowninFig.3.

    coordinatesystemaisattachedtotherootoflinka.the coordinatesystembisattachedtothecenterofhingeand thecoordinatesystemcisattachedtotheendoflinkb. AJlXaxesoftheaeframespointtofishheadandarepar. alleltotheheadtailaxisoffish.andYaxespointtolat eraldirection.

    Thecortfigumtionofframebrelativetoframeais: g()=

    whereistherotationangleofframebrelativetofrmr~a Theconfigurationofframecrelativetofralnebis: g6c()=

    100

    0cosfl-sinfl

    0sin/3cosfl

    000

    0

    /2COSfl

    /2sinfl

    1

    (2)

    where8istherotationangleoffrmr~crelativetoframeb Thustheconfigurationoffralnecrelativetoframea is:

    gac(,)=g()×g6c()

    rcossinasinflsinacosfl12sinasinf1]

    Isingcosflsinfl/2COSfl+11』一

    10cosasinflcoscos12cosasinflfl

    -

    0001j

    =

【】?

    Inthismechanism,therotatingangleaboutaxisYa isconfinedto(0,9O~),andtherotatingangleaboutXbis confinedto(90..9).Withlinkainactiveandlinkb

    001

    口口0?0

    0100

    .i0C

    HIGHTECHNOL0GYIErIERSfVo1.13No.4IDec.2007345 rotatingfrom90~to90~thelocusofpectoralfintipcomes intobeingasasemicirculararc.Furthermore,whenlink andlinkbbothrotate,thelocusofpectoralfintipturns intohemisphericalsurfacewhichisthereachable workspace(showninFig.3)ofpectoralfintip. Fig.3Coordinatesystemofpectoralfinmechanism Workspaceanalysisofpectoralfinprovidesabasis forfutureswimmingcontrolofrobotfish.Inthispaper therearetwomodesofpectoralfinmotions:rowingand flapping[.

    Atlowspeed.therobotfishswimsforward

    bymeansofrowingmotionofpectoralfinandthetraceof nntipintheframeafromlateralviewisillustratedin Fig.4(a).Afullpropulsionperiodincludestwostrokes: thepowerstrokeandtherecoverystroke.Thepower strokeisfromtheoriginalpointpltopointp2orfromp4 top5.Inthisstroke,pectoralfinmovesperpendicularly toswimmingdirectionathighattackangleandthethrust ismainlygeneratedinthisstroke.Therecoverystrokeis fromp2top4throughp3orfromp5totheoriginalpoint

    plthroughp6.Inthisstrokepectoralfinisbroughtback toprepareforthenextpowerstroke.Whentheswimming stateswitchestohighspeedswimming,robotfishispro- pelledbyflappingmotionofpectoralfinandthetraceof 6ntipintheframeafromlateralviewisshowninFig.4 (b).Aflailpropulsionperiodofflappingmotionincludes threephases:adduction,refractoryandabduction.Ad

    ductionphaseisfromtheoriginalpointpltop2orfrom p4top5.Duringtheadduction,pectoralfinmovesto- wardthebodyoffishandthisphaseisabletogenerate notonlythrustforcebutalsoliftforce.Refractoryphase betweenadductionandabductionisfromp2top3orfrom p5top6.Pectoralfinisbroughtbacktoprepareforab- ductionduringrefractoryandthisphaseexerciseslittleef- feetonrobotfishmotion.Abductionphaseisfromp3to p4orfromp6totheoriginalpointp1.Duringabduction phase,pectoralfinmovesawayfrombodyofrobotfish andthisphaseisalsoabletogeneratethrustandlift force.

    Thethrustgeneratedbypectoralfindependsonnot onlytraceof6ntiDbutalsotheattackangleateverypoint oftraceoffintip.Theattackangleisnotrandomatevery tracepointbutobeysEq.(3).Letncandn.represent thedirectionofcordofpectoralfinrelatedtoframecand adifferently,n=(1,0,0),n.=R'n,where

    RisgiveninEq.(3).V=(v,0,0)istheflow

    velocityvectorrelatedtoframea,whereistheabsolute valueofflowvelocity.Hencetheattackanglea= arccos

    ().

/,

    p1一一p25

    \B/,?./

    p6

    

    '

    (a)Fintiptraceof(b)Fintiptraceof

    rowingmotionflappingmotion

    Fig.4Thetracesofpectoralfintipof

    rowingandflappingmotions

    2Designofcaudalmechanismbasedonfish

    bodywavetheory

    Researchesonfishbehaviorhaveindicatedthatthere isatravelingwavefromheadtotailwhenfisharepro. pelledaheadE15,16].Theamplitudeoftravelingwavein creasesdramaticallyfromheadtotail,andevelocityof

    travelingwaveisgreaterthanvelocityoffishpropulsion. Basedonfishbodywaveeory.acaudalmechanismin.

    cludingdrivingmechanismandundulatingmechanismis designed,andtheschematicdiagramisshowninFig.5. Thedrivingmechanismmainlyincludesamotor,three gears.twocamsandtwoslidingrods.Themotoroutput shaftdrivestwomeshinggearswhichtransferrotational motiontotwoconjugatecams.Butthetwoconjugatecams rotateinoppositedirections,andpushtwosliderodsto producereciprocationslidinginthebearings.Thetwo slidingrodsareusedtodriveecaudalundulngmech

    anlsm,whichismadeupoftwocrankguiding-rodmecha- nismshingedatecaudalfin.Thisundulatingmecha

    nismmaybetreatedastwohingedlinksdrivenbyonly

    onemotor.andtheanglesoflinksrelativetomainaxis arecontrolledbytwoconjugatecan3s.

    Beforeeprimarysizesfsuchasprofilesofcan3s andlengthsoflinks)ofcaudalmechanism(illustratedin Fig.5)aredetermined,efishbodywavetheoryisin

    troducedfirst.

HIGHTECHNOIDGYIESJ,,01.13No.4JDec.200r7

    rig.5Caudalmechanism

    ArelativeswimmingmodelforRobeTuna(carangi. form)hasbeenpresentedbyBarretteta1.Ll.whoseun. dulatorymotionisassumedtotaketheformofatraveling waveoriginallysuggestedbyLighthillJ

    y(,t)=[(cl+c2)][sin(+mt)](4)

    where.Ybodyrepresentsthetransversedisplacementof?1e

    fishbody.denotesthedisplacementalongmainaxis (headtotailaxis),kindicatesthebodywavenumber(k =

    ),isthebodywavelength,clisthelinearwave amplitudeenvelope,c2isthequadraticwaveamplitude envelope,andcoisthebodywavefrequency(co=2= ),Tistheperiodictimeofbodywave.

    Oncethebodywavefunctionisspecified,thefol

    lowingthiItobedoneistoselectsuitablebodykinemat

    icparametersset(el,c2,k,co).However,thetaskof tiziJ1gmbetfishpropulsionefficiencyisextremelyar

    duous.Becausecomputercontrolisadigitalcontrol,the fishbodywavefunctionneedtobediscretized.Thefish bodywavecouldbedividedintotwo:a)timeinde

    pendentsplineClllwesequencewithinonewaveperiod

Report this document

For any questions or suggestions please email
cust-service@docsford.com