外文翻译--移栽水稻幼苗机制和发展.doc

外文翻译单行蔬菜钵体苗自动移栽机的设计取苗装置设计原文2：Developmentofamechanismfortransplantingriceseedlings译文2：移栽水稻幼苗机制和发展原文2：Transplantingofseedlingsisalaborintensiveoperationinthecultivationofrice.Itisalsoaskilledjobandinvolvesworkingwithastoopingpostureinapuddledfield.Thereexistsaneedtomechanizethisoperation.Forthispurposethedesignofamechanismwascarriedoutfollowingthemethodofanalyticalsynthesis.Aplanarfour-barlinkagewithcouplerextensionwasselectedasthebasicdesign.Thepathgeneratedbythemechanismwasplottedonacomputerscreen.Byvaryingthedimensionsofvariouslinksinthemechanismdifferentpathsofoutputmotionofthecouplerpointwereobtained.Thepotentiallinkdimensionswereidentifiedbasedonthesuitabilityofthepathforpicking,conveyingandplantingofseedlingsaswellasthereturnmotion.Afour-rowself-propelledtransplanterusingtheabovemechanismandanoptimized-plantingfingerwasthendevelopedandtested.Themachinetransplantingsystemwasfoundtobetechnicallyviable.Indiaispredominantlyanagriculturalcountrywithriceasoneofitsmainfoodcrop.Itproducesabout80milliontonsriceannually,whichisabout22%oftheworldriceproduction.Culturally,transplantingofyoungseedlingsof2035daysageinwater-inundatedfieldispreferredoverdirectseeding.Theformerleadstobetteryieldduetobettercropmanagementpracticesthatarepossibleinatransplantedcrop.Theoperationoftransplantingrequireslargeamountofmanpower(about400man-hour/ha)andthetaskisverylaboriousinvolvingworkinginastoopingpostureandmovinginmuddyfield.Hence,thisisconsideredasanactivitythatneedsmechanization.Mechanizationoftransplantingfacilitatesmechanizationofsubsequentactivitiesalsointheproductionofthecrop.ThemachinesthatarealreadysuccessfulinJapanandKoreacouldnotbeadoptedinIndiabecauseofeconomiccostconstraintsandduetotheprevailingculturalpracticesofthiscountry.Designofplantingmechanismsusedinpoweroperatedtransplanters.Anon.statesthatmostoftheplantingdevicesofpoweroperatedtransplanterscanbeclassifiedascrankandrockermechanismsoffour-barlinkage.Aplantingfinger,whichisapartofthecouplerlinkofthemechanism,separatestheseedlingsfromtheseedlingtrayandplacestheminthesoil.Thecurvetracedbytheplantingfingermayhaveaninfluenceonthestabilityoftheplantedseedlings.Thekinematicanalysisoftheplantingmechanismsisconsideredessentialforanunderstandingofitsoperationanditsfurtherimprovements.DesignofmechanismErdmanandSandorstatemostmechanismtasksrequireasingleinputtobetransferredtoasingleoutput.Therefore,single-degree-of-freedommechanismsaretheformsusedmostfrequently.ShigleystatesthatGrublerscriterionisconcernedwiththenumberoflinksinthemechanismandwiththenumberandkindsofkinematicpairs.Itcanbeusedfordeterminingthedegreeoffreedomofamechanism.ErdmanandSandorstatethatanalysistechniquescanbeusedtoreplacecostlyandtimeconsumingbuildingandtestingofphysicalprototypesinatrialanderrordesignprocess.Analysistechniquesgenerallyformabasicpartofmostsynthesismethods.Nortonstatesthatthefour-barlinkageshouldbeamongthefirstsolutionstomotioncontrolproblemstobeinvestigated.Thefewestpartsthatcandothejobwillusuallygivetheleastexpensiveandmostreliablesolution.NortonstatesthattheGrashofconditioncanbeusedasaverysimplerelationship,whichpredictsthebehaviorofafour-barlinkage,basedonthelinklengths.Zimmermanstatesthatafour-barmechanismisphysicallyimpossibleifoneofthelinkshasalengthgreaterthanthesumoftheotherthree.Hirschhornstatesthatinafour-barlinkagedistincttypesofmechanismscouldbeobtainedbyinversion.Acrank-rockermechanismisobtainedbyfixingoneofthetwolinkspairedwiththeshortestlink.PaulsuggestedthatNewtonRaphsonmethodcouldusedbeusedtosolvethenon-linearequationsdevelopedforsolvingthefour-barlinkagepositionproblem.Zimmermanstatesthatonebasicmechanismdesignproblemforwhichthefour-barchaincanprovidesolutionsisthatoffindingapointofthecouplerofafour-barmechanism,whichdescribesapathcloselyapproximatingthedesiredone.Inamechanicaltransplanterthefingerfollowadesiredpathofmotion.Aplanarfour-barlinkagewithallrevolutepairsischosen,asthisisverysimple,amechanismmadeofthatmaybeE.VareedThomas/MechanismandMachineTheory37(2002)395410397easytomaintainandmaycostlesstomanufacture.Theinputmotionisappliedtothecranksothatthemotioniscontinuousandrotary.Theoutputmotionfollowasuitablepathinordertomeettherequirementsofatransplanterspecifiedbelow.Themechanismshouldhaveonedegreeoffreedomandacouplerpointthatiscapableofmakingaloopmaybeincorporated.Theplantingfingerwillbeattachedatthecouplerpoint.Thedimensionsoffourlinksinthefour-barloop,orientationofthefixedlink,lengthofthecouplerextensionandorientationangleofthecouplerextensionaretobedecidedforthedesign.Sincethesevaluescouldnotbesynthesizeddirectlyitwasdecidedtoexaminevarioustrialvaluesfortheaboveparametersandstudythesuitabilityofthepathgeneratedbysuchmechanismforthepurposeoftransplanting.Theaboveparameterswerechangedsystematicallyusingarbitrarilysetranges.Duringthepresentinvestigationaround0.23millionlinkagedesignswereexamined.Thechoicesoflinkdimensionsweremadefollowingamethodofanalysisandselection.Thelinkdimensionswerevariedasstatedabove.Thepathofmotionofthetransplantingfingerpointwascalculatedanddisplayedonacomputerscreenforeverytrialvalueoflinkdimensions.Initially,linkdimensionswhichmettheoutputmotionrequirementsasstatedinSection2.1wereselected.DetailsaregiveninSection2.4.Inordertostudythelinkagedesignfurtherandtobringoutpathsthatmaybebetter,smallrangesoflinkdimensionsweresetaroundtheaboveselecteddesignvalues.Thepathoffingerpointmotionwasagainexaminedkeepinginmindtherequirementsstatedearlier.Outofseveraldesigns,one,whichwouldlikelygivethebestpath,wasselected.Thus,analysisandselectionformedthemainstrategyinthedesignprocedure.Initiallytheforwardtravelspeedofthetran