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BiosystemsEngineering2006951,35–41doi10.1016/j.biosystemseng.2006.06.007PMPowerandMachineryStrasseopeningfordroppingthepotatointoafurrowinthesoil.plantersareequippedwithtwoparallelrowsofcupsperbeltinsteadofone.DoublingthecuprowallowsARTICLEINPRESSparametersofmachineperformance.Highaccuracyofplantspacingresultsinhighyieldandauniformsortingandthus,ahighercapacityatthesameaccuracyisexpected.Capacityandaccuracyofplantspacingarethemaindoublethetravelspeedwithoutincreasingthebeltspeed15375110/32.0035r2006IAgrE.AllrightsreservedThefunctioningofmostpotatoplantersisbasedontransportandplacementoftheseedpotatoesbyacupbelt.Thecapacityofthisprocessisratherlowwhenplantingaccuracyhastostayatacceptablelevels.Themainlimitationsaresetbythespeedofthecupbeltandthenumberandpositioningofthecups.Itwashypothesisedthattheinaccuracyinplantingdistance,thatisthedeviationfromuniformplantingdistances,mainlyiscreatedbytheconstructionofthecupbeltplanter.Todeterminetheoriginofthedeviationsinuniformityofplacementofthepotatoesatheoreticalmodelwasbuilt.Themodelcalculatesthetimeintervalbetweeneachsuccessivepotatotouchingtheground.Referringtotheresultsofthemodel,twohypotheseswereposed,onewithrespecttotheeffectofbeltspeed,andonewithrespecttotheinfluenceofpotatoshape.Aplanterunitwasinstalledinalaboratorytotestthesetwohypotheses.Ahighspeedcamerawasusedtomeasurethetimeintervalbetweeneachsuccessivepotatojustbeforetheyreachthesoilsurfaceandtovisualisethebehaviourofthepotato.Theresultsshowedthatathehigherthespeedofthecupbelt,themoreuniformisthedepositionofthepotatoesandbamoreregularpotatoshapedidnotresultinahigherplantingaccuracy.Majorimprovementscanbeachievedbyreducingtheopeningtimeatthebottomoftheductandbyimprovingthedesignofthecupsanditspositionrelativetotheduct.Thiswillallowmoreroomforchangesinthecupbeltspeedswhilekeepingahighplantingaccuracy.r2006IAgrE.AllrightsreservedPublishedbyElsevierLtd1.IntroductionThecupbeltplanterFig.1isthemostcommonlyusedmachinetoplantpotatoes.Theseedpotatoesaretransferredfromahoppertotheconveyorbeltwithcupssizedtoholdonetuber.Thisbeltmovesupwardstoliftthepotatoesoutofthehopperandturnsovertheuppersheave.Atthispoint,thepotatoesfallonthebackofthenextcupandareconfinedinasheetmetalduct.Atthebottom,thebeltturnsovertheroller,creatingtheofthetubersatharvestMcPheeetal.,1996PavekThornton,2003.FieldmeasurementsunpublisheddataofplantingdistanceinTheNetherlandsrevealedacoefficientofvariationCVofaround20.EarlierstudiesinCanadaandtheUSAshowedevenhigherCVsofupto69Misener,1982EntzLaCroix,1983Sieczkaetal.,1986,indicatingthattheaccuracyislowcomparedtoprecisionplantersforbeetormaize.Travellingspeedandaccuracyofplantingshowaninversecorrelation.Therefore,thepresentcupbeltAssessmentoftheBehaviourofH.Buitenwerf1,2W.B.Hoogmoed1FarmTechnologyGroup,WageningenUniversity,P.Oemailofcorrespondingauthor2KroneGmbH,HeinrichKrone3IBLerink,LaanvanMoerkerken85,3271AJ4InstituteofAgriculturalEngineering,UniversityReceived27May2005acceptedinrevisedformPotatoesinaCupbeltPlanter1P.Lerink3J.Mu¨ller1,4Box.17,6700AAWageningen,TheNetherlandswillem.hoogmoedwur.nl10,48480Spelle,GermanyMijnsheerenland,TheNetherlandsofHohenheim,D70593Stuttgart,Germany20June2006publishedonline2August2006PublishedbyElsevierLtdforhandlingandtransporting.Manyshapefeatures,usuallycombinedwithsizemeasurements,canbedistinguishedDuSun,2004Taoetal.,1995Zo¨dler,1969.IntheNetherlandsgradingofpotatoesismostlydonebyusingthesquaremeshsizeKoningdeetal.,1994,whichisdeterminedonlybythewidthandheightlargestandleastbreadthofthepotato.Forthetransportprocessesinsidetheplanter,thelengthofthepotatoisadecisivefactoraswell.ARTICLEINPRESSH.BUITENWERFETAL.36Theobjectiveofthisstudywastoinvestigatethereasonsforthelowaccuracyofcupbeltplantersandtousethisknowledgetoderiverecommendationsfordesignmodifications,e.g.inbeltspeedsorshapeand78910Fig.1.Workingcomponentsofthecupbeltplanter1potatoesinhopper2cupbelt3cup4uppersheave5duct6potatoonbackofcup7furrower8roller9releaseopening10groundlevel564321numberofcups.Forbetterunderstanding,amodelwasdeveloped,describingthepotatomovementfromthemomentthepotatoenterstheductuptothemomentittouchestheground.Thus,thebehaviourofthepotatoatthebottomofthesoilfurrowwasnottakenintoaccount.AsphysicalpropertiesstronglyinfluencetheefficiencyofagriculturalequipmentKutzbach,1989,theshapeofthepotatoeswasalsoconsideredinthemodel.Twonullhypotheseswereformulated1theplantingaccuracyisnotrelatedtothespeedofthecupbeltand2theplantingaccuracyisnotrelatedtothedimensionsexpressedbyashapefactorofthepotatoes.Thehypothesesweretestedboththeoreticallywiththemodelandempiricallyinthelaboratory.2.Materialsandmethods2.1.PlantmaterialSeedpotatoesofthecultivarscv.Sante,ArindaandMarfonahavebeenusedfortestingthecupbeltplanter,becausetheyshowdifferentshapecharacteristics.TheshapeofthepotatotuberisanimportantcharacteristicThefieldspeedandcupbeltspeedcanbesettoachievetheaimedplantspacing.Thefrequencyfofpotpotatoesleavingtheductatthebottomiscalculatedasfpot¼vcxc2wherevcisthecupbeltspeedinmsC01andxcisthedistanceinmbetweenthecupsonthebelt.TheangularspeedoftherollerorinradsC01withradiusrrinmiscalculatedasor¼vcrr3Table1ShapecharacteristicsofpotatocultivarsandgolfballsusedintheexperimentsCultivarSquaremeshsize,mmShapefactorSante28–35146Arinda35–45362Marfona35–45168Golfballs42C18100AshapefactorSbasedonallthreedimensionswasintroducedS¼100l2wh1wherelisthelength,wthewidthandhtheheightofthepotatoinmm,withhowol.Asareference,alsosphericalgolfballswithaboutthesamedensityaspotatoes,representingashapefactorSof100wereused.ShapecharacteristicsofthepotatoesusedinthisstudyaregiveninTable1.2.2.MathematicalmodeloftheprocessAmathematicalmodelwasbuilttopredictplantingaccuracyandplantingcapacityofthecupbeltplanter.Themodeltookintoconsiderationradiusandspeedoftheroller,thedimensionsandspacingofthecups,theirpositioningwithrespecttotheductwallandtheheightoftheplanterabovethesoilsurfaceFig.2.Itwasassumedthatthepotatoesdidnotmoverelativetothecuporrotateduringtheirdownwardmovement.ThetimeoffreefalltfallinsiscalculatedwithARTICLEINPRESSASSESSMENTOFTHEBEHAVIOUROFPOTATOES37Thegapintheducthastobelargeenoughforapotatoxclearrcafii9825releaseafii9853xreleaseLineALineCFig.2.Processsimulatedbymodel,simulationstartingwhenthecupcrosseslineAreleasetimerepresentstimeneededtocreateanopeningsufficientlylargeforapotatotopassmodelalsocalculatestimebetweenreleaseofthepotatoandthemomentitreachesthesoilsurfacefreefallrc,sumoftheradiusoftheroller,thicknessofthebeltandlengthofthecupxclear,clearancebetweencupandductwallxrelease,releaseclearancearelease,releaseangleo,angularspeedofrollerlineC,groundlevel,endofsimulationtopassandbereleased.Thisgapxreleaseinmisreachedatacertainangleareleaseinradofacuppassingtheroller.ThisreleaseangleareleaseFig.2iscalculatedascosarelease¼rcþxclearC0xreleaserc4wherercisthesuminmoftheradiusoftheroller,thethicknessofthebeltandthelengthofthecupandxclearistheclearanceinmbetweenthetipofthecupandthewalloftheduct.Whentheparametersofthepotatoesareknown,theanglerequiredforreleasingapotatocanbecalculated.Apartfromitsshapeandsize,thepositionofthepotatoonthebackofthecupisdeterminative.Therefore,themodeldistinguishestwopositionsaminimumrequiredgap,equaltotheheightofapotatoandbmaximumrequiredgapequaltothelengthofapotato.Thetimetreleaseinsneededtoformareleaseangleaoiscalculatedastrelease¼areleaseor5Calculatingtreleasefordifferentpotatoesandpossiblepositionsonthecupyieldsthedeviationfromtheaveragetimeintervalbetweenconsecutivepotatoes.Combinedwiththedurationofthefreefallandthefieldspeedoftheplanter,thisgivestheplantingaccuracy.yrelease¼vendtfallþ0C15gt2fall8wheregisthegravitationalacceleration9C18msC02andthefinalvelocityvendiscalculatedasvend¼v0þ2gyrelease9withv0inmsC01beingtheverticaldownwardspeedofthepotatoatthemomentofrelease.ThetimeforthepotatotomovefromLineAtothereleasepointtreleasehastobeaddedtotfall.Themodelcalculatesthetimeintervalbetweentwoconsecutivepotatoesthatmaybepositionedindifferentwaysonthecups.Thelargestdeviationsinintervalswilloccurwhenapotatopositionedlengthwiseisfollowedbyonepositionedheightwise,andviceversa.2.3.ThelaboratoryarrangementAstandardplanterunitMiedemaHassiaSL46wasmodifiedbyreplacingpartofthebottomendofthesheetmetalductwithsimilarlyshapedtransparentacrylicmaterialFig.3.Thecupbeltwasdrivenviatheroller8inFig.1,byavariablespeedelectricmotor.Thespeedwasmeasuredwithaninfraredrevolutionmeter.Onlyonerowofcupswasobservedinthisarrangement.AhighspeedvideocameraSpeedCamPro,WeinbergerAG,Dietikon,Switzerlandwasusedtovisualisethebehaviourofthepotatoesinthetransparentductandtomeasurethetimeintervalbetweenconsecutivepotatoes.Asheetwithacoordinatesystemwasplacedbehindtheopeningoftheduct,theXaxisrepresentingthegroundlevel.Timewasregisteredwhenthemidpointofapotatopassedthegroundline.StandarddeviationWhenthepotatoisreleased,itfallstowardsthesoilsurface.Aseachpotatoisreleasedonauniqueangularposition,italsohasauniqueheightabovethesoilsurfaceatthatmomentFig.2.Asmallpotatowillbereleasedearlierandthusatahigherpointthanalargeone.ThemodelcalculatesthevelocityofthepotatojustbeforeithitsthesoilsurfaceuendinmsC01.Theinitialverticalvelocityofthepotatou0inmsC01isassumedtoequaltheverticalcomponentofthetrackspeedofthetipofthecupv0¼rcorcosarelease6Thereleaseheightyreleaseinmiscalculatedasyrelease¼yrC0rcsinarelease7whereyrinmisthedistancebetweenthecentreoftherollerlineAinFig.2andthesoilsurface.ARTICLEINPRESSH.BUITENWERFETAL.38ofthetimeintervalbetweenconsecutivepotatoeswasusedasmeasureforplantspacingaccuracy.Forthemeasurementsthecamerasystemwassettoarecordingrateof1000framespersecond.Withanaveragefreefallvelocityof2C15msC01,thepotatomovesapprox.2C15mmbetweentwoframes,sufficientlysmalltoallowanaccurateplacementregistration.Thefeedingratesforthetestoftheeffectofthespeedofthebeltweresetat300,400and500potatoesminC01fpot¼5,6C17and8C13sC01correspondingtobeltspeedsof0C133,0C145and0C156msC01.Thesespeedswouldbetypicalforbeltswith3,2and1rowsofcups,respectively.Afixedfeedingrateof400potatoesminC01cupbeltspeedof0C145msC01wasusedtoassesstheeffectofthepotatoshape.Fortheassessmentofanormaldistributionofthetimeintervals,30potatoesinfiverepetitionswereused.Intheothertests,20potatoesinthreerepetitionswereused.Fig.3.Laboratorytestriglowerrightpartofthebottomendofupperrightsegmentfaced2.4.StatisticalanalysisThehypothesesweretestedusingtheFishertest,asanalysisshowedthatpopulationswerenormallydistributed.TheonesideduppertailFishertestwasusedandawassetto5representingtheprobabilityofatype1error,whereatruenullhypothesisisincorrectlyrejected.Theconfidenceintervalisequalto100C0a.3.Resultsanddiscussion3.1.Cupbeltspeed3.1.1.EmpiricalresultsThemeasuredtimeintervalsbetweenconsecutivepotatoestouchinggroundshowedanormaldistribution.Standarddeviationssforfeedingrates300,400and500potatoesminC01were33C10,20C15and12C17ms,respectively.thesheetmetalductwasreplacedwithtransparentacrylicsheetbythehighspeedcamera
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