实用型多功能割草机的研制英语文献

实用型多功能割草机的研制英语文献毕业设计（论文）英文文献学院：机电工程学院专业 年级 六年级体育公开课教案九年级家长会课件PPT下载六年级家长会PPT课件一年级上册汉语拼音练习题六年级上册道德与法治课件 ：    07机械一班学生姓名:赵丽学号: 20071092                                                                                                                                                                                                                                                                          设计(论文)题目：手扶自走旋刀式草坪修剪机的设计指导教师:丁敬平教研室负责人:日期: 2011年 4月10日AutonomousUtilityMowerM.ZeitzewNavComTechnology,Inc,AJohnDeereCompany,20780MadronaAvenue,Torrance,CA90503,USA.E-mail:mzeitzew@navcomtech.comABSTRACTTwooff-the-shelfJohnDeereutilitymowersweremodifiedforX-by-wirecontrolforthepurposesofconstructingautonomousvehiclesusableinsports-turfmowingapplications.Thepurposeofthesemuleswastoenablethegatheringofrequirementsandcustomerfeedbackonsuchasystem.Theenvironmentselectedinitiallywasthatofabaseballstadium.Theseareascanbecharacterizedasflat,highlycontrolledandwell-groomed,forwhichprecisemowingpatternsarenecessities.Typicallytheoperatorsofthesemowersarehighlyskilled;anautonomoussystemhasthebenefitsofsavingtimeandlabor,permittingtheefficientusageofless-skilledemployees,andallowingskilledpersonneltofocusonmorecomplextasks(suchasinfieldmowingandwarningtrackgrooming).Forthisapplication,therearestringentrequirementsonnavigation,pathplanningandpathtracking,whilethesafeguardingrequirementsarechallenging,butmorerelaxedthan,say,therequirementsforgolfcourses.Thecalculationofprecisepositionandorientationinthisenvironmentrequiressensorfusionandiscomplicatedbythefactthatfrequentlytheoperatingareaissurroundedbyveryhighwalls,limitingskyvisibilityandpreventingtheusageofGPScentricnavigationsystems.Furthermore,itwasdesirabletomaturethedesignfarenoughsothatitcouldbeoperatedregularlybynon-technicaloperators.Theseresultswereachievedbydevelopinganaccuratelocalpositioningsystem,makingthehardwareandsoftwaresubsystemsrobustagainstunexpectedfailuresandconstructingaverysimplegraphicaluserinterface.Thispaperwillreviewotherrelevantexistingsystems,describethehardwareandsoftwaresystemsutilized,andconcludewithdescriptionsontheperformance,customerlearning,anddescriptionofpropertiesofautonomoussystemsthatenabletheirintegrationintoaworksite.Keywords:Mowing,robotic,stadium,turf1.INTRODUCTIONThispaperdescribesaprojecttofullyautomateautilitymowerforasports-turfapplication.Thetargetenvironmentselectedisthatofaprofessionalbaseballstadium.Theprimarygoalforthisprojectistolearnaboutthedurability,performanceandvalueofautonomoussystemsinrealuseenvironmentsasameansofprogressingtowardsacommercialautonomousmachinethatmeetscustomerneedsandapplicationrequirements.Potentialcustomerbenefitsincludesavingtimeandlabor,permittingtheefficientuseofless-skilledemployees,andallowingskilledpersonneltofocusonmorecomplextasks(suchasinfieldmowingandwarningtrackgrooming).Asresearchers,thebenefitsofchoosingthebaseballstadiumenvironmentarethattheyaretypicallycharacterizedbyflat,hardterrainandhighlycontrolled.Whiletheperformancerequirementsarestillquitechallenging,theaforementionedqualitiestendrelaxthemconsiderablyascomparedto,say,mowingapublicgolfcourse.Theoverallintentisthatthissystemrepresentsthefirstgenerationofafamilyofautonomousmachineswithincreasingcapabilityandperformancelevels.Inrecenttimes,severalautonomousconsumermowershavebeguntoappearonthemarketfrommanufacturersincludingFriendlyRobotics,Toro,Husqvarna,Ambrogio,Zucchetti,Electrolux,andBelrobotics.Noneofthesemachinesisnearcapableofmeetingtherequirementsofasportsturfapplication.Therehasalsobeenasignificantamountofresearchfromacademiaintheareaofautonomousmowing,includingCarnegieMelonUniversity(Bataviaet.al.,2002;RothandBatavia,2002)andtheUniversityofFlorida(Chandleretal.,2000).Also,theInstituteofNavigationhasbeensponsoringamowingcontestforthepasttwoyearsandthishasstirredgreateracademicinterestintheproblemdomain.Morerecently,thecompaniesSelf-GuidedSystemsLLC,Michigan,USAandMcMurtryLtd.,Gloucestershire,UKhaveadvertisedcommercialmowerstailoredtowardthesameapplicationspacediscussedhere.Theeffortsofthesetwocompaniesinparticulararenotablesincetheyhaveattemptedtoaddresstheissuesofhighlyaccurate,precisemowingpatternsinareaswithskyobstruction,whereGPS-centricnavigationsystemstypicallydegradebeyondsystemtolerances.First,abriefreviewofapplication-specificrequirementsisgiven.Thisisfollowedbyadescriptionofthesystemhardwareandsoftware.Next,asummaryofactualperformanceispresentedandthenareviewofcustomerlearningaccomplishedduringaseasonofusebytwocustomers.Finally,theconclusionsectionendsthepaperanddiscussesfuturework.2.STADIUMMOWINGStadiummowingisconsideredanartworkandgenerallyrequiresagroupofhighlyskilledgroundskeepersworkingtogether.Whilethestadiuminfieldandsidelineareaareusuallymowedusingawalk-behindmower,theoutfieldmowingisdoneusingaspinningreelmower,suchastheJohnDeere2653A(fig.1)..Figure1.JohnDeere2653AutilitymowerOutfieldmowingpatternscomeinmanyvarieties,butacommonfeatureisthattheyareconstructedbydrivingstraightlinestoproducethedesiredstripingeffect(fig.2).Itisimperativethatthemowingstripeshaveuniformwidthinordertoprovideanicelook.Thestripingitselfiscausedbythebladesofgrassbeingpushedinopposingdirectionsandnecessitatesthatadjacentswathsaremowedinoppositedirections.Excessiveoverlaporanygapsbetweenadjacentstripes,andoscillationsorotherirregularitieswhiledrivingcanruintheappearanceofthefield.Itwasestimatedthatthecompositeerrorinnavigationandcontrol(pathtracking)needstostaybelow5cmduringmowinginordertoproduceacceptableresults.Cursoryevaluationhasshownthatexpertoperatorsofthesemachinesatnormaloperatingspeedsachievethisaccuracy.Theoutfieldmowingtaskcanitselftakeseveralhoursdependingonthedesiredpatternandmayinvolvemorethanonemoweroperatingsimultaneously.Whentwomowersoperateconcurrently,generallytheywillbemowingindifferentdirectionstoproducecheckeredpatterns.Ingeneral,eachstadiummayhavedifferentsetsofmowingpatternstheyutilize.Throughouttheseason,themowingpatternsonthefieldwillchange.Onereasontochangemowingpatternsistopreventexcessiveturfwear.Thecheckeredmowingpatterninfigure2isproducedbymowingthefieldinthedirectionfromhomeplatetocenterfield,andalsomowinginthedirectionfromfoulpoletofoulpole.Thispicturewastakenafteradayoftesting.Duringthistest,themowerwasnotactuallycuttingthegrass,thereelswereloweredwhilemakingthepassesbutwerenotspinning;thevisiblestripingeffectwasproducedfromtherollersonthefrontofthereels.Figure2.ChaseField,Phoenix,Az.Normalmowingoperatingspeedisaround1.5-2.5m/s.Atlowspeedsorwhenthemowerisstationary,thereelsareraisedtopreventdamagetotheturf.Thereelsarealsoraisedanytimethevehicleleavesthegrassarea.Excessiveturningontheoutfieldgrassisalsofrownedupon.Inmanycases,thegroundskeeperswillemptytheclippingsfromthebasketsduringoperationasopposedtolettingthemfalltothesurface.Dependingonthelengthofthegrass,thisemptyingcanoccurasoftenasonceperpassacrossthefield.Thisadditionaltaskcangreatlyincreasetheoperationtimeandeitherrequirescoordinationwithanadditionalvehicleusedtostoreandhaultheclippingsordrivingthemoweritselftoacontaineroffthefieldsomewhere.Particularlyonthedayofabaseballgame,therearemanytasksbeyondtheoutfieldmowingthatmustbeperformed,suchasrakingandinfieldmowing.Anothermotivationformakingthemowerautonomousistofreetheworkerstodotheseothertasks.3.CONCEPTOFOPERATIONThecurrentprototypesystemsareinstalledbyfirstmountingfixednavigationbeaconsaroundthestadium.Next,thefieldboundariesaresurveyedusingthenavigationsystemandareinputintoamapfile.Themap,togetherwitheachsetofpatternpreferences,isusedtocreatetherespectivemissionplanusinganengineeringuserinterface.Anexamplemissionplanisshowngraphicallyinfigure3.Withthiscurrentdesignautonomouslymowingacheckeredpatternrequirestwoseparateoperations,oneforeachdirection.Thesystemisintendedtobeusedinthefieldbyanon-technicaloperator.Assuch,itwasnecessarytonotonlyexecutethedesiredmowingpatternsandmeettheperformancerequirementsmentionedabove,butalsoprovideasimpleandintuitive,small,handhelduserinterfacewithwirelessconnectivitytothevehicle.Figure3FoulpoletofoulpolepatternThefollowingstepsareperformedbytheoperatortoexecutetheautonomousmowingfeature:1.Inspectsandadjustsmachine(mowingheight,reeltobedknife,fluidlevels,etc.).2.Visuallyinspectsmowingareaandremovespotentialobstacles(debris,stuckirrigationheads,etc.).3.Startsonboardcomputersystem.4.Startsmachineandmanuallydrivesontofield.5.Turnsonuserinterface,ensuresproperconnectiontosystemandsysteminitialization.6.Selectspre-computeddesiredmowingpatternfrommenuonuserinterface(fig.4).7.Vehiclebeginsoperation.Operatormonitorsprogressduringoperationvisuallyandfromtheuserinterface,andremainsinviewofvehicle.Operatorhascapabilityofpausingoperationatanytime(toemptyclippings,forexample)orexercisingremoteemergencystop,ifnecessary(hopefullynever).8.Systemnotifiestheoperatorwhenthemowingpatterniscomplete.Operatorpowersoffcomputeranduserinterface,oralternativelycanselectanothermowingpatterntoExecute.Figure4.ScreenshotofuserinterfaceThesystemisdescribedinmoredetailinthenextsection.4.SYSTEMDESCRIPTION4.1ArchitectureMostofthesoftwareiswrittenusingaModelDrivenDevelopmenttoolinC++.Thesystemarchitectureissuchthatitcaneasilybeadaptedtochangesinhardware,technology,andapplication(fig.5).Thesamesoftwarebasehasbeenusedsuccessfullyonseveralprojectsalready,withvariousprocessorsandoperatingsystems,andcombinationsofsensorsandalgorithms,vehiclesandapplications.Therearefivemajorcomponentsthatcomprisethesystem:vehiclecontrolunit(VCU),navigation,perception,intelligentvehiclecontroller(IVC),anduserinterface.Infigure5,“Robot(Vehicle)Controller”referstoIVC.Inthisapplication,allfivemajorcomponentsresideonseparateprocessors,butinotherinstancessomeofthecorecomponentsresideonthesamephysicalprocessingunit.Inthefollowing,eachmajorcomponentisdiscussedinmoredetail.Figure5.Systemarchitecture.4.2VehicleandVehicleControlUnit(VCU)ThevehicleusedinthisprojectisamodifiedversionoftheJohnDeere2653A(fig.6).TheRFrangingantennaisatthetopofthemastinthefrontofthevehicle.AtthebaseofthemastisaSICKTMlaserusedbytheperceptioncomponent,aswellastwoboxesthathousetheperceptionandnavigationsubsystemcomputers.Thethirdboxjustbelowthefacingsideoftheseathousesthecomputerwiththeintelligentvehiclecontroller.Thevehiclecontrolunitisunderneathandisnotvisibleinfigure6.Figure6.ModifiedX-by-WireJohnDeere2653A.Specifically,thevehiclewasconvertedtoX-by-WirecontrolbycreatingaVCUwithaCANmessaginginterfacetoenablecontrolbyanexternalprocessor.Thelow-levelcontrolalgorithms(closed-loopsteeringandvelocity,implementcontrol)wereimplementedinsidetheVCU.CommandandfeedbacksignalsbetweentheVCUandtheIVCenabledautonomousoperation.Atthesametime,itispossibletousethismachinemanually,sothatgroundskeeperscouldalternativelyusethevehicleastheydotheoff-the-shelfversionofthevehicleavailabletoday.4.3NavigationTheuseofGPSrequiresgoodskyvisibility.Inthisapplication,duetothestringentnavigationaccuracyrequirements,anRTK-GPSsolutionisrequired,whichrequirestheuseofabasestation.Becausemanyofthebaseballstadiumshavehighwallsandotherobstructionsaroundthefield,RTK-GPSisinadequate,evenwithaugmentationby(affordable)inertialsensorsand/orodometrysensors.Thisnecessitatedtheuseofalternativetechnology.Otherearlierprototypesystemsfeaturedlocalpositioningsystems(LPS)basedonultrasonicranging,usingtime-of-flightmeasurementsfromavehicletoasetofbeaconsatfixedlocationsintheenvironment(Huntetal.,2006;Zeitzew,2004).Thispositioningsystemhadinsufficientrangetosupportsports-turfareas,whichcaninvolve100meterranges,ormore.Asaresult,anewLPSbasedonradiofrequencysignalswasrecentlydeveloped,whichexceedtherequiredrangeandaccuracyrequirements.TheLPSsystemrequiresanantennaonthevehicleandinvolvesRFrangingtobattery-operatedbeacons,typically6inthisapplication,mountedonthewallsaroundthestadium.TheLPSispartofalargersensorfusioncomponentthatincorporatestheserangestogetherwithvehicleodometryinformationandmeasurementsfrominertialsensors(3-axisgyroscopeandaccelerometers)intoanExtendedKalmanFilter.Thetestingshowsthattheerrorduetothenavigationsystemisontheorderof2cmRMS(rootmeansquared)atnormaloperatingspeeds.Moreover,studiesindicatethatourLPSsystemhasarangeofhundredsofmetersandcanbemass-producedinacost-effectivemannerforfutureproducts.Finally,notethatthesensorfusioncomponentalsoadmitsGPS(orRTK-GPS)insteadoforinadditiontotheLPS;thenavigationsystemwasbuiltflexibilitytoeasilyallowinvestigationofdifferentcombinationsofsensors.4.4PerceptionPartoftheperceptionresearchincludedtheinvestigationofvarioustypesofsensors,includingultrasonic,radarandlaser,andtheusageofdifferingsafeguardingalgorithms.Generally,thebyproductoftheperceptionsystemcanbeusedbyotherelementsforapplication-specificpurposes.Inthepresentcase,theonlyusageoftheperceptiondatawastoenablevehiclesafeguarding.Becausethehighestpriorityinthisapplicationistomaintainprecisemowingpatterns,thisalleviatedtheneedtodeploywhatcangenerallybeaquitecomplicatedobstacleavoidancesystem.Here,theonlyacceptableresponsetoobstaclesduringmowingistoeitherreducevehiclespeedorstop.Furthermore,sincetheimplementationdidnotincludereverseoperation,italloweddeployingagreatlysimplifiedsafeguardingsystemontothefieldedsystem.Specifically,thealgorithmreliedonlyontherangescansfromaSICKTMlasermountedonthefrontofthevehicle(fig.6).Therangescanswerecombinedwithvehiclefeedbackdatainordertodetermineifthecurrenttrajectorywasclear;ifnot,thevehiclewouldreduceitsspeedasafunctionofthedistancetothenearestobstruction,eventuallystoppingifnecessary.Whilethissystemprovedtobereliableandrobustagainstsafeguardinghumans,wallsandotherlargeobstacles,itshighcostandinabilitytodetectpeopleapproachingthemachinefromthesidesorrearindicatethatmoreworkisnecessarytoprovideacomprehensiveandmarketablesafeguardingsystem.4.5IntelligentVehicleController(IVC)TheIVChasseveralresponsibilitieswithinthesystem,including:•MissionPlanning:Abilitytoconstructmissionplansbasedonenvironmentmapsandtunableparameters,aswellasprovidingplanningservicesduringmissionexecution.Thisincludesareacoveragepathplanning(Gray,2006).•MissionExecution:Includesapplication-specificelementsthatrunduringthemission.Onesuchexampleisthepathtracker;theresponsibilityofthepathtrackeristocomputesteeringandvelocitycommandssothatthevehiclefollowsthedesiredpath.ThepathtrackingalgorithmutilizedinthisprojectwasastandardPIDwithfeed-forwardtermtoaccountforpathcurvature,usingthecomputedpathlateraldeviationastheerrorsignal.•UserInterface:Gatewaytosendandreceivedatafromuserinterface(s).•VCUInterface:Gatewaytothevehicle'sactuatorsandsensors.4.6UserInterfaceTwouserinterfaceswereconstructedforthisproject.Thefirstisbestcharacterizedasanengineeringuserinterface,whichprovidedadministrative-levelaccesstothefunctionalityofthesystem.Theseconduserinterfacewasasimplifiedversionthatprovidedonlythefunctionalitythatwasdeemedtobeuseful,usableanddesirable.ThelateruserinterfaceranonasmallPocketPCdeviceasshowninfigure7.Figure7.Screenshotofoperatoruserinterfaceduringmowingoperation.Themowericonisonleftsideandshownwithanotionalhemisphereofcoveragebytheperceptionsystem.Viathisuserinterface,theoperatorisallowedto:•Selectfromavailablemaps.•Selectfromavailablemissionsfortheselectedmap.•Start,stopandpausemissions.•Monitorprogressgraphicallyandothersimplefeedbacksignals.•Teleoperatethevehicleifnecessary.5.PERFORMANCE5.1OperatinginStadiumsTwosuchvehicleswerefieldedintoprofessionalbaseballstadiums,onemajorleagueandoneminorleague.Bothofthesesystemswereutilizedoverthecourseofseveralweeksduringthespring2005baseballseason.Duringthelatterportionoftheseason,thesystemswereusedbytheregulargroundskeeperswhereastheengineeringrolemigratedtothatofoccasionalobservation.Thesystemswerefrequentlyoperatedsolelybythegroundskeepers.Thegroundskeeperswereaskedtologtheircomments,andthesewerecollectedandlateranalyzed,theresultsofwhicharediscussedbelowinthesectiononcustomerlearning.Athirdsystemwasusedforlocaltestingatalargeathleticfacilityoverseveralfields(mostlysoccerfields).5.2PathTrackingTable1summarizestypicalRMSpathtrackingperformance.Transportcorrespondstoperiodswheretheimplement(spinningreels)aredisengaged,likeduringturnsbetweenrows.ThenumberswerecomputedbyaveragingtheRMSerrorscomputedoverseveralmissionsandthetwostadiums.Itshowsthatthesystemwasabletomeettherequiredsubsystemspecifications.Notethatthetotalsystemerroriscomprisedofboththepathtracking(howwellvehicletracksreference)andnavigationsystem(howwellreferencematchesgroundtruth)errors.Thelatterisnotreflectedbythesenumbersandwasvalidatedbyothermeans.Table1.AverageRMSerrorformowingandtransportautonomousoperation.ParameterInitialSpecificationCurrentPerformanceMowing(1.6m/s)        3.5cm2.1cmTransport(2.3m/s)9.0cm3.9cm6.CUSTOMERLEARNINGThepositivefeedbackfromthecustomersincludedappreciationforthestraightnessofmowingstripesandthetimesavingsthatallowedemployeestofocusonothertasks,particularlyduringbaseballteamhomestandsduringwhichtheoutfieldismowedeveryday.Havingtheautonomousmachineinregularoperationwouldallowareductionintheneedforhighlyskilleddriversandpotentiallyallowcompletionoftherequiredworkwithasmallerstaff.Otherobservationsmadeinclude:•Theassumptionsthatoperatorswillbecomfortablebeingafull-timesafetyriderorthatwhenoff-boardwillgivefullattentiontothemachineduringautonomousoperationareerroneous.Veryquicklytheybecomecomfortablewiththeautonomousmachineandwillignoreit,spendingtimerakingthewarningtrack,paintingalogoorotheractivity,oftenwiththeirbackstowardthemachine.•Theneedtoemptytheclippingsinsomestadiums,andtheperformanceofperipheraltaskssuchaslinepainting,presentanengineeringchallengetofurtherexpandthescopestadiumautomation.•Therewouldbevalueinhavingtwo(ormore)autonomousmachinesoperatingsimultaneouslyinordertoprovideevenmoretimeandlaborsavings,consideringthatcheckeredmowingpatternsareprevalentintheindustry.•Theareaborderingtheoutfieldisoftenclutteredwithworkersorotherequipment.Furtherprogressisneededtosafeguardrobustlyagainstthesehazards.•Theperceptionsystemshouldbeupgradedtoaccountforsmallerandmovingobstaclestypicallyfoundintheoperatingenvironment.•Theabilitytodetectstuckirrigationheadsthatfailtoretractbelowsurface,whichcancausedamagetothespinningreels,wouldalsobeofvalue.•Insomecases,asmallpartofthefieldisdamagedorparticularlysensitiveandthegroundskeeperwishestoavoidmowingordrivingoverit.Theabilitytoeasilyadjusttheplannedmowingpatternfromthehandhelduserinterfacewouldbevalued.•Theabilitytodriveinreverseandutilize3-pointturnsattheendofrows,ratherthanalwaysdrivingforwardandturningoutsidethefield,hasoperationalbenefit.•Itisworthrevisitingtheuserinterfacedesignandformfactor,perhapsmigratingtoasmallerandevensimplerdesign.•Thesystemalsofeaturedtheabilitytoteleoperatethevehicle,butitturnedouttonotbesufficientlyinterestingorusefultoanyoneotherthantheengineerswhoworkedontheproject.7.CONCLUSIONThispaperhasdescribedthedeploymentoftwooff-the-shelfJohnDeereutilitymowersthatweremodifiedforX-by-Wirecontrolforthepurposesofconstructingautonomousvehiclesusableinsports-turfapplications.Ithashadtwomainbenefits,firstinprovidingamechanismforincreasingthecompany’sexpertiseinautonomousvehiclesystemsgenerallyandinsports-turfapplicationsinparticularandsecondlyingainingunderstandingofthevalueofsuchsystemstocustomers.Animprovementoftherobustnessofthevehicle,hardwareandsoftware,incrementallyimprovinguponit,andalsoexploreotherapplicationspaceswillbecontinued.Inparallel,arealisticbusinessmodelforthistypeofequipmentneedstobebuilt.8.ACKNOWLEDGEMENTSThemainsponsorofthisprojectwastheCommercialandConsumerEquipmentDivisionofJohnDeere.TheprojectteamincludedJamesC.Beck,AlexD.Foessel,StevenA.Hawkinson,DavidR.Holm,BoyoonJung,MarkP.Kaplan,StewartJ.Moorehead,CameronA.Mott,AndrewJ.Norby,GeoffreyM.Phillippe,JoseO.Quan,JohnF.Reid,MarkA.Schmidt,ScottA.Stephens,ErickC.Velasquez,KurtVanderWielandAutonomousSolutionsIncorporated.WewishtothankGrantTrenbeath,ScottStrickland,KyleWatersandtheirrespectivecrewsforboththeirhelpandpatienceintestingandevaluatingthesystem.9.REFERENCES【1】Batavia,P.,S.A.Roth,andS.Singh.2002.AutonomousCoverageOperationsinSemi-StructuredOutdoorEnvironments.IEEE/RSJInternationalConferenceonIntelligentRobotsandSystems(IROS’02),October2002.【2】Chandler,R.C.,A.A.Arroyo,M.Nechyba,andE.M.Schw