用于受限传感清洁机器人在未知环境的基于扇区的最大在线覆盖范围【中文17000字】
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用于受限传感清洁机器人在未知环境的基于扇区的最大在线覆盖范围【中文17000字】,用于,受限,传感,清洁,机器人,未知,环境,基于,扇区,最大,在线,覆盖,笼盖,范围,规模,中文
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ROBOTICSANDAUTONOMOUSSYSTEMS592011698710SECTORBASEDMAXIMALONLINECOVERAGEOFUNKNOWNENVIRONMENTSFORCLEANINGROBOTSWITHLIMITEDSENSINGTAEKYEONGLEE,SANGHOONBAEK,SEYOUNGOHDEPARTMENTOFELECTRICALENGINEERING,POHANGUNIVERSITYOFSCIENCEANDTECHNOLOGY,POHANG,GYUNGBUK790784,REPUBLICOFKOREAARTICLEINFOABSTRACTARTICLEHISTORYRECEIVED23NOVEMBER2010RECEIVEDINREVISEDFORM22MARCH2011ACCEPTED13MAY2011AVAILABLEONLINE31MAY2011KEYWORDSCLEANINGROBOTSECTORBASEDCOVERAGECELLULARDECOMPOSITIONALTHOUGHCLEANINGROBOTSHAVEBEENINCREASINGLYPOPULARINHOMEENVIRONMENTS,THEIRCOVERAGERATEANDPERFORMANCEHASNOTBEENVERYIMPRESSIVETOTHEIRUSERS,THUSOFTENHAMPERINGTHEIRUSERACCEPTANCEMANYCOMPLETECOVERAGEALGORITHMSDEVELOPEDSOFARUSUALLYMANDATETHEROBOTTOHAVEASOPHISTICATEDNAVIGATIONSYSTEMFORPRECISELOCALIZATIONTHISREQUIRESTHEUSEOFHIGHCOSTSENSORSASWELLASHIGHCOMPUTATIONALPOWERTHUSNOTSUITABLEFORHOMEENVIRONMENTSTHISPAPERPRESENTSANOVELINTEGRATEDCOVERAGESTRATEGYFORLOWCOSTCLEANINGROBOTS,YETDEMONSTRATINGRESPECTABLECOVERAGEPERFORMANCEINMOSTUNKNOWNENVIRONMENTSTHEPROPOSEDALGORITHMCANEFFICIENTLYCOPEWITHHARDWARELIMITATIONSRANGINGFROMLOWCOMPUTATIONALPOWERTONUMEROUSSENSINGPROBLEMSARISINGFROMLIMITEDRANGE,SPARSEDATA,ANDDETECTIONUNCERTAINTYTOFACILITATEAVIABLESOLUTIONTHATCANCOPEWITHTHESELIMITATIONS,WEFIRSTMAKETWOASSUMPTIONSONTHEHOMEENVIRONMENTRECTILINEARANDCLOSED,WHICHSEEMSTOBEMETINMOSTOFOURHOMEENVIRONMENTSNEXT,INORDERTOEFFECTIVELYCIRCUMVENTPOORLOCALIZATIONLOWPRECISIONPOSITIONING,WEDECOMPOSETHESPACEINTOSECTORS,WITHEACHSECTORBEINGSMALLENOUGHTOHAVEREASONABLELOCALIZATIONACCURACYWITHINITSELFOVERALL,THEFINALOUTCOMEISANOVELONLINECOVERAGESTRATEGYTHATPERFORMSSIMULTANEOUSEXPLORATION,INCREMENTALSECTORCREATION,SECTORCLEANING,ANDLOCALIZATION,WITHTHEINTENTIONOFMAXIMIZINGPERFORMANCEWITHMINIMALSENSINGBOTHSIMULATIONANDREALWORLDEXPERIMENTSVALIDATETHEEFFICIENCYOFOURAPPROACH2011ELSEVIERBVALLRIGHTSRESERVED1INTRODUCTIONTHECLEANINGROBOTMAYBETHEMOSTPOPULARSERVICEROBOTUSEDINHOMES1,2,INWHICHTHEROBOTNATURALLYHASNOPRIORINFORMATIONABOUTTHEENVIRONMENTITTHUSFACESTHEGREATCHALLENGEOFONLINECOVERAGETHEROBOTMUSTCOLLECTINFORMATIONONITSOWNLOCATIONANDSURROUNDINGOBSTACLESDURINGTHECOVERAGEPROCESS3,VERYOFTENWITHMINIMALSENSINGDUETOSEVERECOSTCONSTRAINTSFURTHERMORE,ACLEANINGROBOTSYSTEMREQUIRESANINTEGRATIONOFMANYTECHNIQUESEXPLORATIONOFTHETARGETENVIRONMENT,LOCALIZATIONANDMAPBUILDING,COVERAGEPATHPLANNING,WITHALLTHESETASKSBEINGCARRIEDOUTWHILECLEANINGINITSNAVIGATIONSYSTEMINORDERTOMAXIMIZEITSCLEANINGPERFORMANCE4ONEOFTHEMOSTIMPORTANTPERFORMANCEOBJECTIVESISTOCOVERATARGETAREAASCOMPLETELYANDQUICKLYASPOSSIBLETHISTHENREQUIRESKNOWINGTHEROBOTSPRECISEPOSITIONWITHINAPRECISEMAPOFTHETARGETENVIRONMENTHOWEVER,MOSTINEXPENSIVECLEANINGROBOTSRELYONHEURISTICS5ORRANDOMIZEDAPPROACHBECAUSEOFTHETECHNICALDIFFICULTIESOFIMPLEMENTINGCORRESPONDINGAUTHOREMAILADDRESSESDEVILEEPOSTECHACKRTKLEE,TKEB100POSTECHACKRSBAEK,SYOHPOSTECHACKRSYOHLOCALIZATION,MAPBUILDING,ANDPATHPLANNINGWITHLOWCOSTSENSORSASWELLASLOWCOMPUTINGPOWERTHEMETHODSUSEDTHEREINARESIMPLEBUTCANNOTGUARANTEECOMPLETECOVERAGETOACHIEVESOMEGUARANTEEDLEVELOFCOVERAGE,MANYCOVERAGEPATHPLANNERSEITHERIMPLICITLYOREXPLICITLYUSECELLULARDECOMPOSITIONOFTHEFREESPACE6THEYDIVIDETHEENTIREREGIONINTOCELLS,ANDEACHCELLISCOVEREDONEAFTERANOTHER,WHICHISFOUNDTOBEMOREEFFICIENTTHANCLEANINGTHEENTIREREGIONASAWHOLE7CELLULARDECOMPOSITIONCANBECATEGORIZEDINTOTHREECLASSES6THEFIRST,EXACTCELLULARDECOMPOSITION,DECOMPOSESTHECONFIGURATIONSPACEINTOCONVEXPOLYGONSOFVARIOUSSHAPESANDSIZES812THEWELLKNOWNMORSEDECOMPOSITION13FALLSUNDERTHISCATEGORYAPPROXIMATECELLULARDECOMPOSITIONUSESAFINEGRIDTOREPRESENTTHEFREESPACEHERE,THECELLSAREALLOFTHESAMESIZEANDSHAPEEG,SQUAREORTRIANGULAR14,THUSTHEIRUNIONONLYAPPROXIMATESTHESPACETHESPANNINGTREECOVERINGSTCAPPROACH15ANDBACKTRACKINGSPIRALALGORITHMBSA3ACHIEVEONLINECOVERAGEBASEDONTHISDECOMPOSITIONFINALLY,SEMIAPPROXIMATECELLULARDECOMPOSITIONUSESAPARTIALDISCRETIZATIONOFTHESPACE,INWHICHTHECELLSAREFIXEDINWIDTHBUTCANHAVEANYSHAPEATTHETOPORBOTTOMTOCOVERAGIVENSPACE,THEROBOTTRAVERSESALONGASERIESOFPARALLELSTRAIGHTLINESTHATDIVIDETHESPACEEACHREGIONISTHENCOVEREDUSINGBACKANDFORTHMOTION16,17ALTHOUGHTHESEALGORITHMSGUARANTEECOMPLETECOVERAGE,THEYHINGEONONEBASIC09218890/SEEFRONTMATTER2011ELSEVIERBVALLRIGHTSRESERVEDDOI101016/JROBOT201105005CONTENTSLISTSAVAILABLEATSCIENCEDIRECTROBOTICSANDAUTONOMOUSSYSTEMSJOURNALHOMEPAGEWWWELSEVIERCOM/LOCATE/ROBOTTKLEEETAL/ROBOTICSANDAUTONOMOUSSYSTEMS592011698710699ASSUMPTIONTHATAPRECISEESTIMATEOFROBOTPOSITIONISALWAYSAVAILABLEINOTHERWORDS,THEROBOTMUSTHAVEAVERYACCURATEWAYOFLOCALIZATION,SUCHASEXTENDEDKALMANFILTEREKF1820ORPARTICLEFILTER19,21,22THISNORMALLYLEADSTOHIGHCOMPUTATIONALPOWERANDPRECISE/EXPENSIVESENSINGALTHOUGHTHELOCALIZATIONPROBLEMWITHLIMITEDSENSINGHASBEENPARTIALLYADDRESSEDIN23,24,THEIRAPPROACHSTILLCANNOTPROVIDECONTINUOUSPOSITIONESTIMATESTHATAREESSENTIALTOPLANACOVERAGEPATHINSOMECASES,THEVISIONSYSTEMWASUSEDFORCLEANING25,26,BUTITSUFFEREDFROMSUSCEPTIBILITYTOAMBIENTILLUMINATIONANDHIGHERCOSTTHANTHEUSUALRANGESENSORBASEDCLEANINGROBOTSYSTEMSINTHISPAPER,WEAIMTODEVELOPAREALTIMELIGHTWEIGHTALGORITHMFORMAXIMIZINGCOVERAGETHATCANBEAPPLIEDTOMOSTCLEANINGROBOTSWITHLOWCOSTMICROCONTROLLERSANDSENSORS,INCLUDINGULTRASONIC,INFRARED,ANDTOUCHSENSORSTHESEHARDWARELIMITATIONSIMPOSESEVERALCONSTRAINTSONOURAPPROACHTOREDUCECOMPUTATIONALLOAD,WENEEDTOSIMPLIFYSTRATEGIESFORNAVIGATION,MAPBUILDING,ANDPOSITIONCORRECTIONTHROUGHSIMPLEASSUMPTIONSONTHEENVIRONMENTRECTILINEARORTHOGONALITYANDCLOSEDTHEFIRSTSEEMSREASONABLECONSIDERINGTHATMAJORSTRUCTURESOFTHEINDOORENVIRONMENTCANBEREPRESENTEDBYSETSOFLINESTHATAREPARALLELORPERPENDICULARTOEACHOTHER27ACTUALLY,MOSTOFTHEINDOORSETTINGSEITHERCONFORMTOORCANBEAPPROXIMATEDBYTHISMODEL28THESEORTHOGONALLINEFEATURESGREATLYREDUCETHECOMPUTATIONALLOADANDBOOSTLOCALIZATIONACCURACYTHESECONDINDICATESTHATTHEROBOTCANCOMPLETELYEXPLORETHETARGETENVIRONMENTBYWALLFOLLOWING,WHICHLEADSTOMAXIMALCOVERAGEINOURALGORITHMNOTETHATTHETERMWALLINTHISPAPERINDICATESTHEOUTEROUTLINEOFTHEENVIRONMENT,INCLUDINGBOTHTHEACTUALWALLANDTHEOBSTACLESNEARTHEWALLOURALGORITHM,BASEDONTHESEASSUMPTIONS,TAKESTWOPHASESTOIMPLEMENTFIRST,ASEQUENCEOFREGIONSNAMEDSECTORSISCREATEDINCREMENTALLYASTHEROBOTSYSTEMATICALLYEXPLORESTHEUNKNOWNENVIRONMENT,PRIMARILYBYWALLFOLLOWINGASECTORISACONCEPTUALREGIONDERIVEDFROMTHETARGETAREA,WHICHISDEFINEDANDCREATEDTOINCREASETHECLEANINGEFFICIENCYOFTHEROBOTTHEROBOTSIMULTANEOUSLYEXPLORESANDCLEANSTHETARGETAREABYINCREMENTALLYBUILDINGSECTORSALONGTHEWALLWHILEMOVINGALONGSIDETHEWALL,THEROBOTEXTRACTSTHELINEFEATURESFROMITEACHSECTORISBASICALLYCREATEDAROUNDTHENEIGHBORINGWALL,WHOSETYPEANDSIZEISALGORITHMICALLYDETERMINEDACCORDINGTOTHEWALLCONFIGURATIONANDTHEROBOTTRAJECTORYTHEEXTRACTEDLINEFEATURESARETHENUSEDTOCORRECTSECTORPOSITIONANDORIENTATION,ASWELLASTHEROBOTPOSE,ACCORDINGLYAFTERDISCOVERINGANDCREATINGANEWSECTOR,THEROBOTCLEANSITBYEMPLOYINGAPPROXIMATECELLULARDECOMPOSITION,USINGITSOWNSIZEASTHEBASICCELLWIDTHTHESECTORSBOUNDARYINFORMATIONSUPPLIESTHEROBOTWITHALOCALMAPTOPLANCOVERAGE,WHILEALSOALLOWINGITTOCHECKCOVEREDANDUNCOVEREDAREASWITHINTHEMAPITCLEANSTHEINSIDEOFTHESECTORUSINGBACKANDFORTHMOTION16,17WITHTHELOCALMAPPROVIDEDWEFINALLYVALIDATEOURALGORITHMUSINGBOTHAREALISTICSIMULATIONANDAMOBILEROBOTPLATFORMWITHSHORTRANGESENSORSANDALOWPOWEREDMICROCONTROLLERTHEEXPERIMENTALRESULTSDEMONSTRATETHEPRACTICALITYANDCLEANINGEFFICACYOFOURAPPROACHTHEREMAINDEROFTHISPAPERISORGANIZEDASFOLLOWSINSECTION2,THEOVERALLPROCESSOFTHEPROPOSEDCOVERAGEALGORITHMISINTRODUCEDTHENSECTION3,SECTION4,ANDSECTION5DESCRIBERELEVANTCOMPONENTSOFTHEALGORITHMSECTION6DEMONSTRATESANEXPERIMENTALVALIDATIONOFOURAPPROACHINBOTHSIMULATEDANDREALENVIRONMENTS,ANDWECONCLUDEINSECTION72SECTORBASEDONLINECOVERAGEALGORITHMINOURAPPROACH,WEDONOTDECOMPOSETHEWORKSPACEINTOCELLS,BUTINTOSECTORS,ANEWCONCEPTWEDEVELOPEDINTHISSTUDYTOIMPROVECLEANINGEFFICIENCYTHESECTORISAFLEXIBLEREGIONTHATADAPTSTOTHETARGETENVIRONMENT,SOTHATTHEUNIONOFSECTORSCOVERSTHEENTIRETARGETENVIRONMENTWITHOURSECTORS,OVERLAPPEDANDUNCOVEREDAREASCANSHOWUPMOREFREQUENTLYTHANCELLULARDECOMPOSITIONBASEDONPRECISEPOSITIONINGHOWEVER,INTHEREALWORLDOFCLEANINGROBOTSWHERETHEPRECISELOCALIZATIONASSUMPTIONISVIOLATED,OURSECTORAPPROACHMAYPROVIDEAMOREVIABLESOLUTIONWITHINTHESECTOR,HOWEVER,WEEMPLOYTHEUSUALAPPROXIMATECELLULARDECOMPOSITIONMETHODTOCOMPLETELYCOVERTHESECTORINTHEPROPOSEDALGORITHM,THESECTORISDEFINEDASARECTANGULARREGION,SATISFYING1THEREGIONISSMALLERTHANLBYL,WHERELISADEFAULTLENGTH2THERECTANGLEISPARALLELTOTHEWALLSORTHOGONALPORTIONSINOURAPPROACH,THEROBOTPOSEDURINGTHEEXPLORATIONOFASECTORISESTIMATEDPURELYBYADEADRECKONINGODOMETRYSYSTEMHOWEVER,ODOMETRYERRORUSUALLYACCUMULATESDURINGMOVEMENTDUETOSYSTEMATICERROROREXTERNALEVENTSSUCHASWHEELSLIPANDUNEVENFLOORCONDITIONSTHEREFORE,THEPARAMETERLSHOULDBECAREFULLYCHOSENSOTHATTHEODOMETRYERRORACCUMULATEDDURINGCOVERAGEISCONFINEDTOACERTAINALLOWABLELEVELALARGERVALUEOFLISDESIRABLEFOREFFICIENTCOVERAGESO,LISEMPIRICALLYSETDEPENDINGONTHEACCURACYOFTHEODOMETRYSYSTEM,WHEREAPRECISEONEALLOWSALARGERVALUEOFLBECAUSEOFODOMETRYERRORACCUMULATION,THESECTORCONDITION2ISNOTUSUALLYSATISFIEDTHEREFORE,WEAPPLYASECTORCORRECTIONFORBOTHROTATIONANDTRANSLATIONBASEDONLINEFEATURESANDEXPLOITINGTHEORTHOGONALITYASSUMPTIONWHENTHESECTORISCORRECTED,THEROBOTPOSEISALSOADJUSTEDACCORDINGLYOURALGORITHMGENERATESANDCOVERSSECTORSALONGSIDETHEWALLUNTILLOOPCLOSINGISDETECTEDINTHISPAPER,WEDETERMINETHEDIRECTIONOFEXPLORATIONBYARIGHTHANDRULE,SUCHTHATTHEWALLISPLACEDONTHERIGHTSIDEOFTHEROBOTWHENTHEROBOTMOVESTOTHENEXTSECTORBYWALLFOLLOWINGMOTIONTHEDIRECTIONMAYBEREVERSEDONDEMANDTHEFLOWCHARTOFTHEPROPOSEDSECTORBASEDONLINECOVERAGEALGORITHMISSHOWNINFIG1TOGENERATEASECTORNEARTHEWALL,WEDETERMINETHESECTORBOUNDARYDURINGAWALLFOLLOWINGMOTIONHOWEVER,ATTHEOUTSETOFCOVERAGE,THEROBOTMAYNOTBEPLACEDNEARTHEWALLTHEREFORE,THEROBOTFIRSTNEEDSTOACCESSTHEWALLBYMOVINGFORWARDUNTILANOBSTACLEISDETECTED,BUTTHEROBOTMAYNEEDMOREINFORMATIONTOASSURETHATTHEDETECTEDOBSTACLEISACTUALLYAPARTOFTHEWALLTHOUGHSOMEHEURISTICSOLUTIONSEXIST,THISPROBLEMISNOTDEALTWITHINTHISPAPER,ANDWESIMPLYASSUMETHATTHEROBOTDOESNOTENCOUNTERANYOBSTACLESOTHERTHANTHEWALLDURINGTHEWALLACCESSAFTERTHEWALLACCESS,THEROBOTDETERMINESANEWSECTORBOUNDARY,ANDTHESECTORISADDEDTOTHEGLOBALSECTORMAPTHISSECTORDETERMINATIONSTEPALSOINVOLVESSECTORCORRECTIONIFTHENEWSECTORISTOOSMALLORHASALREADYBEENCOVERED,THECOVERAGEPROCEDUREISBYPASSEDOTHERWISE,ITISCOVEREDBYACOMPLETECOVERAGEALGORITHMTHENTHEROBOTMOVESTOTHESTARTPOSITIONOFTHENEXTSECTORANDACCESSESTHEWALLATTHISPOINT,THEROBOTCHECKSTHELOOPCLOSINGCONDITIONS,ANDIFITRETURNSANEGATIVERESPONSE,THEROBOTREPEATSCOVERAGEOFTHENEXTSECTOROTHERWISE,THEROBOTSEARCHESFURTHERFORUNEXPLOREDSECTORSTHATARENOTNEARTHEWALL,ANDTHEROBOTSEQUENTIALLYCOVERSTHESESECTORSIFNOUNEXPLOREDCELLEXISTS,THEROBOTMOVESTOACHARGINGSTATION,CALLEDAHOMINGMOTIONHERE,WEASSUMETHATTHECHARGINGSTATIONISPLACEDORNOTANYWHEREINTHEENVIRONMENTANDEMITSSIGNALSWITHINALIMITEDRANGETHATTHEROBOTCANDETECTWHENTHEROBOTISMOVINGTOTHEUNEXPLOREDSECTORSORTOTHECHARGINGSTATION,ITFOLLOWSTHEWALLINREVERSEWHILELOCALIZINGITSELFRELATIVETOTHEGLOBALSECTORMAPGENERATEDSOFAR,USINGASIMPLELINEFEATUREMATCHINGANEXAMPLEOFSECTORGENERATIONISILLUSTRATEDINFIG2,WHICHSHOWSONLYAPORTIONOFTHEENTIRESEQUENCETHESIZEOFASECTORISLBYLBYDEFAULT,BUTITCANCHANGEACCORDINGTOTHELOCALENVIRONMENTCONFIGURATIONAROUNDTHESECTOR,ASFIG2INDICATESSOMEPREVIOUSLYCOVEREDSECTORSALSOPARTICIPATEINTHEDETERMINATIONOFTHESECTORSIZETOINCREASECOVERAGEEFFICIENCYBYREDUCINGTHEOVERLAPPEDREGIONNOTETHATAFTERTHEWHOLEPROCESS,3TKLEEETAL/ROBOTICSANDAUTONOMOUSSYSTEMS592011698710FIG3EXAMPLEOFASECTORCOORDINATEFRAMEINDICATINGITSLOCATIONINTHEWORLDREFERENCEFRAMETHEBOUNDARYOFTHESECTORCANBESIMPLYDEFINEDBYMINIMUMANDMAXIMUMVALUESOFTHELOCALXANDYCOORDINATES31DETERMINATIONOFTHESECTORBOUNDARYANDTYPEFIG1FLOWCHARTOFTHEPROPOSEDCOVERAGEALGORITHMFIG2ONLINEGENERATIONOFSECTORSBASEDONTHERIGHTHANDRULEEACHSECTORISCOVEREDRIGHTAFTERITSGENERATIONTHEUNFINISHEDREGIONSWILLEVENTUALLYBECOVEREDAFTERTHEWHOLEPROCESSTHEUNFINISHEDREGIONS,INCLUDINGTHEONEABOVETHEFIRSTSECTOR,WILLEVENTUALLYBECOVEREDINTHEFOLLOWINGTHREESECTIONS,RELEVANTCOMPONENTSOFTHEALGORITHMAREGIVENSECTION3DESCRIBESTHESECTORDETERMINATIONANDCORRECTIONSCHEME,ASWELLASTHEGLOBALSECTORMAPMANAGEMENTSCHEME,INCLUDINGTHELOOPCLOSINGDETECTIONALGORITHMTHEN,INSECTION4,WEEXPLAINHOWEACHSECTORISCOVEREDCOVERAGEOFTHEUNEXPLOREDSECTORS,HOMING,ANDTHERELATEDLOCALIZATIONAREPRESENTEDINSECTION53SECTORDETERMINATIONANDGLOBALSECTORMAPMANAGEMENTINTHISSECTION,WEDESCRIBEHOWTOGENERATESECTORSWITHFLEXIBLESIZESTOFITTHELOCALENVIRONMENTANDTOREDUCEOVERLAPALSO,WEEXPLAINHOWWECORRECTSECTORINFORMATIONANDTHEROBOTPOSEUSINGLINEFEATURESANDTHEORTHOGONALITYASSUMPTIONINTHELASTSUBSECTION,WEDESCRIBEGLOBALSECTORMAPMANAGEMENTASWELLASALOOPCLOSINGDETECTIONMETHODSECTORGENERATIONINVOLVESFIVESTEPSISETTINGTHECURRENTSECTORSREFERENCEFRAMEIISETTINGTHESECTORSINITIALBOUNDARYIIIDECIDINGONTHESECTORTYPEIVAPPLYINGBACKWARDEXPANSIONFORBLOCKEDSECTORSVDETERMININGTHEACTUALSECTORBOUNDARYANDVIESTIMATINGTHENEXTSECTORSREFERENCEFRAMEINTHISSUBSECTION,WEASSUMETHATTHEWORLDCOORDINATEISINITIALLYALIGNEDTOTHEORTHOGONALDIRECTIONOFTHEENVIRONMENTANDNOODOMETRYERROREXISTS,BECAUSEERRORCORRECTIONISADDRESSEDINTHENEXTSUBSECTIONEACHSTEPOFSECTORDETERMINATIONISDETAILEDINTHEFOLLOWING311SETTINGTHEREFERENCEFRAMEOFTHECURRENTSECTOREACHSECTORISREPRESENTEDBYITSOWNLOCALCOORDINATESYSTEMASSHOWNINFIG3,WHICHILLUSTRATESTHERELATIONSHIPBETWEENTHEWORLDANDTHESECTORREFERENCEFRAMESTHESECTORREFERENCEFRAMESHOULDSATISFYTHATTHEORIGINISPOSITIONEDNEARTHEWALLANDTHEDIRECTIONOFTHEXAXISISPARALLELTOTHEADJACENTWALL,WHILETHEWALLISONTHERIGHTSIDEOFTHEAXISCONSIDERINGTHERIGHTHANDRULEBECAUSEWEASSUMEARECTILINEARENVIRONMENT,THEDIRECTIONISQUANTIZEDINFOURANGLES90,0,90,180BYREPRESENTINGTHEPOSITIONANDTHEORIENTATIONOFTHEITHSECTORINTHEWORLDREFERENCEFRAMEASTI,THEWORLDANDTHESECTORCOORDINATESARERELATEDBYTHEFOLLOWINGEQUATIONSXWTIX,1XTIXW,2WHEREXWANDXREPRESENTTHESAMEPOSEBUTAREREFERENCEDBYWORLDANDSECTORFRAMES,RESPECTIVELYANDARECOMPOUNDINGANDREVERSALOPERATIONS,RESPECTIVELY29FOLLOWINGTHEALGORITHMSEQUENCEINFIG1,INTHESECTORDETERMINATIONSTEPTHEROBOTISALREADYPLACEDNEARTHEWALLANDTHEPOSITIONINDICATESTHEORIGINOFTHENEWSECTORREFERENCEFRAMEHOWEVER,DETERMINATIONOFTHEDIRECTIONISMOREINVOLVED,BECAUSEITREQUIRESKNOWLEDGEABOUTTHEENVIRONMENTAROUNDTHESECTORORIGINWHENITCOMESTOTHEFIRSTSECTOR,NOSUCHKNOWLEDGEISAVAILABLE,SOTHEROBOTMOVESAWHILETODETERMINETHEDIRECTIONOFTHENEARBYWALLHOWEVER,THEDIRECTIONSOFTHEOTHERSECTORSAREJUDICIOUSLYSELECTEDUSINGTHEINFORMATIONOFTHEPREVIOUSSECTORTHISSCHEMEISCOVEREDINSECTION316TKLEEETAL/ROBOTICSANDAUTONOMOUSSYSTEMS592011698710701AOPENSECTORBNORMALSECTORFIG4DETERMINATIONOFTHESECTORSMAXIMUMBOUNDARY,WHEREN3THEWIDTHANDHEIGHTISDETERMINEDSUCHTHATTHESECTORDOESNOTOVERLAPWITHTHEPREVIOUSNSECTORSBYMORETHANTHEMAXIMUMOVERLAPDISTANCEMOCBLOCKEDSECTORIDBLOCKEDSECTORIIEOPENSMALLSECTOR312SETTINGTHESECTORSINITIALBOUNDARYHAVINGESTABLISHEDTHESECTORFRAME,ITSBOUNDARYCANBEASSIGNEDANDEXPRESSEDUSINGTHEMINIMUMANDMAXIMUMVALUESOFXANDYSECTORCOORDINATESXMIN,XMAX,YMIN,YMAXASSHOWNINFIG3INTHISSTEP,XMINANDYMINARESETTO0,WHILEXMAXANDYMAXARESETASTHEWIDTHANDHEIGHTOFTHESECTOR,RESPECTIVELYSIMPLYSETTINGXMAXANDYMAXASTHEDEFAULTVALUELMAYCAUSETOOMUCHOVERLAPBETWEENSECTORS,ESPECIALLYINACORRIDORENVIRONMENTSHOWNINFIG4TOMINIMIZETHISPOSSIBLEOVERLAPINCOVERAGE,WEIMPOSESOMECONSTRAINTSFIRST,THESECTORSIZESHOULDNOTEXCEEDTHEDEFAULTSIZELSECOND,THESECTORSHOULDNOTOVERLAPWITHPREVIOUSLYCOVEREDSECTORSBYMORETHANAPREDEFINEDMAXIMUMOVERLAPDISTANCEMO,ASSHOWNINFIG4THEMAXIMUMOVERLAPDISTANCEISINTRODUCEDHERETOCOMPENSATEFORTHERELATIVEPOSITIONERRORBETWEENNEIGHBORINGSECTORSDUETOODOMETRYIFWEASSUMETHESAMEAMOUNTOFERRORFORXANDYCOMPONENTSOFODOMETRY,THEUNCERTAINTYREGIONOFASECTORCOULDBEREPRESENTEDBYUNIFORMLYTHICKENINGTHEORIGINALSECTORBOUNDARIESHERE,HALFOFTHISTHICKNESSISDEFINEDASMO,WHICHISSETTOTHESTANDARDDEVIATIONOFTHEODOMETRYERRORBECAUSEWENEEDTOMAXIMIZECOVERAGEEVENINTHEWORSTCASE,WEMAINTAINTHISOVERLAPBETWEENADJACENTSECTORSFORSIMPLICITY,WEEMPIRICALLYSETMOASACONSTANTVALUETHIRD,WECONSTRAINTHENUMBEROFPREVIOUSSECTORSUSEDFORSIZEDETERMINATION,LABELEDASN,BECAUSETHERELATIVEPOSITIONERRORBETWEENTHECURRENTANDTHEPREVIOUSSECTORSMAYEXCEEDPREDEFINEDMOTOSOMEEXTENT,AGAINDUETOLOCALIZATIONERRORACCUMULATIONHERE,WEUSEALINEARERRORACCUMULATIONMODELTHATINCREASESINPROPORTIONTOTHESECTORSIZETHENNISDETERMINEDASFINTERNALSECTORGISLANDSECTORFIG5SECTORTYPEDETERMINATIONANDSIZEADJUSTMENTTHESECTORFRAMESORIGINANDTHEXAXISDIRECTIONAREREPRESENTEDBYAREDCIRCLEANDABLACKBARWITHINITCONCEPTUALLY,THEFOURMAJORSECTORTYPESOPEN,NORMAL,BLOCKI,ANDBLOCKIIAREDETERMINEDBYTHEBOUNDARYCROSSINGDIRECTIONASINDICATEDINTABLE1HOWEVER,THEREALENVIRONMENTMAYNOTBEPERFECTLYRECTILINEARTHERECTILINEARASSUMPTIONCOULDBEPARTIALLYVIOLATEDANDTHEROBOTCANHAVEPOSITIONERRORTHEREFORE,WEADDAMARGINALVALUETOTOYINTHEOPENSECTORCONDITIONWHENTHEENVIRONMENTISLOCALLYDIAGONAL,ITISALSOAMBIGUOUSWHATTHESECTORTYPESHOULDBE,WHETHERNORMALOROPENINTHISCASE,ASSUMINGTHATTHEDIRECTIONOFTHEWALLCANBEAPPROXIMATEDBYTHEROBOTORIENTATIONDURINGTHEWALLFOLLOWING,IFTHEORIENTATIONISCLOSERTOTHELOCALHORIZONTALDIRECTIONLOCALXAXIS,ITBECOMESNORMALOTHERWISE,OPENDURINGWALLFOLLOWING,WEMAINTAINALOCALTRAJECTORYBUFFERBYSAMPLINGTHEROBOTPOSESINTHELOCALFRAMEAFTERTHESECTORTYPEDETERMINATION,THETRAJECTORYBUFFERISUSEDTOADJUSTTHESECTORBOUNDARYASINTABLE1,WHERETTTTTHENUMBEROFPREVIOUSSECTORSFORWHICHTHEERRORACCUMULATIONISSMALLERTHANMO313SECTORTYPEDETERMINATIONFIRSTADJUSTMENTAFTERDECIDINGTHEINITIALBOUNDARY,THEROBOTFOLLOWSTHEWALLUNTILITMOVESOUTOFTHEPREDEFINEDBOUNDARYTHETYPEOFTHESECTORISDETERMINEDACCORDINGTOTHEDIRECTIONOFTHEBOUNDARYCROSSING,ANDTHENTHEBOUNDARYISADJUSTEDACCORDINGLY,ASSHOWNINFIG5INTHISWAY,WECANADAPTIVELYDETERMINETHESIZEOFASECTORONLINEACCORDINGTOTHENEIGHBORINGENVIRONMENTSACONVENIENTWAYOFDECIDINGTHESECTORTYPEISTOCHECKTHECONDITIONSINTHESECTORFRAMENOTINTHEWORLDFRAME,BECAUSECOMMONCONDITIONSCANBEAPPLIEDREGARDLESSOFSECTORORIENTATIONTHEREFORE,WEFIRSTREPRESENTTHEROBOTPOSEINTHESECTORFRAMEUSING2,ANDTHENTHISLOCALPOSEISUSEDTOCHECKTHECONDITIONSINTABLE1XMIN,XMAX,YMIN,ANDYMAXREPRESENTTHEMINIMUMANDMAXIMUMOFXANDYVALUESOFTHETRAJECTORYPOINTSINTHETABLE,WOREPRESENTSANEXTRAWIDTHADDEDTOTHEOPENSECTORFOREFFICIENTCONTROLOFTHEROBOTWEALSODEFINESOMESPECIALCASESOFSECTORTYPESWHENTHEWIDTHORTHEHEIGHTOFAGENERATEDSECTORISSMALLERTHANAPRESETTHRESHOLDVALUETS,ITISDETERMINEDASASMALLTYPE,
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