ECSE 211 - Autonomous Block Stacking Robot - Project Documentation

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Roy Breidi

Alexander Hugh Sam

Payom Meshgin

Paul Sticea

April 8, 2011

Team18:ProjectDocumentation

Team 18

McGill Department of Electrical & Computer Engineering

ECSE-211: Design principles & methods

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TableofContents1.Requirements1.1.0‐Capabilities1.1.1‐Purpose1.1.2‐Scope1.1.3‐Constraints1.1.4‐UserFunctions1.1.5‐OperatingEnvironment1.1.6‐Performance1.2.0‐Compatibility1.2.1‐ComponentRe‐use1.2.2‐Compatibilitywiththirdpartproducts2.Constraints2.1‐EnvironmentalIssuer2.2‐HardwareConstraints2.3‐SoftwareConstraints2.4‐AvailabilityofResources2.5‐Budget3.Capabilities

3.1‐TeamMembers3.2‐Capabilities3.3‐PossibleApplicationAreas3.4‐Availability

4.Systemdescription4.1SystemModel4.2HardwareAvailableandCapabilities4.3SoftwareAvailableandCapabilities4.4Compatibility4.5Re‐usability4.6Structures4.7Methodologies4.8Tools

AppendixA:GanttChartsAppendixB:BudgetbreakdownAppendixC:MechanicalandPhysicalStructureAppendixD:SoftwareDevelopmentAppendixE:TestingDocumentGlossaryofTermsReferences

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1.Requirements1.1.0CAPABILITIES

1.1.1PURPOSEThe purpose of this project is to design an autonomous machine capable of navigatingwithinanenclosedmaze.ThemazewillcontainStyrofoamblocksthatneedtobegatheredandstackedatagivenposition.Therewillalsobeobstaclesthattherobotneedstoavoidwhilecompletingitstask.Byautonomouswemeanthattherobotshouldbeabletolocalizeitselfinsidethemazeandnavigate towanted locationswithout assistance from the user. The robot is expected tocircumventobstaclesandavoidcollisionswiththewall.TheStyrofoamblocksshouldbepiledintoasinglestablestructureataspecificlocation.

1.1.2SCOPE

Thesizeofthemazewillbe12x12feetandwillbesubdividedintosquaresof30.48cmoflength. The squares are separated by black lines of 7mm in thickness. The height of thewallsaroundthemazeis7.625inches.ThesizeofoneStyrofoamblockis2x2x4inches.Thesizeofonecinder‐blockis7.625x7.625x15.625inches.Thecompetitionwillconsistof3independentrounds.Allroundsinvolvethesametaskofbuildingthetalleststablestructurepossible.Rounds1and2willaresimilarintermsoftheevaluationmethodwhiletheevaluationinround3isbasedonascorecalculatedfromtheheightofthestructureandthetimetobuild.Eachattemptwillhaveamaximumdurationof10minutes.Thefinalproductisaone‐shotoperation.

1.1.3CONSTRAINTSThe final product must be composed of at most 3 Lego Mindstorm NXT Kits and anyadditionalcomponentsshouldbeapprovedinadvancebytheclient.Also,TherobotmustbeprogrammedusingJava.Theclienthasimposedatimedeadlineonthedesign,itshouldbe completed by Wednesday April 6th 2011.The design process will be spread over aperiodof6.5weeks,overwhichnomorethan234man‐hoursareallocatedforthepurposeofthisprojectbeingateamof4people.

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Therehavebeen specifications on the size but none on theweight. The robot should bemade inaway such that the center is locatedwithin the cornergrid square.Thismeansthat therobot’scentershouldbeatmost30cmfromits farthestpointon therobot.Thebricksarealsopoweredby6AAbatterieseach.Wemustensurethattherobotisabletorunfor the10minutesrequired for the finalcompetitionwithoutrunningoutofbattery.Formoredetailsontheconstraints,pleaserefertosection2. 1.1.4USERFUNCTIONSTheuserisallowedtomakechangestothedeviceatanytimeoutsideofarun.TherewillbeanaccessiblemenuontheNXTbrickscreen inordertostart therobotandpair itup,usingBluetooth.However, theuser isnotallowedto interferewith therobot’soperationafter it receives its destination from themain computer using Bluetooth. If the robot isusingmore than 1NXTbrick, they should be all started, and then programs running onthemwillconnecttoeachotherandtakeoverfutheroperations.

1.1.5OPERATINGENVIRONMENT

The competitionwill be held on the second floor in the LorneM. Trottier building. Therobotwilloperateona12x12footflatbrightwoodensurfacesubdividedintogrid‐linesof30.48 cm apart. When the maze is setup, appending the 4x4 tiles might lead to cracksvaryingthegrid‐linethickness.Alsoatsomeplaces,thecolorofthegrid‐lineiswashedoutwhichmightaffectthelocalizationoftherobot.Theambientlightmightchangebasedonthe time of day or the location of the maze which should be taken into account whenimplementing the light sensor. Also we should take into consideration the presence ofspectators that could falsify the readings taken by the light sensors, because of theirshadows.Thereislikelygoingtobealotofsoundatcompetitiontimebutitisnotexpectedtoaffect theoperationof therobot.Temperaturewillbeveryclosetoroomtemperaturesince the competition is held indoors and thus there is no worry concerning having adifferentgripofthewheelsthantheonetestedinthelabs..

1.1.6PERFORMANCETherobot is supposed tooperate forat least for thedurationof1 round(10min). Itwillhavetotravelinsidethemazeuntilitachievesitsgoal.Therobotmustreactrelativelyfasttocommandsbecauseoftimeconstraints,itcannotgoover10minpersingleround.(Alsorefertosection1.1.2and1.1.3)

1.2.0COMPATIBILITY 1.2.1COMPONENTRE‐USEComponentreusefromthelabsisencouragedwhilereusefromexternalsourcesrequiresproofofauthorization.AllthesoftwarecomponentsthatwereprogrammedforbasictasksduringtheR&Dlabssuchasfilteringandodometrycanbereusedforthisproject.

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1.2.2COMPATIBILITYWITHTHIRDPARTPRODUCTSThe systemwill have to interfacewith an IDE such asEclipse. Itwill have to implementBluetoothtechnologytocommunicateduringboththedesignandthecompetitionphase.

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2.Constraints2.1ENVIRONMENTALISSUESRefertosection1.1.5“OperatingEnvironment”.2.2HARDWARECONSTRAINTSTheautonomousmachinewillbeassembledusingcomponentsfromthreemindstormkitswhichisprovidedwith1NXTBrick.Anyothermaterialmustbeapprovedbytheclient.TheNXTbrickiscomprisedof:‐1USB2.0port,touploadthesoftware.‐3outputports,toconnecttheservomotorstothebrick.‐4inputports,toconnectthesensorstothebrick.‐4sensors(touch,light,ultrasonic,sound)‐3interactiveservomotors.Legocomponentscomewithpredeterminedshapesandlengthsanditissometimeshardifnotimpossibletoimplementanyimagineddesign.Oneunitinlegois9mm(fromholetohole).Andtheincludedpartsmakeanglesofaminimumof45degrees,soitisalsohardtomakesolidstructureswithangleslessthan45degrees.Theprovidedaxes(thatfitinsidethemotors)arebendableandmightbendunderheavyweight.TheNXTbrickuses6AAbatteries,supplyingpowertothesensorandtheservomotorswhichmighthavedifferentbehaviourrelativetotheremainingbatterypower.Ifweusemorethanonebrick,andchoosetocommunicatethroughanRJ12cable,weshouldreserveport#4ontheNXTsforthisactionsinceitistheonlycapableofestablishinganRS485connection.ThisisalistofthehardwarespecificationsoftheNXTbrick(takenfromthelegowebsite):

32‐bitARM7microcontroller 256KbytesFLASH,64KbytesRAM 8‐bitAVRmicrocontroller 4KbytesFLASH,512ByteRAM Bluetoothwirelesscommunication(BluetoothClassIIV2.0compliant) USBfullspeedport(12Mbit/s) 4inputports,6‐wirecabledigitalplatform(OneportincludesaIEC61158Type 4/EN50170compliantexpansionportforfutureuse) 3outputports,6‐wirecabledigitalplatform 100x64pixelLCDgraphicaldisplay Loudspeaker‐8kHzsoundquality.Soundchannelwith8‐bitresolutionand2‐16

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KHzsamplerate. Powersource:6AAbatteries Threeservomotors Atouchsensor Anultrasoundsensor Asoundsensor Alightsensor

2.3SOFTWARECONSTRAINTSSinceweareusingLeJOS(LegoJavaOperatingSystem),allcodemustbewritteninjavausingtheclassesthatcomewiththeMindstormkitsandsomealreadyavailablejavaclassessuchastheMathclass.TheNXTbrickfeaturesapowerful32‐bitARM7microprocessor,a256kbytesFlashmemoryanda64kbytesRAM.ItalsohasasupportforBluetoothandRS485.Afterreceivingthepositionatwhichthestructuremustbebuilt,thesoftwareshouldbecompletelyautonomous,onlyinputusedbeingtheonefromthesensors.Thesoftwareusedallowsustoprogramandcontrolthedifferentservomotorsandthemultiplesensors.Also,thenumberofthreadsshouldbekeptsmallerthanadeterminedthresholdsothatitdoesnotaffecttheperformanceoftherobot.

2.4AVAILABILITYOFRESOURCESTherewillbeatleastoneweeklymeetingeachWednesdayfrom9:30to11:30.AnyothersupplementalnecessarymeetingcanbeaccommodatedonMondayorFridaymorningduringthesametime.Outsideofthemeetingtimes,eachteammembercanworkindividuallyondifferentpartsoftheprojectordocumentationassignedbytheteammanager.Whendifferentintersectingpartsoftheprojectsneedtobeconnectedorintegratedintothedesign,allconcernedteammembersshouldbepresentinordertoquicklymaketheirfixesoradaptationsincaseoffailure.Themaincriticalpathtaskishavingthestructureoftherobotreadyinordertobeabletointegrateandtestthesoftwareonit.Pleaserefertosection3.4formoredetailedinformationonteamavailability.2.5BUDGETConcerningthetimebudget,eachteammemberbeingexpectedtoworkforanaverageof9hrs/week,thiswillsumuptoamaximumof250hours.Thistotaltimewillbedividedforthedifferenttasksasspecifiedintheganttchart(AppendixA).TheprojectwillbecompletedbyApril6th2011,butweexpecttohaveafunctionalrobotbyApril23rd2011,sothelasttwoweekswillbededicatedtotestingandoptimizationofthesoftwareandhardwarecomponents.Otherthanthetimebudget,weexpecttohavespendingsonbatteries(max40$)andacolorposter(max40$).Thefundingfortheseitemswillcomefromtheteammembers.

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3.Capabilities

3.1TEAMMEMBERS

Name McGillEmail

RoyBreidi

roy.breidi

PaulSticea

paul.sticea

AlexanderHugh

Sam

Alexander.hughsam

PayomMeshgin

payom.meshgin

3.2‐CAPABILITIES

Thefollowingtableunderlinestheteammember’scapabilitiesaswellastheirinterestinallofthedifferentfieldsrelatedtotheproject.(Allvaluesareover10)

Roy Paul Alexander Payom

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Electrical Experience 4 5 3 4

Interest 5 4 5 5

Mechanical Experience 4 5 4 3

Interest 5 6 8 5

Software Experience 9 8 5 6

Interest 9 10 5 6

Documentation Experience 5 6 3 4

Interest 4 5 6 2

Management Experience 8 6 4 4

Interest 8 6 5 4

3.3‐POSSIBLEAPPLICATIONAREASWehadaroughsubdivisionoftasks:RoywillberesponsibleforLocalization,PCCommunicationandinter‐brickcommunication,Odometrywithitscorrection.PayomwillberesponsibleforNavigation,blockdetectionandobstacledetection.Paulwillberesponsiblefortheoverallstrategyincludingtheobstacleavoidance.Alexwillberesponsibleforthephysicalstructureoftherobotandthemechanics.Sinceweareshortstaffed,wewillallbeworkingonpartsofthedocumentation.

3.4‐AVAILABILITYWeeklyAvailability:

AweeklymeetingwillbeheldonWednesdaysfrom9:00amto11:30amwherealltheteammemberswillbepresent.Thisdoesnotpreventothersmallersessionstooccurduringeachweek.Everytwoweeks,twoofthemembershaveanElectricCircuitsquizandmaynotbepresentonthemeetings.

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4.SystemDocument4.1SYSTEMMODELTherobotshouldbeabletoperformsomebasicfunctionslikethefollowing:Localization:Therobotwillbeplacedinanyorientationonanyofthebottomcorners.Itwillfirstbeabletolocalizeandalignitselfonthefirstgridintersection.Navigation:‐Therobotshouldbeabletonavigateaccuratelyinsidethemazeaccordingtoacertainstategytofindblocksandavoidobstacles.Objectdetection:‐Therobothastodifferentiatetheblocksthatshouldbepickedupfromtheobstacles(bricks)soitdoesn’tcrashintothem.ObjectsStacking:‐Therobotmustpickuptheblocksandstackthemcorrectlyintoourcageuntilitreachesthedrop‐offarea.ObjectDelivery‐Therobotshouldbeabletogetthepalletstotheonebyonefootdrop‐offareaanddropthemoffcorrectlystackedwithinthe10minutesconstraint.ObstacleAvoidance:‐Therobotshouldbeabletoaccomplishtheprevioustaskswhileavoidinganyobstaclesonitspath.Communication‐RecevingtheinformationfromtheserverviaBluetooth.UsingtwoNXTStheyshouldbeabletocommunicatewitheachother,onebeingthemasterandtheothertheslave.BelowisapreliminaryClassdiagramsummarizingthebasicfunctionsoneachNXT:

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4.2HARDWAREAVAILABLEANDCAPABILITIESReferto2.2forthehardwareconstraints.Themajorelectromechanicalconstraintthatwehavewouldbethelimitedpowergivenbythebatteries.Thismeansthatwhenthebatterieshavebeenused,theoverallsystemperformancewillalsodegrade.TheNXTBlockisa48MHzprocessorandhasamaximumof256KBofFLASHmemory,andcontains64KBofRAM.Italsouses32‐bitcalculations,soeverydoublewillbeconvertedtofloat.4.3SOFTWAREAVAILABLEANDCAPABILITIESReferto2.3forthesoftwareconstraints.Eclipseisoneofthemajortoolsthatweusetoprogramtherobot.Itispreferredtoothersimilarsoftware,sinceEclipsehasacapabilitytofunctionwithLEJOS,whichisneededtoactuallyrealizethisproject.Eclipsealsohasabuiltinerrordetection,similartoMicrosoftWord’sspelling&grammardetection,whereitcoulddetectoursyntacticalmistakesthusmakingthedevelopmentprocessmorefluidandefficient.Javaistheprogramminglanguageofchoice,sincewealreadyuseitinapre‐requisiteforthiscourse,COMP‐202.Wearealreadyfamiliarwiththislanguage,soitiseasiertoadapttoallthedifferentcomplicationswecouldhavewhenusingtheLejoscomponents.

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4.4COMPATIBILITYThelegocomponentswehaveinourkitshavecertainrequirements,sinceyoucanonlyattachcertainpiecesinacertainway,andcannotputanypieceyouwanthoweveryouwant.Wehavetousea32‐bitJavacompiler,sincementionedabove,theNXTbrickprocessorworkswith32‐bitcodesonly.Bluetoothwillbeathirdpartysystemthatwewillusetogiveourrobotthecoordinatestogoto.Duringthefirstsixweeksofclass,wehavedevelopedalotofdifferentcodethatwewillbeusingforthisproject,likethenavigatorclass,theodometryclass,thelocalizationclassandtheBluetoothclass.Theseclassesshouldworkinanyenvironmentthatwecouldpossiblyfaceduringthisproject,sotheydonotbringanyconstraintstothemakingofourrobot.Wewillnotbeusingthemechanicaldesignswehaveusedinourpreviouslab,sincewewillbeusingtwoNXTbricks,thereforewearegoingtodesignourownmachine.4.5REUSABILITYRefertosection1.24.6STRUCTURESTomakesuretheStyrofoamblockswillbedetectedbythelightsensorandwillbegrippedin the right direction by the grippingmechanism,wewill use a “Y” shaped structure infrontoftherobottoserveasafunneltoplacetheblockinagoodposition.Wearegoingtouseacagestructuretocontainalltheblocksthatwewillbepickingupandit will also prevent from the stack of styrofoam blocks to fall.We have decided on thisstructure,sinceitwillbeeasier,saferandfasterthantakingonlyoneblockatatimeandpiling themupat thedropzone.Furthermore, therewillbea lift thatwillbeperformingtwo functions in our blockmanipulation. At first, wewanted to use a lift thatwill slideundertheblocksandwewouldthenproceedtolifttheblockupusingaliftingmechanism,butwesoonrealizedthatslidingundertheblockisaverydifficulttasktodo.Instead,webuiltagrippingmechanismthatwillholdtheblock inplace,whilethe liftingmechanism,willliftit.Fortheliftingmechanism,weoptedtousefishwire,sinceitisverysolidandwillbestrongenoughtoliftthegripperandtheStyrofoamblock.Thegripperwillbeputonarailing system,whichwill aid the fishingwire,which is attached to amotor, to lift it upconsistently,andwithoutanywobbling.TwoNXTbrickswillbeusedtocompensateforthelack of input and output ports. They will be linked using a RJ12 wire to be able tocommunicatewitheachotherandwithoutusingBluetooth, sinceweexpect thewirelessconnectiontobeunreliable.OursoftwarestructurewillbeonlyusingTimerListenerinsteadofThreads,sincewelearnedfromthelabsthatthreadsarelessreliablewhenitcomestosynchronizationandtiming.Everysensorwillbepolledinsideitsownthread(timerListener)sothatmeasurementsaretakenatregularpreciseintervals.

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4.7METHODOLOGIESRefertotheStructuresparagraphabove.4.8TOOLSEclipseAdvantages:Refertosection3.Disadvantages:Largeapplicationsize.Windows7Advantages:AvailabilityinDPMlabandonteammember’slaptops.Extensivedocumentationandsupportavailableonthewebincaseofmalfunction.Disadvantages:GanttProjectAdvantages:Makesscheduletrackingandtaskdivisioneasiertovisualize.Showsdependenciesbetweentasks.Disadvantages:Doesn’tfocusontherelativesizesoftheworkelementsLEGODigitalDesignerAdvantages:Givesaveryrealisticrepresentationofthemodel.Disadvantages:UnintuitiveuserinterfacewhichmakesthemodeldesigntimeconsumingDropBox(filesharing)Advantages:Easyfreeintuitivesharing.HasalargecapacityDisadvantages:Notreliablewhentrackingchangesandversioningofsourcecode.GoogleGroups(internalcommunication)Advantages:Easytoorganizeteamdiscussions.Disadvantages:Cannotreplacemeetings.Winmerge:Advantages:EasytocompareandmergefilesDisadvantages:‐ObjectAidpluginforeclipse:Advantages:AutomaticallygeneratesaclassdiagramfromtheexistingcodeDisadvantage:Hardtocustomizesometimes.JautoDocpluginforeclipse:Advantages:AutomaticallygeneratesjavadocforthecodeDisadvantage:Sometimesovergeneratesuselessdescriptions

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AppendixA:GanttChartsThefollowingGanttchartsshowtheevolutionofthedevelopmentprocessovertheprojecttimespan:GanttChartforweek2:

GanttChartforweek4:

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GanttChartforweek6:

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FinalGanttChart:

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AppendixB:BudgetbreakdownBeing4peopleinourteaminsteadof6,wehad⅔thebudgetoftheotherteams.Everyteammemberhadabudgetof9hoursperpersonperweek.Theprojectdevelopmenthadatime‐spanof6weeksplus3daysofthe7thweekwhichwasconsideredas“halfaweek”budgetwise.Sothetotalbudgetwouldsumupto9x6.5x4=234hours.Laterinthedevelopmentprocess,ourteamgotveryclosetothebudgetlimitandourrobotrequiredmoretesting.Soweaskedtheclient(Prof.Ferrie)forabudgetincreaseandhewillinglygrantedourteam30additionalman‐hoursconsideringitasagoodinvestment.Belowisatablesummarizingourtimebudgetdivisionoverthespanoftheproject:

PlanningandTeam

Meetings

GeneratingDocumentation

PhysicalDesign

CodeImplementation Testing Total

Week1 Roy 4 1 1 0 0 6Feb15 Paul 4 1 2 0 0 7

Alex 4 0.5 0.5 0 0 5 Payom 4 0 0 0 0 4Week2 Roy 2 2 1 3 1 9Feb28 Paul 1 3 5 9

Alex 1 0 10 0 0 11Payom 1 0 2 4 0.5 7.5

Week3 Roy 1 1 3 4 2 11March7 Paul 1 1 5 2 9

Alex 1 0 9 0 0.5 10.5 Payom 2 0.5 3 6 1 12.5Week4 Roy 1 1 1 3 2 8March14 Paul 1 0 3 3 1 8

Alex 1 3 3 0 0.5 7.5Payom 1 0.5 3 2 2 8.5

Week5 Roy 1 1 1 2 4 9March21: Paul 1 2 4 3 10

Alex 1 6 1 0 0 8 Payom 0 0 0 5 5 10Week6 Roy 1 1 1 3 5 11March28: Paul 1 1 0.5 4 4 10.5

Alex 1 7 0.5 0 0.5 9Payom 1 0.5 0 4 5 10.5

Week7(3days) Roy 0 1 0 2.5 9 12.5April4: Paul 0 0 0 3 10 13

Alex 0 9.5 0 0 1 10.5Payom 0 0 0 4 9 13

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Thetotalnumberofhoursusedwas260.5whichrepresents98.7%ofourtotalbudgetBelowisagraphgeneratedfromtheabovedata(excludingweek7).

C‐1C‐2

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AppendixC:MechanicalandPhysicalStructureKnowingthatwewerehandicappedandhadtwomemberslessthantheotherteams,weknewthatweshouldusetheleastamountoftimepossibleandbeaseffectiveaswecanbe.Withthatsaid,thisiswhywewentforamodulardesign,sothateachcomponentcanbedevelopedinparallelwitheachotherandsomoretimecanbesaved.

Thegrippingmechanism:Twodifferentdesignswereinitiallyproposedforthe“pick‐up”blocksystem:awedgethatwouldgoundertheblockandwouldbelifteduporaclaw‐likemechanism,whichwouldgrabtheblockbyit’ssideandwillthenbelifted‐up.Afterourfirstpresentation,weweretoldthatnopinswouldbeplacedundertheStyrofoamblocks.Thisnewsmeanttheendforthewedgeandthestartoftheclaw

mechanism.TheinitialclawmechanismwasverycloselyinspiredbyaproductseenfromtheNXTprogramwebsite(SeefigureC‐1).However,itwasimmediatelymodifiedsinceitwasnotstrongenoughtogripontheblock.

Thesecondrevisioncompromiseduschangingtheclawsfor2pairofrails.Thischangedemonstratedsignificantimprovement.UsingtheNXJconsole,wewereabletoseehowwellitwasabletoholdontotheblocksanditwasafirstsuccess.Nonetheless,afterafewmoretrials,wefiguredthatitdidnothaveenoughfrictionontheStyrofoamblocks.

TherubberpiecesfoundintheNXTMinstormkitwereaddedtoeachrailtoprovidetheneededfrictionandalsomaximizethesurfaceareaforbettergripping.Aflawwaseventuallyfound,sincethebottomrailwouldgripontooneblock,whiletheupperrailwouldgetthesecondblock.Thiswouldleadtolesspressurewhengrippingontheblocks.Anothermodificationhadtobemadetocompensateforthisflaw.Theendpartoftheupperrailwasremove,sothatonlythelowerpartwouldbeabletogrip.Yetagain,anewproblemwastobefound:therewerecasedwherethegrippingwasn’talignedcorrectly(thegripperwasnotstraightalongtheframe).Thisrevisionintroducedamovableendgripper(SeefigureC‐2)andthealignmentproblemwasfinallycorrected.

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Wesoonfoundoutthattheupperrailhadbecomeunnecessaryandaddedweighttoourgripper,sowetookitoutinfavourforagripperwhichwaslighterandhadbettermanoeuvrability.Thelastrevisionhappenedattheverylastweekbeforethecompetition.Werealisedthatsometimes,blockscouldhitandgetstuckunderthecage.ThisproblemwassolvedbuyimputinganL‐shapedblockontheleftrailofthegripper(SeefigureC‐3).Thiswouldmakesurethatnoblockwillgetstuckunderthecage,andwasalsousedtoalignthetwoblocks.Thebase:Theinitialdesignusedforthebasehadnorealthoughtputintoit.Theteamdecidedtogo with a similar structure to theStronger US Patbot and just addedanother brick on top of it. Multipleproblems have been observed, once thedesignwas done. Themajor flaw of thisbasewas that it had absolutely noplacewhere it could put the grippingmechanismtoeffectivelywork.Aseconddesignwasmadeadaylater,butwasquicklydemolished,since itwasasworstasthepreviousone, ifnotevenworst since it’s structurewaswaymoreunstable.This design was very high, butused fourwheels to travel (2 bymotorsand2thatwereinstalledintheback). The next designwas thought of after seeingmultiple teams using this structure. Thistime,theNXTbrickswereontheirsideandhadtobeattachedtotheirrespectivemotor.Theallwasthenattachedtootherpiecestosolidify thestructure.Wefoundout that thewheelsaxeswerebendingandwantedtoaddsomethingtopreventthis fromhappening.Theteamthoughtitwouldbeagoodideatomodifythebasetomakeitmorestabletohelpthetiresfromnotbendinganymore. The new and final base designintroduced a better structure to thewholerobot,whilealsohavingabetterrailing system. This new design alsointroducessomeaddedgeartopreventthe tires frombending and a fixed rodfrom the tires,which are also used forthesamepurpose(SeefigureC‐4andC‐5).Thecage:

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Eventhoughwewereatatwomandisadvantage,westillaimedforthetop,anditwasnosurprisethatweneededacagetodothis.Thecagehelpeduskeeptheblocksfromfallingwhenthestackwashigherthantwo.Theinitialdesignhadacagethatwasreallyhighandhadaverytightspacefortheblockstomanoeuver(SeefigureC‐6).Thisledtosomeinconsistencies,whichisnotacceptableinthistypeofcompetition.Also,thecagewasuselessifwedidnotpick‐upmorethanthreeblocks,whichstartedtobecomedangerous,sincethestackofthreecouldhavefalled.Thenextdesignwastheopposite:thestructurewasverylowandlarge.Thisalsoledtoproblems,sincewecouldnotpick‐upmorethanfourblocks(whichatthetimethoughtitwould be easy to accomplish) and the blocks had a high chances of falling due to thespacinginsidethecage.

Obviously,anewcagehadtobemade.Thisonewasthebestofbothworlds.Itwasnottoohigh,nortooshort,andhadtheperfectamountofmanoeuvrability,withoutgivingtheblockssomuchspace.Aftertesting,weconcludedthatthiswouldbethefinaldesignofthecage(SeefigureC‐7).

Therailingsystem: The railing system was one of the easiestmechanicalpartsof thewhole robot todo. InspiredbyanotherproductfromtheNXTProgramswebsite(SeefigureC‐7), teamMaestrosuccessfully installeda railing system which included the grippingmechanism.Unfortunately,itseemedabittoofragile,and was solidified when the team rebuilt the base(SeefigureC‐8).The liftingmechanism:

The lifting mechanism is the only part whichwent through very minor changes. For the lifting partitself,theteamoptedtogoforafishingwirestring,sinceitisknowntobeverystrong,whichweneedtobeableto lift‐up the whole gripping mechanism plus a fewblocks.Fromtheinitialdesign(seefigureC‐9),onlyonegear and one rimwheel have been added to the lifter.Thesechangeshelpedmaintainthefishingwireinplace(SeefigureC‐10).Thedoor: Initially, theteamwantedtouseasortofplatformtokeeptheStyrofoamblocksinthecage,without falling out. The first designwas too heavy to support the cage and it alsointerferedwiththeascensionofthegripper.

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Thefinaldesignwasmadewhenwemadethefirstcage:Insteadofusingaplatform,theteamoptedtogowitha“door”instead.Thisprovided more stability than the platform and was more easilyinstalled.Wedidnotneedaplatformanymore,sincewedecidedtoliftthegrippingmechanismduringthewholetimeithadpicked‐upablock.Thedoorwasused toprevent theblocks from fallingup‐front(seefigureC‐11)Thefunnel:The funnel is the frontpartof therobot thatserves to guide the block in position for

grabbing. Initially, wemade the funnel very long so it would have avery good reach on Styrofoamblocks (See figureC‐12).However,wefound out it might not be a good idea to make it long, since we

increasedourchancesintohittingacinder block, which would harshlydiminish our chances of gettingmeetingtherequirements.Thus,westillkeptour funnelandonlymadeitshorter(SeefigureC‐13).In conclusion,manymodifications have beenmade tofinally have awinning robot, or sowe thought. In theend, these multiple changes might have been ourdownfall,consideringittookplentyofourtestingtime.However,thewholeteamwasveryhappywiththefinalstructureof the robot, since itwasverysolidandalsovery clean, compared to most of the other competingteams.

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NXTPortAllocation:

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AppendixD:SoftwareDevelopmentOverallstrategyAfterdoingtheinitiallocalisationandtravellingtothecenterofthefirstsquare,ourrobotwasmovingacrossthefieldbytravellingfromthecenterofthecurrentsquaretothecenterofanotheradjacentsquare.TheclassStrategywasresponsiblewithfindingaviablepathfortherobottofollow,usingamodifiedversionofleealgorithm,whichwillbedescribedlater.Aftereachdisplacementtherobotwasdoinga180degreessweep(90towardsrightand90towardsleft)inordertodetectobstaclesandfoamblocksthatitcanpickup.Thesquarescontainingthepositionofthedetectedobstacleswasrecordedinamatrix.Alsothepositionatwhichfoamblocksweredetectedwasrecorded,andafterdetectingthesurroundingobstacles,adecisionwasmadeweatheritissafefortherobottotrypickingthedetectedblocks.Inordertopickablocktherobotwasadvancingtowardsituntilthelightsensordetectsitandstartstheliftingmechanismoruntiladistanceof25cmwascovered.Afterpickingupablock,therobotreturnedtothecenterofthesquareandcontinueditspath.Whenthenumberofblockswasreachingathreshold,therobotwasnotlookingforanyfoamblockanymore,butsimplytravelsafelytothedestination.Incaseanobstaclewasdetectedontheway,theleealgorithm(seebelow)wasaskedtorecalculateanewpath.Atthedestination,therobotdeposedtheblocks,openedthecagedoorandbackedup.ImprovedLeealgorithmTheLeeAlgorithm[1]findstheshortestpathbetweentwopointsina2‐dimensionalmatrix,byavoidinggivenobstacles.Ourversionofthealgorithmwasusing3matrices:thefirsttostoretheobstacles,thesecondtostorevisitedsquares,thethirdtoruntheLeealgorithm.The“Obstacle”matrixwasupdatedwheneveranobstaclewasdetected,andthe“Visited”matrixwasupdatedeverytimetherobotwasdone“visiting”asquare.Incasemorethanonepathofminimallengthexisted,thelee()functionwasreturningtheonethatminimizesthenumberofturnsandchoosesunvisitedsquaresinsteadofvisitedones.Asasafetymeasure,allobstacleswereerasedfromtheobstaclematrixincasenopathtothedestinationwasfound,thentherobotwaslookingagainforadjacentobstaclesandrecalculatingthepath.Ifthedestinationisreachedwithinsufficientblocks,thealgorithmwasgeneratingupto4additionalpathsthattherobotcanfollowstartingfromthedestinationpoint.

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Belowisthestep‐by‐stepproceduresusedintheleealgorithm:1) Initialization - Select start point, mark with 1 - i := 1 2) Wave expansion - REPEAT - Mark all unlabeled neighbors of points marked with i with i+1 - i := i+1 UNTIL ((target reached) or (no points can be marked)) 3) Backtrace - go to the target point REPEAT - go to next node that has a lower mark than the actual node - add this node to path UNTIL (start point reached) 4) Clearance - Block the path for future wirings - Delete all marksGraphicalrepresentationofthealgorithm:

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SoftwareArchitecture:BelowarerepresentationofourclassdiagramsonbothNXTS:Master:

Slave:

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AppendixE:TestingDocumentTest1:Generaltestswiththeultrasonicsensor

Date:March7to10

Conditions:Atestrobotisplacedonanopenfieldinfrontofafoamblockwhichisinclinedatdifferentanglesfromtherobotandatdifferentdistancesfromtherobot.Therobotthenmovestowardstheblockataconstantspeedwhilerecordingtherawdistancevaluesreadfromtheultrasonicsensor.

Results:

Blockfacingtherobot(~0degrees)

Blockat45degreeswithrespecttotherobot:

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Blockat15degreeswithrepecttotherobot:

Throughtheseinitialexperiments,itwasdeterminedthattheultrasonicsensorisabletoreceiveapingfromablockprovidedtheblocksurfaceisfacingtherobot(towithin10degrees).Thisinformationrevealedthatinmanycases,thesensorisincapableasinglevalueshowingtheexistenceofablock.Thusnofiltercanhelptherobotifitslineofsightisnotperpendiculartothesurfaceoftheblock.

Ontheotherhand,ifthelineofsightofthesensorISperpendiculartothesurfaceoftheblock,thenthevaluesreturnedbythesensorarenearlyflawless.

TEST1:Lightsensor‐basedgridlinedetection

When:March5,2011

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Conditions:Thetestrobotisplacedonanopenfield,withitscentreofrotationonanintersection.Itisprogrammedtorotate360degreeswhilecontinuouslyprintingthevaluesentbythesensorafterasimpledifferentialfilterisapplied.

Results:

Therobotobservesalineoncetheabsolutevalueofthedatafromthedifferentialfilterisveryhigh.

Othercomments:Moretestsweretakenusingthisdifferentialfilterontherobot.Therobot,forinstanceissettodriveoverasetoflines(oneofwhichisactuallya“crack”betweenthe4x4squaretiles)atdifferentspeedsandreleasesasoundcuewhenthesensordetectsacrossedline.Thetestswereverysuccessful.

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TEST2:Lightsensorbasedgridlinedetection

When:March14,2011

Conditions:Thetestrobotisplacedonanopenfield,withitscentreofrotationonanintersection.Itisprogrammedtorotate360degreeswhilecontinuouslyprintingtherawvaluesentbythesensortothecomputerconsole.

Results:

Asexpected,asthesensorbeginstosweepacrossaline,thevaluereturnedbethesensorincreasessignificantly.Conversely,whenthesensorsweepsoutofaline,thevaluedecreasesconsiderably.

Sincethevaluesreturnedwerejitteringastherobotwasrunning,arunningaveragefilterwasappliedtothevalues.Furthermore,duetotheunknownlightingconditionsonthefieldduringthecompetition,anadditionaldifferentialfilterwasappliedtothevalues.

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Aftersomemoretesting,itwasobservedthattherobotdefinitelycrossesalineoncethevaluereturnedfromtheaverageanddifferentialfilterssurpasses10.

Othercomments(aftertesting):Wehaveimplementedthefilterabovetoouractualrobotandhaveconfirmeditseffectiveness.Wefoundthattherewasnonoticeablechangeinthedetectionrateoftherobot.Eventually,itwasdecidedthatthelocalizingsensorwilloperatewithadifferentialfilterandwithoutarunningaveragefilter.

TEST3:Lightsensorbasedblockdetection

When:March14,2011

Conditions:Thetestrobotisplacedonanopenfieldwitthafoamblockdirectlyinfrontofit(i.e.thesurfaceofthefoamblockisperpendiculartothe“lineofsight”ofthelightsensor).Therobotisprogrammedtomoveforwardataconstantspeedwhilecontinuouslyprintingtherawvaluesentbythesensortothecomputerconsole.Onceablocksucessfullycontactsthesensor,thetestends.

Anothersimilartestisrepeated,buttheblockisplacedata45degreeanglesuchthatthesensorneverdirectlytouchesthesensor(whichsimulatesablockgettingstuckontheframe).Onceablockcontactstherobot,thetestends.

Results:

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Thegraphaboveshowsthedifferencebetweenthevaluesreadbytheultrasonicsensorwhenablockissuccessfullyenteringtheframeoftherobotandwhenablockgetsstuckontheframe.Astheapprochestheblock,thelightsensorreturnsagraduallyincreasingvalue.Whentheblock’ssurfacecompletelycoversthelightsensor,thevaluereturnedbythesensordropssubstancially.However,iftheblockgetsstuck,thesensor’sreadingdoesnotdecreaseatall(untiltheblockisremovedfromtheframe).

Theprogressionofthevaluesreturnedbythesensorrevealsinterestingthingsaboutthenatureofthesensor.Forone,itwasdeterminedthatthemaximumeffectiveoperatingrangeofthesensor(themaximumdistancefromwhichthesensor’sreturnedvaluecanchange)wasabout15cm.

Othercomments:Wehavecontinuedwithmoretests,coveringcasessuchaswhentheblockslidesalongtheinneredgeoftheframe.Onceblockshavesuccessfullybeendetectedinaconsitentmanner,wefinalisedthefilteringofthelightsensor

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Test5:Ultrasonicobstacledetectionwithmedianfilter

Date:March14,2011

Conditions:Thetestrobotisplacedinthemiddleofthefieldanddirectlyinfrontoftwocinderblockswhichisfacingit.Therobotissettorotatewhilerecordingthedistancereadfromtheultrasonicsensor.Inaddition,amedianfilterisappliedtotherawvaluesgivenbythesensor.

Results:

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Thefollowingsectionwilldescribesomegeneraltestsmadeontherobot:

E‐1:UnitTests

# Category Description Pass/Fail Comments

1 Front“Funnel”mechanism

ManuallyapproachaStyrofoamblockindifferentanglestoseeiftheblockgoesintoapositionwhereitcanbegripped.

Conditional

Theblockwillnotgetstuck,unlessitfollowsasideofthefunnelexactly,butinreal‐time,itisalmostimpossibletoachieve.Eventhough,thiswillbecorrectedinthecoding.

2 Grippingmechanism

UsingtheNXJcontrolfoundintheLejosNXTfolder,wewereabletocontrolthemotorofthethegrippingmechanism,soitcanactuallytakeastyrofoamblock.Then,wemanuallyliftupthemechanism.Werepeat

theprevioustaksuntilthestackofstyrofoamblocksfall.

Pass

Thistextdemonstratedthatwecanonlysupport5blockswithoutmakingthestackfall.

Note:Thisisbeforewe

implementedthecagetosupportmoreblocks

3 Liftingmechanism

UsingtheNXJcontrolfoundintheLejosNXTfolder,wewereabletocontrolthemotoroftheliftingmechanismandthegrippingmechanism,

soitcanactuallytakeastyrofoamblockandliftit.Werepeattheprevioustaksuntilthestackofstyrofoamblocksfall.

Pass

Thistextdemonstratedthatwecanonlysupport5blockswithoutmakingthestackfall.

Note:Thisisbeforewe

implementedthecagetosupportmoreblocks

4

LightSensorFiltering(odometrycorrection)

Testsensoronusualblackline;onwornoutlines;onlineseparatingtwo4x4tiles;withhighambientlight;withlow/noambientlight;

PassThetilebordersaredetectedsuccessfully

5UltrasonicSensor(blockdetection)

Testtheultrasonicsensor’sabilitytopickuppingsfromablockorientedatdifferentangles(0,22.5,45degrees)

FAIL

TheUltrasoniccanonlydetectablockwhenthechirpsbouncedirectlyoffit,255isreturned

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otherwise6 Odometry

Testingdoneusingatestvehicle,beforetherobotconstructionwasready

Conditional Needscalibration

7 OdometryCorrection

8 Navigation

9Inter‐brick

CommunicationSendingstatuses(integers)betweentwobricksusingtheRJ12cables Pass

Needtodefineandidentifythestatuscodes

10PC‐Brick

CommunicationControltherobotusingBluetoothandreceivedata(ex:measurements

fromsensors) PassNeedtotestwithsimilarserveras

inlab5

E‐2:Integrationtests

11Integration

Testing(Demo#1)

Thepurposeofthedemowastoshowthatourmechanicalbuildwasabletopickupatleastonestyrofoamblock.Thisdemonstration

integratesabasiccodeofthetraveltomethod,thegrippingmechanismandtheliftingmechanism

Pass

Ourdemowentverywell,wewereabletomaketherobotmovestraightinlineandpickuptherobotsthatwereinhisway.Itdidpassthe

demo,thoughwestillhadsomedifficultieswhentheyweremorethan1blockto

pickup.

12Cage

implementation

Usingthegrippingandliftingmechanisms,take3styrofoamblocksinarowandseeifeverythingissmoothandtheblocksdonotgetstuck

somewhere.Fail

Theblocksometimesgetsstuckonthebottomofthe

cage,iftheblockissomewhatcrooked.Thus,thegrippingand

liftingmechanismstop

workingcorrectly.

Note:Wethenaddedapieceoneachsideofthe

grippingmechanismtostraightenouttheblocks.

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*Usingthegrippingandliftingmechanisms,take3styrofoamblocksinarowandseeifeverythingissmoothandtheblocksdonotgetstuck

somewhere.

*Afterthepiecewasaddedtothegripper

Pass

Afterweaddedthepiecetostraightenouttheblocks,ineverycase,thegripperandthe

liftingmechanismdidnotgetstuck

13`Styrofoamblock

detection

Usingtherobottester,maketherobotsweepfrom90o to‐90o.Iftherobotfindsablock,makeitadvancehalfthedistanceitseesandmakeit

sweepagain.Then,advanceandcapturetheblock.Fail

14IntegrationTesting

(Demo#2)

Thepurposeofthedemowastodemonstratethestyrofoamblockdetectionofourrobotandmakeitpickatleastoneofblockupandthedropitataspecifiedlocationbytheclient.ThisdemointegratestheUltrasonicSensor,theLightSensor,thegrippingmechanismandthe

liftingmechanismofourrobot.

Fail

Therobotwasnotabletopickupablockby

itselfconsistently

withouthumanassistance(i.e.manipulatingthestyrofoamblocktoputitin

positionfortheUltrasonic

sensorwillseeit)

UltrasonicSensorLocalization

ImplementationoftheFallingEdgeusedinlaboratory4onourmechanizedrobot

Pass

LightSensorLocalization

Maketherobotmakea360turn.Usingthelightlocalizer,itshouldbeabletocorrecttheodometer.Andtheodometershouldshowexactly

wheretherobotis.Pass

15 PathFindingcode

Lee’salgorithmwasimplementedinourrobotandwastestedtoseeifitsuccessfullyfoundthepathtoitsdestination.(SoftwareTest)

Pass

Thistestwasdoneona

matriximitatinga12x12maze.

15 PathfindingIntegration

Therobotwasgivenhardcodedobstacles.IthadtoapplytheLeealgorithmtofinditswaythroughthemaze.

Pass

Therobotsuccessfullyavoidedtheobstaclesandfinditswaytothespecifieddestination

16Styrofoamblock

detection

Usingthemainrobot,maketherobotsweepfrom90o to‐90o.Iftherobotfindsablock,makeitadvancehalfthedistanceitseesandmakeit

sweepagain.Then,advanceandcapturetheblock.

17Obstacle

detectioninitialtest

Puttingtherobotinsideamazewith2obstacles.Therobotshouldfinditswaytothedestination

ConditionalPass

Therobotwasdetectingmoreobstaclesthanthereactually

was.Processwastoolong.

18Odometry

correctionwithaddedheading

Arelativelylongpathwasgivenfortherobottofollow. PassNeedtotrya10minutelongpath

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correction

19

Lee'sAlgorithmimplementation

Atestprogramwascreatedtoverifyifthealgorithmwasimplementedcorrectly,byinsertingvaluesmanuallyfortheobstaclematrixandthenprintingthematrixon

whichtheleewasoperatingandthefoundpath

Pass Manycasesweretried,includingonesinwhichallpathwere

blocked,andhadafewproblemswithrunningintoinfiniteloops,

butthatwascorrected

20

Identifyingobstacles

positionandstoringitintoa

matrix

Robotwasprogramedtomovearoundthefieldandusingthepositionatwhich

obstacleswerefound,updatetheObstaclematrix.Bluetoothwasusedtoprinteachnewobstacleontotheconsole,andthe

completematrixeach5seconds.

Pass Mostdifficultieswereencounteredwhenimplementingformulathatwouldgivethepositioninthematrixofthe

obstacle,giventhecurrentrobotorientation,positionanddistance

readbysensor

E‐3:SystemTests

SystemTest#1:4/03/2011

Test:SendviaBluetoothinitiallocation1withdestinationx:3y:3,noobstacles,4surroundingblocks.

Result:Therobotwenttodestinationandwasabletopickup1blockontheway.Itdepositedatdestination.Cagedidnotopen.TherobotfollowedandLshapedpath.

Comments:Theblockwaspickedupduetotherobot“bumpingintoit”andnotbecauseofblockdetection.


Test:SendviaBluetoothinitiallocation1withdestinationx:4y:4,oneobstacle,5surroundingblocks.

Result:Therobotinitiallyavoidedtheobstacle,butcollidedwithitlaterwhilesweepingnexttoit.Thissetofftheodometerandfailedthetest.

Comments:Therobotshouldbetoldtoavoidalargerareaaroundablockwhennavigatingandsweeping.Probablyaddsurroundingpointstoobstaclematrix.

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Test:SendviaBluetoothinitiallocation2withdestinationx:5y:4,twoobstacles,8surroundingblocks.

Result:Therobotavoidedbothobstaclesandtheywereaccuratelyrepresentedinthematrix.However,rightbeforearrivingtodestinationSlavewentoff.

Comments:Slavewentoffmostprobablybecauseofbatteries


Test:SendviaBluetoothinitiallocation1withdestinationx:5y:4,twoobstacles,8surroundingblocks.

Result:Therobotpickup2blocksanddepositedthematthedestination,offbynearly10cm

Comments:Odometrycorrectionshouldbecalibrated


Test:SendviaBluetoothinitiallocation3withdestinationx:4y:4,twoobstaclesatanangleof45degrees,8surroundingblocks.

Result:Therobotavoidedoneoftheobstaclesbutcollidedwiththeotherone.Noblockspicked.

Comments:Hardtoseeobstacleat45degrees.Perhapsdecreasesweepspeedorimprovefilter

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GlossaryofTermsBlocks:Foamblocks(shouldbestackedatthedestination)theymightalsobereferredtoaspalletsorobjects.Obstacles:Cinderblocks(shouldbeavoided)Brick:NXTBrickSquare:a1footsquaredelimitedbygrid‐linesonthemaze

References[1]C.Y.Lee"Analgorithmforpathconnectionsanditsapplications",IRETrans.Electron.Comput.,vol.EC‐10,pp.3461961.[2]DaveParker“Clawwithgamecontroller”http://www.nxtprograms.com/claw_car/steps.html[3]DaveParker“Forklift”http://www.nxtprograms.com/NXT2/forklift/index.html

ECSE 211 - Autonomous Block Stacking Robot - Project Documentation

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