colin lea mapping and remote operation

8/8/2019 Colin Lea Mapping and Remote Operation

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State University of New York at BuffaloDepartment of Mechanical and Aerospace Engineering

MappingandRemoteOperationofthe

LegoMindstormsNXTPlatform

by

ColinLea

Fundedby

Gustav and Greta Zimmer Research Scholar Award

NSF Research Experience for Undergraduates

Advisor:Dr.VenkatKroviFall2008


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TableofContents Pages

MappingandRemoteOperationoftheLegoMindstormsNXTPlatform

Abstract 3

Chapter1:Introduction 4

1.1Background 41.2FIRSTRobotics 5

Chapter2:Equipmentandsoftware 7

2.1Software 7

2.2RemoteControl 8 2.3Goals 92.4SettinguptheLegoMindstormsNXT 112.5ProgrammingtheNXTinMatlab 11 2.6ProgrammingtheWiimoteinMatlab 12

Chapter3:MechanicalDesign 14

Chapter4:SoftwareDesign 18

4.1VersionHistory 18

4.2FeatureImplementation 21 4.3Modes 28 4.4ObjectAvoidance 34

Chapter5:InternetOperation 37 5.1Server 37 5.2Webpage 38

Chapter6:FinalRemarks/FutureWork 41

AppendixA:BluetoothSetup 42

AppendixB:InternetOperationCode

nxtControl.php 53 update.php 54

DuetolengthofMatlabcode,itisavailableseparately.


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Abstract.

ThisexperiencereportdocumentsmyapplicationoftheLegoMindstorms

NXTroboticplatformandNintendoWiicontrollerwithinMatlabtocreatea

mappingandremotelyoperatedsystem.UsingsensorinputsfromtheNXTIhave

createdasystemtoidentifyobstaclesinfrontoftherobotandstorethemto

memory.Withthisinformation,theNXTiscapableofavoidingpreviouslydetected

obstacles.Mappingisamethodofstoringinformationaboutalocation.Therobot

canbeusedtosurveyanareaandprovidefeedbacktothecomputer.Emphasishas

beenputonuserinput.Itispossibletocontrolusing(1)aNintendoWiicontroller,

(2)agraphicaluserinterface,and(3)viatheInternet.


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Chapter1:Introduction

Creatingarobotfromscratchtakesalotoftime,money,intelligence,and

craftsmanship.Todevelop,manufacture,andcodeawholeplatformbyyourselfis

beyondthescopeofaonesemesterproject.Inordertofocusonasingleaspectof

roboticsonemustisolatetheirareaofinterest.Thiscouldinvolvecreatingarobotic

vehicle,creatingasystemofelectronics,orinmycaseprogrammingamostly

prebuiltroboticplatform.

1.1Background

Therearemanyroboticplatformsonthemarket.Manyofthesearesoldas

kitsthatallowuserstocreatearobotoftheirowndesign.TheLegoMindstorms

NXTandVexRoboticsDesignSystemaresuchplatforms.Includedinthesekitsare

wheels,motors,sensors,connectors,andotherpieces.Thesetypesofkitsenableall

sortsofrobotstobemade.Otherroboticsplatformscanbelessmodular,only

allowingforafewconfigurations.Forexample,theParallaxScribblersbodycannot

bechanged.ItusesaBasicStamp2plussensorstoallowuserstoprogram

movementoftherobot.Differentroboticplatformsaremeantfordifferentlevelsof

controlandfunctionality.

Figure1Lego

MindstormsNXT

Figure2VexSystem Figure3Parallax

Scribbler


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MyprojectstemmedfrominterestintheFIRSTTechChallenge(FTC).Thisis

asixweekcompetitionduringwhichteamsof10highschoolstudentsplusmentors

worktocompeteinaroboticcompetition.TeamsuseaLegoMindstormsNXT,

motors,andotherpartstocreateasemiautonomousrobotabletocarryoutatask.

Mygoalwastogetmorefamiliarwiththesystemandhopefullyactasastudent

mentorforalocalschool.

1.2FIRSTRobotics

ThegoalofFIRSTistogetkidsinterestedinscience,technology,engineering,

andmath(STEM)throughroboticscompetitions.Differentchallengesexistfor

differentages.TheJuniorFIRSTLegoLeague(Jr.FLL)isforages69andinvolves

basicresearchonatopicandmodelingusingLegobricks.TheFIRSTLegoLeague

(FLL)isforages914andinvolvesdesigningandbuildinganautonomousrobot

usingtheLegoMindstormsNXTplatform.Thestudentscompeteinafriendly

competitionwherelearningisstressedoverwinning.TheFIRSTTechChallenge

(FTC)isforhighschoolagedstudentsandislikeamoreadvancedversionofthe

FLL.ItusestheLegoMindstorms,motors,andothermechanicalpiecestocompete

inacompetition.TheFIRSTRoboticsChallenge(FRC)isalsoforhighschool

studentsandusesaNationalInstrumentsCompactRioplatform,motors,andother

partstocreateanautonomousrobot.ThisismuchmorecostlythantheFTC.The


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studentsareexpectedtodotheworkbutadultandstudentmentorsshouldbe

availabletoguideandteach.

Afewproblemssurfacedthatthwartedmyinitialeffortstogetinvolvedwith

theFTC.First,therearenolocalteamscurrentlycompetingtheclosestschoolis

morethananhouraway.Second,thekickoffwasSeptember13thwhichdidntallow

enoughtimetotrytoorganizeateamatalocalschool.

BecauseofmyinitialresearchintoFIRSTIwasalreadyfamiliarwiththe

capabilitiesoftheLegoMindstormsNXTplatform.Combinedwiththelargeuser

baseandplethoraofonlinedocumentationtheNXTwasasuitableplatformtodo

myownresearch.


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Chapter2:EquipmentandSoftware

TheNXThasanopenprogramminginterfacewhichmakesitrelativelyeasy

fordeveloperstointeract.Legooffersasoftwaredevelopmentkit(SDK),hardware

developmentkit(HDK)andBluetoothdevelopmentkit(BDK)ontheofficial

website.Thismeansthatwiththenecessaryskillanyonecanbuildtheirown

languagethatiscapableofworkingwiththeNXTplatform.Developershavetaken

fulladvantageoftheSDKandHDKallowingmuchgreatercapabilitiesandmore

advancedrobots.

2.1Software

OneoftheadvantagesoftheNXTisitslargesupportinthesoftware

community.Independentdevelopersanduniversitystudentshavecreatedmany

programminglanguagesandlibrariestointerfacewiththeNXT.Thesoftware

includedisinadequateforanythingmorethanbasicmanipulationanddata

acquisition.SeverallanguageshavebeencreatedthattakeadvantageofCandJava

libraries.Whiletherearedozensofworkinglanguages,onlyahandfulofthem

continuetohavemuchsupport.SomemorepopularonesincludeRobotC,LeJos,

MatlabandtheLabviewToolkit

Likewise,becauseofLegosopenhardwaredevelopmentkit,companiesareable

tocreateadditionalsensorsandmotorstointegratewiththeMindstormsNXT.

HiTechnic,Vernier,andothercompaniesselladditionaladaptorsforproximity


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detection,orientationandcolorsensing.Vernieroffersmanysensorsforgeneral

dataacquisitionsuchasaflowratesensor,barometer,andthermocouple.Itiseven

possibletocreateyourownsensorsandattachthemusingaconnectoravailable

throughLego.

2.2RemoteControl

WhiletheMindstormsNXTisfullycapableofworkingautonomously,itisnot

alwaysideal.Therearemanysolutionsavailabletoprovidesuchcontrol.However,

usingMatlablimitsthenumberofusablecontrollers.Anyunsupportedcontroller

wouldrequireanewlibrarytobewritten.Therearesomepopulardevicesthathave

lotsofsupportanddocumentationonline.Forconvenience,Ichosesomethingthat

isalreadysupported.

OnepopulardeviceistheNintendoWiicontroller(Wiimote).Itfeaturesan

ADXL3303axisaccelerometer,aPixArtopticalsensorforinfrareddetection,a

directionpad,and7pushbuttons.

ItisalsocapableofconnectingwithaNunchuckcontrollerattachment.This

Figure4NintendoWiimote Figure5NintendoNunchuck


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providesanadditional3axisaccelerometer,ananalogstickfordirectionalcontrol,

andtwopushbuttons.TheWiimotehasgainedalotofattentionoverthelastcouple

ofyears.Whilenothingaboutthecontrolleriscompletelyrevolutionary,its

significanceisinbringingmotioncontrolintotheeyeofthepublic.Becauseofits

compact,capabledesignandinexpensiveprice,theWiimoteisbeingusedinmany

roboticslabsacrosstheworld.Forexample,researchon3Dtrackingfordesktop

virtualdisplayswasrecentlydonebyGraduatestudentsattheHumanComputer

InteractionlabatCarnegieMellon1.

TheuniqueabilitiesalongwithavailableMatlabdriversanddocumentation

madetheWiimoteapracticalchoice.

2.3Goals

AftertinkeringwiththeNXTandWiimoteforaweekorsoIdeviseda

generalgoalforwhatIwantedtoaccomplish.Isoughttotakeadvantageofwhat

bothproductshadtooffer.Ihadexperimentedwiththeaccelerometerdatafrom

theWiimotebutwantedtoimplementsomethingonamorebroadlevel.Iwanted

somethingthatcouldtakeinformationfromtheWiimote,manipulateit,take

informationfromsensorsontheNXT,andcombinethedatainMatlabtoperforma

functionontherobot.Ialsowantedtobeabletotakeinformationfromthe

accelerometerandothercontrolbuttonsontheWiimoteaswellastakeinputfroma

1http://www.cs.cmu.edu/~johnny/projects/wii/


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graphicaluserinterface(GUI)onacomputerallowingforpossiblefuture

developmentusingnetworkingtocontroltherobotfromasecondcomputer.With

allofthedataIwantedtoshowtheuserwhatwashappeningwiththesystemonthe

GUI.

Idecidedtocreateasystemformappingandremotecontrol.Thegoalwasto

createasystemthatdepictedwheretherobotwasinrelationtoobstacles.Themap

isusedtostoreinformationaboutanareasuchasthelocationofobstacles.

Obstaclesshouldbeabletobeinputtedeitherbytheuserordetectedbytherobot.I

wantedthreemodes:

WiiNav:ControlledusingthedatafromtheaccelerometerontheWiimote FineControl:ControlusingthedirectionalpadontheWiimoteorusing

controlsontheGUI.Itallowsfortherobottoturnleft,turnright,goforward

asetdistance,andgobackwardasetdistance.

PointFind:Theuserinputsapointandtherobothastomovetothatlocation Attheendofcreatingthissystem,Idecidedtosetupremotecontroloverthe

Internet.IhadlittleexperiencewithwebdevelopmentsoIlearnedhowtosetupa

server,scriptwithPHP,andcontrolthisinputthroughMatlab.

IstartedwithbasicknowledgeofMatlabfromanintroprogrammingfornon

computerscienceengineerscoursefromfreshmanyear(EAS230).Accomplishing

mygoalsnotonlyrequiredsolvingtheproblemsofcontrollingtheNXTbutalso

learningMatlabingreaterdetail.


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2.4SettinguptheLegoMindstormsNXT

OneadvantagesoftheNXTisitsabilitytocommunicatewithacomputer

overmultipleprotocols.ItispossibletoconnectusingUSBaswellasviaBluetooth.

WithNXTGitispossibletodownloadprogramsdirectlytotheNXTunitusing

eithermethod.BeingabletouseBluetootheliminatesproblemswithwiresand

makestestingmoreconvenient.Unfortunately,currentMatlablibrariesonly

transferdataoverBluetooth.IhadseveralproblemsgettingtheNXTsetuponmy

MacbookPro.DetaileddocumentationofhowIgotittoworkislocatedinAppendix

A.WhileitworkedsporadicallywiththeBluetoothcardinmylaptop,mybest

resultswerewithusingaBroadcamadapter.

2.5ProgrammingtheNXTinMatlab

WhileMathworks,acompanyrenownedforitsexcellenthelpsystem,created

theMatlabNXTlibrary,thereisnotalotofdocumentationabouthowtocontrolthe

robot.Thedocumentationthatdoesexistdoesnotprovideenoughdetailed

information.ItwouldbehelpfultohavepreviousexperiencehandlingCOMports.

ThebestplacetogetstartedisonablogentrywrittenbyaMathworksemployee2.

Basiccontrolsarelistedbelow.

2http://blogs.mathworks.com/loren/2008/06/30/legomindstormsnxtinteaching/


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Function Description

NXT = legoNXT('COM18') InitiatesNXThandle(COM#determinedbytheBluetooth)

Left_Motor = NXT.portB Initiatesvariabletooutputport.OutputportisABorC.

Start(Left_Motor, p) Startsmotorwithpowerpwherepisanumber0100

Stop(Left_Motor) Stopsmotor

Ultrasonic = NXT.port1 Initiatesvariabletoinputport.Inputportis12or3.

set(NXT.Port4, 'type','distance');

Initializeultrasonicsensor

Ultrasonicdata =getdata(nxt.Port1) Getinputdata

2.6ProgrammingofaWiimoteinMatlab

TwoprominentMatlablibrariesfortheWiimotearefWIIneandWiiLAB.

fWIIneisanopensourceprojectthathasntbeenupdatedrecently.WiiLABwas

developedduringasummerundergraduateresearchprogramsponsoredbythe

NationalScienceFoundationatNotreDameUniversity.WiiLABprovidesample

controlthroughfunctionsthatenableaccelerometerdataacquisition,button

readingsandinfrareddetection.Itisalsocapableofgatheringdatafromthe

Nunchuckaddon.


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MfileslocatedintheWiilab_Matlabfolderarewelldocumentedandprovide

enoughinformationtostartusingtheWiimotewithlittleadditionalresearch.Basic

controlsareshownbelow.

Function Description

initializeWiimote() InitializesWiimotes.

isWiimoteConnected() ReturnstrueifaWiimoteisconnected.

[x y z] = getWiimoteAccel() Getsaccelerometerdata.Itisarangefrom10to10.Valuesarereturnedtovariablesxyandz.

isButtonPressed('A') ChecksifbuttononWiimoteispressed(Availablebuttons:A,B,ONE,TWO,UP,DOWN,LEFT,RIGHT,Minus,Plus,Home)


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Chapter3:MechanicalDesign

TheLegokitincludesamanualwithinstructionsonhowtobuildarobot

capableofmovingaroundandswingingagolfclublikeLegopiece.Iputthis

togetherratherquicklysothatIcouldstartsettingitupinMatlab.AtthebeginningI

wasinterestedintheautonomousaspectoftheprojectmorethanthemechanicsof

thephysicalrobot.Therobothadamyriadofsensorsbutdidnothavegreat

mobility.Itfeaturedtwomotorstomovetherobot,onemotortoswingthegolf

clublikepiece,abumpsensoronthebacktostopitifitranintoawall,anaudio

sensorinfronttodetectnoises,alightsensortodetectbrightnesslevels,andan

ultrasonicsensorpointedforwardtodetectobstaclesintherobotsway.I

constructedthisrobotwithoutanyofmyownadditionssoIcouldbegin

programming.

Figure5InitialDesign(http://www.symbian-freak.com)

ProblemsarosebeforeIevenstarteddevelopingmymappingsystem.While

testing,Inoticedthattherobotdidnotturnwell.Itwasinconsistentandwobbled

someofthetime.Thedrivetrainworkedusingtwomotorscontrollingthefront


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wheelsandathirduncontrolledwheelintheback.Unlikeanomnidirectional

wheel,thebackwheelmustbealignedwiththedirectionoftheturninorderto

rotateeffectively.Ifthewheelwasperpendiculartotheturn,themovementwould

notbesmoothandthewholerobotwouldwobble.Insteadofarollingmotionfrom

thewheel,itincreasesfriction,whichcreatesdragonthevehicle.Thisisabig

problembecausethewheelisperpendiculareverytimethattherobotmoves

forwardorbackward.Evenifthewheelisatthecorrectangletoturn,thereare

problemswhentherobotthenhastomoveforward.

Figure6Three-wheeledrobot

Theproblemwasfixedbychangingthewholedesignoftherobot.Ioptedfor

askidsteerdrivetrainandonlyoneadditionalsensor.Skidsteerworksbyisolating

theleftandrightsetsofwheels.Thefrontandbackofeachsideareconnectedso

bothwheelsmovesimultaneously.Thismovesthecenterofrotationinward,


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allowingtherobottoturnonapoint.Thissolutionisnotperfectbutallowsforgood

movementusingonlytwomotors.

Figure7SkidSteerrobot

Normallyaxlesareconnectedwithchainsheldonbygears.TheMindstorms

kitdoesnotcomewithanythinglikethissoIhadtocomeupwithmyownsolution.

Iattachedrubberbandstohubsfixedtoeachaxleandgotdesirableresults.Itdoes

notworkperfectlybutissatisfactoryformyneeds.Rubberbandsoffermoreslack

thanchainsbecausetheonlythingholdingtheminplaceisfriction.Onmyrobot,the

motorsareattachedtothefrontaxles.Byexperimenting,Ifoundthatthefrontand

backwheelsmovedatthesamerateaswhenitwasdrivenbythemotors.Ifyou

manuallyturnthebackwheels,thefrontwheelsmoveataslowerrate.Thisis

becausethemotorsaddagreaterresistanceforcethanthefrictionalforceinthe

rubberbands.


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Inlargervehicles,askidsteerdrivetraincancauseexcessivewobbling.

BecausemyrobothasalowweighttosizeratioIhavenotnoticedsignificant

problems.

Figure8FinalDesign


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Chapter4:SoftwareDesign

Thefinalprogramwastheproductofseveraliterationsofcode.Each

revisionusedanewapproachandbroughtnewinsightintohowtouseMatlabmore

effectively.Iwillbrieflyexplainthedifferentiterationsandthentalkabout

individualcomponentsofthefinalprogram.Adiagramofhowthepartsofthe

systemworkisbelow.

Figure9SystemOverview

4.1Versionhistory

TheprogramstartedfromthecodeIwrotewhileplayingaroundwiththe

NXTandWiimote.Everythingwascrudelyimplemented.Ihadasystemtocontrol

themotorsontheNXTbasedontheaccelerometerdataanddirectionpad(dpad)


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fromtheWiimote.AccelerometerdatafromtheWiimoteandthepositionofthe

robotweredisplayedonseparatefigures.AllofthecodewaskeptinoneMatlabfile,

whichrancontinuouslywiththeuseofawhileloop.

Version2Functionbased

Irealizedhowinefficientandunreadablethecodewasinsomeareas.I

removedmuchofthecodefromthemainMatlabfileandcreatedroutinesthatwere

storedinnewmfiles.Ihadamainwhileloopthatcalledseparatefunctionsfor

differentoperationmodes.Ialsoaddedcommentstothefilesforbetterreadability.

Version3GUIDEbased

Atthispoint,Iwasconcernedaboutoverallusability.Themainstructureof

theprogramhadbeencreatedbutitwasntintuitiveandreliedonthecommandline

forrelayinginformationtotheuser.Ispentalotoftimelearningabouthowto

createGUIsinMatlabsoIcouldcreateoneunifiedinterface.MatlabsGraphicalUser

InterfaceDesignEnvironment(GUIDE)helpssimplifythecreationofGUIs.It

includedseveraltypesofbuttons,sliders,andothercontrolsthatallowtheuserto

interfacewiththeprogram.


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Theproblemwiththiswasthatitrequiredacompleteoverhaulofmycode.

Itworksbyrunningcallbackfunctionswheneverabuttonispressed.Thereisa

functionforinitializingvariablesandcommandsandthentheprogramrunsthrough

therestofthecoderepeatedlyuntilitisstopped.Insteadofrunningthrougha

whileloop,checkingwhethercertainmodeshavebeenselected,theprogramis

interruptedbybuttonpresses.Mybiggestproblemwasallowingforcontrolthrough

theWiimoteandonscreenatthesametime.IcouldntpolltheWiimoteusinga

whileloopbecauseitwouldessentiallystoptheprogramfromprocessingother

information.Thisrequiredtheimplementationofatimer.Atimerissettoruna

certainfunctionatasetinterval.Forexample,mytimerchecksforWiimotebutton

pressesevery0.5seconds.

Version4InternetControl

Figure10GUIDesignEnvironment


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ThelastrevisiondealswithremotelyaccessingtherobotovertheInternet.I

setupaserverinWindowsthatcanbeaccessedfromanyInternetconnection.This

isdiscussedindetailinchapter6.

4.2FeatureImplementation

4.2.1Handle

ThehandleisthebasisofanygraphicaluserinterfacecreatedwithGUIDE.It

actsasastructureforallinformationintheinterface.Inmyprogram,everythingis

storedinthehandleincludingthemap,robotinformation,andbuttondata.The

storedvariablesareinthetablebelow.

Variable Description

clearMap Button:ClearscurrentmapMap Plotofmap

DistanceText Text:showsvalueofdistanceslider

DistanceSlider Slider:Controlsdistancerobottravels

Turn_Right Functionforturningright

Turn_Left Function

text10 Text:Xposition

ExitMode Function

Heading Text

Ypos Text

Xpos Text

WiimoteControl Function

ExitProgram Function

RIGHT Button:

LEFT Button:DOWN Button:

UP Button:

text5 Text:RobotPosition

text11 Text:Yposition

text3 Text:Distance

Ultrasonic Plot

WiiY Plot

text2 Text:YAxis

text1 Text:XAxis


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WiiX Plot

internet_mode Function

PointFind_indicator Indicator

Internet_indicator Indicator

WiiNav_indicator Indicator

Point_Find_Mode Function

NXT_Connected_indicator Indicator

Wii_Connect_indicator Indicatortext4 Text:WiimoteConnection

text6 Text:NXTConnection

output Unusedpartofhandle

MODE Variable:1forWiiNav,2forFineControl,3forPointFind

EXITPROGRAM Variable1onexit,0whilerunning

NXT_Connect Variable:trueifNXTisconnected

Lmotor Variable:Storestheporttheleftmotorisattachedto

Rmotor Variable:Storestheporttheleftmotorisattachedto

wii:[1x1Wii] Wiistructure;includesaccelerometerdata

map_length Variable:previouslydefinedlengthofmap

map_height Variable:previouslydefinedheightofmap

robotX Variable:CurrentXcoordinate

robotY Variable:CurrentYcoordinate

robotH: Variable:Currentheading

object_Up Avoidance:1ifobjectabovetherobot

object_Down Avoidance:1ifobjectbelowtherobot

object_Left Avoidance:1ifobjecttoleftofrobot

object_Right Avoidance:1ifobjecttorightofrobot

object Avoidance:1ifobjectwithinsurroundingareaofrobot

Clk Variable:storesprevioustime;usedtofindchangeintime

T Timer:Getsdatafromwiimoteandrunswiifunctions

internet_timer Timer:Getsinformationfrom

timeInit Variable:Getscputimeatinitialization

Theprocessofusingthehandleduringacallbackisunique.Atthebeginning

ofthecallbackitmustbereassignedtoanewvariable.Togettheinformationyou

mustusethefunctionhandles = guidata(hObject).Variablescanthenbe

accessedintheformathandles.[variable].Forexample,theXpositionofthe

robotwouldbehandles.robotX.Attheendofthecallbackthehandlemustbesaved

usingthefunctionguidata(hObject, handles).

4.2.2Initialize

AtthebeginningoftheprogramtheNXT,Wiimote,timer,map,andvariables

mustbeinitialized.Theseareallassignedtothehandletobestoredforlateruse.


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FortestingpurposesthereneededtobeawaytousetheprogramwithouttheNXT

orWiimoteconnected.Withoutsomemethodofdetection,thereisanerrorandthe

programstops.IftheNXTisdetected,motorsandtheultrasonicsensorare

initialized.Ifitisnotthemotorsmustbesettodummyvalues.

tryNXT = legoNXT('COM16'); %try to initialize the NXThandles.Lmotor = NXT.portB; %assign ports to left and right motorshandles.Rmotor = NXT.portC;handles.NXT_Connect = 1; %used to check for NXT in routines

set(NXT.portB, 'StopType', 'brake'); %motors stop immediately%instead of coming to a rolling stop

set(NXT.portC, 'StopType', 'brake');

set(NXT.Port4, 'type', 'distance'); %initialize ultrasonic sensor

start(wii.Lmotor, 0); %initializes motors to a speed of 0start(wii.Rmotor, 0);

catch E1 % if the NXT is not connected set dummy variablesdisp('NXT not connected')set(handles.NXT_Connected_indicator, 'BackgroundColor', 'r')

handles.NXT_Connect = 0;handles.Lmotor = 0;handles.Rmotor = 0;

end

ThecommandinitializeWiimote()takescareoferrorsanddoesnotcause

anyproblems.Othervariablesareassignedinthefollowingformat.

handles.wii = Wii(handles.Lmotor, handles.Rmotor, 2, -4);handles.map = Coordinates(70, 50, 30, 10); %(Size X, Size Y, X robot

position, Y robot position)


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4.2.3Map

Figure11GUIoverview

TheMapisarguablythemostimportantpartoftheGUI.Itisusedtoshow

wheretherobotis,whereobstaclesare,andwheretheboundariesare.Allofthe

informationforthemapiscontainedinadoubleindexedarraywithapredefined

widthandheight.ZeroesandOnesareusedtoidentifywhereobstaclesarelocated.

Themapisprintedtothescreenusingtheplot()command.Thewholemapisonly

printedatthestartoftheprogramandwhentheClearMapbuttoniscalled.

Wheneveranobjectisfoundortherobotmovesthemapsarrayismodifiedbut

onlythenewpointisplotted.Thissavesprocessingtimebecausethemapdoesnt


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havetoreloadeverytimeaneweventoccurs.Bluediamondssignifyobstaclesand

bordersandredcirclessignifythepositionoftherobot.Previousrobotstates

remainshowntoremindtheuserwheretherobothasalreadybeen.

Whiletesting,oneannoyanceIfoundwasresettingtheprogramwhenever

themapbecameclutteredorImovedtherobot.InordertoclearthemapIhadto

exittheprogramandrestart,aprocessthattakesatleast10seconds.Thiscanbea

hindrancetoanybodyplayingwiththerobotinmultipleenvironmentsortestingit

withdifferentobstaclesorindifferentscenarios.ThisiswhyIincludedthefunction

ClearMap.Thisbuttonzeroesthemapsarray,addsanewborder,andredraws

themap.

Obstacleavoidanceisoneofthemainreasonsforcreatingthemapping

system.WhenIdidnthavetheNXTconnected,Ineededawaytotestiftherobot

couldsuccessfullyevadeobjects.Ialsothoughtitwouldbeusefultobeabletoadd

knownobjectstohelpeliminateerrorsintheobjectdetectionsystem.Iwanteda

systemthatwasquickandintuitivetoaddobjectsonthefly.ThemethodI

implementedallowsyoutoclickanywhereonthemapanditwillimmediatelyadd

anobjectinthatlocation.Whenyouclick,thefigure1_WindowButtonDownFcn()

callbackisinitiated.Itgetsinformationfromthefigurewindowtofindtheposition

ofthemouseonthemap.Thisvalueisturnedintoanintegertobestoredinthe

mapsarray.Thepointisthenplottedinthefigure.


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pos = get(H.Map, 'CurrentPoint');x = uint8(pos(1)); %uint8 used to get integer valuey = uint8(pos(1,2));H.map.map(x, y) = 1;plot(H.Map, x,y, 'bd')

OnefeatureIwouldliketoseeaddedisanexpandablemap.Currentlywhen

therobotgoesoutsideoftheboundary,itcreatesanerror.ThisisthereasonIadded

boundarymarkers.Anewnumberingsystemwouldhavetobeusedbecausean

arraydoesnotacceptnegativenumbers.

4.2.4Datagraphs:

ThegraphsprovidevisualoutputofdatafromtheWiimote.Itisusefulfor

testingandmonitoringinputs.Itdisplaysthelast10secondsofdata.Originally,I

plottedtheXandYvaluesfromtheWiimoteandtheUltrasonicdatafromtheNXT.

TheUltrasonicdatadidnotappeartobeusefulsoIreplaceditwiththeZvalues

fromtheWiimote.TheZdataisnotcurrentlyusedbutmightbeinthefuture.

Figure12GUIgraphs


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4.2.5Timer:

ThetimerisusedtochecktheWiimoteforinformationevery0.5second.If

theA,B,orOnebuttonsaretriggereditswitchesthemode.Ihadtrouble

settingthetimerup.ThefunctionIusedwashandles.T = timer('TimerFcn',

@(h, ev) timer_callback(hObject, eventdata),'execution', 'fixedRate',

'Period', .5). Itmustthenbestartedusing start(handles.T). Myproblem

hadtodowiththeinputarguments.Thetimerchecksforthecurrentmodeandruns

WiinavandFineControlwhennecessary.Whentheprogramquitsthetimermust

bestoppedanddeletedusingstop(handle.T)anddelete(handle.T).

4.2.6OtherGUIElements:

Severalindicatorsareinplacetoincreaseusability.Whenamodeisselected,

thecorrespondinglightturnsfromredtogreen.Thisdesignaspectissimplyusedto

remindtheuserofthecurrentmode.Therobotspositionisalsousedtogivean

exactlocationsotheuserdoesnthavetoestimateavaluebasedonthemap.

TheExitProgramcallbackstopsrunningprocessesanddeletesthefigure.

Itchangesthehandle.MODEto0whichstopsothermodesfromrunning.Itstops

anddeletestimersthatotherwisewouldcontinueinthebackground.


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4.3Modes:

4.3.1Wiimotecontrol

ControllingtheNXTthroughtheWiimotewasoneofmyfirstgoals.Using

Wiilab,itwaseasytoacquiresensordatafromtheWii.Iwantedtobeableto

controltherobotusingbothaccelerometerdata(allowingtheusertotiltthe

controllertomove)andmovebypressingdirectionsonthedpad.Becausethere

aremultipleoptionsthereneedstobeawaytoaccesseachmode.Every0.5seconds

MatlabpollstheWiimoteforbuttondata.

IftheAbuttonispresseditenablesWiiControlMode.Whenthisis

enabled,MatlabrepeatedlypollstheWiimoteforaccelerometerdata.Figuringout

howtobestusetheaccelerometerdatatooklotsoftesting.Manywaysof

manipulatingtheNXTmotorswiththisdatamakesmovementawkwardorunstable.

Forexample,ifyouusetheXaxisaccelerationforturningcontrolandYaxisfor

forward/backwardcontrolsitisnoteasytogostraight.Itishardtokeepyourhand

steadyenoughthatyoudontdrifttotheleftorright.TocounterthisIimplemented

thresholdstotheturningspeeds.IftheXvalueisbelowathresholditisdisregarded

andifitisabovethethresholditaddsthevaluetooneofthemotors.Thethreshold

is6onascaleof019.6(2*Gravity).

Whengoingstraight,thepowerofbothmotorsissettovel_R = vel_L =

Wii.Y_value*y_multiplier.Theymultiplieris4andwassetempirically.Thex

multiplieris2.Therobotslocationonthemapischangedwiththefunction

H.robotX = (H.robotX + v*cosd(H.robotH)*dt) where vistheaveragevelocity


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oftheleftandrightmotors, cosdreturnsthecosineofthefunctionindegrees,and

dtisthetimesincethelastfunction.

Whileturningleftthepowerineachmotorisgivenbyvel_L =

(Wii.Y*y_multiplier) + (Wii.X*x_multiplier - 6)) and vel_R =

Wii.Y*y_multiplier.Turningrightisthereverse.

Whileturning,thechangeinangleiscalculatedbydh = atand((vel_R-

vel_L)/width) thisisaddedtothecurrentanglebythefunctionH.robotH =

mod((H.robotH + (dh*dt)), 360).Theuseofmodreducestheangletoavalueof

0359.ThisangleisusedtofindthenewXandYcoordinatesoftherobot.

OneproblemwithWiiControlModepertainstothemappingsystem.

BecausetheNXTcanmoveatanyangleandatanyspeed,therearesometimes

problemswheretheactuallocationoftherobotdriftsfromthemappedlocation.

Figure13GeometryforChangein

Heading


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Thisisinpartduetowheelslippageanderrorsvarywiththefloorssurface.Adding

adigitalcompasscouldhelpeliminatepartofthisproblem.

IftheOnebuttonispresseditenablesFineControl.Inthismode,users

canmovetherobotforwardorbackwardorturnitleftorrightusingthedpadon

theWiimote.AswithWiiControlMode,MatlabrepeatedlypollstheWiimotefor

buttonpressesfromalldirectionsonthedpad.WhenpushingUporDownthe

robotmovesadistanceof5centimeters.LeftorRightturnstherobot90degrees

counterclockwiseorclockwise.Thisusesthesameroutinestalkedaboutlaterinthe

FineControlsection.

Regardlessofwhichmodeitsin,MatlabalsopollstheBbutton.TheB

buttonisusedtoexitamode.WhileinWiiControlModeexitingimmediatelystops

theNXT.WhileinFineControlthepreviousactionisfinishedbeforestopping.

4.3.2FineControl:

ThismodeacceptsinputfromtheGUIandWiimote.Itsuseittoaccurately

movetherobotadefineddistance.Bydefault,therobotmoves5cmatatime.This

canbechangedwithasliderontheGUIbutisunchangeableviatheWiimote.


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Figure14DistanceSlider

OntheWiimote,thedpadcontrolsarerelative.TheUpbuttoncallsthe

forward()function,Downisbackward(),Leftisturn_Left,andRightis

turn_Right().Forexampleiftherobotisturnedleft,pushingUpwillmoveittothe

leftonthemap.OntheGUI,controlsareabsolute.Eachbuttonrunsitsowncallback

function.Theorientationischeckedandifitisnotfacingthedirectionchosenthenit

turnsleftbeforemovingforward.

% --- Executes on button press in UP.function UP_Callback(hObject, eventdata, handles)

H = guidata(hObject); %handlewhile (H.robotH ~= 90) %if the heading isnt 90 degree turn left

H = turn_Left(H);end

H = forward(H); %move forwardplot(H.Map, H.robotX, H.robotY, 'or') %plot the new location

guidata(hObject, H); %save the handle

Becauseitisnonholonomic(meaningitcanonlymoveinthedirectionthat


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itispointed),anytimetherobotmovesadistanceitmustusetheforwardor

backwardfunction.forward()andbackward()getthevaluefromtheDistance

slidertodeterminehowlongtoturnthemotorsonfor.Onmytestingsurfacethe

timefunctionwasdeterminedexperimentallytobetime = .094*distance.The

multipliervariesdependingonthefloorstexture.

4.3.3PointFinding:

InPointFindingmode,theuserinputsapairofXandYcoordinatesand

thentherobotmovestothatlocation.Itusesabasicalgorithmtofindthenewpoint.

Thegeneraloutlineofthealgorithmisasfollows.

while (H.robotY ~= H.yInput) || (H.robotX ~= H.xInput)% ^ while the robot isnt at this location, do the following

%if point is higher than current robot position:if (H.yInput > H.robotY) && H.object_Up == 0

while (H.robotH ~= 90) %while not facing up, turnH = turn_Left(H);

end

H = forward(H); %move forward

%if point is lower than current robot position:elseif (H.yInput < H.robotY)&& H.object_Down == 0

while (H.robotH ~= 270) %while not facing down, turnH = turn_Left(H);

end

H = forward(H);

%if point is more left than current robot position:elseif (H.xInput < H.robotX)&& H.object_Left == 0

while (H.robotH ~= 180)%while not facing left, turn

H = turn_Left(H);endH = forward(H);

%if point is more right than current robot position:elseif (H.xInput > H.robotX)&& H.object_Right == 0

while (H.robotH ~= 0)%while not facing right, turnH = turn_Left(H);

endH = forward(H);

endend


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Oneknownproblemisthepossibilitythattherobotcangetcorneredinto

obstacles.Theproblemoccurswhenthereareobjectsonthetwofacesclosesttothe

endpoint.Furtherinvestigationintoabetteralgorithmwouldprovidebetterresults

andfewerproblems.Intheimagebelow,theprogramhascrashedbecausethereis

nowayfortherobottogo.

Figure15PointFindError


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4.4ObjectAvoidance:

Avoidanceisimplementedwithafunctionthatisruneverytimetherobot

moves.Itspurposeistopreventtherobotfromrunningintoobstacles.Itchecksa

squareareaequaltotwicethetraveldistanceplusoneinlengthandwidth.By

defaultthisisan11x11centimeterarea;therobotmovesfivespacesatatimeand

5x2+1=11.Thefunctionchecksforanynonzeronumberinthemapsarray.

Becauseonlyobjectsinthewayoftherobotspathneedtobeavoidedthereneedsto

beawaytodifferentiatewhichobjectsmatter.TodothisIaddeddifferentzones

withintheavoidancefunction.Theimagebelowshowsthefourzones.Inthecode,

thezonesarehandle.object_Left, handle.object_Up, handle.object_Right,

and handle.object_Down.Inthisexampleobject_Left, object_Up,and

object_Rightequal1.Wheneverthereisanobstacleanywherewithinthezonethe

valueis1,otherwiseitsvalueis0.

Theavoidancefunctioniscalledbeforeeverymovement.Thecallislocated

intheforward,backward,turn_left,andturn_rightmfiles.Mycontrolsystemis

basedontherobotscurrentheadingwhichcreatedproblems.Initiallyiftherewas

anobstacleabovetherobotandyouweremovingright,thesystemwouldthinkthe


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objectwasinyourway.Thesystemwastreatingtheforwardandbackward

commandsasabsolutedirections.TofixthisIusedaswitchinbothoftheroutines.

switchhandle.robotH %robotHistherobotsheadingindegrees

case{0,360}

obj=handle.object_Right;

case90

obj=handle.object_Up;

case180

obj=handle.object_Left;

case270

obj=handle.object_Right;

otherwise

obj=handle.object;

end

Thevariableobjisassignedtothedirectionoftherobot.Thiswaythe

commandisonlycheckingforobjectsinthewayofitspath.

OnethingIwouldliketoseedoneisbetterintegrationwiththepointfinding

function.Currentlytheavoidancefunctioniscalledeverytimetherobotmoves.If

thereareobstaclesinthewayoftherobotspath,itmustavoidthem;thisincreases

thetimeittakestotraveltotheendpoint.Ifavoidancewascalculatedbeforeany

movementthenitcouldchoosetotakeamoreefficientpath.Intheexamplebelow,

thereddottedpathshowsthecurrentpaththerobottakestomovetopoint(60,40).

Thegreenlinedepictsabetterpathusingonly90degreeturns.Theyellowlineis

theoverallmostefficientpath.


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Figure16OptimalPath


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Chapter5:Internetcontrol

AftercompletingthestructureoftheMatlabprogram,Iponderedtheideaof

controllingtherobotovertheInternet.Ihadlittleexperiencewithweb

developmentsotheenddesigncomesfromasomewhatbasicapproach.Duringthe

process,Ilearnedhowtocreateawebserverhostedonmylaptopandhowtouse

HTMLandPHPtocreatescriptsforaccessingandwritingdatatofilesand

controllinguserinput.

5.1Server

ApacheHTTPServerisanopensource,commercialgradeimplementationof

anHTTPwebserver(http://httpd.apache.org/ABOUT_APACHE.html).Itisfreeand

easytosetupforWindowsandLinux.Itrunsinthebackgroundandallowsanyone

toconnecttofileshostedonmycomputerovertheInternet.

PHPisascriptinglanguageforwebdevelopment.Thesescriptscanbe

executedbybuttonpressesorotherinputsfromawebpage.WithPHPitispossible


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towritetofilesonthehostcomputer.Inordertoenablethesescripts,PHPmustbe

installedontheserver.IfollowedthisguideforsettingupApacheandPHP

(http://thecodecentral.com/2007/03/24/settingupyourownwebserverwith

apachehttpserverphpandmysqlonawindowsmachine#change_dir).

5.2Webpage

IwantedtherobottomovewithinputovertheInternet.Iaddedtwo

functions:FineControlandPointFind.UsingHTMLIaddedbuttonsforUp,

Down,Left,Right,aswellasXandYinputsforPointFind.Totherightof

thecontrolsisaprintoutoftheGUIfromMatlab.


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Eachofthebuttonsopensupdate.phpandpoststhedirectionorcoordinates

selected.update.phpreadstheactionandrewritestextfileupdate.txtintheservers

directory.Anexampleofoneofthebuttonsisbelow.

TheInternetModebuttonontheMatlabGUIstartsatimerthatchecksthis

fileeverysecond.Theformatofthefileis[U][D][L][R][X][Y][Comment]

[Timestamp].IftheDownbuttonispushedthetextmightread01000000(UP,

DOWN,LEFT,RIGHT|X,YCOORD)1231101682.MatlabwouldthenruntheDown

buttonfunction.Thefunctionsaveas(H.Map, 'C:\...\htdocs\map.jpg') printsa

JPEGimageoftheGUItoafileontheserver.


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Refreshingtheimagefortheuserbecameaproblem.Duetotheway

websitescacheimages,theGUIdidntupdateaftereverymovement.Acombination

ofsolutionsprovidedonwebforumsfixedtheissue.IsetJavascripttoruna

functionthatreloadstheimageafter2seconds.Ihadtotrickthepageintothinking

itwasloadingadifferentimagebyappending?r=1totheURLoftheimagewhenit

isfirstloadedand?r=2whenitisreloaded2secondslater.Theletterris

arbitrary.

function reloadPage()

{document.images[0].src="map_old.jpg";document.images[0].src="map.jpg?r=2";}

setTimeout('reloadPage()', 2000);


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Chapter6:FinalRemarks/FutureWork

OverthecourseofthisprojectIhavebecomemuchmoreproficientatMatlab

andhaveabetterunderstandingofhowtomixhardwareandsoftwareforremote

operationofarobot.Ithinkithasgivenmesomeofthebasicskillsnecessaryfor

moreadvancedresearch.InthefutureIwouldliketoexpandonthiswork,possibly

implementingthefollowingideas:

AttachaWiimotetotherobot.Thisallowsfordeadreckoning,whichwouldgivemoreaccuratelocationinformation.

ImplementabetteralgorithmintoPointFindmodesotherobotdoesntgetstuckbehindobstacles.

FurtherrefinethewaytherobotmoveswhilecontrollingitwithaWiimote. UseotherNXTsensorstodetectotheractionssuchassound. Obtainadigitalcompass(availablethroughHiTechnic)formoreaccurate

control.

UseanadditionalWiimotetocreatea3Dmappingsystem. Useadditionalrobotstosimulatearobotcollective.

Creatingthissystemhastakenalotofworkbuthasbeenafunexperience

andhassolidifiedmyinterestsinrobotics.Thecombinationofmechanicaland

computerengineeringhaslongintriguedme,butuntilnow,Ihavehadlittle

experiencemixingthetwo.Ilookforwardtodoingmoreworkinthisarea.


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3.1.2ConnectingOSX

ConnectingthroughOSXisrelativelysimplecomparedtoWindows.Before

tryingtoconnect,youmustcloseanypreviousconnectionswiththeNXTthatyou

mighthavewiththatcomputer.Afterclosinganyconnections,youshouldresetthe

NXTbeforetryingtoconnectagain.

ToconnectyoumustfirstopentheBluetoothdeviceswindow,whichcanbe

foundinsystempreferences.ClickSetUpNewDevice


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ClickContinueandthenselectAnyDevicewhenaskedwhatdevicetype.Onthe

nextscreenselectNXTandclickcontinue.

OntheNXTitwillaskforapasskey.Itshoulddefaultto1234.Clickthe

orangebuttonforOK.Itwillthenaskforthepasskeyonthecomputer.Ifyouchose

anythingotherthan1234youwillhavetorepeatthepasskeyontheNXT.

ClickcontinueonGatheringmoreinformation.Thenextscreenwillsayit

cannotfindanyinformationaboutthedevice.Thisiscorrect.

YoushouldnowbepairedwiththeNXT.Thisisnotthesamethingasbeing

connected.Atthispointyoucannotcommunicatebetweentheplatforms.

Connectingrequiresonemorestep.IntheBluetoothwindowonyourcomputergo

toEditserialports


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Clickthe+toaddaserialout.BydefaultthedeviceserviceshouldbeDevB.

Ifitisnot,changetheservicetype.


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TocheckinformationabouttheNXTthereisaprogramcalledNXTBrowser6.

Thisgivesinformationsuchasbatterylifeandfirmwareversionaswellasitallows

youtorunbuiltincommandsontherobot.

IfyougetaLineisBusyerrorontherobotitmeansyoudidnotsetitup

correctlyinOSX.Itmaystillworkintermittentlybutoccasionallyyoumayface

connectionerrors.

3.1.3ConnectingWindowsXP

ConnectingthroughWindowsXPgivesmoreproblemsifyoudontdoit

correctly.Whiletheconnectionmayworktemporarilyevenifyoudontdoitright,it

ismorepronetoflakingout.ToconnectyoumustuseeitherWindowsnative

BluetoothdriversorifyoucompanysupplieddriversifyouhaveaWidcommor

BroadcomBluetoothadapter.

Undermytestsetup(runningWindowsXPthroughVMwareorBootcamp)

connectingcanbetrickyandinconsistent.Thereislittledocumentationonline

aboutusingtheNXTwithVMwareandafterspendingmanyhours,Istillhave

problems.Thereareseveraldifferentmethodsthatwhencombinedwillusually

work.

6http://web.mac.com/carstenm/Lego/NXT/NXT.html


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StartbyclosinganyconnectionsinBluetoothDevicesontheNXT,resetting

theNXTandclearinganypreviousNXTBluetoothdevicesfromtheBluetooth

ControlPanelinWindows(whichcanbefoundinthesystemtrayorinthecontrol

panel).

OnWindows,inBluetoothDevicesclickaddundertheDevicespanel.

CheckMydeviceissetupandreadytobefoundandclickNext.

TheNXTshouldshowupasanewdevice.SelectitandclickNext.Ifitisnot

listedmakesuretheNXTisturnedonandclicksearchagain.


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Next,selectUsethepasskeyfoundinthedocumentationorLetmechoose

myownpasskey.Eithermethodshouldwork.Enter1234asthepasskey.


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2)InBluetoothDevicesselecttheCOMPortspanel.Thereshouldbetwo

connectionsOnethatisoutgoingandonethatisincoming.

IftheoutgoingismissingthengotoAddatthebottomofthewindow.Select

OutgoingandchangethedevicetoNXTinthedropdownmenu.ChooseDevBand

clickOK


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3)GotoBluetoothontheNXTandselectsearch.Youshouldseeyourcomputer

onceitsdonesearching.Selectitandchoseanynumber.ItshouldsayConnecting.

OnceitisdoneitwilleithersayFailed,Lineisbusy,oritwillreturntocomputer

selection.

IfitreturnstothecomputerselectionscreenitmeansthattheNXTis

connected.YoucanchecktheconnectionbygoingbacktoBluetoothontheNXTand

selectingConnections.

IfitsaysFailedresettheNXT,deletetheconnectiononthecomputer,and

tryagain.

IfitsaysLineisbusythenitcanmeanacoupleofthings.Itmayactually

workwiththecomputer.Ifthisisthecaseyoushouldtestusingavailablesoftware.

Ifitdoesntworkthenyouneedtotrysomethingelse.Acombinationoftheother


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solutionsmaywork.Inthiscase,theNXTusuallydetectsthecomputerbutis

missingavalidconnection.

TousetheconnectionwithotherprogramsgototheCOMPortspanelin

BluetoothDevicestocheckwhichportisoutgoing.Thisportisneededtosend

commandstotheNXT.

3.1.4Bluetoothremarks

IfyoustillcannotgettheNXTtowork,searchonline.Therearedozensof

webpostsdedicatedtoconnectingtheNXToverBluetooth.Manygounsolvedbut

readingthroughthemmayprovidenewproblemsolvingtechniques.Makesureyou

areusingtherightdriversandhaveacompatibledevice.Ihavefoundcertain

methodswillonlyworksomeofthetime.Accordingtoonlineposts,ifyouhavethe

NXTGsoftwareitissomewhatsimplertosetup.Thissoftwareonlycomeswiththe

consumerNXTset.Itisavailableforabout$50fortheusersoftheEducationalkit.

BluetoothontheNXTisfarfromperfectandasidefromusingitwithLegosown

NXTGdoesnothavethebestsupportfromLego.

Itisworthnotingthatonceyougetaconsistentconnectionyoumaynever

haveproblemsagain.Ikeptthesameconnectionforoveramonthwithno

problems.


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AppendixB:InternetOperationCode

nxtControl.php

NXT Control

X:Y:


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function reloadPage()

{document.images[0].src="map_old.jpg";document.images[0].src="map.jpg?r=2";}

setTimeout('reloadPage()', 2000);


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update.php

Used:update.php?action=Up,update.php?action=Down,update.php?action=Left,

update.php?action=Right,andupdate.php?action=coord&X=x&Y=y

NXT Control


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if (strlen($X) == 1) $X = ("0" . $X); //make sure the number has2 digits

if (strlen($X) > 2){$length = strlen($X);$X = $X($length-2) . $X($length-1);}

if (strlen($Y) == 1) $Y = ("0" . $Y);if (strlen($Y) > 2)

{$length = strlen($Y);$Y = $Y($length-2) . $Y($length-1); // /keep digits}

$directions = '0000 ';$coords = $X . ' ' . $Y . ' ';

$comments = '(UP, DOWN, LEFT, RIGHT | X,Y COORD)';$writethis = $directions . $coords . $comments . $time;

}

else{echo "no action data";}

fwrite($file, $writethis);fclose($file);

header("location: nxtControl.php");

?>

colin lea mapping and remote operation

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