机器人编队Word下载.docx
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ECE575
ByFanYangandTheodoreElhourani
1.Problemstatement
Fromourpreviousexperienceintheareaofroboticswehavelearnedthatthedevelopmentofintelligentcontrolsisatedioustaskrequiringintensiveexperimentation.Tolocateflawsinthebehaviorofamultiagentsystemthesameexperimentmayhavetoberepeatedseveraltimesunderthesamesettings.Inadditiontodiscoveringflaws,simulationisprovedtobeahelpfulandaffordabletoolintheprocessofevaluatingvariousroboticsettingssuchashybridandhomogeneoussystems.Inthisprojecttheproblemofformationcontrolandcollaborativeobstacleavoidanceofahybridroboticsystemisaddressed.
Sixrobotsaretotravelinaknownenvironmentandtopassthroughtunnelsoftheshapegiveninfigure1whilekeepingaformation.
Fig.1Shapeofthetunnelthattherobotwillgothrough.
Ifthecurrentformationcannotpassthroughthetunnelthentherobotsarerequiredtoautonomouslyswitchformation.Forinstance,ifthecurrentformationistriangular(seeFig2.)andthebaseofthetriangleislargerthanthewidthofthetunneltherobotswillneedtoswitchintoeitherformations2and3.
1.Triangularformation
2.Rectangleformation
3.Lineformation
Fig.2.Thethreepossibleformations
Itisdesirabletomaintainthemostcompactformationwhenevertheconstraintsoftheenvironmentallowit.Thetriangularformationisidealhowevergeometricalconstraintsoftheenvironmentsuchasthetunnelwillrequirethesystemtotemporarilyswitchintoalineformation.Aftertherobotsleavethetunneltheyarerequiredtoswitchbacktothedesiredtriangularformation.Formationbehaviorsallowbettersensorfusionandsharingofresources.Inotherwords,dependingonitspositionintheformationarobotcanconcentrateitssensingresourcesononepartoftheenvironment,whileotherrobotsconcentrateontheremainingparts[1].
Inthisprojectwewillshowhowrobotscanmaintainthreegeometricalformationswhilenavigatinginthefreespace.Alsowewilladdresstheproblemofswitchingformationsinordertosatisfygeometricalconstraintslikethetunnel.
2.GeneralDescriptionoftheSystem
Inthissectionwewillgiveageneraloverviewofthesystem.Thesystemconsistsofsixrobotsnavigatingina2Dspaceinaleaderfollowermotion.Hence,theroboticsystemconsistsoftheleaderandfivefollowerrobots.Theleader’sresponsibilityistodetectobstaclesandtosendtheformationcommandstothefollowers.Theleaderisaswellsupposedtosenditspositionandvelocityinformationtoeveryfollower.Herewenotethattheleaderisgivenapredeterminedpath.Thispathisencodedintheformofasequenceofvelocities,whicharesequentiallyfedtotheleaderatsomerate.
Giventheinitialpositionandcurrentvelocityinthe2Dspacetheleadercancalculateitspositionaftertheelapseoftimet.Thefollowingequationisusedtocalculatethepositionoftheleader:
Wherex1isthenextposition,xthecurrentposition,ttheelapsedtimeandvxthevelocityinthex-axisdirection.
Ontheotherhand,everyfollowerrobotcombinesfourparameterstodetermineitsnextpositioninthe2Dspace.Theseparametersare:
currentpositionoftheleader,currentpositionofthefolloweritself,velocityoftheleader,aswellastheformationinformationthatisreceivedfromtheleader.Thefollowercanchooseoneofthreedifferentkinematicsequations,respectivelyrepresentingeachofthethreeformations.Forexample,infigure3wecanseethesimplecaseofalineformation.Therobotsareoriginallymovinghorizontally.Thentheleaderdecidestochangeitsdirectionasshown.Thenextcoordinatesoftheleaderare(x1,y1)andthenewpositionofthefollower2iscalculatedusingequationR2forlineformations(seeappendixA).
Fig.3.Lineformationchangeofdirection.
Knowingitscurrentandnextpositionalongwiththetimestepttherobotcancalculateatwhatspeedandinwhatdirectionitshouldmove.
Asmentionedearlierthisisahybridsystemofrobots.Infreespacecase,thereisnocameraused.Leaderrobotwillactfollowingthemotionplanned,anditwillsendtheformationanditscurrentpositionandvelocityinformationtoallfivefollowers,sofollowerswilltrytokeeptheformationandmovewiththeleaderrobot.Alltheobstacleexperimentsweareconducting,oneormorecamerasaremounted.Insecondexperiment,acamerawillbemountedonsite,whichmeansthatitcanwatchthemovementofrobotsandthepositionofobstacles(suchastunnels).Whenthevisionsystemdetectethereistunnelinfrontofthemotiondirectiontotherobotsgroup,neccessaryformationchangingcommandwillbegeneratedtoavoidcollisionswiththetunnelbycomparingthedimensionoftunnelwiththesizeofrobotsgroup.Whentherobotsgroupleavingthetunnel,thevisionsystemwilldetectitandissuescommandtorecoverthedefaultformation.Thirdexperimentlettheleaderrobot(ingreen)willalwayshaveacameraasitsmainsensor.Conversely,otherfollowerrobotsintheformationwillnothaveacamera.Theleadercameraandtheassociatedvisionsystemcandetectobstaclesinfrontoftheleader.Whenthevisionsystemindicatesthatatunnelisahead,theleaderrobotordersallfollowerstochangeformationifnecessary.Itcandecidewhetheraformationchangeisnecessaryornotbycomparingthedimensionsofthetunnelandtheformation.Whentheitleavesthetunneltheleader(orfollower6insomeexperiments)isrequiredtodetectthateventandgenerateappropriateoutputstoreconstructtheoriginalformation.Thereissomeuncertaintythatwhentheleaderrobotleftthetunnel,otherfollowingrobotsarestillintunnel.Sochangingformationundersuchsituationwillresultincollisionbetweenrobotsandtunnel.Thiswillbeshownintheexperiment.Inordertoovercomethisshortcoming,wemountanothercameraonthelastrobot,whichwilldetectedwhetherthelastrobothasleftthetunnelornotandgeneratethecommandofreconstructthedefaultformation.
Theexperimentalframecontainsavelocitygeneratortodrivetheleaderrobot.Italsocontainstheenvironmentmodel,whichiscomposedofzeroormoreobstacles.Theenvironmentmodelcanreceivepositioninformationfromallsixrobots,butmainlythepositionofleaderandlastrobots.Itisresponsiblefortriggeringthevisionsystemoftheleaderrobot(andfollowerinsomeoftheexperiments)whenthedistanceseparatingrobotandobstacleexceedsacertainthreshold.Theexperimentalframewillbediscussedinmoredetaillaterinthisreport.
3.ObjectivesoftheModelingandSimulationStudy
Asmentionedearlier,simulationisconsideredtobeaveryusefultoolinthedevelopmentofmultiagentroboticsystems.Throughsimulation,flawsinthedesignoftheagentscanbedetectedintheearlystages.Suchflawsrangefromtrivialcalculationandlogicerrorstomorecomplexfailuresinthehighlevelbehaviorsofthesystem.Forexample,inthesystemwedescribeheremodelingandsimulatingouragentshelpsustodiscovererrorsinthemathematicalmodel(kinematicsequations..etc)wederived.Simulationcanalsoproveordisprovethatacertainmodelissuccessfulinachievingitsgoals.Inourcase,wecanknowiftheRobotsmodelwedesignediscapableofmaintainingthemostcompactformationandatthesametimeproperlytraverseatunnel.
Anotherimportantgoalofthemodelingandsimulationofamultiagentsystemistheevaluationofavarietyofroboticsettings.Thesameexperimentcanberunwithdifferentrobotconfigurations.Inthisprojectthesameexperimentisrunwithtwodifferentconfigurations:
leaderonlyhasacameraorbothleaderand“follower6”havecameras.Thustheadvantagesanddisadvantagesofeachconfigurationcanbeassessed.
4.TheSimulationModel
a.SystemEntityStructure–seeFig.4ofnextpage
b.ExplanationofOperations
world–itisthedescriptionoftheexperimentsworld,itincludesfreespaceworldandworldwithobstacles.
experimentalframe–itwillgivetheexperimentalframe,whichincludesagenerator,environmentorencamera.
Fig.4SystemEntityStructure
generator–thismodelwillgivetheinitialformation,T(timeperiodtosendoutpositioninformation),L(lengthusedtocontrolthesizeofformation),velocitycontroloftheleaderrobotandcontrolwhenthestartoftheexperiments.
environment–thismodelwillgivetheenvironmentsoftherobotsstay,itcontainsseveralobstacles.
encamera–thismodelwillwatchtheobstaclesandthepositionofleaderrobotandthelastrobot(r6).
Robots–itwillgivethe6robotsinformation.
r1–itwillincludear1cameraandar1controller,wherer1camerawatchestheobstaclesandthepositionofr1,r1controllerwillguider1movefollowingthemotiongivenbygenerator.
followers-itoffersinformationabout5followingrobots.
r6–itwillincludear6cameraandar6controller,wherer6camerawatchestheobstaclesandthepositionofr6,r6controllerwillguider6movefollowingtheleaderwithsomekindofformation.
r2,r3,r4andr5–thecontrollerofrobots2to5,willguidethoserobotsmovingfollowingtheleaderwithsomekindofformation.
display–itwillprocessthepositiondatareceivedanddisplayobstaclesand6robots’positionintheCellSpace.Theobstacleswillbedisplayedbeforetherobots’running.Thedisplayorderof6robots’positionisfromtheleaderrobot(r1)tolastrobotr6.Fromitwecanseetheformationofrobotsgroupkeep.BecausetheDEVSJAVAIu