Scientific Methods in Mobile Robotics: Quantitative Analysis of Agent Behaviour PDF
Preview Scientific Methods in Mobile Robotics: Quantitative Analysis of Agent Behaviour
Scientific Methods in Mobile Robotics Ulrich Nehmzow Scientific Methods in Mobile Robotics Quantitative Analysis of Agent Behaviour With116Figures 123 UlrichNehmzow,DiplIng,PhD,CEng,MIEE DepartmentofComputerScience UniversityofEssex ColchesterCO43SQ UnitedKingdom BritishLibraryCataloguinginPublicationData Nehmzow,Ulrich,1961- Scientificmethodsinmobilerobotics:quantitative analysisofagentbehaviour.-(Springerseriesinadvanced manufacturing) 1.Mobilerobots2.Robots-Dynamics-Simulationmethods I.Title 629.8’932 ISBN-10:1846280192 LibraryofCongressControlNumber:2005933051 ISBN-10: 1-84628-019-2 e-ISBN 1-84628-260-8 Printedonacid-freepaper ISBN-13: 978-1-84628-019-1 ©Springer-VerlagLondonLimited2006 Apartfromanyfairdealingforthepurposesofresearchorprivatestudy,orcriticismorreview,as permittedundertheCopyright,DesignsandPatentsAct1988,thispublicationmayonlybereproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers,orinthecaseofreprographicreproductioninaccordancewiththetermsoflicencesissued bytheCopyrightLicensingAgency.Enquiriesconcerningreproductionoutsidethosetermsshouldbe senttothepublishers. Theuseofregisterednames,trademarks,etc.inthispublicationdoesnotimply,evenintheabsenceof aspecificstatement,thatsuchnamesareexemptfromtherelevantlawsandregulationsandtherefore freeforgeneraluse. Thepublishermakesnorepresentation,expressorimplied,withregardtotheaccuracyoftheinfor- mationcontainedinthisbookandcannotacceptanylegalresponsibilityorliabilityforanyerrorsor omissionsthatmaybemade. PrintedinGermany 9 8 7 6 5 4 3 2 1 SpringerScience+BusinessMedia springeronline.com S.D.G. DedicatedtotheRobotMODICgroup: SteveBillings,TheocharisKyriacou,RobertoIglesiasRodr´ıguez, KeithWalkerandHugoVieiraNeto, anditssupportteam: ClaudiaandHenriettaNehmzow, MariaKyriacou,MicheleVieiraandMaxineWalker Foreword Mobilerobotsarewidelyappliedinarangeofapplicationsfromtransportation, surveillancethroughtohealthcare.Inalltheseapplicationsitisclearlyimportant to be able to analyse and control the performance of the mobile robot and it is thereforesurprisingthatformalisedmethodstoachievethisarenotreadilyavail- able. This book introduces methods and procedures from statistics, dynamical systemstheory,andsystemidentificationthatcanbeappliedtoaddresstheseim- portantproblems.Thecoreobjectiveistotrytoexplaintheinteractionbetween therobot,thetaskandtheenvironmentinatransparentmannersuchthatsystem characteristicscanbeanalysed,controllerscanbedesigned,andbehaviourscan be replicated in a systematic and structured manner. This aim of constructing a formalised approach for task-achieving mobile robots represents a refreshingly newapproachtothiscomplexsetofproblems. Dr Nehmzow has done an outstanding job of constructing and describing a unifiedframework,whichclearlysetsoutthecrucialissuesforthedevelopment of a theory for mobile robots. Thanks to the careful organisation of the topics andaclearexposition,thisbookprovidesanexcellentintroductiontosomenew directionsinthissubjectarea.DrNehmzow’sbookrepresentsamajordeparture from the traditional treatment of mobile robots, and provides a refreshing new lookatsomelong-standingproblems.Iamsurethatthisisjustthebeginningof an exciting new phase in this subject area. This book provides a very readable account of the concepts involved; it should have a broad appeal, and will I am sureprovideavaluablereferenceformanyyearstocome. SABillings Sheffield,May2005 vii Preface This book is about scientific method in the investigation of behaviour, where “behaviour”standsforthebehaviourofany“behaving”agent,beitlivingbeing ormachine.Itthereforealsocoverstheanalysisofrobotbehaviour,butisnotre- strictedtothat.Thematerialdiscussedinthisbookhasbeenequallysuccessfully presentedtobiologistsandroboticistsalike! “Scientificmethod”herestandsfortheprinciplesandproceduresforthesys- tematic pursuit of knowledge [MerriamWebster,2005], and encompasses the followingaspects: • Recognitionandformulationofaproblem • Experimental procedure, consisting of experimental design, procedure for observation,collectionofdataandinterpretation • Theformulationandtestingofhypotheses The hypothesis put forward in this book is that behaviour — mainly mo- tion—canbedescribedandanalysedquantitatively,andthatthesequantitative descriptions can be used to support principled investigation, replication and in- dependentverificationofexperiments. Thisbookitselfisanexperiment.Besidesanalysingthebehaviourofagents, itinvestigatesthequestionofhowreadyweare,asacommunityofroboticsprac- titioners,toextendthepracticesofroboticsresearchtoincludeexactdescriptions of robot behaviour, to make testable predictions about it, and to include inde- pendent replication and verification of experimental results in our repertoire of standardprocedures. Ienjoyeddevelopingthematerialpresentedinthisbookverymuch.Itopened up a new way of doing robotics, led to animated, stimulating and fruitful dis- cussion, and new research (the “Robot Java” presented in Section 6.7 is one example of this). Investigating ways of interpreting experimental results quan- titatively led to completely new experimental methods in our lab. For example, insteadofsimplydevelopingaself-chargingrobot,say,wewouldtrytofindthe ix x Preface baseline,the“standard”withwhichtocompareourresults.Thismeantthatpub- lications would no longer only contain the description of a particular result (an existence proof), but also its quantitative comparison with an established base- line,acceptedbythecommunity. The responses so far to these arguments have been truly surprising! There seems to be little middle ground; the topic of employing scientific methods in robotics appears to divide the community into two distinct camps. We had re- sponses across the whole spectrum: on the one hand, one of the most reputable journalsinroboticsevendeniedpeerreviewtoapaperontaskidentificationand rejected it without review, and in one seminar the audience literally fell asleep! On the other hand, the same talk given two days later resulted in the request to stay an extra night to “discuss the topic further tomorrow” (and this was after two hours of discussion); the universities of Palermo, Santiago de Compostela and the Memorial University Newfoundland requested “Scientific Methods in Robotics”asanextramuralcourse,changedthetimetablesforalltheirrobotics studentsandexaminedthemontheguestlectures! I am encouraged by these responses, because they show that the topic of scientific methods in mobilerobotics is notbland and arbitrary,but either ared herringoranimportantextensiontoourdiscipline.Thepurposeofthisbookis to find out which, and to encourage scientific discussion on this topic that is a principledandsystematicengagementwiththeargumentpresented.Ifyouenjoy agoodargument,Ihopeyouwillenjoythisone! Acknowledgements Science is never done in isolation, but crucially depends on external input. “As iron sharpens iron, so one man sharpens another” (Prov. 27,17), and this book provesthispoint.Imayhavewrittenit,buttheexperimentsandresultspresented here are the result of collaboration with colleagues all over the world. Many of them have become friends through this collaboration, and I am grateful for all thesupportandfeedbackIreceived. Most of the experiments discussed in this book were conducted at the Uni- versityofEssex,whereournewroboticsresearchlaboratoryprovidedexcellent facilitiestoconducttheresearchpresentedinthisbook.Ibenefitedgreatlyfrom the discussions with everyone in the Analytical and Cognitive Robotics Group at Essex — Theo Kyriacou, Hugo Vieira Neto, Libor Spacek, John Ford and DongbingGu,tonamebutafew—aswellaswithmycolleagueJeffReynolds. MuchofthisbookwasactuallywrittenwhilevisitingPhillipMcKerrow’sgroup at the University of Wollongong; I appreciate their support, and the sabbatical Preface xi granted by Essex University. And talking of sabbaticals, Keith Walker (Point LomaNazareneUniversity,SanDiego)andRobertoIglesiasRodriguez(Dept.of ElectronicsandComputerScienceattheUniversityofSantiagodeCompostela) made important contributions during their sabbaticals at Essex. I am also in- debtedtomanycolleaguesfromotherdisciplines,notablythelifesciences,who commented on the applicability of methods proposed in this book to biology, psychology etc. I am especially grateful for the support I received from Wolf- gang and Roswitha Wiltschko and their group at the J.W. Goethe University in Frankfurt. The RobotMODIC project, which forms the backbone of work discussed in this book, would not have happened without the help and commitment of my colleagueandfriendSteveBillingsattheUniversityofSheffield,thecommitted workbymycolleagueandfriendTheoKyriacou,andthesupportbytheBritish EngineeringandPhysicalSciencesResearchCouncil.Ibenefitedgreatlyfromall this scientific, technical, financial and moral support, and thank my colleagues andsponsors. Finally,IthankallmyfamilyinGermanyfortheirfaithful,kindandgenerous supportandlove.MywifeClaudia,aswithbook#1,wasaconstructivehelpall alongtheway,andHenriettawasajoytobe“criticised”by.Thankyouall! As before, I have written this book with Johann Sebastian Bach’s motto “SDG”firmlyinmind. UlrichNehmzow Colchester,Essex,October2005 Contents 1 ABriefIntroductiontoMobileRobotics ..................... 1 1.1 ThisBookisnotaboutMobileRobotics..................... 1 1.2 WhatisMobileRobotics? ................................ 1 1.3 TheEmergenceofBehaviour.............................. 5 1.4 ExamplesofResearchIssuesinAutonomousMobileRobotics .. 7 1.5 Summary .............................................. 9 2 IntroductiontoScientificMethodsinMobileRobotics .......... 11 2.1 Introduction............................................ 11 2.2 Motivation:AnalyticalRobotics ........................... 13 2.3 Robot-EnvironmentInteractionasComputation .............. 15 2.4 ATheoryofRobot-EnvironmentInteraction ................. 16 2.5 RobotEngineeringvsRobotScience........................ 18 2.6 ScientificMethodandAutonomousMobileRobotics .......... 19 2.7 ToolsUsedinthisBook .................................. 27 2.8 Summary:TheContrastBetween ExperimentalMobileRoboticsandScientificMobileRobotics .. 28 3 StatisticalToolsforDescribingExperimentalData............. 29 3.1 Introduction............................................ 29 3.2 TheNormalDistribution ................................. 30 3.3 ParametricMethodstoCompareSamples.................... 33 3.4 Non-ParametricMethodstoCompareSamples ............... 43 3.5 TestingforRandomnessinaSequence ...................... 55 3.6 ParametricTestsforaTrend(CorrelationAnalysis) ........... 57 3.7 Non-ParametricTestsforaTrend .......................... 65 3.8 AnalysingCategoricalData ............................... 69 3.9 PrincipalComponentAnalysis............................. 80 xiii xiv Contents 4 DynamicalSystemsTheoryandAgentBehaviour.............. 85 4.1 Introduction............................................ 85 4.2 DynamicalSystemsTheory ............................... 85 4.3 Describing(Robot)BehaviourQuantitativelyThroughPhase SpaceAnalysis ......................................... 95 4.4 SensitivitytoInitialConditions:TheLyapunovExponent ......100 4.5 Aperiodicity:TheDimensionofAttractors...................116 4.6 Summary ..............................................119 5 AnalysisofAgentBehaviour—CaseStudies ................. 121 5.1 AnalysingtheMovementofaRandom-WalkMobileRobot.....121 5.2 “ChaosWalker”.........................................126 5.3 AnalysingtheFlightPathsofCarrierPigeons ................133 6 ComputerModellingofRobot-EnvironmentInteraction ........ 139 6.1 Introduction............................................139 6.2 SomePracticalConsiderationsRegardingRobotModelling.....141 6.3 CaseStudy:ModelAcquisitionUsingArtificialNeuralNetworks143 6.4 LinearPolynomialModelsandLinearRecurrenceRelations ....150 6.5 NARMAXModelling....................................155 6.6 AccurateSimulation:EnvironmentIdentification..............156 6.7 TaskIdentification.......................................173 6.8 SensorIdentification .....................................184 6.9 WhenAreTwoBehaviourstheSame? ......................185 6.10 Conclusion.............................................193 7 Conclusion............................................. 195 7.1 Motivation .............................................195 7.2 QuantitativeDescriptionsofRobot-EnvironmentInteraction ....196 7.3 ATheoryofRobot-EnvironmentInteraction .................197 7.4 Outlook:TowardsAnalyticalRobotics ......................199 References................................................. 201 Index..................................................... 205
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