Intelligent Flight Control of an Autonomous Quadr

12IntelligentFlightControlofanAutonomousQuadrotorSyedAliRazaandWailGueaiebUniversityofOttawa,Canada1.IntroductionThischapterdescribesthedifferentstepsofdesigning,building,simulating,andtestinganintelligentflightcontrolmoduleforanincreasinglypopularunmannedaerialvehicle(UAV),knownasaquadrotor.Itpresentsanin-depthviewofthemodelingofthekinematics,dynamics,andcontrolofsuchaninterestingUAV.Aquadrotoroffersachallengingcontrolproblemduetoitshighlyunstablenature.Aneffectivecontrolmethodologyisthereforeneededforsuchauniqueairbornevehicle.Thechapterstartswithabriefoverviewonthequadrotor'sbackgroundanditsapplications,inlightofitsadvantages.ComparisonswithotherUAVsaremadetoemphasizetheversatilecapabilitiesofthisspecialdesign.Forabetterunderstandingofthevehicle'sbehavior,thequadrotor'skinematicsanddynamicsarethendetailed.Thisyieldstheequationsofmotion,whichareusedlaterasaguidelinefordevelopingtheproposedintelligentflightcontrolscheme.Inthischapter,fuzzylogicisadoptedforbuildingtheflightcontrollerofthequadrotor.Ithasbeenwitnessedthatfuzzylogiccontroloffersseveraladvantagesovercertaintypesofconventionalcontrolmethods,specificallyindealingwithhighlynonlinearsystemsandmodelinguncertainties.Twotypesoffuzzyinferenceenginesareemployedinthedesignoftheflightcontroller,eachofwhichisexplainedandevaluated.Fortestingthedesignedintelligentflightcontroller,asimulationenvironmentwasfirstdeveloped.Thesimulationsweremadeasrealisticaspossiblebyincorporatingenvironmentaldisturbancessuchaswindgustandtheever-presentsensornoise.Theproposedcontrollerwasthentestedonarealtest-bedbuiltspecificallyforthisproject.Boththesimulatorandtherealquadrotorwerelaterusedforconductingdifferentattitudestabilizationexperimentstoevaluatetheperformanceoftheproposedcontrolstrategy.Thecontroller'sperformancewasalsobenchmarkedagainstconventionalcontroltechniquessuchasinput-outputlinearization,backsteppingandslidingmodecontrolstrategies.Conclusionswerethendrawnbasedontheconductedexperimentsandtheirresults.1.1QuadrotorbackgroundLouisBréguetandJacquesBréguet,twobrothersworkingundertheguidanceofProfessorCharlesRichet,werethefirsttoconstructaquadrotor,whichtheynamedBréguetRichetGyroplaneNo.1Breguet-Richet-1907.ThefirstflightdemonstrationofGyroplaneNo.1MotionControl246withnocontrolsurfaceswasachievedon29September1907.Figure1showsthehugequadrotorwithdoublelayeredpropellersbeingpreparedforitsfirstmannedflight.Fig.1.BréguetRichetGyroplaneNo.1Rumerman(2002).Later,twoadditionaldesignsweredevelopedandexperimentalflightswereconducted.Thefirst,byGeorgesdeBothezatandIvanJeromein1922,hadsix-bladedrotorsplacedateachendofanX-shapedtrussstructure,asshowninFigure2.Fig.2.QuadrotordesignedbyGeorgeDeBothezat,February21,1923Rumerman(2002).Thesecond,showninFigure3,wasbuiltbyÉtienneŒhmichenin1924,andsetdistancerecords,includingachievingthefirstkilometerlonghelicopterflight.Fig.3.Œhmichenquadrotordesignedin1924Rumerman(2002).Atpresent,apartfrommilitaryendeavours,UAVsarealsobeingemployedinvariouscommercialandindustrialapplications.Inparticular,theseincludetheuseofunmannedhelicoptersforcropdustingorprecisionfarmingSugiuraetal.(2003),andmicrowaveIntelligentFlightControlofanAutonomousQuadrotor247autonomouscoptersystemsforgeologicalremotesensingArcheretal.(2004).STARMACWaslanderetal.(2005)isamulti-agentautonomousrotorcraft,whichhaspotentialinsecurity-relatedtasks,suchasremoteinspectionsandsurveillance.ThecommerciallyavailablequadrotorkitcalledDraganFlyerInc.(2008)hasbecomeapopularchoiceforaerialmappingandcinematography.UAVsaresubdividedintotwogeneralcategories,fixedwingUAVsandrotarywingUAVs.Rotarywingedcraftsaresuperiortotheirfixedwingcounterpartsintermsofachievinghigherdegreeoffreedom,lowspeedflying,stationaryflights,andforindoorusage.Aquadrotor,asdepictedinFigure4,isarotarywingUAV,consistingoffourrotorslocatedattheendsofacrossstructure.Byvaryingthespeedsofeachrotor,theflightofthequadrotoriscontrolled.Quadrotorvehiclespossesscertainessentialcharacteristics,whichhighlighttheirpotentialforuseinsearchandrescueapplications.CharacteristicsthatprovideaclearadvantageoverotherflyingUAVsincludetheirVerticalTakeOffandLanding(VTOL)andhoveringcapability,aswellastheirabilitytomakeslowprecisemovements.Therearealsodefiniteadvantagestohavingafourrotorbasedpropulsionsystem,suchasahigherpayloadcapacity,andimpressivemaneuverability,particularlyintraversingthroughanenvironmentwithmanyobstacles,orlandinginsmallareas.AsillustratedbytheconceptualdiagraminFigure4,thequadrotorattitudeiscontrolledbyvaryingtherotationspeedofeachmotor.Thefrontrotor(Mf)andbackrotor(Mb)pairrotatesinaclockwisedirection,whiletherightrotor(Mr)andleftrotor(Ml)pairrotatesinacounter-clockwisedirection.Thisconfigurationisdevisedinordertobalancethedragcreatedbyeachofthespinningrotorpairs.Figure5showsthebasicfourmaneuversthatcanbeaccomplishedbychangingthespeedsofthefourrotors.Bychangingtherelativespeedoftherightandleftrotors,therollangleofthequadrotoriscontrolled.Similarly,thepitchangleiscontrolledbyvaryingtherelativespeedsofthefrontandbackrotors,andt