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1、AIAAGuidance,Navigation,andControlConferenceandExhibitAIAA2004-490016-19August2004,Providence,RhodeIslandANewNonlinearGuidanceLogicforTrajectoryTrackingSanghyukPark¤,JohnDeysty,andJonathanP.HowzMassachusettsInstituteofTechnology,Cambridge,MA,02139,USAAnewnonl
2、inearguidancelogic,thathasdemonstratedsuperiorperformanceinguidingunmannedairvehicles(UAVs)oncurvedtrajectories,ispresented.Thelogicapprox-imatesaproportional-derivativecontrollerwhenfollowingastraightlinepath,butthelogicalsocontainsanelementofanticipatorycon
3、trolenablingtighttrackingwhenfollow-ingcurvedpaths.Themethodusesinertialspeedinthecomputationofcommandedlateralaccelerationandaddsadaptivecapabilitytothechangeofvehiclespeedduetoexternaldisturbances,suchaswind.FlighttestsusingtwosmallUAVsshowedthateachaircraf
4、twascontrolledtowithin1.6metersRMSwhenfollowingcircularpaths.Thelogicwasultimatelyusedforairrendezvousofthetwoaircraft,bringingthemincloseproximitytowithin12metersofseparation,with1.4metersRMSrelativepositionerrors.NomenclatureVVehiclevelocityL1Alinede¯nedfro
5、mvehiclepositiontoareferencepointonadesiredtrajectory´AnglecreatedfromVtothelineL1(clockwisedirectionispositive)ascmdAccelerationcommandsidewaysi.e.perpendiculartovehiclevelocitydirectiondCross-trackerrorRRadiusofcircleorcircularsegmentLLyapunovfunctionI.Intr
6、oductionTwoapproachescanbeconsideredfortheproblemoftrajectorytracking.Onemethodseparatesthevehicleguidanceandcontrolproblemsintoanouterguidanceloopandaninnercontrolloop.Theinnerloopcontrolsthevehicletofollowaccelerationcommandswhicharegeneratedbytheouterloop.
7、Simplestrategies,basedongeometricandkinematicproperties,aretypicallyusedintheouterguidanceloop.Thealternativemethodusesanintegratedapproachwhereintheinnerandouterloopsaredesignedsimultaneously.Inthiscase,anumberofmoderncontroldesigntechniquescanbeapplied,such
8、asrecedinghorizon[1],di®erential°atness[2,3]andneuralnetworkbasedadaptivecontrols[4].Inmostactual°ightapplicationstheseparateinnerandouterloopapproachismorecommonlytakenbecauseitisusually