Predictor-Corrector Entry Guidance for Low Lifting Vehicles.pdf

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1、AIAAGuidance,NavigationandControlConferenceandExhibitAIAA2007-642520-23August2007,HiltonHead,SouthCarolinaPredictor-CorrectorEntryGuidanceforLowLiftingVehiclesPingLu∗IowaStateUniversity,Ames,IA50011-2271Thispaperdescribestworelatednumericalpredictor-correctorentryguidancealgo-rithmsforvehiclesw

2、ithlowlift-to-dragratios,suchastheOrionCrewExplorationVehi-cle.Thedesignphilosophyistokeepthenumberofsearchparametersatminimumforsimplicityandefficiencyofthealgorithm,andmaintainsufficientmarginsintheguidancesolutionforenhancedrobustnesstotrajectorydispersionsanduncertainties.Thefirstalgorithmfindsac

3、ompletethree-dimensionalfeasibleentrytrajectoryfromthecurrentconditiontothelandingsite.Itdoessobysearchingon-lineforaconstantbank-angleprofileandthebankreversalinitiationpointbeforethebankreversaloccurs,andalinearbankangleprofileafterthebankreversal.Thesecondalgorithmisconcernedwithfindingafeasibl

4、elongitudinaltrajectorybydeterminingthebankanglemagnitudeprofile.Acon-ventionallateralguidancelogicforbankreversalsisusedtogetherwiththelongitudinalpredictor-correctorapproach.Thefirstalgorithmisidealforon-boardplanningof3-Dentrytrajectories,whereastherobustifiedversionofthesecondalgorithmishighly

5、suitedforclosed-loopguidanceinthepresenceoflargedispersionsandmodelinguncertainty.Forcrewedvehicles,aneffectiveandsimpleload-reliefstrategyisproposedthatisbestappliedusingthe3-Dpredictor-correctoralgorithmforreducingthepeakloadfactorwhenevernecessary.I.IntroductionPredictor-correctorentryguidanc

6、ealgorithmshavelongbeenusedinmissionanalysesandsimulationsforfeasibilityandtradestudiesofvariousentryvehiclesandaerobrakingmissions.References1–6representjustasmallchronologicalsamplingoftherelevantliterature,andtheyarechosentoreflectthediversityoftheapplications.Thecommontraitsamongthisclassofm

7、ethodsarenumericaloranalyticalpropagationofthetrajectoryforpredictionofthefinalcondition,andcorrectionalstepstoadjustthedesignparameterstonulltheerrorsinmeetingtheterminalconstraints.Thedifferenceslieintheproblemparameterization,num