简介：

简介：

简介：Amodelhelicopterismoredifficulttocontrolthanitsfullscalecounterpart.Thisisduetoitsgreatersensitivitytocontrolinputsanddisturbancesaswellashigherbandwidthofdynamics.Thisworkisfocusedondesigningpracticaltrackingcontrollerforasmallscalehelicopterfollowingpredefinedtrajectories.Atrackingcontrollerbasedonoptimalcontroltheoryissynthe-sizedasapartofthedevelopmentofanautonomoushelicopter.Someissueswithregardstocontrolconstraintsareaddressed.Theweightingbetweenstatetrackingperformanceandcontrolpowerexpenditureisanalyzed.Overallperformanceofthecontroldesignisevaluatedbasedonitstimedomainhistoriesoftrajectoriesaswellascontrolinputs.

简介：

简介：Helicopterinspectionofultrahighvoltage(UHV)transmissionlineshasunmatchedadvantagescomparedtomanualworkduetotheinspectionangleandhigh-techequipmentonboard,especiallyindetailedinspectionsoftowerheadsanddefect-detectionsinvirtueofinfrared/ultraviolettechniques.Thispaperdealswithsomekeytechnicalproblemsintheinspectionsof1000kVUHVAClineswithahelicopter,suchasthesafedistanceoflive-lineworking,electromagneticfieldintensityandflightcontrol.Basedonthestudyresults,asetofUHVlineinspectionmethodswasworkedoutandappliedtotheinspectionofliveUHVlines.

简介：[摘要] 电动直升机从产生到发展经历了很长一段时期，如今相关技术趋于成熟，动力解决方案发展也愈加明朗，国内电动航空器的发展也取得了长足的进步。

简介：Thispaperproposesanewasymptoticattitudetrackingcontrollerforanunderactuated3-degree-of-freedom（DOF）laboratoryhelicoptersystembyusinganonlinearrobustfeedbackandaneuralnetwork（NN）feedforwardterm.Thenonlinearrobustcontrollawisdevelopedthroughamodifiedinner-outerloopapproach.TheapplicationoftheNN-basedfeedforwardistocompensateforthesystemuncertainties.Theproposedcontroldesignstrategyrequiresverylimitedknowledgeofthesystemdynamicmodel,andachievesgoodrobustnesswithrespecttosystemparametricuncertainties.ALyapunov-basedstabilityanalysisshowsthattheproposedalgorithmscanensureasymptotictrackingofthehelicopter＇selevationandtravelmotion,whilekeepingthestabilityoftheclosed-loopsystem.Real-timeexperimentresultsdemonstratethatthecontrollerhasachievedgoodtrackingperformance.

简介：High-resolutionspectralradiancemeasurementsweretakenbyaspectralradiometeronboardahelicopterovertheUSOklahomaSouthernGreatPlainneartheAtmosphericRadiationMeasurements(ARM)siteduringAugust1998.Theradiometerhasaspectralrangefrom350nmto2500nmat1nmresolution.Themeasurementscoveredseveralgrassandcroplandscenetypesatmultiplesolarzenithangles.DetailedatmosphericcorrectionsusingtheModerateResolutionTransmittance(MODTRAN)radiationmodelandin-situsoundingandaerosolmeasurementshavebeenappliedtothehelicoptermeasurementsinordertoretrievethesurfaceandtopofatmosphere(TOA)BidirectionalReflectanceDistributionFunction(BRDF)characteristics.Theatmosphericcorrectionsaremostsignificantinthevisiblewavelengthsandinthestrongwatervaporabsorptionwavelengthsinthenearinfraredregion.AdjustingtheBRDFtoTOArequiresalargercorrectioninthevisiblechannelssinceRayleighscatteringcontributessignificantlytotheTOAreflectance.Theoppositecorrectionstothevisibleandnearinfrarredwavelengthscanaltertheradiancedifferenceandratiothatmanyremotesensingtechniquesarebasedon,suchasthenormalizeddifferencevegetationindex(NDVI).ThedatashowthatsurfaceBRDFsandspectralalbedosarehighlysensitivetothevegetationtypeandsolarzenithanglewhileBRDFatTOAdependsmoreonatmosphericconditionsandtheviewinggeometry.ComparisonwiththeCloudsandtheEarth＇sRadiantEnergySystem(CERES)derivedclearskyAngularDistributionModel(ADM)forcropandgrassscenetypeshowsastandarddeviationof0.08inbroadbandanisotropicfunctionat25°solarzenithangleand0.15at50°solarzenithangle,respectively.