简介:Animalflightandswimminghavelongbeenofgreatinteresttopeople.Besidescuriosityabouthowtheirsophisticatedaero-andhydrodynamicfeatsareperformed,researchesareveryinterestedinthemechanicsofanimalflightandswimmingforthefollowingtworeasons.Oneisthatbiologistsneedtounderstandtheeffectsofaero-andhydrodynamicforceproductionandenergyexpenditureonthephysiology,behavior,evolutionandotheraspectsoftheanimals.The
简介:AnartificialdisturbanceisintroducedintotheboundarylayeroveraflatplatetoinvestigatetheeffectonthetransitionprocessintheMach6.5windtunnelatPekingUniversity.Alinearstabilitytheory(LST)isutilizedtopredicttheevolutionoftheeigenmodes,andthefrequencyoftheartificialdisturbanceischosenaccordingtotheLSTresults.Theartificialdisturbanceisgeneratedbyglowingdischargeonthesurfaceoftheplateclosetotheleadingedge.TheRayleigh-scatteringvisualizationandparticleimagevelocimetry(PIV)measurementsareperformed.Bycomparingtheexperimentalresultswithartificialdisturbanceswiththoseunderthenaturalcondition(withoutartificialdisturbances),thepresentpapershowsthatthesecond-modeinstabilitywavesaresignificantlystimulatedbytheartificialdisturbances,andtheboundarylayertransitioniseffectivelytriggered.
简介:作为盘子由作者更早开发了的压电的横梁类型的颤动控制的小浪途径的延期,这份报纸建议为压制把压成薄片的矩形的盘子的颤动的混合activepassive控制策略经由薄粘弹性的结合层与分布式的压电的传感器和致动器结合了。由于在直角的小浪理论放大函数变换的低通行证的过滤性质,这个waveletbased控制方法有能力自动地在反馈控制循环滤出像噪音的信号,因此减少剩余联合的风险完成哪个通常是溢出的来源不稳定性。而且,薄粘弹性的结合层的存在能进一步通过浪费数字错误在控制过程期间部分导致的任何另外的可能的噪音的体力改进系统的坚韧性和可靠性。一个模拟过程基于一种先进wavelet-Galerkin技术被建议认识到混合活跃被动的控制进程。数字结果表明建议途径的效率。
简介:稳定性和机械系统的围住的海角是重要研究话题之一。在这糊一个干燥磨擦振荡器的最终的围住的海角,属于非光滑的机械系统,被建议一个控制器设计方法调查。第一,为有推迟的州的反馈的名字的系统的稳定性的一个足够的条件被构造LyapunovKrasovskii功能导出。推迟的反馈获得矩阵被使用线性矩阵不平等方法计算。第二根据推迟的州的反馈,一个连续函数被Lyapunov重新设计设计保证磨擦振荡器系统的解决方案最终在全面控制下面被围住。而且,最终的界限能被选择适当参数在实践调整。因此导致磨擦的颤动或不稳定性能有效地被控制。数字结果证明建议方法是有效的。
简介:Itisconcernedwiththeproblemofdisturbanceattenuationwithstabilityforuncertainnonlinearsystemsbyadaptiveoutputfeedback.Byapartial-stateobserverandBacksteppingtechnique,anadaptiveoutputfeedbackcontrollerwasconstructed,whichcansolvethestandardgaindisturbanceattenuationproblemwithinternalstability.
简介:Strongasymmetricalvorticesappearontheleewardofslenderbodyathighanglesofattack,whichhasveryunfavorableeffectonthestabilityandcontroloftheaircraft.Amethodisdevelopedtocontrolthesideforceofslenderbodyathighanglesofattack,andisverifiedinwindtunnel.Athin-filmtriangularself-excitedoscillationflagisfixedatthetipoftheslenderbodymodelwhosesemi-apexangleis10°.Sideforceisapproximatelylinearlyproportionaltoroll-settingangleofself-excitedoscillationflagathighanglesofattack,andtheslopoffittingstraightlineobtainedbytheleastsquaremethodis-0.158.Thelinearrelationshipbetweensideforceandroll-settingangleprovidesconveniencefordevelopingsideforcecontrollawofslenderbodyathighanglesofattack.Experimentaldatashowsthatthesideforcecoefficientsvarylinearlywithroll-settingangleswhenaspecificplasticself-excitedoscillationflagisusedasthecontrolflag.Therangeofsideforcecoefficientandroll-settingangleare,respectively,-3.2to3.0and-20°to20°.Thedeviceissimple,effective,andisofgreatpotentialinengineeringapplication.
简介:Inthe'90sDEMsimulationresearchwassuccessfulinexploringitspotentialinthesimulationoffiuidizationphenomenaandinitsapplicationtothedesignoffluidized-bedprocesses.Nevertheless,notmuchprogresshasbeenmaderegardingtherealistictreatmentofcollisionprocessesthatarecriticalindeterminingmacroscopicmodeoffiuidization.Allthroughthesecondhalfofthe'90s,theauthorinvestigated/demonstratedtheissuebyintroducingdifferentsurfaceinteractionscausedbyformationofliquidand/orsolidbridges,vanderWaalsforceandtheexistenceofsurfaceroughness.Inthefirstpartofthepresentationthesearetobesummarizedandthetasksremainingarediscussed.Inthesecondpart,arepresentedtheresultsfromanewlydevelopedforce-deformationmetertodemonstratethesignificanceofthesurfaceroughnessanditselasto-plasticcharacteristics.
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简介:Thispaperpresentstheproblemofcontrolofanti-aircraftmissilelaunchermountedonamovingcarrier-vehicle.Directexcitationsonthevehiclefromtheroadcauseadversevibrationsofthelauncher.Inordertoincreasetheprecisionoftheguidingsystemintheconditionsofself-propelledmovementofthesetuponabumpyroad,theadaptivecontrolalgorithmwasproposed.Someresearchresultsofcomputersimulationarepresentedinagraphicalform.
简介:Atheoreticalmodelingapproachaswellasanunsteadyanalyticalmethodisusedtostudyaerodynamiccharacteristicsofwingflappingwithasymmetricstroke-cyclesinconnectionwithanobliquestrokeplaneduringinsectforwardflight.Itisrevealedthattheaerodynamicasymmetrybetweenthedownstrokeandtheupstrokeduetostroke-asymmetricalflappingisakeytounderstandtheflowphysicsofgenerationandmodulationoftheliftandthethrust.Predictedresultsforexamplesofgivenkinematicsvalidatemorespecificallysomeviewpointsthatthewingliftismoreeasilyproducedwhentheforwardspeedishigherandthethrustisharder,andtheliftandthethrustaregeneratedmainlyduringdownstrokeandupstroke,respectively.Theeffectsofthreecontrollingparameters,i.e.theanglesoftiltedstrokeplane,thedifferentdownstrokedurationratios,andthedifferentanglesofattackinbothdown-andup-stroke,arefurtherdiscussed.Itisfoundthatlargerobliqueanglesofstrokeplanesgeneratelargerthrustbutsmallerlift;largerdownstrokedurationratiosleadtolargerthrust,whilemakinglittlechangeinliftandinputaerodynamicpower;andagain,asmallincreaseoftheangleofattackindownstrokeorupstrokemaycauseremarkablechangesinaerodynamicperformanceintherelevantstroke.
简介:Magneto-rheologicalvisco-elastomer(MRVE)asanewsmartmaterialdevelopedinrecentyearshasseveralsignificantadvantagesovermagneto-rheologicalliquid.Theadjustabilityofstructuraldynamicstorandomenvironmentalexcitationsisrequiredinvibrationcontrol.MRVEcansupplyconsiderablyadjustabledampingandstiffnessforstructures,andtheadjustmentofdynamicpropertiesisachievedonlybyappliedmagneticfieldswithchangelessstructuredesign.IncreasingresearchesonMRVEdynamicproperties,modeling,andvibrationcontrolapplicationarepresented.RecentadvancesinMRVEdynamicpropertiesandstructuralvibrationcontrolapplicationincludingcompositestructuralvibrationmitigationunderuniformmagneticfields,vibrationresponsecharacteristicsimprovementthroughharmonicparameterdistribution,andoptimalboundedparametriccontroldesignbasedonthedynamicalprogrammingprinciplearereviewed.RelevantmainmethodsandresultsintroducedarebeneficialtounderstandingandresearchesonMRVEapplicationanddevelopment.
简介:Thispaperaddressesamaster-slavesynchronizationstrategyforcomplexdynamicsystemsbasedonfeedbackcontrol.Thisstrategyisappliedto3-DOFplanarmanipulatorsinordertoobtainsynchronizationinsuchcomplicatedaschaoticmotionsofend-effectors.AchaoticcurveisselectedfromDuffingequationasthetrajectoryofmasterend-effectorandapiecewiseapproximationmethodisproposedtoaccuratelyrepresentthischaotictrajectoryofend-effectors.Thedynamicalequationsofmaster-slavemanipulatorswithsynchronizationcontrollerarederived,andtheLyapunovstabilitytheoryisusedtodeterminethestabilityofthiscontrolledsynchronizationsystem.Innumericalexperiments,thesynchronousmotionsofend-effectorsaswellasthreejointanglesandtorquesofmaster-slavemanipulatorsarestudiedunderthecontroloftheproposedsynchronizationstrategy.Itisfoundthatthepositivegainmatrixaffectstheimplementationofsynchronizationcontrolstrategy.Thissynchronizationcontrolstrategyprovesthesynchronization'sfeasibilityandcontrollabilityforcomplicatedmotionsgeneratedbymaster-slavemanipulators.
简介:Theactivecontrolofvibrationforabeamsubjectedtomulti-disturbancesisinvestigatedbasedonwavepropagatingsuppression.Inthiscontrolsystem,therearethesamenumbersofthesensors,thesignalinputtingtothecon-trollerandthedisturbances,butthereisonlyonecontroller.Itisalocalcontrolsystem,thesystemparametersdependonlyonthecharacteristicsofthestructureboundedbythesensorsandthecontroller,andweneednottakeintoaccounttheboundaryconditionsandthepropertiesofstructuresoutsideofthisfield.Thesys-temisefficientwhenastructurevibratesinmiddleandhighfrequencyregions.Somecontroldesignrulesaredevelopedfromthecalculationresults.
简介:传统的被动吸收器在一个狭窄、肯定的频率乐队以内是充分有效的。解决这个问题,推迟时间的加速反馈被介绍把一个被动吸收器变换成活跃的。两固有并且故意的时间延期被包括。前者主要来自信号获得并且处理,计算,并且适用使活动力量,和它的值被修理。后者在控制器被介绍,并且它的价值是活跃地可调节的。第一,机械模型被建立,频率反应方程被获得。稳定性的区域在控制参数的飞机被描出。第二,控制帕拉的设计计划--米被执行帮助选择反馈获得和时间延期的值。第三,试验性的研究被进行。否定、积极的反馈控制的效果被调查。试验性的结果证明控制参数的合适的选择可以拓宽颤动吸收的有效频率乐队。而且,当被动吸收器完全失败时,推迟时间的吸收器极大地压制主要系统的反响的反应。试验性的结果在对理论预言和数字模拟的好同意。
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简介:ThispaperstudiesMulti-modescontrolmethodforlibrationpointsformationestablishmentandreconfiguration.Firstly,relationsbetweenoptimalimpulsecontrolandFloquetmodesareinvestigated.Methodofgeneratingmodesisproposed.Characteristicsofthemodecoefficientsstimulatedatdifferenttimearealsogiven.Studiesshowthatcoefficientsofcontrolledmodescanbeclassifiedintofourtypes,andformationestablishmentandreconfigurationcanbeachievedbymulti-impulsecontrolwiththepresentedmethodofgeneratingmodes.Then,sincelibrationpointsformationisgenerallyunstable,mutli-modeskeepingcontrolmethodwhichcanstabilizefiveFloquetmodessimultaneouslyisproposed.Finally,simulationonformationestablishmentandreconfigurationarecarriedoutbyusingmethodofgeneratingmodesandmutli-modeskeepingcontrolmethod.Resultsshowthattheproposedcontrolmethodiseffectiveandpractical.
简介:Optimalcontrolsystemofstatespaceisaconservativesystem,whoseapproximatemethodshouldbesymplecticconservation.Basedonthepreciseintegrationmethod,analgorithmofsymplecticconservativeperturbationispresented.Itgivesauniformwaytosolvethelinearquadraticcontrol(LQcontrol)problemsforlineartime-varyingsystemsaccuratelyandefficiently,whosekeypointsaresolutionsofdifferentialRiccatiequation(DRE)withvariablecoefficientsandthestatefeedbackequation.Themethodissymplecticconservativeandhasagoodnumericalstabilityandhighprecision.Numericalexamplesdemonstratetheeffectivenessoftheproposedmethod.
简介:Inthisstudy,afowsolverwasdevelopedbasedonthegoverningRANSequationsofcompressiblefowsandwasfurtherextendedtoincludetheefectsofelectromagneticforcesnamelyLorentzforces.Lorentzforcesmaybeaddedasasourceterminthegoverningfuidfowequations.NumericalstudieswerecarriedoutforNACA0015aerofoilathighanglesofincidencesfrom15to30andcomparedwithsomeavailablecasesofexperimentalandincompressiblenumericalsolutions.Thehydrodynamicsperformancewasimprovedusingamagneticmomentumcoefcientofupto0.048.Thesizeoffowseparationzonewasdecreasedorcompletelyeliminatedbyincreasingthiscoefcient.Theoveralldragwasnotchangedconsiderably,howevertheoverallliftwasincreasedupto80percentatstallangles.