简介:Theanalysisanddesignoftheextendedstateobserver(ESO)involvesacontinuousnon-smoothstructure,thusthestudyoftheESOdynamicrequiresmathematicaltoolsofthenonlinearsystemsanalysis.ThispaperestablishesthesufficientconditionsforabsolutestabilityoftheESO.Basedonthisstudy,amethodologytoestimateseveralnonlinearfunctionsindynamicssystemsisproposed.
简介:Thedynamicsofclassicalroboticsystemsareusuallydescribedbyordinarydifferentialequationsviaselectingaminimumsetofindependentgeneralizedcoordinates.However,differentparameterizationsandtheuseofanonminimumsetof(dependent)generalizedcoordinatescanbeadvantageousinsuchcaseswhenthemodeleddevicecontainsclosedkinematicloopsand/orithasacomplexstructure.Ononehand,theuseofdependentcoordinates,likenaturalcoordinates,leadstoadifferentmathematicalrepresentationwheretheequationsofmotionaregivenintheformofdifferentialalgebraicequations.Ontheotherhand,thecontroldesignofunderactuatedrobotsusuallyreliesonpartialfeedbacklinearizationbasedtechniqueswhichareexclusivelydevelopedforsystemsmodeledbyindependentcoordinates.Inthispaper,weproposeadifferentcontrolalgorithmformulatedbyusingdependentcoordinates.Theappliedcomputedtorquecontrollerisrealizedviaintroducingactuatorconstraintsthatcomplementthekinematicconstraintswhichareusedtodescribethedynamicsoftheinvestigatedserviceroboticsysteminrelativelysimpleandcompactform.TheproposedcontrollerisappliedtothecomputedtorquecontroloftheplanarmodeloftheACROBOTERservicerobot.Thestabilityanalysisofthedigitallycontrolledunderactuatedservicerobotisprovidedasarealparametercasestudyforselectingtheoptimalcontrolgains.
简介:ThispaperpresentsacanonicalHamiltonianmodelofliquidsloshingforthecontainercoupledwithspacecraft.Ellipticalshapeofrigidbodyisconsideredasspacecraftstructure.Hamiltoniansystemisanimportantformofmechanicalsystem.Itmostlyusedtostabilizethepotentialshapingofdynamicalsystem.Freesurfacemovementofliquidinsidethecontaineriscalledsloshing.Ifthereisuncontrolledresonancebetweenthemotionoftankandliquid-frequencyinsidethetankthensuchsloshingcanbeareasonofattitudedisturbanceorstructuraldamageofspacecraft.Equivalentmechanicalmodelofsimplependulumormassattachedwithspringforsloshingisusedbymanyresearchers.MassattachedwithspringisusedasanequivalentmodelofsloshingtoderivethemathematicalequationsintermsofHamiltonianmodel.AnalyticalmethodofLyapunovfunctionwithCasimirenergyfunctionisusedtofindthestabilityforspacecraftdynamics.Verticalaxialrotationistakenasthemajoraxialsteadyrotationforthemovingrigidbody.
简介:Theresonancefrequenciesandstabilityofananobeaminalongitudinalmagneticfieldareinvestigated.Tothisaim,athreedimensionalbeammodelisusedinwhichthesmall-scaleeffectistakenintoaccountbasedonthenonlocalelasticitytheory.TheLorentzforcesareobtainedintermsofthelocalelasticrotationsofthebeamandthethermalstressduetocurrentismodeledasanaxialcompressiveforce.UsingtheGalerkinmethod,thegoverningequationsofmotionaresolvedandthestabilityboundaryofthenanobeamisdetermined.
简介:一条全球存在定理为一个起始边界的值问题被建立,与时间依赖者边界数据,在脉搏燃烧的一个lumped参数模型产生;在问题的模型产生一个非线性的混合夸张寓言的系统。用以前为联系线性问题建立的结果,固定的点争论被采用与人工的粘性为非线性的问题的一个调整版本证明存在本地。适当-priori估计然后被导出它暗示本地存在结果能为调整问题被扩大到一条全球存在定理。最后,priori估计的一个不同集合被产生当人工的粘性参数收敛到零,它允许拿限制;调整问题的相应答案然后被证明收敛到原来的、非线性的、夸张寓言的系统的起始边界的价值问题的唯一的答案。
简介:Inthepresentpaper,thelateraldynamicflightstabilitypropertiesoftwohoveringmodelinsectsarepredictedbyanapproximatetheorybasedontheaveragedmodel,andcomputedbynumericalsimulationthatsolvesthecompleteequationsofmotioncoupledwiththeNavier-Stokesequations.Comparisonbetweenthetheoreticalandsimulationalresultsprovidesatesttothevalidityoftheassumptionsmadeinthetheory.Oneoftheinsectsisamodeldroneflywhichhasrelativelyhighwingbeatfrequency(164Hz)andtheotherisamodelhawkmothwhichhasrelativelylowwingbeatfrequency(26Hz).Thefollowingconclusionhasbeendrawn.Thetheorybasedontheaveragedmodelworkswellforthelateralmotionofthedronefly.Forthehawkmoth,relativelylargequantitativedifferencesexistbetweentheoryandsimulation.Thisisbecausethelateralnon-dimensionaleigenvaluesofthehawkmotharenotverysmallcomparedwiththenon-dimensionalflappingfrequency(thelargestlateralnon-dimensionaleigenvalueisonlyabout10%smallerthanthenon-dimensionalflappingfrequency).Nevertheless,thetheorycanstillcorrectlypredictvariationaltrendsofthedynamicpropertiesofthehawkmoth'slateralmotion.
简介:聚苯乙烯涂的硅石(SiO2@PS)核心壳有大约290nm的平均直径的合成粒子被准备由在在直径的2050nm的-methacryloxypropyltrimethoxysilanegraftedSiO2nanoparticles的表面上的苯乙烯的situ乳剂聚合。在10wt%PS答案的SiO2@PS暂停的Rheological行为和分散稳定性与未经治疗的SiO2的暂停相比,silane修改了SiO2nanoparticles。暂停未经治疗并且silane修改了展出的SiO2明显砍变瘦。SiO2@PS暂停展览砍比暂停更加小的粘性未经治疗并且silane修改了SiO2在低砍率。传播电子显微镜学证明合成粒子能一致地并且稳定地与另外的暂停相比在PS答案分散,暗示PS壳罐头有效地提高与在答案的PS大分子的粒子相容性。
简介:所谓的blisks,即不可分地bladed磁盘,被描绘由很低粘滞抑制的材料并且使flutter预言更批评。在那个框架,展示片和高eigenfrequency的复杂变丑的空间汽轮机blisk的二维的数字研究(>40kHz)被执行。模拟基于不稳定的雷纳兹平均Navier司烧在频率域线性化的计算并且在重叠在于一不稳定线性(及时)压力地,由泛音不安产生了,在之上一稳定非线性(在空间)流动。空气动力学的抑制系数在节的直径的一个范围上被计算,并且片被预言气动弹性变形地稳定。然而,强烈变化发生并且自从在稳定性的突然、大的偏差出现,是相当批评的。在那上下文,从串联宣传的波浪的性质被评估。如此的一条途径关于罐头也宣传到的不安提供基本知识远地(切上模式)或腐烂(截止模式)。流动的能力被不稳定的不安从串联被转移到的方法强烈影响抑制或放大片运动,这被期望远地。波浪的性质首先从上述的线性化的结果被估计,当时,他们是评估经分解并且最后比较。尽管有分析模型的强壮的假设,一个好协议被发现。结果显示出在cut-on/cut-off条件和稳定性之间的清楚的关联。最不稳定的配置在插头在入口和没有波浪对应于截止模式。没有从串联的出去的波浪,片是容易的不太稳定:从片颤动的体力必然被浪费或由串联发送了。