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1.
    
气动发动机设计需要考虑多个参数间的耦合对性能优化的影响,且对理想功率、工作效率等多个性能指标难以建立客观的综合评价函数.为此以发动机进气压力和进排气机构部分控制参数为设计变量进行正交设计,利用灰色关联度分析法计算贴合期望指标组合的最优参数组合,并结合参数指标趋势图,依据计算结果对参数区间进行调整,通过有限次循环得到最优设计参数.经测试该算法快速有效,且设计参数与性能指标数量可扩展,对气动发动机的样机设计和实验具有重要的理论和工程意义.  相似文献   

2.
利用气动参数对未知气动力建模是提高高超声速滑翔目标跟踪精度的有效途径。对目标气动加速度及其导数项进行分析,在非耦合气动参数模型的基础上,考虑气动加速度在转弯和俯仰方向存在的先验信息,推导滚转和螺旋2种耦合气动参数模型。利用一种分离估计模型对目标状态与气动参数进行估计,分别给出状态滤波器和气动参数滤波器的表达式。同时,考虑不同飞行模式下参数的机动频率,构建基于耦合气动参数的交互多模型跟踪算法。仿真表明,本文所提算法精度显著高于针对该类目标的其他跟踪算法。同时,滚转模型的性能优于螺旋模型,且计算复杂度更小。   相似文献   

3.
气动布局的多目标优化是飞行器设计中的关键技术。提出一种新的高超声速再入飞行器气动外形参数的多目标优化方法,证明外形优化对高超声速流下飞行器性能的影响。通过实例仿真对飞行器所受阻力和升力对制导性能影响进行详细验证分析,将飞行器落点圆概率偏差、末速大于500 m/s的占比、最大飞行过载小于60g的占比这3个性能指标作为优化目标,将升力特性作为中间参数,将气动布局优化问题分解为2个子问题,通过基于搜索算法的升力特性优化和基于改进的模拟退火算法的外形参数优化,减少优化计算时间、提升计算效率、实现对飞行器主体和襟翼的气动布局优化、获得高超声速流下的最佳飞行器外形。仿真结果表明:在确定的约束条件下,优化算法增加了飞行器在超音速流下的气动升力,有效提高了升阻比。在不影响最大飞行过载的前提下,优化后的飞行器表现出更高的气动性能,显著提升了命中精度,同时末速也满足指标要求,制导系统性能得到有效改善。  相似文献   

4.
吸气式高超声速飞行器多参数灵敏度分析   总被引:3,自引:0,他引:3  
为实现吸气式高超声速飞行器多参数情况下的灵敏度分析及参数分类,降低设计的复杂度,在吸气式高超声速飞行器参数化建模的基础上,首先采用正交试验设计生成样本,再通过计算流体力学(CFD)进行高精度气动力性能计算,最后运用方差分析法进行气动性能的参数灵敏度分析,在运用较少的试验样本点的情况下,即可完成多参数、复杂构型条件下气动性能的参数灵敏度分析。结果表明,该方法可以正确地分析出参数对飞行器气动性能的敏感程度,得到参数对气动性能的影响规律。同时,通过灵敏度分析的计算样本,还可以初步选出气动性能较优的飞行器构型,为地面试验和优化设计提供参考。  相似文献   

5.
缝道参数对多段翼型气动性能的影响   总被引:1,自引:0,他引:1  
数值模拟研究缝道参数对着陆构型多段翼型气动性能的影响,采用有限体积法求解雷诺平均N-S(Navier-Stokes)方程,湍流模型采用S-A(Spalart-Allmaras)模型,给出了多段翼型升力系数与表面压力系数随各缝道参数的变化规律.计算结果表明:采用的计算模型可用于二维多段翼型的计算;缝道参数对多段翼型气动性能的影响显著,在各个缝道参数的变化范围内升力系数均存在最优值,适当的缝道参数可以抑制后翼上表面逆压梯度,消除后翼分离,并保持前翼尾迹不与后翼边界层相掺混,提高多段翼型的气动性能.   相似文献   

6.
深空探测器在执行姿态机动任务中,通常需要优化多个性能指标参数.此外,姿态指向约束和有界约束的存在显著减小了姿态机动路径的可行空间.在复杂的多约束条件下,多目标姿态机动优化对深空探测器系统是一个极大的挑战.提出多目标组合的概念,通过物理规划方法将多目标优化转换为单目标规划问题.考虑到欧拉路径的低能量特性,提出一种多目标组...  相似文献   

7.
基于在线气动参数修正的预测制导方法   总被引:3,自引:1,他引:2  
针对高超声速滑翔飞行器,提出了一种基于在线气动参数修正的预测制导方法.研究了再入过程中受到的各种飞行约束,给出了多约束下控制量设计的基本方案.分析了传统预测制导法在落点预测过程中存在的气动参数偏差影响,引入综合升力系数与综合阻力系数,并对其进行在线参数估计以及参数修正,以提高制导方法的适应性.基于气动参数修正方法,完成了纵向与横侧向制导律设计.设定较大的轴向力、法向力系数组合偏差对该方法进行了验证,并考虑再入初始条件和再入气动参数的不确定性,进行了蒙特卡洛仿真.结果表明:预测制导法中引入气动参数的在线估计与修正环节,可保证其制导精度,尤其对再入过程的气动扰动具有较强的适应能力.  相似文献   

8.
  总被引:1,自引:0,他引:1  
针对战术导弹外形气动隐身多目标优化问题,提出了一种新的快速优化方法.采用物理规划将多目标问题转化为单目标问题间接求解,利用遗传算法(GA,Genetic Algorithm)对问题进行设计空间搜索.为降低计算成本,通过变量筛选来降低设计变量空间维数,通过构建径向基函数(RBF,Radial Basis Function)代理模型来减少高精度分析模型的调用次数.最后以类BGM-109导弹模型的气动隐身多目标优化为例对该方法进行校验.在满足升力系数不小于初始升力系数的约束下,进行导弹几何外形优化使全弹阻力系数和前向雷达散射截面(RCS,Radar Cross Section)最小.与标准GA相比,在两者优化结果基本相同的情况下,该方法节约了83%的计算成本.  相似文献   

9.
飞行器气动布局的选型和优化技术在总体设计中处于关键地位,在临近空间飞行的飞行器对升阻比和操控性能都提出了更高的要求。翼身组合的升力体外形由于兼顾内部装填以及升阻特性成为了目前高速飞行器主要的设计方向。以一类具有普适性的面对称升力体外形为基础,采用相关性分析手段提取出飞行器的关键几何参数,挖掘出几何参数对所关心的总体性能指标的影响度大小,并建立起基于CFD方法的气动布局优化平台,以总体性能指标为约束,优化出高升阻比外形,通过风洞试验验证了优化设计方法的有效性,为高速飞行器的气动布局工程化设计提供了有效的技术手段。   相似文献   

10.
多变量气动伺服弹性系统的鲁棒稳定性研究   总被引:2,自引:0,他引:2  
根据现代控制理论,对多输入-多输出气动伺服弹性系统的鲁棒稳定性进行研究.分别采用小增益原理和最小奇异值理论两种方法,对涉及飞行器互相耦合的横滚和偏航回路的控制系统进行分析,得出了气动伺服弹性系统抵抗建模误差、保持鲁棒稳定的范围.这两种方法都分别给出了稳定性判据,根据判据可以确定其鲁棒稳定性(或稳定裕度).作为系统扰动的表达形式,文中还对系统不确定性矩阵进行了描述.算例是在某ACT战斗机的计算模型上完成的,两种方法的计算结果取得了一致.   相似文献   

11.
The Houston Museum of Natural Science, in collaboration with Rice University has an outreach program taking portable digital theaters to schools and community sites for over five years and has conducted research on student learning in this immersive environment. By using an external independent evaluator, the effectiveness of NASA-funded Education and Public Outreach (EPO) projects can be assessed. This paper documents interactive techniques and learning strategies in full-dome digital theaters. The presentation is divided into Evaluation Strategies and Results and Interactivity Strategies and Results. All learners from grades 3–12 showed statistically significant short-term increase in knowledge of basic Earth science concepts after a single 22-min show. Improvements were more significant on items that were taught using more than one modality of instruction: hearing, seeing, discussion, and immersion. Thus immersive theater can be an effective as well as engaging teaching method for Earth and Space science concepts, particularly those that are intrinsically three-dimensional and thus most effectively taught in an immersive environment. The portable system allows taking the educational experience to rural and tribal sites where the underserved students could not afford the time or expense to travel to museums.  相似文献   

12.
A monthly average solar green coronal index time series for the period from January 1939 to December 2008 collected from NOAA (The National Oceanic and Atmospheric Administration) has been analysed in this paper in perspective of scaling analysis and modelling. Smoothed and de-noising have been done using suitable mother wavelet as a pre-requisite. The Finite Variance Scaling Method (FVSM), Higuchi method, rescaled range (R/S) and a generalized method have been applied to calculate the scaling exponents and fractal dimensions of the time series. Autocorrelation function (ACF) is used to find autoregressive (AR) process and Partial autocorrelation function (PACF) has been used to get the order of AR model. Finally a best fit model has been proposed using Yule-Walker Method with supporting results of goodness of fit and wavelet spectrum. The results reveal an anti-persistent, Short Range Dependent (SRD), self-similar property with signatures of non-causality, non-stationarity and nonlinearity in the data series. The model shows the best fit to the data under observation.  相似文献   

13.
We address the problem of interacting relativistic current sheets in self-consistent kinetic plasma simulations within the framework of the Particle-In-Cell model. The interaction is enforced in head-on collisions of up to 10 current sheets at relativistic bulk speeds. The simulations are motivated by the general problem of Poynting flux dissipation in ‘striped wind’ configurations presumably governing the relativistic outflows pervasive in pulsar winds and gamma-ray bursts. We identify the generation of non-thermal particles and formation of a stable power-law shape in the particle energy distributions f(γ) dγ ∝ γs dγ. In 1D, a spectral index s ∼ 2 is observed and attributed to a stochastic Fermi-type acceleration mechanism. In 2D, the generic index of s ∼ 3–4 is retained as in previous simulations of individual current sheets. Whereas in 2D the high energy cut-off is constrained by the limited dissipation of magnetic energy, in 1D the process converts the bulk motion of current sheets towards directed particle momentum of an exclusive class of non-thermal particles.  相似文献   

14.
In the frame of the 2009 Mars Science Laboratory (MSL) mission a new sample preparation system (SPS) compatible with gas chromatography–mass spectrometry (GC–MS) has been developed for the in situ analysis of complex organic molecules in the Martian soil. The goal is to detect, if they exist, some of the key compounds that play an important role in life on Earth including carboxylic acids, amino acids and nucleobases.  相似文献   

15.
Various aerial platforms intended for long endurance survey of the Titan surface are presented. A few novel concepts are introduced, including a heated methane balloon and a balloon with a tethered wind turbine. All the concept options are predicted to have lower scientific payload fractions than the Huygens probe. It is concluded that the selection of the best aerial platform option depends on more accurate mass estimates and a clear decision on whether, or not, in situ surface composition measurements are required in conjunction with aerial remote sensing.  相似文献   

16.
To understand the evolution of organic molecules involved in extraterrestrial environments and with exobiological implications, many experimental programs in the laboratory are devoted to photochemical studies in the gaseous phase as well as in the solid state. The validity of such studies and their applications to extraterrestrial environments can be questioned as long as experiments conducted in space conditions, with the full solar spectrum, especially in the short wavelength domain, have not been implemented. The experiments that are described here will be carried out on a FOTON capsule, using the BIOPAN facility, and on the International Space Station, using the EXPOSE facility. Vented and sealed exposition cells will be used, which will allow us to study the chemical evolution in the gaseous phase as well as heterogeneous processes, such as the degradation of solid compounds and the release of gaseous fragments.  相似文献   

17.
基于LuGre模型的电液加载系统摩擦补偿   总被引:2,自引:2,他引:2  
为了提高电液加载系统控制精度,针对摩擦问题提出了基于LuGre摩擦模型的前馈补偿方法.建立了用于摩擦仿真分析和补偿器设计的电液加载系统数学模型;通过实验获取并分析了相关的摩擦数据;基于实验数据进行LuGre模型参数辨识,把LuGre模型和辨识结果引入电液加载系统数学模型,并进行仿真结果与实际摩擦数据的对照,证明了LuGre摩擦模型的准确性.设计前馈补偿器,进行了实验对比,实验结果表明前馈补偿器可将摩擦产生的控制误差有效地降至未补偿时的30%左右.   相似文献   

18.
The ESA scientific programme has, so far, provided several significant astrophysics experiments and further important missions are scheduled for execution during the next decade. These missions are briefly summarised together with several astrophysics investigations presently under study.  相似文献   

19.
The space-borne observatories CoRoT (Convection Rotation and planetary Transits) and Kepler have provided photometric time series data of unprecedented precision for large numbers of stars. These data have revolutionized the fields of transiting exoplanets and asteroseismology. In this review some important asteroseismic results obtained using data from the CoRoT and Kepler space missions concerning stars that show solar-like oscillations are discussed. These results comprise, among others, measurements of the location of the base of the convection zone and helium second-ionization zone in main-sequence stars, the presence (or not) of core-helium burning in red-giant stars, as well as differential rotation in these stars.  相似文献   

20.
Missions to explore Europa have been imagined ever since the Voyager mission first suggested that Europa was geologically very young. Subsequently, the Galileo spacecraft supplied fascinating new insights into this satellite of Jupiter. Now, an international team is proposing a return to the Jupiter system and Europa with the Europa Jupiter System Mission (EJSM). Currently, NASA and ESA are designing two orbiters that would explore the Jovian system and then each would settle into orbit around one of Jupiter’s icy satellites, Europa and Ganymede. In addition, the Japanese Aerospace eXploration Agency (JAXA) is considering a Jupiter magnetospheric orbiter and the Russian Space Agency is investigating a Europa lander.  相似文献   

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