一种减小再入飞行器侧向气动非线性的布局优化方法

为改善升力式再入飞行器在跨声速段出现的侧向气动特性非线性问题,发展了一种基于Kriging代理模型的自适应迭代气动布局优化方法。设计了一种常规升力式再入飞行器布局,计算了该布局在跨声速段的侧向气动力,分析了可能影响侧向气动特性的机翼布局参数。根据气动布局优化流程,计算了气动布局样本气动特性,建立了布局参数到侧向力矩系数导数的代理模型,完成了以减小飞行器侧向非线性为目标的布局优化设计。优化布局的气动特性计算结果表明,所发展的方法是可行和有效的。该项研究为再入飞行器减小侧向气动非线性提供了新的布局设计途径,有利于降低控制系统设计难度,保障飞行安全。     

小卫星侦察星座性能评估研究

针对小卫星侦察星座性能评估问题，从覆盖、成本和弹性三方面对小卫星侦察星座的性能指标进行研究，分别构建了考虑存储容量约束的覆盖能力评估模型、成本估计模型以及弹性能力评估模型。在覆盖能力评估模型中，将卫星存储容量作为约束条件，结合卫星覆盖几何模型分析了卫星对地侦察的工作条件，提出考虑存储容量的覆盖指标计算方法；通过小卫星成本模型(small satellite cost model,SSCM)对星座各分系统的成本进行估计；在弹性评估模型中，提出了星座性能损失率指标，并根据星座失效状态概率函数确定了不同失效状态下星座性能损失率的权重。将上述模型应用于SkySat和吉林一号星座的性能评估过程中，结果表明SkySat比吉林一号覆盖能力强、成本低，弹性差。提出的三个模型可用于评价星座优劣，为小卫星侦察星座的建设和性能评估工作提供参考。     

基于代理模型全局优化的自适应参数化方法

对于翼型气动隐身设计问题，设计变量的配置对设计结果影响很大，而简单地增加设计变量不能保证得到理想的结果。提出一种适用于代理模型全局优化的自适应参数化方法：利用全局敏感性分析方法——基本效应法，得到设计空间关于目标函数的敏感区域信息，并以此为根据增加设计变量；利用节点插入算法将低维样本在高维空间内进行重构，避免了重新取样的工作量。相对于传统固定设计空间维度方法，自适应参数化方法在设计空间的敏感区域扩展维度，能够更加精准地描述外形并反映目标的变化趋势。通过飞翼布局翼型的气动隐身优化算例，证实自适应参数化方法可以大幅提高优化设计质量和效率。     

基于双环滑模控制的直/气复合控制系统设计

直/气复合控制导弹具有强干扰、强非线性以及强耦合等特点，传统的姿态控制器难以适用于该种复杂干扰并存的情况，文章提出了基于双环滑模控制的直/气复合控制器。首先采用有限时间收敛趋近律分别构造内外环滑模控制器，并将角速度回路的滑模变量量化为直接力指令，以解决空气舵与姿控发动机之间的耦合问题。接着使用非线性扩张状态观测器估计综合干扰，从而设计控制器补偿侧向喷流干扰及模型不确定性等综合干扰的影响。然后基于李雅普诺夫方法证明了控制系统闭环稳定，分析了干扰补偿对控制器收敛域的影响。最后仿真结果表明，该方法跟踪速度快，动态过程平稳，具有较强的干扰抑制能力，具有很强的鲁棒性。     

离心压缩机密封及空腔流动的一维/三维耦合建模研究

为了在保证数值预测精度的同时降低离心压缩机的建模复杂度,以一维密封泄漏计算替代完整的密封及空腔建模,开展了离心压缩机盖盘密封及空腔流动的源项建模方法研究。结果表明:基于源项方法的密封及空腔简化建模仅需在主流道建模基础上施加泄漏质量流量、总温和摩擦损失源项边界条件,即可较高精度地还原完整的盖盘密封及空腔建模的性能和关键流动细节。与完整建模相比,在全工况下源项建模预测的等熵效率的绝对偏差小于0.65%,总压比和等熵效率的相对性能偏差小于1%。该方法可在满足下游部件匹配设计精度需求的同时,减少50%以上的网格数量,并显著提高计算的经济性和收敛性。泄漏流量的计算精确度是影响源项建模法性能预测准确性的最关键因素,耦合建模可以采用一维计算中推荐的密封泄漏系数值。      

Heading control strategy assessment for coaxial compound helicopters

The coaxial compound helicopter has two possible strategies for heading control: collective differential and rudder deflection. A flight dynamics model is developed to assess the effect of different heading control strategies. This includes the trim characteristics, steady flight performance,controllability, and manoeuvrability. The trim study demonstrates that heading control strategies are less influential on trim results, and the steady flight performance is also not significantly affected by the heading control strategy adopted. The controllability analysis shows although heading bandwidth and phase delay results at various speeds with different heading control strategies are all satisfied, the control derivative of the collective differential decreases as speed increases, and its heading aggressive agility is degraded into Level 3 in high-speed flight. In addition, using collective differential would lead to severe heading-rolling coupling as forward speed increases. On the contrary, the control derivative and aggressive agility of the rudder deflection is improved with forward speed, and there is no evidence of heading-rolling coupling. Finally, the transient turn MissionTask-Element(MTE) is utilized to investigate the heading manoeuvre characteristics in different heading control strategies, which indicates that the collective differential would add the amplitude of control input and the power consumption during this MTE.     

Comparison of observed ionospheric vertical TEC over the sea in Indian region with IRI-2016 model

The vertical ionospheric TEC values obtained from GAGAN grid based ionospheric delay correction values over the sea in the Indian equatorial region have been compared with the corresponding values derived from the International Reference Ionosphere model, IRI-2016. The objective of this work is to study the deviation of the vertical TEC derived from the IRI model from ground truths over the sea for different conditions. This will serve the basic intention of assessing the candidature of the IRI model as an alternative ionospheric correction model in navigation receivers in terms of accuracy. We have chosen different solar activity periods, seasons, geomagnetic conditions, locations etc. for our comparison and analysis. The TEC values by the IRI-2016 were compared with the actual measured values for the given conditions and errors were obtained. The measured vertical TEC values at the ionospheric grid points were derived from the GAGAN broadcast ionospheric delay data and used as reference. The IRI model with standard internal functions was used in estimating the TEC at the same ionospheric grid points. The errors in the model derived values are statistically analysed. Broadly, the results show that, for the Indian sector over the sea, the IRI model performs better on quiet days in off equatorial regions, particularly in the northern region. The overall performance degrades for other conditions with the model generally underestimating the true TEC values and most severely in the equatorial region. The performance is worst in this region for the disturbed days of the equinoctial period. The comparison study is also done with the TEC data measured directly by dual frequency GPS receivers. The results were found to be in general agreement with those obtained by comparing the model with GAGAN broadcast data as reference. This study will be useful in considering the IRI-2016 model for real time estimates of TEC as an alternative to the current parametric model in a satellite navigation receiver in absence of other options.     

基于伴随方法的单级低速压气机气动设计优化

采用梯度方法对某型4.5级压气机最后级进行气动设计优化研究，梯度由连续伴随方法计算确定，多排伴随方程采用伴随掺混面模型进行数值求解。首先，采用基于经验修正的初步设计方法设计带进口导叶的4.5级低速、低压缩比压气机的原始气动外形。之后，在压气机近失速工况对最后级静子叶片进行伴随气动设计优化，通过优化叶型和安装角降低流动损失，目标函数定义为加权求和形式的熵增和流量偏差，优化中对流量进行约束。最后，开展基于伴随方法的多工况气动设计优化研究，改善两个不同转速条件下最后级的气动性能。优化结果表明，基于伴随方法的多排气动设计优化可以通过改变叶片气动外形提升多排全工况气动性能。     

航天器姿态预设性能控制方法综述

针对存在不确定惯量矩阵及其它未知不确定性(如执行器故障、航天器结构发生突变等)下的航天器姿态控制问题，综述了预设性能控制及其应用的研究进展。首先阐释了预设性能控制方法的基本内涵及其关键步骤；然后分析总结了现有航天器姿态控制以及预设性能控制研究的基本概况与发展趋势；最后面向未来复杂化、智能化的空间任务对航天器控制系统提出的新需求，提出航天器预设性能控制值得研究的问题和方向。     

太阳能飞机循环飞行的高度剖面能量策略

为满足设定的太阳能飞机多日连续飞行条件，依据飞行过程中当前时刻的飞行高度、光伏输出功率、动力电池组余量等系统状态参数，研究如何分配动力电池组充放电和电推进系统输入等功率。所用策略立足于实时功率平衡，充分利用正午前后的光伏峰值功率用于飞机爬升及充电，在午后下滑过程中利用全部光伏输出，以最大化利用光伏资源；在光伏有效输出不足时则以一定的维持功率下滑，使能量的综合损失最小。方法能够提高以预定夜间飞行高度连续多日续航的成功率，提升飞行高度、纬度、季节范围或搭载能力，或者拓展这几种飞行条件的组合域，优化太阳能飞机的适用性。