基于多元特征的终端区运行场景分类分析方法

为了提升对气象影响下终端区运行场景的认知理解,支撑基于场景的终端区预战术辅助决策及管制新模式的建立,提出了一种基于多元特征的终端区运行场景分类分析方法。针对终端区场景描述与分类需求,构建由终端区气象、交通、流量策略三个领域构成的多元特征,通过多源异构数据的预处理进而建立了终端区场景量化指标集,并选取模糊C均值聚类(FC...     

卫星时分多址信号高精度快速时频差联合估计方法

针对传统时频差估计方法对时分多址(TDMA)信号进行参数估计时会出现不同用户相互影响、估计精度差,以及计算复杂度高不利于系统实时信号处理等问题,文章提出一种高精度快速时频差联合估计方法.首先,基于循环平稳特征对主站接收数据进行信号检测;然后,基于小波阈值去噪和短时电平和进行TDMA信号时隙分离;在此基础上,基于不同调制信号特征参数设计多级分类器,对每个分离的信号时隙进行调制样式判别,进而分选不同用户对应的信号时隙;接着,利用主站分选的各个用户信号分别与辅站信号进行时频差粗值估计;根据粗时频差估计值减小细化时差搜索范围,以获取精细时频差估计值;最后,利用二阶曲面拟合方法进一步提升参数估计精度.仿真结果表明:文章所提方法能够有效实现TDMA信号高精度快速时频差联合估计,可为后续卫星频谱感知体系的建设提供理论支撑.     

超燃冲压发动机燃烧室主动冷却设计研究

超燃冲压发动机燃烧室主动冷却模型制造和热考核试验的费用高昂、周期长,为了降低试验风险,采用三维计算和经济的验证试验相结合的方法开展了超燃冲压发动机燃烧室主动冷却设计。冷却结构基本参数设计和侧壁冷却流动设计是确定设计方案的两大基础,前者采用三维传热计算结合冷却面板传热验证试验完成,后者采用超临界燃料流动三维并行计算结合水流动验证试验完成。在此基础上,经过多轮的结构设计与三维传热及强度计算评估迭代,确定了最终的燃烧室主动冷却结构。设计的主动冷却燃烧室在来流马赫数2.5,总温1700K条件下成功通过200s热考核试验,表明所采用的设计方法、验证试验和计算工具是有效和可信的。     

Aeroelastic two-level optimization for preliminary design of wing structures considering robust constraints

An aeroelastic two-level optimization methodology for preliminary design of wing struc- tures is presented, in which the parameters for structural layout and sizes are taken as design vari- ables in the first-level optimization, and robust constraints in conjunction with conventional aeroelastic constraints are considered in the second-level optimization. A low-order panel method is used for aerodynamic analysis in the first-level optimization, and a high-order panel method is employed in the second-level optimization. It is concluded that the design of the abovementioned structural parameters of a wing can be improved using the present method with high efficiency. An improvement is seen in aeroelastic performance of the wing obtained with the present method when compared to the initial wing. Since these optimized structures are obtained after consideration of aerodynamic and structural uncertainties, they are well suited to encounter these uncertainties when they occur in reality.     

Investigations into sensing characteristics of circular thin-plate electrostatic sensors for gas path monitoring

Circular thin-plate electrostatic sensors are promising in gas path monitoring due to their advantages of non-intrusiveness and easy installation. The spatial sensitivity and filtering effect are two important performance parameters. In this paper, an analytically mathematical model of induced charge on a circular thin-plate electrode is first derived. Then the spatial sensitivity and filtering effect of the circular electrostatic sensor are investigated by numerical calculations. Finally,experimental studies are performed to testify the theoretical results. Both theoretical and experimental results demonstrate that circular thin-plate electrostatic sensors act as a low-pass filter in the spatial frequency domain, and both the spatial filtering effect and the temporal frequency response characteristics depend strongly on the spatial position and velocity of the charged particle. These conclusions can provide guidelines for the optimal design of circular thin-plate electrostatic sensors.     

几种常用格式和湍流模型在高速流动中的适用性研究

针对高超声速飞行器中存在的强激波、激波/边界层干扰、分离、湍流等复杂流动现象,对比分析了当前计算流体力学中的主要空间离散格式及湍流模型,发现不同格式对强激波的分辨率基本相同,Roe和LDE(low diffusion E-CUSP(convective upwind split pressure))格式对摩擦因数和传热系数的模拟优于其他格式;S-A(Spalart-Allmaras)一方程湍流模型计算的摩擦因数比k-ωSST(shear stress transport)两方程湍流模型高10%左右,而后者预测的分离区约为前者的2倍,且分离点靠前.     

脉冲雷达凝视模式下低轨碎片相对运动特征分析

脉冲雷达凝视模式是一种探测低轨小碎片的重要方式,其中低轨碎片与雷达的径向运动关系是碎片统计分析的基础.为推算碎片相对雷达的运动特征,基于坐标系的相互转换,先利用雷达测站信息,得到可见碎片在地惯坐标系下的轨道信息;再逆向将目标不同时刻的位置转换至测站坐标系下,得到目标的径向运动特征.在不同要素（雷达波束指向、雷达仰角、测站纬度、目标距离）下,仿真及对比分析了各个参数对速度模糊度、雷达可见性等的影响,得出在凝视模式下目标相对雷达近似做径向匀加速运动,这为后续试验工作提供有力的依据.     

大气层内导弹姿态控制方法研究

本文以大气层内导弹为研究对象,对导弹的姿态控制方法进行研究.根据大气层内导弹运动方程组及空气动力方程等得出导弹的姿态控制系统数学模型.由于导弹的姿态控制数学模型是强耦合、非线性的,因而在控制器设计之前,采用小扰动理论进行线性化处理,得到俯仰、偏航、滚转三个通道的传递函数.针对特征点,采用PD控制方法分别设计三通道的控制律,在此基础上,进一步设计了基于增益调度的PD控制规律.仿真结果表明,提出的姿态控制方法可以实现大气层内导弹的姿态控制,满足指标要求.     

牵制缓释放过程中火箭动力响应特性分析

为研究运载火箭在牵制缓释放过程中的结构动力响应特性,将牵制缓释放发射过程依次分为静态竖立、点火牵制和缓释放三个阶段进行计算。运用MSC.Patran有限元程序的场功能来实现上一阶段的全部计算结果场向下一阶段初始条件场的传递,运用MSC.Nastran有限元程序的非线性弹簧单元的非线性位移载荷函数功能来模拟运载火箭缓释放过程中的缓释力,实现运载火箭牵制缓释放过程结构动力响应的数值计算,并对比分析运载火箭几种常用发射释放方式的结构动力响应特性。结果表明:采用牵制缓释放系统可有效减小运载火箭释放时所受冲击载荷,减小运载火箭全箭结构动力响应。     

Disturbance observer based model predictive control for accurate atmospheric entry of spacecraft

Facing the complex aerodynamic environment of Mars atmosphere, a composite atmospheric entry trajectory tracking strategy is investigated in this paper. External disturbances, initial states uncertainties and aerodynamic parameters uncertainties are the main problems. The composite strategy is designed to solve these problems and improve the accuracy of Mars atmospheric entry. This strategy includes a model predictive control for optimized trajectory tracking performance, as well as a disturbance observer based feedforward compensation for external disturbances and uncertainties attenuation. 500-run Monte Carlo simulations show that the proposed composite control scheme achieves more precise Mars atmospheric entry (3.8?km parachute deployment point distribution error) than the baseline control scheme (8.4?km) and integral control scheme (5.8?km).