战场复杂电磁环境下的无人机作战应用探讨

通过对战场复杂电磁环境的研究,分析总结无人机系统在侦察作战全过程中可能受到各种电磁干扰,结合无人机系统抗干扰特性,提出应对战场复杂电磁环境的无人机系统作战运用方法,有效提高了无人机在战场中的作战效能和生存能力。     

Modelling of air temperature using remote sensing and artificial neural network in Turkey

The aim of this research was to forecast monthly mean air temperature based on remote sensing and artificial neural network (ANN) data by using twenty cities over Turkey. ANN contained an input layer, hidden layer and an output layer. While city, month, altitude, latitude, longitude, monthly mean land surface temperatures were chosen as inputs, and monthly mean air temperature was chosen as output for network. Levenberg–Marquardt (LM) learning algorithms and tansig, logsig and linear transfer functions were used in the network. The data of Turkish State Meteorological Service (TSMS) and Technological Research Council of Turkey–Bilten for the period from 1995 to 2004 were chosen as training when the data of 2005 year were being used as test. Result of research was evaluated according to statistical rules. The best linear correlation coefficient (R), and root mean squared error (RMSE) between the estimated and measured values for monthly mean air temperature with ANN and remote sensing method were found to be 0.991–1.254 K, respectively.     

Detached-eddy simulation of supersonic flow past a spike-tipped blunt nose

Space vehicle in atmosphere travels mostly at supersonic speed and generates a very strong bow shockwave around its blunt nose. Oblique shock and conical separated flow zone generated by a forward disk-tip spike significantly reduce the drag by reducing the high pressure area on the blunt nose. This study employs improved delayed detached eddy simulation to investigate the characteristic flow structures around a spike-tipped blunt nose at Mach number of 3 and Reynolds number(based on the blunt-body diameter) of 2.72x10~8. The calculated time-averaged quantities agree well with experimental data. Characteristic frequencies in different flow regions are extracted using fast Fourier transform. It is found that two distinct instability modes exist: oscillation mode and pulsation mode. The former is related to the foreshock/turbulence interaction with nondimensional frequency at around 0.004. The latter corresponds to the interaction between turbulence and shock structures around the blunt nose, with a typical coherent structure shedding frequency at 0.092.     

Study of atmospheric air pollutants during the partial solar eclipse on 15 January 2010 over Udaipur: A semi-arid location in Western India

The paper describes behavior of surface ozone, its precursor gases, BC along with TOCC, TWVC, AOT1020 nm as well as UV and IR radiation intensities observed during the partial solar eclipse of 15th January, 2010 over Udaipur, where 52% solar disc is obscured due to the moon’s shadow. During the beginning to main eclipse phase, the deviation values of several air pollutants concentrations from eclipse to control day values vary in a small range from −9 to −2 ppb in case of surface ozone and −180 to −80 ppb for CO. The corresponding change in the values of BC observed from −3.3 to −.5 μg/m³. No significant change is found in NO₂, NO or in ratio of NO₂/NO values during the partial eclipse time. TOCC values decrease from 3 to 5 DU along with a reduction in UV radiation intensity from 20 to 35% from starting to the main eclipse phase. The AOT1020 nm values are found to increase from .2 to 1.0 along with a reduction in IR radiation intensity order of 50%. However, TWVC values decrease from .22 to .1 cm during the eclipse hours. The low level of dilution in surface ozone in eclipse period may be attributed with change in local atmospheric boundary layer dynamic conditions or limited air pollutants dispersion, in term of decreases in planetary boundary layer height, wind speed and hence ventilation coefficient in the same eclipse hours. Thus, present studies support the argument for the leading roles of photochemical reactions with its precursor gases under presence of solar radiation in surface ozone variability. Other possible controlling factors are advection of air pollutants from the polluted region as evident from backward wind trajectories and altering the local meteorological conditions.     

无人机桨叶损伤的在线模型估计新方法

无人机在复杂高对抗环境中极易出现桨叶结构受损故障，造成无人机控制性能退化甚至失稳，给无人机带来灾难性后果。桨叶结构损伤条件下无人机动力学模型的在线估计与重建是保障无人机控制系统稳定的重要前提。由于桨叶损伤干扰隐含于无人机动力学模型的内部，可观测性较低，典型的干扰观测器难以实现对此类干扰的估计。提出了一种新型穿透型干扰观测器，通过构造穿透函数，将模型内部的干扰映射到一个新建的平行空间，实现了对桨叶损伤的估计和故障后无人机的建模，并给出了所设计穿透型干扰观测器的稳定性条件。以四旋翼无人机为应用对象，对桨叶损伤形成的干扰进行在线估计与量化，反演出桨叶随机出现的损伤，实现了桨叶损伤后无人机动力学模型的在线精细重建，解决了无人机桨叶损伤故障下力矩输入难以直接测量的问题。半物理仿真实验验证了所提方法的有效性。     

基于网格自适应的飞行器防热材料热传导系数辨识

为准确辨识高超声速飞行器防热材料热传导系数，构造了针对热传导偏微分方程系统的约束泛函极值问题，基于表征多项式逼近性能的Weierstrass定理，采用Lagrange多项式对热传导系数进行参数化建模，进而将无穷维的约束泛函极值问题转化为有限维的非线性规划问题，再利用基于动态优化方程的优化方法将此非线性规划问题转化为常微分方程初值问题进行求解。为从较有限的测量数据中准确地“学习”热传导系数，建立采用“过拟合”判别准则的网格自适应迭代算法改善辨识精度。研究表明本文采用的辨识策略与优化方法有效，辨识结果可以较准确地反映材料热传导系数的变化规律。     

运载火箭捷联惯组全自主对准技术应用研究

我国运载火箭发射前通常通过光学瞄准确定初始方位角,采用捷联惯组自对准解算获取水平姿态角。以可实现简易、快速发射的新型火箭为背景,在发射场阵风等干扰引起箭体低频微幅晃动的环境下,研究了捷联惯组自主对准技术。分析了运载火箭全自主对准的特点,利用以惯性系为参考基准的解析对准法和卡尔曼滤波精对准方法,对高精度全自主对准技术和其在运载火箭上的应用展开了详细论述。开展了全自主对准试验验证,结合新一代运载火箭首飞数据进行了分析。结果表明:捷联惯组全自主对准技术可替代复杂的光学瞄准系统,实现运载火箭发射前初始姿态的确定。     

固体运载火箭抗强电磁脉冲优化设计方法

本文分析了火箭在飞行过程中的强电磁脉冲(EMP)环境，建立了箭上敏感设备受强电磁脉冲干扰的优化设计模型，包括传导干扰及辐射干扰两种设计模型。针对起飞质量对火箭总体参数设计的制约问题，以最小质量增量为目标函数，采用模拟退火(SA)算法，对箭上典型电气系统抗强电磁脉冲防护进行优化设计研究，为箭上敏感设备抗强电磁脉冲指标与质量增量提供了平衡选取方法。优化结果表明,火箭在飞行过程中典型电气系统的抗强电磁脉冲性能指标达到要求的同时，实现了火箭质量增量最小的目标。     

高超声速巡航飞行器在线自适应反馈控制设计

由于飞行器模型的强非线性,各种建模不确定性以及飞行环境的复杂性,高超声速飞行器控制成为一个研究难点.针对某类具有参数不确定性的非线性系统,提出了一种反馈线性化与自适应估计相结合的方法,对非线性系统的输入输出动态应用反馈线性化处理以得到拟线性模型,并设计反馈控制律;对不确定参数采用自适应在线估计,利用Lyapunov方法分析稳定性;针对选择不同输出的情况,对如何消除内动态进行了讨论.为了验证该方法的可行性,将其应用于某高超声速飞行器巡航段纵向非线性模型,对速度和高度通道进行跟踪控制仿真,由于飞行器和大气环境存在建模不确定性,利用自适应控制对不确定参数进行在线估计.仿真结果显示该方法能够快速收敛,并且具有良好的在线自适应能力.     

航天器发射飞行安全智能决策研究与实现

针对航天发射的特点,将智能决策和空间信息处理技术运用于航天发射飞行的安 全判决中,建立发射场及其飞行航区的基础地理数据库和基础信息数据库。分析飞行过程中 瞬时落点区域的地理属性,实现火箭飞行过程中安全管道、预示落点、飞行参数和飞行轨迹 等在数字地图上的实时显示,实时监控火箭的飞行状态。在决策中提出了“目标-规则基-特 征状态体”的领域知识表示模型,为火箭飞行的安全提供实时辅助决策。