导弹纵向机动飞行鲁棒控制

将非线性无源方法,用于导弹纵向机动飞行控制,并通过H_∞控制器补偿系统的不确定性。此方法设计的控制器,能保证系统的鲁棒稳定性。将此方法用于导弹地形跟踪控制,仿真结果表明,此种方法在导弹纵向机动飞行中控制效果较好。     

A surface reflectance correction model to improve the retrieval of MISR aerosol optical depth supported by MODIS data

Combined use of different satellite sensors are known to improve retrievals of aerosol optical depth (AOD). In this study, we propose a new method for retrieving Multi-angle Imaging SpectroRadiometer (MISR) AOD data supported by Moderate Resolution Imaging Spectroradiometer (MODIS) data in Jiangsu Province, China, over the period of 2016–2018 using MODIS L1B, bidirectional reflectance distribution function (BRDF), MISR 1B2T, and ground-measured AOD data. This method is based on the surface reflectance determined by the MODIS V5.2 algorithm. Through the observation angle and spectral conversion between different sensors, the MISR AOD can be obtained. The correlation coefficient (R) and root-mean-square error (RMSE) between the retrieved MISR and ground-measured AOD data varied between different seasons. The accuracy of the MISR AOD retrieval was notably improved after correcting the MISR surface reflectance. Therefore, the method proposed in this study is feasible for the retrieval of MISR AOD supported by MODIS data, and will be applicable to atmospheric environmental monitoring over large areas in the future.     

用Schamberg方法计算卫星阻力系数

Schamberg的“超热自由分子流”粒子-表面作用模型比较真实地反映了高空大气分子与空间飞行器材料之间的相互作用,它可以用来计算卫星的阻力系数。本文简要叙述该模型的基本思想,介绍几种常见简单几何形体卫星的阻力系数计算公式,并给出计算曲线。     

Ballistic Trajectory Extrapolation and Correction of Firing Precision for Multiple Launch Rocket System

The research on multiple launch rocket system(MLRS)is now even more demanding in terms of reducing the time for dynamic calculations and improving the firing accuracy,keeping the cost as low as possible. This study employs multibody system transfer matrix method(MSTMM),to model MLRS. The use of this method provides effective and fast calculations of dynamic characteristics,initial disturbance and firing accuracy. Further,a new method of rapid extrapolation of ballistic trajectory of MLRS is proposed by using the position information of radar tests. That extrapolation point is then simulated and compared with the actual results,which demonstrates a good agreement. The closed-loop fire correction method is used to improve the firing accuracy of MLRS at low cost.     

二维抛物化稳定性方程的特征分析

在对抛物化稳定性方程(PSE)的基本流场没有做任何近似假定的情况下,分析了PSE的特征性质。分析表明,当法向速度不为零时,PSE有一个非零主特征值,其余主特征值都为零。PSE的次特征值与扰动波的空间波数α有关,α的实部代表扰动波的波动情况,它可以直接导致复特征值出现;α的虚部表示扰动波的增长(衰减)情况,当它的绝对值超过一定范围时,也会在边界层内亚声速区的局部区域导致复特征值出现。增大求解PSE的空间推进步长,可以克服PSE的椭圆性。     

An Algorithm for Determination of Projectile Attitude Angles in Projectile Trajectory Prediction

A fast and accurate algorithm is established in this paper to increase the precision of ballistic trajectory prediction.The algorithm is based on the six-degree-of-freedom(6 DOF)trajectory equations,to estimate the projectile attitude angles in every measuring time.Hereby,the algorithm utilizes the Davidon-Fletcher-Powell(DFP)method to solve nonlinear equations and Doppler radar trajectory test information containing only position coordinates of the projectile to reconstruct the angular information.The″position coordinates by the test″and″angular displacements by reconstruction″at the end phase of the radar measurement are used as an initial value for the trajectory computation to extrapolate the trajectory impact point.The numerical simulations validate the proposed method and demonstrate that the estimated impact point agrees very well with the real one.Morover,other artillery trajectory can be predicted by the algorithm,and other trajectory models,such as 4 DOF and 5 DOF models,can also be incorporated into the proposed algorithm.     

高效率E类功率放大器在某调频电台发射机中的应用

高效率E类功率放大器是一种新型的开关模式功率放大器,由Sokals发明,Raab作了理论上的分析,但至今还不完善,近年来,工程应用研究是讨论的主要课题。本文根据某调频电台发射机的具体情况,讨论了它的设计方法和理论,并给出了试验结果。实验结果表明,应用了E类放大器之后,发射机的输出功率增加,整机效率提高,电池寿命延长,通信距离增加,效果明显改善,体现了应用高效率E类放大器的优越性。     

J—7飞机最小阻力重心位置的探讨

本文验算了J-7飞机的稳定边界和前操纵边界,简单分析了其重心使用范围。进一步讨论,估算了J-7飞机和J-7改型机最小阻力的重心位置,对估算方法也作了简单介绍。结果表明:J-7改型机最小阻力重心位置较原J-7飞机有所前移,但是,只有在平尾处相对下洗角很大时,两者的最小阻力重心位置才有可能在稳定边界之内,否则均在稳定边界之外。     

机舱内部超宽带确定性信道建模

将室内无线信道仿真中常用的几何光学和射线追踪技术,引入到对客机机舱内部的超宽带(Ultra-WideBand,UWB)信道研究当中。信道仿真的主要算法基于一种称为射线密度归一化(RayDensityNormalization,RDN)的方法。该方法使用射线密度的概念来计算每条射线对接收点处总信号强度的贡献。为了验证方法的有效性,实验构建了一个Boeing737-200客机机舱模型进行仿真。仿真将接收机设置在每个座位的顶部、扶手和底部,以研究不同水平高度信道的差别。仿真中对路径损耗和均方根(RMS)时延扩展两类大尺度信道参数进行了统计和分析,部分仿真结果与国外实测结果进行了对比。对比结果证明了仿真结果的保真度以及现有仿真工具的有效性。     

浅论回收型卫星气动外形设计

本文首先简要介绍回收型卫星重返大气层概貌。从工程设计角度出发论述卫星再入舱气动外形设计依据,评述美、苏两国现有空间再入飞行器外形的特点,然后论述卫星再入舱与导弹再入弹头的主要差别,指出再入舱特有的主要空气动力学问题。最后展望回收型卫星气动外形未来发展趋势,推荐一种有发展前途的新型再入舱气动外形—平头双锥体。