世界典型火星探测发射轨道及窗口拓展分析（英文）

由于运载火箭自身特点及飞行航、落区约束的差异,致使世界典型运载火箭直接火星探测任务的发射轨道存在明显不同。从直接火星转移的飞行力学原理的角度进行了分析,重点关注了典型火星探测任务的轨道剖面设计及窗口拓展方法,完成了对当前火星探测任务典型出发轨道特点的分析总结。     

基于神经网络线性系统的速归辨识

本文提出了一种基于神经网络的系统辨识方法，给出了有效的基于最速下降法的神经网络学习算法。经过仿真实验表明，这种训练出的模型能有效地进行系统辨识。     

基于神经网络线性系统的递归辨识

本文提出了一种基于神经网络的系统辨识方法，给出了有效的基于最速下降法的神经网络学习算法。经过仿真实验表明，这种训练出的模型能有效地进行系统辨识。     

一种基于视觉的火星车自主导航方案设计

火星车的自主导航是其顺利完成火星探测任务的重要保障,是目前火星车需要亟待解决的关键技术之一。首先,对几种不同的视觉定位方法进行论述,分析了不同视觉定位方法的优缺点。然后,给出了天文导航系统的定姿原理。最后,根据惯性、视觉、天文三种导航系统各自的特点,设计了一种适用于火星车的惯性/视觉/天文自主组合导航方案,通过有机融合三种导航系统的信息,使该方案能够满足火星车在复杂环境下对长时间、远距离、高精度自主导航的要求。     

火星飞机的多胞LPV鲁棒控制器设计

随着火星探测的日益发展,火星飞机作为一种中尺度探测手段,能够很好地补充轨道和地表探测器之间的能力空白。针对火星飞机的强非线性、参数不确定性的特点,提出了一种火星飞机的多胞LPV变增益H∞控制器设计方法。首先依据火星飞机的纵向非线性模型,在进行研究的飞行包线内选取适量平衡工作点进行雅可比线性化,通过线性化后的线性时不变系统数值拟合得到系统的LPV模型;然后通过张量的高阶奇异值分解理论进行张量积建模,实现火星飞机LPV模型的多胞形表示。最后设计基于LMI求解的鲁棒变增益控制器,使对象能够克服不利特性的影响,能够完成指令信号的快速跟踪并且使系统具有较强的鲁棒性。     

超高速撞击波阻抗梯度材料形成的碎片云相变特性

在超高速碰撞下,波阻抗梯度材料能使弹丸的动能更多地转变为靶板材料内能,使其发生熔化、气化等相变,分散和消耗弹丸的动能,进而实现航天器对空间碎片的防护。以钛、铝、镁3种 材料组成的波阻抗梯度材料为研究对象,借助于光滑粒子流体动力学数值模拟方法,采用Tilloston状态方程和Steinberg-Guinan本构模型,给出各材料的冲击相变判据,结合速度为7.9 km/s的超高速碰撞实验结果,验证数值模拟结果的有效性。计算结果表明：钛、铝、镁波阻抗梯度材料在受到大于4 km/s速度撞击时,形成的碎片云会发生不同程度的熔化和气化;钛、铝、镁3种组分分别在受到6 km/s、5 km/s、4 km/s速度撞击时碎片云会发生熔化,在受到8 km/s、9 km/s、6 km/s速度撞击时碎片云会发生气化。     

日-地系拉格朗日点任务及其转移轨道设计方法

绕日-地系拉格朗日点的深空探测任务越来越多,这些任务的目标轨道一般为Halo轨道或Lissajous轨道.介绍了3种从地球停泊轨道出发到拉格朗日点的转移轨道设计方法,并进行了对比.最后以Az=-800 000 km的Halo轨道为例,验证了直接转移轨道设计方法的有效性.     

用直接优选法设计最大推力喷管型线

本文提出了用直接优选法设计最大推力喷管型线的方法。喷管型线是按具有一固定初始膨胀型线的二次多项式造型的。借直接优选法改变多项式系数来确定最大推力型线。考虑了三种直接优选法:多维线性搜索法,最速下降法和牛顿法。文中提供了计算结果,用以阐明这三种直接优选法的特征,并证明了二次多项式型线所产生的推力基本上与变分法计算确定的喷管型线所产生的推力是一致的。     

火星环绕器次表层探测雷达发展综述

火星环绕器次表层探测雷达能够实现环火轨道火星次表层结构高分辨探测,为深入研究火星地质结构提供科学数据。针对目标介质分层的探测问题,进行了火星环绕器次表层探测雷达发展综述。详细介绍了火星环绕器次表层探测雷达的发展现状、探测原理、指标计算方法及关键技术,并对火星环绕器次表层探测雷达的发展趋势进行了展望。     

中国首次火星探测任务着陆器悬停避障试验完成

正2019年11月14日,中国首次火星探测任务着陆器悬停避障试验在河北省怀来县完成。此次试验是中国火星探测任务首次公开亮相,试验模拟了着陆器在火星环境下悬停、避障、缓速下降的过程,对其设计正确性进行了综合验证。火星探测器分为环绕器与着陆器两部分,由航天科技集团     

Stability of the Third Generation Intensifier under Illumination

The stability under illumination of transmission-mode GaAs photocathode sealed in the third generation intensifier is investigated by use of spectral response testing instruments. The variations of spectral response with the illumination times under weak and intense illumination are compared. The variations of photoemission performance parameters are also characterized. The results show that during initial several weak illuminations photocathode behaves no evident decay and a maximum sensitivity is achieved, while under intense illumination the sensitivity of photocathode begin to decrease largely at the first illumination. The calculated performance parameters show that the variation of surface escape probability with illumination times is a direct cause of instability of photocathode. It is also found that under intense illumination peak wavelength is moved towards short-wave and peak response is decreased, which shows that the ability of long-wave response of photocathode is decreased.     

Passive Acoustic Radar for Detecting Supersonic Cruise Missile

A Passive Acoustic Radar is presented as a necessary complement to electromagnetic wave radar, which will be expected to be an effective means for detecting cruise missiles. Acoustic characteristics of supersonic flying projectiles with diverse shapes are expounded via experiment. It is pointed out that simulation experiment could be implemented using bullet or shell instead of cruise missile. Based on theoretical analysis and experiment, the ““acoustic fingerprint““ character of cruise missile is illustrated to identify it in a strong noise environment. After establishing a locating mathematical model, the technique of acoustic embattling is utilized to resolve a problem of confirming the time of early-warning, considering the fact that velocity of sound is much slower than that of light. Thereby, a whole system of passive acoustic radar for detecting supersonic cruise missile is formed.     

Design and Analysis of Test Schemes of Static Postponing Time on Shrapnels Used to Riot Control

The test scheme of static postponing time given in our actual national military test standard on shrapnels used to control riot is a nine-point test scheme on the combined action of three kinds of temperatures and three kinds of pressures,the consumed ammunitions are more excessive. Statistic analysis and tentative checkout about a lot of test data are done,feasibility gists are put forward for optimizing of the test design scheme. The optimizing design and data analysis of test scheme of the item are done by managing uniformity design theory, two scientific and reasonable six-point test schemes are confirmed. The feasibility and reliability of the optimizing design schemes put forward above are proved ulteriorly by test validating. The gained schemes not only have good design uniformity and little ammunition wastage and meet the test demand, but also have better forecast ability for the result data of other points using the mathematic models from the actual test points.     

Super-resolution Restoration of Remote-sensing Images

A novel image restoration scheme, which is super-resolution image restoration algorithm Poisson-maximum-afterword-probability based on Markvo constraint （MPMAP） combined with evaluating image detail parameter D, has been proposed. The advantage of super-resolution algorithm MPMAP incorporated with parameter D lies in the fact that superresolution algorithm MPMAP model is discrete, which is in accordance with remote-sensing imaging model, and the algorithm MPMAP is proved applicable to linear and non-linear imaging models with a unique solution when noise is not severe. According to simulation experiments for practical images, super-resolution algorithm MPMAP can retain image details better than most of traditional restoration methods; at the same time, the proposed parameter D can help to identify real point spread function （PSF） value of degradation process. Processing result of practical remote-sensing images by MPMAP combined with parameter D are given, it illustrates that MPMAP restoration scheme combined PSF estimation has a better restoration result than that of Photoshop processing, based on the same original images. It is proved that the proposed scheme is helpful to offset the lack of resolution of the original remote-sensing images and has its extensive application foreground.     

Design and Simulation of TF and TA Controller for Missile

A nonlinear terrain following(TF) and terrain avoidance(TA) controller is proposed for missile control systems. Based on classical TF algorithm (adaptive angle method), a new method for TF controller is proposed by using angle of attack. A method of obtaining terrain outline data from digital elevation map (DEM) for TF control is discussed in order to save store space. A TA algorithm is proposed by using bank-to-turn technique. The block control model, which is suitable for backstepping design, is given for nonlinear model of missile. Making full use of the characteristics of the system and combining block control principle and backstepping technique, a robust controller design method is proposed. Uncertainties in every sub-block are allowed, and can be canceled by using the idea of nonlinear damping. It is proved that the state tracking errors are converged to a neighborhood of the origin exponentially. Finally, nonlinear six-degree-of-freedom simulation results for the missile model are presented to demonstrate the effectiveness of the proposed control law.     

Expert Systems Aimed at General Design of Projectiles

Expert systems aimed at the general design of projectiles can implement a series of intelligent designs, such as the design of HE shell, the scheme expounded and proved, the emulation analysis and calculation, etc. Aiming at the product design feature, the expert system adopts the object-oriented knowledge representation and all kinds of inference control engines to describe and reason the relevant knowledge regarding the product through the microcomputer. It embodies the foundation of emulation analysis and simulated manufacturing of the shell. It makes use of the method that knowledge expression is combined with condition of inference to carry out the overall design and emulation and reference.The paper gives the ways through which the functions can be achieved, gives the modularization of reference and the design methods of systematization, puts forward the method of knowledge expression and working interface, and supplies a platform for similar products of the shell category that can be quickly designed.     

Design of Non-fragile Satisfactory Estimator for Linear Continuous Perturbed Stochastic Systems

The design problem of non-fragile estimator is addressed for a class of perturbed linear continuous systems. The perturbations occur on the plant and estimator parameters. The estimator designed should force the error system to achieve the desired decay rate and force the steady error variance less than the specified upper bound irrdevancy of the admissible plant perturbations and estimator perturbations. Consistency problem of the decay rate with the variance upper bound is first considered via linear matrix inequality （LMI） approach. The solution of the estimator parameter under specifications to be consistent is then discussed. The consistency condition of specifications and estimator parameter solution are transformed to feasible or minimum problems subject to a set of LMI respectively. The method is illustrated by a numerical example.     

An Improved Scene-based Nonuniformity Correction Algorithm for Infrared Focal Plane Arrays Using Neural Networks

The improved scene-based adaptive nonuniformity correction （NUC） algorithms using a neural network （NNT） approach for infrared image sequences are presented and analyzed. The retlna-like neural networks using steepest descent model was the first proposed infrared focal plane arrays （IRFPA） nonuniformity compensation method, which can perform parameter estimation of the sensors over time on a frame by frame basis. To increase the strength and the robustness of the NNT algorithm and to avoid the presence of ghosting artifacts, some optimization techniques, including momentum term, regularization factor and adaptive learning rate, were executed in the parameter learning process. In this paper, the local median filtering result of Xij （ n ） is proposed as an alternative value of desired network output of neuron Xij （ n ）, denoted as Tij （ n ）, which is the local spatial average of Xij （ n ） in traditional NNT methods. Noticeably, the NUC algorithm is inter-frame adaptive in nature and does not rely on any statistical assumptions on the scene data in the image sequence. Applications of this algorithm to the simulated video sequences and real infrared data taken with PV320 show that the correction results of image sequence are better than that of using original NNT approach, especially for the short-time image sequences （several hundred frames） subjected to the dense impulse noises with a number of dead or saturated pixels.     

Piecewise Filter of Infrared Image Based on Moment Theory

The disadvantages of IR images mostly include high noise, blurry edge and so on. The characteristics make the existent smoothing methods ineffective in preserving edge, To solve this problem, a piecewise moment filter （PMF） is put forward. By using moment and piecewise linear theory, the filter can preserve edge. Based on the statistical model of random noise, a related-coefficient method is presented to estimate the variance of noise. The edge region and model are then detected by the estimated variance. The expectation of first-order derivatives is used in getting the reliable offset of edge. At last, a fast moment filter of double-stair edge model is used to gain the piecewise smoothing results and reduce the calculation. The experimental result shows that the new method has a better capability than other methods in suppressing noise and preserving edge.     

Bistatic Sonar Localization Based on Best Linear Unbiased Estimation

A best linear unbiased estimation （BLUE） algorithm for bistatic sonar localization is proposed. The Cramer-Rao bound for bistatic Sonar and the geometrical dilution of precision （GDOP） in different conditions are given. The simulation results show that the location accuracy of BLUE algorithm is higher than the weighted least square method.