连续小推力非开普勒悬浮轨道研究综述

连续小推力非开普勒悬浮轨道在深空探测与地球极地观测任务中有着重要的应用前景.归纳了电推进、太阳帆推进等连续小推力技术的发展历程与现状;阐述了日心、行星悬浮轨道的动力学特性、稳定性、轨道保持策略;分析了三体问题下人工拉格朗日点的优势及其在深空探测方面的应用;讨论了悬浮轨道编队飞行的研究方法与控制策略.最后针对小推力悬浮轨...     

基于环路滤波器的低复杂度LMS算法设计

研究利用多天线结构对测控信号内存在的干扰进行对消和信号增强的技术。首先介绍传统空域干扰对消算法LMS，以及LMS的诸多改进算法，分析当前这些LMS算法在强干扰存在时收敛稳定性和收敛速度之间的折中关系以及参数调节的难度，分析了定步长和变步长LMS算法的优劣。针对变步长LMS由于动态环境以及大功率干扰的存在引起的收敛速度变慢和步长计算复杂的问题，提出了一种基于二阶环路滤波器累计误差的低复杂度LMS算法LF-LMS，该算法弱化单次误差的不稳定性并提高累计误差的稳定性，利用大步长和可变误差以实现快速收敛并缩小进入稳定状态后的误差波动，且计算量较小，可以有效应用于DSP工程实现，并通过仿真验证了算法在收敛速度和动态环境下的鲁棒性。     

基于变论域模糊控制算法的仿真与FPGA优化实现

针对单力臂模型的复杂动力学行为，设计了一种不依赖于被控对象的精确数学模型的变论域模糊控制器。在闭环系统中，角位移量的跟踪偏差和其变化率作为系统输入，并将控制器的初始论域设为［-3，3］，其值可通过伸缩因子来调节。基于Matlab软件仿真，验证单力臂模型对预期指令的跟踪性能。另外，基于现场可编程门列阵(FPGA)硬件，采用移位操作和分段线性化两种方法对控制器进行优化。由此，无乘法器和片上内存零占用的设计结构显著降低了硬件资源负担。实验结果表明:本文所提变论域模糊闭环控制方法在精确度(低于0.02)、自适应性以及实时性等方面性能较优越，具有一定工程应用价值。     

Validation of IRI-2012 TEC model over Ethiopia during solar minimum (2009) and solar maximum (2013) phases

This paper investigates the capacity of the latest version of the International Reference Ionosphere (IRI-2012) model in predicting the vertical Total Electron Content (vTEC) over Ethiopian regions during solar minimum (2009) and solar maximum (2013) phases. This has been carried out by comparing the IRI-2012 modeled and experimental vTEC inferred from eight ground based dual frequency GPS (Global Positioning System) receivers installed recently at different regions of the country. In this work, the diurnal, monthly and seasonal variation in the measured vTEC have been analyzed and compared with the IRI-2012 modeled vTEC. During the solar minimum phase, the lowest and highest diurnal peak of the experimental vTEC are observed in July and October, respectively. In general, the diurnal variability of vTEC has shown minimum values around 0300 UT (0600 LT) and maximum values between around 1000 and 1300 UT (1300 and 1600 LT) during both solar activity phases. Moreover, the maximum and minimum monthly and seasonal mean hourly vTEC values are observed in October and July and in the March equinox and June solstice, respectively. It is also shown that the IRI-2012-model better predicts the diurnal vTEC in the time interval of about 0000–0300 UT (0300–0600 LT) during the solar minimum phase. However, the model generally overestimates the diurnal vTEC except in the time interval of about 0900–1500 UT (1200–1800 LT) during the solar maximum phase. The overall result of this work shows that the diurnal vTEC prediction performance of the model is generally better during the solar minimum phase than during solar maximum phase. Regarding the monthly and seasonal prediction capacity of the model, there is a good agreement between the modeled and measured monthly and seasonal mean hourly vTEC values in January and December solstice, respectively. Another result of the work depicts that unlike the GPS–TEC the IRI-2012 TEC does not respond to the effect resulted from geomagnetic storms.     

Spectra of the two official GLEs of solar cycle 24

Based on ground-level data and on satellite data we determine in this work the observational spectrum of both, the Ground Level Enhancement of May 17, (2012) the so-called GLE71 and the Ground Level Enhancement of September 10, 2017 (GLE 72). We describe a simplified method to obtain the experimental spectrum at ground level. Data of the GLE71 and GLE72 indicate the presence of two different populations, each one with a different energy spectrum. On the other hand, we explore the kind of phenomena that take place at the source in these two particular events. In contrast with other methods based on the temporal synchronization between electromagnetic emissions of flares and coronal mass ejections (CME), here we develop an alternative option based on the study of the accelerated particles, by adjusting our theoretical spectra to the observational spectra. The main results of this work are the derivation of the source and acceleration parameters involved in the generation process. These results lead us to construct possible scenarios of particle generation in the source for each one of the two studied GLEs.     

航天器太阳圆面速度差/太阳视方向组合导航

针对航天器，尤其是深空探测器的自主导航问题，提出了一种新的太阳圆面速度差天文量测信息，该信息利用太阳的较差自转所造成的太阳圆面各点速度不同的特性，是探测器当前位置的函数，其几何本质是一个探测器的位置圆锥。在此基础上，基于太阳圆面速度差和太阳视方向互补的特性，提出了一种太阳圆面速度差/太阳视方向组合导航新方法，将太阳圆面速度差与太阳视方向2种量测量结合起来，实现了量测量之间的优势互补，进一步提高了导航性能。以太阳探测器为例进行了仿真，仿真结果表明相比较于单独用太阳圆面速度差或太阳视方向的导航方法，基于太阳圆面速度差/太阳视方向的组合导航方法精度分别提升了10.2%和16.0%。此外，还分析了光谱仪精度、采样周期和光谱仪数量对导航性能的影响，为深空探测自主导航提供了新的理论与方法。     

含多间隙柔性可展帆板动力学建模及仿真

为研究柔性和多级铰链间隙对帆板展开过程动力学特性的影响，以月球车两级往复可展太阳帆板为研究对象，采用修正Coulomb模型表述摩擦力，通过接触碰撞力描述间隙，运用有限元法进行帆板柔性化，进而建立多间隙-柔性耦合的动力学模型。采用变步长伦哥库塔法进行数值求解，模拟帆板展开过程，分析了多间隙和柔性对帆板质心加速度、铰链间隙碰撞力等参数的影响。结果表明，在保证展开机构刚度要求的前提下，帆板柔性可补偿因铰间隙引起的加速度波动，减弱间隙处碰撞的剧烈程度，减小碰撞力幅值，进而改善帆板展开机构的动态特性。研究结果可用于指导月球车两级往复可展太阳帆板等同类型的可展机构动态优化设计。     

高速RS编码器的FPGA实现

ＲＳ码广泛应用于卫星通信,移动通信和数据存储等领域中,研究用现场可编程编辑阵列（ＦＰＧＡ）实现高速ＲＳ码编码器;对硬件实现中的主要问题做了分析和讨论,仿真和实际测试结果均表明,编码器原理样机功能正常,吞吐率可达２００Ｍｂｉｔ／ｓ。     

太阳电池片间隙区域充电电场的数值计算

高压太阳电池阵在空间带电粒子环境中易发生静电放电,特别是太阳电池片间隙区域存在着诱发二次放电的风险。文章建立了太阳电池片间隙区域充电模型,基于静电理论研究了计算太阳电池片间隙区域充电电场的算法。数值计算结果表明:太阳电池片间隙区域两侧,充电电场呈对称分布;玻璃盖片与基底之间存在明显的电位差,且玻璃盖片的电位高于其他部位。     

UltraFlex太阳电池阵的结构优化

以提高圆形太阳电池阵的展开过程稳定性和固有频率为优化目标,以UltraFlex太阳电池阵为模型,采用有限元软件SAMCEF对其进行结构优化。以承重梁材料、斜梁开口高度、斜梁位置、梁截面高度及厚度5种结构参数为优化变量,进行了多种工况的展开动力学仿真和模态计算。经分析发现,结构展开后期太阳毯与支撑梁拉扯会导致支撑梁剪切应力激增;梁材料、斜梁位置与支撑梁截面高度对太阳电池阵的展开过程稳定性影响较大;当梁材料为碳纤维,斜梁位置为1100 mm,梁截面高度为20 mm时,展开过程稳定性最好;斜梁位置和承重梁截面厚度对结构固有频率影响较大;当斜梁位置为900 mm或1100 mm、承重梁截面厚度从3 mm增至3.5 mm时,系统固有频率涨幅最大,由此带来的质量增加可以接受。