基于本体知识库的遥感图像智能定轨

针对遥感图像的自主定轨方法存在图像误匹配和匹配速度慢的问题,基于本体知识库理论提出一种判断遥感图像观测资料有效性的智能推理方法。对遥感信息进行预处理,用于提取特征信息;分析基于图像定轨的知识结构框架,利用本体技术构建相应知识库系统;设计图像模板选择和判误规则,调用推理机进行推理得出观测资料有效性。将所提方法应用于基于图像特征点的卫星自主定轨,验证了方法的可行性。仿真结果表明:所提方法通过图像匹配模板选择和图像判误推理,计算速度提高了59.58%,导航位置精度和速度精度分别提高了10.58%和12.49%,有效提高了卫星自主定轨精度。

基于地面图像的卫星自主定轨方法可观测性及定轨性能分析

卫星自主定轨是航天发展趋势之一。近年来,高分辨率遥感卫星不断发展,为利用光学遥感图像进行自主定轨提供了可能。在此背景下,提出了一种基于地面特征点图像的自主定轨方法。通过构造局部可观测矩阵分析了该定轨系统的可观测性,并用局部可观测矩阵的条件数表征可观测度,估计系统的定轨性能。通过Monte-Carlo仿真实验评估了系统的定轨表现,结果表明:该定轨方法与多点定位方法相比可以得到更高的定轨精度。

基于遥感图像的无固定标志点卫星自主定轨

目前基于事先选取地面标志点的卫星自主导航可能会造成误匹配和漏匹配,并且不包含地标点的遥感图像也有可能存在导航信息。为了解决这两个问题,本文提出了一种不依赖事先标定地面标志点的自主导航方法,通过YOLOv3深度学习对获得的遥感图像进行目标识别缩小图像匹配区域,将识别后的目标区域进行图像匹配获得匹配特征点及其像平面坐标,最后利用成像模型计算特征点的地理坐标用于自主导航。仿真结果表明:本文方法相比于有控点精度更高,平均误差为31.9438 m,平均速度误差为0.0384 m/s。在引入测角信息与本文所提出的无地面标志点构成多源信息情况下,可以较为快速准确地实现航天器自主定轨。

基于分级目标传递的流体和结构多学科设计集成优化方法

以小水线面双体船(SWATH)的设计为载体,讨论多学科优化设计在其油耗问题中的应用.利用三维造型软件Solidworks对SWATH进行三维建模,对其中结构的部分运用有限元软件Hyper Works进行结构仿真分析,运用流体计算仿真软件FLUENT进行流体仿真分析.结合分级目标传递(Analytical Target Cascading,ATC)方法,借助Isight平台实现该问题多学科设计优化问题的求解,获得了良好的优化结果,实现了减小SWATH油耗量的目标.

Long-term semi-autonomous orbit determination supported by a few ground stations for navigation constellation

In view of the present technology of autonomous orbit determination for navigation satellite constellation(NSC) and the geographical conditions of China,we propose a long-term semi-autonomous orbit determination scheme supported by a few ground stations for NSC in this paper.Since the effect of rotation and translation of the entire constellation relative to the inertial reference frame can bring large errors to the autonomous orbit determination using only cross-link range measurement,a few ground stations(such as 1-3) are supposed to construct the connection between the NSC and the ground.Supported by such a few ground stations,the NSC can realize long-term orbit determination called semi-autonomous orbit determination.The simulation results based on the IGS ephemeris indicate that,for a certain degree of measurement errors,the NSC can maintain its semi-autonomous orbit determination in a period of 240 days within 5 meters of URE.

Feasibility study of autonomous orbit determination using only the crosslink range measurement for a combined navigation constellation

In order to expand the coverage area of satellite navigation systems, a combined navigation constellation which is formed by a global navigation constellation and a Lagrangian navigation constellation was studied. Only the crosslink range measurement was used to achieve long-term precise autonomous orbit determination for the combined navigation constellation, and the measurement model was derived. Simulations of 180 days based on the international global navigation satellite system（GNSS） service（IGS） ephemeris showed that the mentioned autonomous orbit determination method worked well in the Earth–Moon system. Statistical results were used to analyze the accuracy of autonomous orbit determination under the influences of different Lagrangian satellite constellations.

双码元X射线通信信号调制与误码率分析

为提高X射线通信效率,提出一种利用双靶材X射线源实现双码元通信的方案。通过调节磁场强弱和方向变化,控制电子不打靶、均匀打靶、轰击铬靶或铜靶,完成了基于磁场调制的双靶材X射线源的双码元通信信号调制实验,取得了间隔为10 s、距离为40 cm条件下的200组实验数据。基于实验数据,利用遗传优化二元泊松分布模型对通信误码率进行了分析,分析结果表明:当信号衰减值低于400时,可以实现误码率低于10^(-4),在此条件下,探测端每时隙内留存大约500个光子;遗传优化算法提高了识别精度,在衰减值超过1000的环境中误码率优化幅度为10^(-1)左右,误码率在10^(-4)范围内,优化幅度约为10^(-5),本研究为基于多靶材X射线源的X射线通信技术的发展提供了方向。