Multivariate bootstrapped relative positioning of spacecraft using GPS L1/Galileo E1 signals

GNSS-based precise relative positioning between spacecraft normally requires dual frequency observations, whereas attitude determination of the spacecraft, mainly due to the stronger model given by the a priori knowledge of the length and geometry of the baselines, can be performed precisely using only single frequency observations. When the Galileo signals will come available, the number of observations at the L1 frequency will increase as we will have a GPS and Galileo multi-constellation. Moreover the L1 observations of the Galileo system and modernized GPS are more precise than legacy GPS and this, combined with the increased number of observations, will result in a stronger model for single frequency relative positioning. In this contribution we will develop an even stronger model by combining the attitude determination problem with relative positioning. The attitude determination problem will be solved by the recently developed Multivariate Constrained (MC-) LAMBDA method. We will do this for each spacecraft and use the outcome for an ambiguity constrained solution on the baseline between the spacecraft. In this way the solution for the unconstrained baseline is bootstrapped from the MC-LAMBDA solutions of each spacecraft in what is called: multivariate bootstrapped relative positioning. The developed approach will be compared in simulations with relative positioning using a single antenna at each spacecraft (standard LAMBDA) and a vectorial bootstrapping approach. In the simulations we will analyze single epoch, single frequency success rates as the most challenging application. The difference in performance for the approaches for single epoch solutions, is a good indication of the strength of the underlying models. As the multivariate bootstrapping approach has a stronger model by applying information on the geometry of the constrained baselines, for applications with large observation noise and limited number of observations this will result in a better performance compared to the vectorial bootstrapping approach. Compared with standard LAMBDA, it can reach a 59% higher success rate for ambiguity resolution. The higher success rate on the unconstrained baseline between the platforms comes without extra computational load as the constrained baseline(s) problem has to be solved for attitude determination and this information can be applied for relative positioning.     

NAEV图为3—自中心图的充分必要条件及计算机判定

本文证明了一个非邻接离心点(NAEV)图G是3-自中心图,当且仅当G是一个块并且G的每个顶点都有长度为6的最长局部测地圈。本文还给出判定一个图是否为自中心图的算法,以及求出3-NAEV自中心图每个顶点的长度6的局部测地圈算法。     

基于先验子图检测的失效航天器SLAM方法

基于激光雷达的航天器位姿估计技术是当前在轨服务研究热点。针对失效航天器位姿估计,将通用的图优化SLAM技术应用到空间非合作目标的研究中。为解决SLAM算法在动态场景中产生累积误差问题,利用失效航天器自身运动特点,提出一种基于先验子图检测改进的SLAM算法。在该算法中,通过激光雷达和惯性测量单元分别采集失效航天器及周围环境的点云数据、服务航天器的运动信息,构建出服务场景下航天器的相对位姿图;再采用先验子图检测方法建立不连续的位姿节点间的约束关系;最后用约束信息对位姿图进行优化。仿真结果表明,相较于通用的SLAM算法的位姿估计,该方法减小了累积误差,提高了相对位姿估计精度,可以为后期的导航、控制等在轨任务提供信息。     

编队无人机的高生存力协同航路规划方法

提出了一种基于多目标遗传算法的编队无人机高生存力协同航路规划方法。方法由备选航路生成和协同规划两个步骤组成。备选航路生成的目的是为编队中的每一个无人机生成多条航路,该步骤采用的算法是多目标遗传算法。协同规划的目的是为各个无人机从备选航路中选择航路,使得各个无人机同时到达目标区域,以增加任务突然性,提高整个编队的生存力。通过仿真算例,把方法与基于Voronoi图的方法作了对比,给出了方法的优缺点分析。     

基于约束人工势场法的弹载飞行器实时避障航迹规划

针对弹载飞行器飞行高度低、需实时避障的需求,提出了一种三维约束人工势场法用于弹载飞行器的实时避障航迹规划.该方法将人工势场法扩展到三维空间,增加了一个势场函数——高度调节势场函数,并将弹载飞行器的动力学约束条件引入人工势场法中.该方法继承了传统人工势场法计算速度快、占用内存少的优点,并能保证所规划航迹的可飞性.仿真结果显示约束人工势场法相比于传统人工势场法,具有以下优势:所规划的航迹更具有可飞性;可明显减弱在障碍物附近的抖动现象;可显著改善在狭窄通道中的摆动现象;不易陷入局部最小点.     

2边连通3正则平面图的边着色

对具有正常３边着色的２边连通３正则平面图的顶点定义了方向,并且在这样的图上建立了路径上的积分,进一步给出了２边连通３正则平面图是３边可着色的等价条件。     

电磁探测卫星星上自主规划模型及优化算法

电磁探测卫星自治(AEDS)是一类对地观测卫星,其搜集的信息对工业、科研和军事等领域有着重要的意义。针对电磁探测卫星有效载荷特点,建立了基于动态拓扑结构无环路有向图的星上自主规划数学模型,提出了基于标记更新最短路径搜索的星上自主规划精确算法,对其完备性和时间复杂度进行了分析。并对精确算法时间复杂度较高的缺点,将近似支配概念引入到模型中,提出了标记更新最短路径搜索近似算法,分析了算法的近似程度和时间复杂度。最后,根据模拟的数据进行实验及分析,表明该方法能有效解决电磁探测卫星自主任务规划问题。     

Robust image-based coordinated control for spacecraft formation flying

This paper addresses a coordinated control problem for Spacecraft Formation Flying (SFF). The distributed followers are required to track and synchronize with the leader spacecraft. By using the feature points in the two-dimensional image space, an integrated 6-degree-of-freedom dynamic model is formulated for spacecraft relative motion. Without sophisticated three-dimensional reconstruction, image features are directly utilized for the controller design. The proposed image-based controller can drive the follower spacecraft in the desired configuration with respect to the leader when the real-time captured images match their reference counterparts. To improve the precision of the formation configuration, the proposed controller employs a coordinated term to reduce the relative distance errors between followers. The uncertainties in the system dynamics are handled by integrating the adaptive technique into the controller, which increases the robustness of the SFF system. The closed-loop system stability is analyzed using the Lyapunov method and algebraic graph theory. A numerical simulation for a given SFF scenario is performed to evaluate the performance of the controller.     

温度对约束阻尼板振动性能影响分析

基于复模量本构关系,推导各向同性约束阻尼板的动力学控制方程,求出了四边简支约束阻尼板的固有频率以及损耗因子的解析解,与利用有限元方法数值计算结果进行了对比验证。根据粘弹性材料特性曲线,插入取样温度点,分析不同温度下约束阻尼结构的减振性能,与数值结果进行了对比验证。结果表明,存在最佳温度,使约束阻尼结构减振效果最好。     

基于多信号流图的分层系统测试性建模与分析

为了对分层系统进行测试性分析,提出基于多信号流图模型的分层系统测试性建模与分析方法.该方法利用多信号流图模型建立分层系统的层次结构模型,进行测试性分析时,首先利用相关性模型法对顶层模型进行测试性分析,当层次性模块与其它模块不能区分时,再利用相关性模型法对模糊组进行测试性分析,最终实现对分层系统的诊断设计.最后,利用某具有层次性结构的滤波放大器电路对该方法进行了验证,试验结果证明,该方法对于分层系统的测试性建模与分析是有效的,能够为分层系统制定有效的诊断策略.