【作者】 陈景伟；

【导师】 徐青；

【作者基本信息】 解放军信息工程大学 ， 摄影测量与遥感， 2008， 硕士

【摘要】 随着月球探测、火星探测以及小行星与彗星等小天体探测计划的实施,深空探测已成为21世纪航天技术发展的热点和重点领域。自主导航技术是深空探测任务必需的关键技术之一,可视化技术是深空探测任务方案设计与论证的重要辅助手段。本文以深空小天体探测为背景,结合国家863计划课题的研制任务,以NASA“深度撞击”小天体接近与撞击探测任务为参考,重点对小天体探测中的光学自主导航与可视化技术进行了深入研究,主要工作与创新点包括:1.基于摄影测量成像与定位理论初步形成一种小天体探测光学自主导航方案。(1)在深入分析小天体接近阶段导航特点的基础上,探讨了运用数字图像特征提取与匹配技术及摄影测量空间后方交会理论进行深空探测器自主导航、制导与控制(Guidance,Navigation and Control,GN&C)的技术途径,初步形成了一种基于光学测量的小天体探测自主导航方案。通过提取与跟踪导航相机拍摄到的小天体表面上的导航目标并辅以激光测距设备测量探测器与导航目标之间的距离,在轨进行导航参数的解算。(2)研究了基于图像处理技术的导航目标在轨提取与跟踪的方法。系统阐述了导航图像在轨处理的内容和流程,提出了一种基于图像分块和灰度局部方差的导航目标在轨提取算法,并利用图像匹配技术实现了导航目标的跟踪。(3)建立了自主导航参数的光学测量模型,研究了基于导航相机和激光测距设备的观测量进行探测器自主导航参数计算的过程和方法,分析并比较了探测器和小天体相对位置和姿态参数的测量算法,推导了探测器瞄准撞击点位置矢量在自主导航不同阶段的计算方法,分析了本文提出的导航方案的导航精度及影响因素。2.以“深度撞击”任务为背景研究并实现了小天体探测可视化的部分关键技术。(1)提出了一种基于图形硬件优化的深空目标三维建模与可视化方法,针对图形硬件的特点设计了基于索引机制的深空目标模型数据组织方式,避免了大量冗余数据的处理,提高了模型绘制的效率,实现了对复杂深空目标的三维实时绘制;(2)利用粒子系统技术逼真再现了小天体撞击的效果,根据GPU的并行处理特性设计了基于GPU通用计算技术(GPGPU)的大规模粒子系统,可以很大程度地增加粒子系统实时仿真应用中的粒子数量,并具有远高于普通粒子系统的实时渲染效率,从而大大提高了小天体撞击效果可视化的逼真程度。(3)集成了本文完成的可视化算法,对小天体接近与撞击的全过程进行了可视化模拟,取得了较好的效果。更多还原

【Abstract】 With the implementation of Moon, Mars and small celestial bodies (such as asteroid and comet) exploration, Deep space exploration becomes the hotspot and significant filed of the development for spaceflight technology in the 21st century. Spacecraft autonomous navigation technology is a regarded key technology in the deep exploration fields. The Visualization technology plays an important role in designation and demonstration for the missions of deep Space exploration. With the supports of 863 Program, this dissertation detailed analyzes the autonomous optical navigation and visualization of the small celestial bodies exploration. The main work and innovations are listed as follows:1. An autonomous navigation system scheme for small celestial bodies exploration is proposed based on the theory of photogrammetry and the technology of image processing(1) Based upon the detailed analysis on characteristics of navigation during small celestial body approaching phase, an autonomous navigation system scheme based on the theory of optical measurement is designed. Several visual small features on the surface of small celestial body are extracted from the images taken by the navigation camera, which are also tracked robustly and accurately. The distance from probe to those navigation targets are measured using the laser range finder. And then the navigation parameters are computed on board.(2) An investigation is made on the extraction and tracking method of targets on board on the basis of navigation image processing, technology. The content and flow of navigation image processing is expatiated systemically. An algorithm for on board extraction of navigation targets is put forward based on image decomposition and local gray variance. The tracking of navigation targets is realized by the technology of image matching.(3) The optical measure principle of navigation parameters is founded. The method and process on computation of navigation parameters are investigated according to the observation of navigation camera and laser range finder. Comparisons and discussions on measuring algorithms for relative position and attitude between the probe and the small celestial body are brought forward. The computation method of Impactor Targeting Vector (ITV) in the different phases of navigation is proposed. The precision of our autonomous navigation system scheme and influencing factors are analyzed.2. The main contents and key technologies on the visualization of small celestial body exploration are investigated with the background of small celestial body approaching and impacting.(1) A method of space objects modeling and visualization is put forward based on the graphics hardware. Aiming at the characteristics of graphics hardware, an index mechanism is introduced to optimize the data structure of space objects, which can facilitate the redundant management effectively and improve the .efficiency of visualization dramatically. Real-time rendering of complex space objects is carried out based on the proposed method.(2) The impact result between small celestial body and the impactor probe is simulated vividly by making use of particle system technology. According to the characteristics of multiple passages of GPU, Anew realization of particle system is proposed based on the GPGPU(General-Purpose Computing on Graphics Hardware), which is probable to increase a numerous of particles in the real-time simulation to enhance the reality of the scene. The particle system based on GPU has a great ability in real-time simulation than the ordinary particle systems.(3) By integrating the proposed algorithms, the whole course of small celestial body approaching and impact is simulated visually.更多还原