Relative State Measurements Of Spacecraft In Formation Flying Based-on Stereo Vision

Since 1950s, the space technology has been in its blooming time, and there have been many kinds of spacecrafts based on its application area, such as communication, weather, navigation, resource & environment, military reconnaissance, science research, and etc. Also it has been in the way of high performance and high integration. Although with the growing requirements in budget and development period, spacecraft formation flying has been the focus of many research institutes, and the need to the measurements of relative state has been the key issue.There have been several solutions of the measurement, such GPS, microwave radar, laser radar, monocular visible light, passive infrared, and etc. This thesis discussed the measurements based on stereo vision, and has focused on two types of measurements of spacecraft relative state.1. Analyze the characters of spacecraft formation flying, analyze the environment constraints of the observation based on stereo vision, including the relative movements of the spacecrafts in formation flying, draw out equations for the relative movements. Analyze the radiation characters of the lamp-house in space, the reflection of the surface of the spacecraft based on some assumption on materials, the imaging characters of the target, and estimate the target's spectrum and luminance.2. Base on the constraints of operation environment of spacecrafts, a geometrical constraint based corner detection and camera calibration method is presented. Firstly a traditional corner detection algorithm is used to extract corners from the image, and find the edge points of the tessellated pattern by using the above detected corners as the initial seeds. And then the edge points are fitted with a set of cubic polynomial curves and the intersections of the curves are used as real corners in the image. Finally, these extracted corners are used to perform the task of camera calibration. The experimental results show that the geometrical constraint based method can improve the performance of the feature detection and camera calibration and give results with high precision.3. Give the method of relative state measurement of spacecraft in formation flying based on stereo vision, compared to existing methods, the means by stereo vision has fewer outer constraints, fewer requirements on on-board equipments, once more, it can provide the 3D information of the target, improving the accuracy of measurements; to improve the accuracy and robustness, an EKF based observation for coordinate target has been constructed to estimate the relative state of the target.4. Analyze the optical constraints and requirements for the observation of the non-coordinate target in large distance, give the method of constructing a large baseline stereo vision system for this kind of measurement, give the method of attitude determination algorithm based on computer vision and the simulation of attitude based on virtual imaging, discussed observing time constraints on several kinds of formations, also the system architecture has been drawn out in the text.