Elliptical Feature Extraction on Spacecraft Based on Texture Boundary Detection.

In order to determine the relative position and attitude of a non-cooperative target, such as a failed spacecraft, an algorithm based on the texture boundaries is developed for ellipse extraction. It is assumed that the elliptical feature represents the boundary of the two different texture regions on the surface of the spacecraft. With the relative position and attitude information from last time, a discrete geometric model of the target is projected onto the image plane. The texture boundary points are detected by the method of probability along the normal direction of each discrete point. Then the points with large errors are eliminated by the random sample consensus (RANSAC). Subsequently, the parameters of the extracted elliptical feature are obtained. As the texture feature is robust lo changes in illumination, the proposed algorithm can extract the elliptical features rapidly and accurately in the image in the complex cases, such as the changes in illumination and unevenness of the surface reflection on the spacecraft. Considering the feature extraction of a docking ring as an example, the simulation is performed. The influence of the parameters and noise on the accuracy of the proposed algorithm is investigated, and the cost time of the result is analyzed. The proposed algorithm and the algorithm based on the gradient information are compared in real images. The results show that the proposed algorithm has high accuracy and low computational cost. [ABSTRACT FROM AUTHOR]