Feature-extraction and motion-measurement method for noncooperative space targets

Abstract

<p indent="0mm">Space targets served on the orbit have a noncooperative characteristic. Thus, it is difficult to extract their features and measure their motions. To resolve this problem, a feature-extraction and motion-measurement method for noncooperative space targets is proposed in this paper. First, threshold segmentation is performed with the images captured using the binocular camera to separate the satellite-rocket docking ring section from the surrounding background. Additionally, the Canny operator method is used to detect the edge of the satellite-rocket docking ring. Based on the analysis of the characteristic of the edge’s shape, Hough transformation is employed to extract the line feature of the cross. The contour of the satellite-rocket docking ring is fitted using the least square method. Furthermore, the parallel equivalent projection and the epipolar line alignment methods are used to match the images of the left and right cameras in the convergence binocular vision. Finally, the relative position of the satellite-rocket docking ring is obtained through a three-dimensional reconstruction of the feature points on the satellite-rocket docking ring and cross. Additionally, the dual-vector pose-determination method is employed to obtain the relative pose of the satellite-rocket docking ring. The ground simulation test shows that this algorithm can measure the relative position and pose of the satellite-rocket docking ring effectively. At a distance of <sc>1.5 m</sc> from the target, the precision of the relative position is <sc>15 mm,</sc> and that of the relative pose is 1.12°. This research can achieve an accurate measurement of the relative position and pose of the noncooperative target’s docking ring, providing the measurement basis and important support for on-orbit service missions, such as the grasping, repairing, refueling, and module replacement of noncooperative space targets; thus, it has important practical application value.