星箭对接环抓捕点单目视觉导航方法

Monocular visual navigation method for capture point of docking ring

星箭对接环是空间飞行器上普遍存在的结构,常在空间非合作抓捕任务中作为位姿测量与抓捕固定的特征部件。采用对接环空间圆特征进行视觉测量可以计算圆心位置,但圆心并非对接环实体结构,无法直接作为抓捕导航点。考虑对接环轮廓在图像中的几何不变特征,提出一种基于最短路径原则的环上抓捕点单目视觉导航方法,并给出了抓捕点导航参数计算模型。同时针对视觉测量中复杂目标环境的测量图像,提出了一种类圆轮廓提取方法,处理过程包括了图像中轮廓的分割、筛选与组合。通过数字仿真试验和半实物仿真试验进行验证,结果表明本方法能够有效剔除噪声轮廓,对接环上抓捕点测量准确稳定,抓捕点位置计算误差小于1 mm,角度误差小于0.5°。

Docking ring is a typical structure on spacecraft, which is often used for position measurement as a single circle feature and a capture object in space non-cooperative capture operations. Based on the spatial circle feature of the docking ring, the center of the docking ring circle can be positioned by vision measurement. However, the center of the docking ring is not a physical structure and cannot be directly used as the capture point. Considering the geometric invariance of the contour in pictures, a monocular visual navigation method is proposed, which is based on shortest path principle. A calculation model of the capture point parameters is described. At the same time, a circular contour extraction method including segmentation, selection and combination of contours in the picture is proposed, to solve the problem of contour extraction of docking ring in complex images. Finally, the method is verified by digital simulation experiments and semi-physical simulation experiments. The results indicate that the proposed method is robust to the noise and the capture point is accurate and stable. The position error of the capture point is less than 1 mm and the angle error is less than 0.5°.