Virtual stereovision pose measurement of noncooperative space targets for a dual-arm space robot

Noncooperative target pose (position and attitude) measurement is very important for on-orbital servicing tasks, such as malfunctioned spacecraft capturing and repairing, space debris removal, and so on. Traditional stereovision-based methods require the two cameras to observe the same object and form a common observation area, limiting system flexibility, and measurement distance. In this paper, a virtual stereovision (VSV) modeling and pose measurement method are proposed for a dual-arm space robotic system. Each arm only carries one camera to observe different objects. The geometry features (i.e., the triangle, quadrilateral, or circular features) are independently extracted from the images of each camera. The two separate cameras are mapped to a stereo measurement range and the, respectively, identified features are converted into an equivalent “virtual common feature.” Then, a “VSV measurement system” is constructed. The rocket nozzle and the triangular support of the satellite are considered as different objects to be observed by the two cameras of a dual-arm space robot. The pose of the nozzles and the triangular brackets is further achieved based on the VSV information. Finally, we developed an experimental system, which is composed of a satellite mockup, two monocular cameras, and high precision laser tracker (used to evaluate the vision measure accuracy). The experimental results verified the proposed method. The average position error of the method is less than 6.1367 mm, and the average attitude error is less than 2.415°.