Robust image-based control for spacecraft uncooperative rendezvous and synchronization using a zooming camera

摘要

This paper presents a new image-based control scheme for spacecraft rendezvous and synchronization with an uncooperative tumbling target, which is capable of autonomously adjusting the camera focal length, in order to extend the working range of visual servoing and guarantee that the target remains within the camera field-of-view. Unlike conventional visual servoing, the new scheme is based on a system model that is invariant to changes in camera-intrinsic parameters. An active zooming strategy is proposed which ensures that the target remains in the image plane with a proper size during the visual servoing. By utilizing the image features as feedback information, a finite-time controller is designed, which is robust to the unknown target's motion as well as the external perturbations, with the ability to estimate and adapt to the upper bound of the uncertainties. The closed-loop system stability is proved using the Lyapunov theory. Simulation scenarios are studied for two different onboard cameras, namely, a fixed-focal-length camera and a zooming camera. In addition, a comparative study with a conventional sliding-mode controller is performed to evaluate the convergence and accuracy of the proposed control scheme.