Application of the vision-based navigation and control for autonomous spacecraft docking

Abstract

This thesis deals with a methodology for unmanned autonomous spacecraft docking using vision-based sensor and its on-ground implementation with space robotics experiment facility (SREF). Automated rendezvous and docking problem between two spacecrafts have become of increasing importance in a recent decade coincidence with space station era. Two vehicles in docking phase are: one is chaser and the other is target. The chaser, having vision sensor, can detect relative attitude/position to the target. In this case, a priori knowledge is not required. Simple geometric calculation makes it possible to obtain attitude/position and performance of estimation will be improved when extended Kalman filter (EKF) is utilized imposing spacecraft dynamics. As experimental study of autonomous docking, free-flying robot is also used to simulate in-plane motion of spacecraft. The robot which contains whole sub-systems itself flies a few micro meters from the flat granite table minimizing the surface friction so that it makes similar environment of real space. For planar motion, the command system of robot has state feedback controller as well as vision-based estimator using one CCD camera and beacon combination. Sensor fusion technique is implemented to correct inertial sensor drift error. The robot has total eight on-off thrusters as an actuator and their each operation algorithm for desired force/torque is also included in flight software.