Vision-guided capture of a free-flying object using a redundant serial manipulator

One important area for application of space robotics is autonomous on-orbit servicing of failed or failing spacecraft. An important aspect of these operations is the autonomous capture of the client satellite based on information obtained from a vision system. In this work, we describe laboratory experiments that verify the feasibility of autonomous capture of a slowly spinning non-cooperative satellite by a redundant serial manipulator. The main autonomous capture problem is divided in two separate tasks: the generation of a Cartesian trajectory to achieve the capture and the control of a manipulator to realize the generated Cartesian trajectory. Strategies that utilize the redundancy of a manipulator to optimize its posture are analyzed, implemented and used in the experimental validation of the autonomous capture. An online vision-based trajectory generation algorithm that generates a task-space velocity command to safely approach the target satellite and match its motion has been developed. The redundancy resolution and the trajectory generation algorithms are implemented and tested on two seven degree-of-freedom redundant manipulator systems: one located at McGill University and the other at the Canadian Space Agency. At both facilities, a scenario emulating the capture of a free-floating satellite have been created and used to validate the efficiency of the developed capture algorithm.