A Geometric Controller for Fully-Actuated Robotic Capture of a Tumbling Target

In this paper, we investigate the task of approaching a rigid tumbling satellite (Target) with a fully-actuated manipulator-equipped spacecraft (Servicer). We consider a Servicer with an end-effector-mounted exteroceptive sensor for feedback of Target motion. This sensor, however, provides only a noisy relative pose (position and orientation) of the tumbling Target's grasping frame. For this time-varying scenario, we propose a novel method, which is a cascade interconnection of a geometric Extended Kalman Filter (EKF) observer and a geometric controller. The key idea is to estimate the unforced Target's full state-space with the proposed EKF, and then use these estimates in feed-forward and feedback terms of the control law, while exploiting the fully-actuated Servicer. This results in a cascade interconnection, for which we prove the Local Asymptotic Stability (LAS) property. Furthermore, the effectiveness of the proposed method for the approach task is demonstrated through simulation.