Theoretical Limitations of Visual Navigation of Lifesaving USV using Small UAS

This paper presents a theoretical analysis of the problem of visual navigation of an unmanned surface vehicle (USV) using visual feedback from a small unmanned aerial system (sUAS) in drowning victim recovery scenario. Manually teleoperated life-saving USVs have been used by responders to assist drowning victims. However, the teleoperation is difficult and requires additional manpower. In this project, the rescue is automated by using a sUAS to navigate the USV to the victims autonomously. This enables the responders to focus on the actual rescue. In this paper, the focus is given to the theory behind the problem. The problem is divided into visual position estimation, visual orientation estimation, and motion planning subproblems. For each subproblem, a theoretical analysis is provided and lower bound limits on how well the subproblem can be solved are determined. This will help to understand the theoretical limitations and to drive further research. Lastly, the previously published system is compared with the lower bound limits to identify the areas of potential improvement.