This paper proposes an approach method that enables an autonomous underwater vehicle (AUV) to accurately approach an unmanned aerial vehicle (UAV)-deployed station in the final stage of a mission. AUVs are increasingly used as fully autonomous underwater survey platforms, yet their operation is still constrained by the need for human or vessel support during deployment and recovery. To remove this constraint, the UAV deploys an underwater station that provides a positioning reference and acts as a recovery system. Using onboard acoustic positioning and communication devices, the AUV and the station mutually transmit signals, allowing the AUV to estimate its state relative to the station and guide its approach. Sea experiments evaluated the resulting approach accuracy relative to the station, showing that the AUV can converge to the station vicinity with the precision required for subsequent recovery. This study validates only the pre-recovery approach phase to the recovery station. Full docking and recovery are beyond the scope of this article. The proposed method provides fundamental technology for a reliable close-range approach, which is a key prerequisite for fully autonomous recovery without human or vessel assistance.
Matsuda et al. (Fri,) studied this question.