A vertical docking system based on the autonomous underwater shuttle for seafloor communication relay

Abstract

The autonomous seafloor observation system enables flexible deployment for long-term marine in-situ observations, but communication with land remains a challenge. This paper presents a novel vertical docking system based on an Autonomous Underwater Shuttle (AUS), designed to efficiently shuttle between the seafloor and surface for data relay. The designs of the AUS and Vertical Docking Station (VDS) are introduced, and a mathematical model of the AUS focusing on vertical motion is established with coordinate frames to address attitude singularity. A vertical docking strategy is proposed, including a DBLT-based AUS attitude control method and a three-stage guidance method integrating acoustic and optical guidance. Two motion modes—a gliding mode for long-range transit and a precise control mode for docking—are incorporated to balance energy consumption and docking accuracy. The system's feasibility is validated through simulations and experiments. The complete seafloor communication relay process was simulated under deep-sea conditions, confirming the effectiveness of the proposed vertical docking strategy. The DBLT-based attitude control method achieved rapid and precise regulation in both pool tests and lake trials. A 100 % vertical docking success rate and preliminary verification of the underwater communication relay function were demonstrated in lake trials, proving the effectiveness of the proposed system.