Moored underwater docking system for resident UUVs with acoustic guidance: Design and experiment

Developing a seafloor docking system to recover and recharge Unmanned Underwater Vehicles (UUVs) is crucial to address the energy needed for persistent observation. However, many existing seafloor docking systems prefer a flat seabed to enable UUV docking operations conveniently. Besides, recovery can be challenging or even impossible if stuck in the mud. This paper presents a novel Moored Underwater Docking System (MUDS) for UUV. The MUDS consists of a funnel -shaped docking module, a suspending module with a hexagonal prism design, and an anchor. It is designed to keep a steady attitude in the sea and work on various subsea terrains. Further, the system is easy to deploy and recover. In addition, we design an acoustic guidance algorithm comprised of an interactive acoustic localization and a proportional guidance strategy to guide a UUV to the docking station. The former accurately measures the relative position and orientation between the UUV and MUDS without needing an expensive attitude sensor. The latter reduces cross -track error and heading deviation as the UUV approaches the entrance. The prototype system has been tested in lake and sea environments, demonstrating successful deployment, recovery, localization, and docking, even in turbid water with poor visibility.