Acoustic-based Guidance for Automatic Docking of Holonomic AUVs

This paper describes a system to automatically dock an AUV onto a docking station without precise knowledge of the position and orientation of the latter, in the presence of unknown ocean currents, using a fully acoustic sensing architecture. The system relies on a pair of Ultrashort Baseline sensors, one onboard the vehicle and one installed on a seabed-resident docking station, enabling operation in low-visibility environments where cameras are ineffective. Relative orientation is estimated by a nonlinear complementary filter on $SO(3)$, while an Extended Kalman Filter provides relative position, supplying pose estimates to a geometric controller on $SE(3)$ that executes the docking manoeuvre. The complete system is implemented in a dedicated software suite and validated in simulation and water trials.