Aiming at developing underwater battery recharging system, we have been researching on automatic docking of an underwater robot using stereo-vision-based visual servoing and 3D marker. The docking function deems to be an important role not only for battery recharging but also for other advanced applications, such as information transmissions. The authors have proposed a optical docking system and conducted real sea experiments to verify the practicability of the proposed docking system composed of stereo-vision-based 3D pose (position and orientation) realtime measurement system. The docking experiments have forced laboratory members to endure heavy burdens of preparing, conducting, and dismantling the experimental devices at sea, which hinders the efficiency of experiments at real sea. To improve the efficacy, firstly, the authors report that permanent stage for underwater robot experiments has been constructed on a shallow sea. Secondly, we propose a docking station that can adapt and change its docking direction to the current direction, through which the burden of controlling the underwater robot’s heading can be reduced. Thirdly, the effectiveness of the docking station adaptive to the changing current direction has been proven by successful repeated docking experiments in the environment with fluctuating current and turbidity disturbances in real sea. This also has shown that the combined system of the stereo-vision based 3D pose estimation and the current-adaptive docking station can improve the adaptive abilities against current changing disturbances, having shown the practicality of the combined system has been enhanced.
