A docking and control system for an autonomous underwater vehicle

Autonomous underwater vehicles are unmanned underwater vessels to investigate sea environments, oceanography and deep-sea resources autonomously. Docking systems are required to increase the capability of the AUVs to recharge the batteries and to transmit data in real time underwater. This paper presents a docking system for an AUV to dock into underwater station with a camera. To make a visual servo control system, this paper derives an optical flow model of a camera mounted on AUV, where a CCD camera is installed at the nose center of the AUV to monitor the docking condition. This paper combines the optical flow equation of the camera with the AUV's equation of motion, derives a state equation for the visual servoing AUV. This paper also proposes a MIMO controller minimizing a cost function. The control inputs of the AUV are automatically generated with the projected target position on the CCD plane and with the AUV's motion. To demonstrate the effectiveness of the modeling and the control law of the visual servoing AUV, simulations of docking the AUV to a target station are performed with the 6-dof nonlinear equations of REMUS of WHOI and a CCD camera.