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.