In this paper we present the concept of a multi-AUV system interconnected by a smart cable that contains 3D positioning sensors for rapid inspection of large underwater structures in a limited mission timeframe. The smart cable provides not only the position of the end-points (AUV locations) but also its own shape in real-time, while also acting as a communication link between AUVs. Using this cable, we propose a Hand-in-hand System(HS) for AUV localization and development of an obstacle avoidance strategy to accomplish the given task. For applying the smart cable underwater, versatile tank tests and field experiments were carried out to demonstrate and confirm the efficiency of the proposed system.
Marine structures such as bridges, dams and ports play an important role in daily life and this require routine inspection and maintenance work to be carried out in dangerous underwater environments. Robots can undertake these tasks more accurately and efficiently than humans while eliminating risk to human life (Ura,1994). In view of introduction of robots, underwater structures related tasks can be classified into 2 groups; construction/repair and inspection. 1)Construction/Repair: These tasks require powerful robots with complicated and maneuvers to be carried out dexterous manipulations and thus the human interface and power transmission via a tether cable offered by ROVs (Remotely Operated Vehicles) means that they can effectively undertake such tasks. 2)Inspection: Most of inspection tasks involve collecting data such as taking photos of the targets and their environment which are spread over an extensive area. Such tasks require excellent maneuverability as opposed to intelligence. We propose the application of AUVs(Autonomous Underwater Vehicles) to inspection tasks, taking advantage of free movement of AUVs allows efficient data collection over an extensive inspection area or about intricate structures with light deck supports.