Observation of breakwaters and their rock mound by AUV "Tri-Dog 1" at Kamaishi Bay

This paper proposes a navigation method for an Autonomous underwater vehicle (AUV) operating around structures whose major configuration given in advance. The method consists of a state estimator and a motion controller, enabling localization in the configuration map as well as following pregiven waypoints without any external help. The state estimator is based on a "particle filter" where the vehicle's state, horizontal position and heading, is stochastically updated in real time using multisensor data. This method was implemented on the AUV "Tri-Dog 1" and experiments were carried out around breakwater caissons at the mouth of Kamaishi bay, Iwate Prefecture in Japan. This is the first time a vehicle has succeeded in fully autonomous observation around breakwater caissons. Mosaics of the foot protection blocks, rock mound and caisson's surface are made from the observed images based on the estimated state of the AUV, to verify the performance of the method.