The positioning system integrated LBL and SSBL using seafloor acoustic mirror transponder

Abstract

Utilization of autonomous underwater vehicle (AUV) and remotely operated vehicle (ROV) is absolutely necessary when we explore and develop submarine resources. Positioning of underwater vehicle is one of the keys to the development of submarine resources. Many researchers have been seeking the method to locate a position of underwater vehicle with high accuracy for many years. Then, we designed the positioning system integrated long base line (LBL) navigation system and super short base line (SSBL) navigation system using seafloor acoustic reference station: acoustic mirror transponder (MT)[1]. The positioning system consists of seafloor and on-board units. The seafloor unit is set of a MTs. MTs are deployed on the seafloor and serve as seafloor reference points for subsea positioning. The onboard unit, which should be mounted on the underwater vehicle, consists of a ring laser gyro (RLG) which gives the unit's attitude and the positioning system integrated LBL and SSBL, and so on. LBL system uses more than three MTs to measure distances. Meanwhile, SSBL system uses a MT to measure distance and direction. We conducted a performance test of the positioning system in Tateyama bay in November 2012. The purpose of this test is to evaluate the accuracy of the positioning based on units of LBL and SSBL of the positioning system. Three sets of the reference seafloor MT were installed on the seafloor. The positioning system was mounted on the surface platform. We had towed the surface platform along designed traverse lines. During the sea trials, the positions of the platform are estimated with ranging and direction data from the LBL and SSBL units. RLG measures the attitude of the platform. The attitude of platform is necessary to change platform's relative coordinate system to absolute coordinate system. Positions of the platform are also measured with a GPS system. We will evaluate newly developed positioning system by comparing between these two sets of the positions. Then, we developed the essential part in the system integrated LBL and SSBL.