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ABSTRACT: There are concerns about the impact that global warming will have on our environment, and which will inevitably result in expanding deserts and rising water levels. AUVs (autonomous underwater vehicle) were considered and chosen, as the most suitable tool for conduction survey concerning these global environmental problems. JAMSTEC has started to build a long range cruising AUV. The plan for its development is in several steps. As the first step an AUV, named URASHIMA was built in 1999, and sea trials have been held since 2000. URASHIMA dived to 3,518 m depth in 2001. At the end of February 2005, the vehicle was able to cruise autonomously and continuously for 317 km. This paper describes outline of the vehicle, presents some experimental results.
Industrial Technology, 2009. ICIT 2009. IEEE International Conference on; 03/2009
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ABSTRACT: An autonomous underwater vehicle (AUV) is equipped with an inertial navigation system (INS) in order to understand its own position in real time while it cruises without the communication with the external environment such as a support ship and GPS. Japan Agency for Marine-Earth Science and Technology has the cruising AUV URASHIMA, and it is also equipped with the INS. However the INS outputs its own absolute position containing the error that increases with time. It means, it is very difficult for URASHIMA to cruise dependent only on the position data outputted by the INS for a long time. So we have proposed the method to improve the performance of the INS, and its effect was confirmed in experiments. In the method, it was put on a turntable with assumption that it is fixed inside URASHIAM and the INS has been rotated by it around one rotation axis according to some rules. Consequently, the INS's position error was decreased by the rotational motion. In order to cause this effect, a precondition had to be met. It was that URASHIMA keeps its own posture to near-horizontal while cruising. However URASHIMA usually cruises with the roll motion which is caused by its shape. So the roll motion such as URASHIMA's one in a sea trial was applied to the turntable, and the INS was rotated in the situation. As the result, the INS's position error was decreased about half of the original one.
OCEANS 2007 - Europe; 07/2007
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ABSTRACT: An Autonomous Underwater Vehicle (AUV) is equipped with an Inertial Navigation System (INS) in order to detect its own current position for the autonomous cruise. It has a sensor part and an arithmetical part. The sensor part is composed of three gyros and three accelerometers, and the three-dimensional coordinate system (INS coordinate system) is defined in the arithmetical part. And an accelerometer and a gyro are set on each axis in the coordinate system. The INS calculates AUV's position using outputs of the sensors. So the position accuracy of it depends strongly on the precision of the sensors. However they have drift-bias errors which increase with the passage of the time. So, a method, which applies the rotational motion to the INS, is proposed in order to reduce the errors. In this method, the INS is put on the turntable and the INS is rotated by it around an axis of the INS coordinate system. And the errors of sensors, which are set on non-rotation axis, were reduced on average. This causes the position accuracy improvement. As the experimental results, the position error of the INS is reduced up to four times if suitable methods are given to it.
Underwater Technology and Workshop on Scientific Use of Submarine Cables and Related Technologies, 2007. Symposium on; 05/2007
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ABSTRACT: JAMSTEC has been developing AUVs: the cruising AUV "Urashima" and the working AUV "MR-X1". The cruising AUV is able to collect sea data and samples automatically in long range cruising. The working AUV which would be equipped with manipulators is also needed as alternated for ROVs. The MR-X1 is designed for the scientific work, such as installing or recovering observation equipment, tracking and sampling benthic feeders, and supporting ROV's works. We had started of development of the MR-X1 in 2000. Its body (2.5 m long, 800 kg weight) had been assembled by 2002. The control hardware using CAN bus interface was installed in 2003. Presently, we are mainly investigating the control system software. In this paper, we describe the system configurations of the MR-X1, focused on its control system. In addition, we report some results of sea trials.
OCEANS '04. MTTS/IEEE TECHNO-OCEAN '04; 12/2004
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ABSTRACT: Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has advanced the development of an ocean going Autonomous Underwater Vehicle (AUV). Technical problem on an AUV is to develop instruments for highly accurate positioning, an efficient power source and digital telemetry in the sea. The AUV in JAMSTEC has accurate positioning system, fuel cell and digital telemetry. Sea test started in 2000, results were fed back to instruments to improve AUV performances. Its energy source was replaced to closed-cycle fuel cell system from lithium-ion battery in 2002. The AUV was successfully cruised 220 km range in 2003 along the pre-programmed route while having submerged. This paper presents result and navigational data obtained in a long distance test with the AUV
OCEANS '04. MTTS/IEEE TECHNO-OCEAN '04; 12/2004
