Shinichi Takagawa

Exploration of Teisi Knoll by autonomous underwater vehicle "R-One robot"

Outlines the exploration of Teisi Knoll by the autonomous underwater vehicle the R-One Robot, as carried out October 19-22, 2000, and presents images taken by the sidescan sonar fitted to the bottom of the vehicle. The R-One Robot was launched from the R/V Kaiyo, started diving near the support ship, followed pre-determined tracklines which were defined by waypoints and finally came back to the destination where it was recovered by the support vessel. In order to minimize positioning error, which is determined by the inertial navigation system and Doppler sonar, the robot ascended to the surface several times to ascertain its precise position using the Global Positioning System, the antenna of which is fitted on the vertical fin. Taking advantage of this positioning system, the robot followed the pre-determined tracklines with an error of less than 40 meters in 30 minutes of continuous diving. Disturbance to the robot is small enough compared to towed vehicles that its movement can be regarded as stable. This stability resulted in clear side scanning images of the knoll and the surrounding sea floor. The robot stopped at the center of the knoll, and descended vertically into the crater. When the vehicle was in the crater, anomalous manganese ion concentrations were detected by the in situ trace metal micro-analyzer GAMOS at the front of the robot.

Study on spherical pressure vessel of ceramics for deep-sea buoyancy module applications

Remotely operated vehicles (ROVs) for deep-sea operation should be as light as possible for Improvement of maneuverability and payload increase. Engineering ceramics has been one of the candidate materials for deep-sea pressure vessels because of its high compressive strength. The plan, which lessens its specific gravity and enlarges its pressure tolerance, had been prepared with installation of ceramic macro-spheres into syntactic foam, however it had failed due to the chain reaction of collapse of the ceramics macro-spheres. The main purpose of this study is to establish the methodology of fabricating the ceramic pressure vessels for deep-sea operation. As the first step, the spherical pressure vessel of ceramics was studied for deep-sea buoyancy module application. It is very important to keep the reliability on the macro-sphere, and the shape (=sphericity and thickness) should be controlled as good as possible. Thus, the ceramic hemispheres were fabricated, and their local radius of curvature and wall thickness was precisely measured by use of the simple measuring instruments. The measured results showed that the spherical irregularities were significantly improved compared with the sample of approximately 20 years ago.

Feasibility Study on DMFC Power Source for Underwater Vehicles

Power source for underwater vehicle is required to be air independent system. There are so many types of applications of various power sources, such as lead acid battery, silver-zinc battery, and recent lithium-ion battery, etc. hydrogen-oxygen fuel cell has been also applied to an AUV recently. AUV seems to be expected to become the major underwater vehicle in the future, but at the same time, tremendously long duration and/or long cruising range shall be required. It is thus necessary to have options of the power sources for this application. Fuel cell seems one of the best solutions for this purpose. Recently, development of DMFC (direct methanol fuel cell) system is underway vigorously for the application to the mobile unit, and some are already on market as outdoor power source. This paper proposes the application of DMFC as underwater power source system, and feasibility study results are shown here.

Manipulator system for deep sea survey

Japan Marine Science and Technology Center (JAMSTEC) has developed several deep sea exploration systems and is operating them. These exploration systems are equipped with manipulators to get samples of rocks and marine life or deploy instruments at the deep sea floor. The manipulator system used underwater has different features from that used for industrial robots on land. In this paper, features and problems of the manipulator system for deep sea survey at JAMSTEC are described.