Automatic sediment sampling ROV at full ocean depth

The ABISMO system and its 11,000m-cable store winch are mounted on the dedicated ship Kairei. The ABISMO system consists of an on-board control module which is installed in the ship, a sampling station, a sediment probe, and two samplers. Fig. 16 shows a recovery scene of the station housing the probe. The on-board control module is connected with the station via the primary cable. The secondary cable, which has been newly developed, connects the station and the probe. The sampling station houses the probe and one of the samplers in the bottom cage. The station is mounted with a docking-undocking system and a secondary cable drum for the probe, sampler release gear and a rope-hoisting winch for the sampler. The station furthermore serves as a repeater between the on-board equipment and the probe. The probe cruises below the station freely within the reach of the 160 m cable to survey the sea-bottom surface with a TV camera. The probe is able to take a small sediment sample with a mini manipulator. Two types of sediment samplers - a gravity core sampler and a grab bottom sampler have been prepared. Scientists can choose either sampler in accordance with the intended use. The system specifications are shown in Table 7.

Sampling Rov
Fig. 16. The full depth ROV, ABISMO

Item

Launcher

Vehicle

Rated Depth

11,000 m

11,000 m

Dimensions

3.28 x 2.09 x 1.76(2.78*) m

1.22 x 1.30x 1.215m

Weight in air

3,070 kg

327 kg

Weight in water

2,300 kg

97 kg

Depth rating

11000 m

11000 m

* overall height including the vehicle Table 7. Specifications of ABISMO

a. The first sea trial of the ABISMO system in January 2007

The first dive was made at Yokosuka 4th district in Tokyo bay to check system function on January 5. The test results were good and the ship then headed to Sagami Bay. During the second dive an assessment was made as to whether the station thruster could constrain its self rotational motion caused by the primary cable twisting or not. The thrusters behaved well during the 200 meter dive. On January 8 we tried sampling with the gravity core sampler at a location where the bottom sediment was softish, at a depth of 480 m. The station was controlled keeping its heading, coming as close as about 80 meters off the bottom. Keeping its altitude, the sampler was dropped. The sampler was recovered after about ten minutes. A sediment sample about 200 mm long then was obtained.

b. The successful sea trial in the Mariana Trench in June 2008

The fourth sea trial including dives in the Mariana trench had been made from 26th May to 8th June 2008. Before going to the Mariana trench, one dive at Sagami-Bay and also one dive in the Izu-Ogasawara trench were conducted to confirm the additional functions and also the functions that had not been tested in the previous sea trials. In the Mariana Trench ABISMO made three dives within three days to depths below 10,000m and marking a 10,257m dive. This depth was limited by the length of the primary cable. The 2-m long gravity core sampler was dropped down in free fall and sediment cores of 1.6 m length were obtained (Figure 17). ABISMO also succeeded in obtaining 12 bottles of water samples from the Mariana trench in each dive.

Underwater Vehicle Scuba

Fig. 17. Mud sample obtained from the sea floor in the Mariana trench (2m-core sampler) 4.2 Cutting edge autonomous underwater vehicles

The prototype AUV Urashima is an LCAUV with a range over 300 km, as shown in Figure 18. Its specifications are listed in Table 1. The vehicle consists of titanium frames covered with FRP (Fiberglass Reinforced Plastics) faring covers, pressure vessels made of titanium alloy for protecting control systems and other electrical devices, and buoyancy materials used for additional buoyancy. The vehicle has a cylindrical shape for reducing hydrodynamic drag. The vehicle is equipped with six actuators: a main thruster (D.C. brush-less motor, 1.5 kW) for cruising, two vertical thrusters, one horizontal thruster at the stern, a vertical rudder, and a horizontal rudder. The vehicle also has a pitch control system like a level adjuster and buoyancy control system which consists of an oil tank contained in a pressure vessel (VBT: Variable Ballast Tank) and an oil bladder. The system is able to change buoyancy from 0kg to 60kg according to water depth. The vehicle is powered by a fuel cell-battery hybrid power system as mentioned.

Fig. 17. Mud sample obtained from the sea floor in the Mariana trench (2m-core sampler) 4.2 Cutting edge autonomous underwater vehicles

The prototype AUV Urashima is an LCAUV with a range over 300 km, as shown in Figure 18. Its specifications are listed in Table 1. The vehicle consists of titanium frames covered with FRP (Fiberglass Reinforced Plastics) faring covers, pressure vessels made of titanium alloy for protecting control systems and other electrical devices, and buoyancy materials used for additional buoyancy. The vehicle has a cylindrical shape for reducing hydrodynamic drag. The vehicle is equipped with six actuators: a main thruster (D.C. brush-less motor, 1.5 kW) for cruising, two vertical thrusters, one horizontal thruster at the stern, a vertical rudder, and a horizontal rudder. The vehicle also has a pitch control system like a level adjuster and buoyancy control system which consists of an oil tank contained in a pressure vessel (VBT: Variable Ballast Tank) and an oil bladder. The system is able to change buoyancy from 0kg to 60kg according to water depth. The vehicle is powered by a fuel cell-battery hybrid power system as mentioned.

Sediment Sampling
Fig. 18. Deep & Long range Cruising AUV, Urashima.

Item

Specification

Dimension

10.6 m x 2.55 m x 2.4 m

Weight in air

10,000 kg / 75,000 kg without the FC system

Depth rating

3,500 m

Cruising speed

3 kt

Endurance

60 hours

Navigation instrumentation

Inertial Navigation System, Doppler Velocity Log, Acoustic Homing Sonar, Obstacle Avoidance Sonar

Experiment payload

Side Scan Sonar, Multi Beam Echo Sounder, Sub Bottom Profiler, TV camera, CTDO, Digital Camera

Table 8. Specifications of the Urashima vehicle

Table 8. Specifications of the Urashima vehicle

Urashima Auv
Fig. 19. General arrangement of Urashima with the Fuel Cell

The Urashima, the biggest AUV in the world, has a large payload capacityof about 500kg. Regular equipment for observations are a TV camera, digital still camera, a CTDO, a side scan sonar, a multi-beam echo sounder and a sub-bottom profiler. The side scan sonar, which has maximum range of 500 m, is a dual frequency type that projects acoustic waves at 120 and 410 kHz at central frequency. The sub-bottom profiler is a chirp sonar that uses frequencies from 1 to 6 kHz, having maximum range of about 50 m. A receiver in an array with 6 channels can record phase data. The multi-beam echo sounder observes bathymetry. The sounder uses 400 kHz burst acoustic waves,ranging about 300 m. The sounder works in a stand-alone mode. The control parameters of the sounder is set before a deployment. The development project for the Urashima is started in 1998. The vehicle powered by a lithium-ion battery system has had 10 sea trials and 40 dives by 2002. In these sea trials, the vehicle both achieved a dive to 3,518m in depth and cruised a distance of 132.5 km in autonomous navigation mode over 29 hours.

In 2003, the lithium-ion battery system was replaced with the fuel cell system and then tests of the fuel cell vehicle started. In February-March 2005, the vehicle achieved a cruising distance of 317km under autonomous navigation mode. The average cruising speed was 2.8 knots. The vehicle maintained a cruising depth of 800m. The performance of the fuel cell system was good throughout the test. Cruising time was 54 hours.

Figure 20 shows the track which measured by the INS at survey on a mud volcano obtained in July 2006 in the Kumano trough. The maximum depth of the survey area was almost 2,100m. Cruising speed was 2.5 knots. Although the vehicle sometimes had almost 30m differences from programmed altitude during rapid slope angle variations, the vehicle kept a stable altitude at approximately 80m above the seafloor while cruising in autonomous mode. The difference is 0.5m between the programmed course and the obtained course by the INS. The vehicle came to within 20m of the seafloor, and cruised at slopes up to 35 degrees. Cruising distance was 28km and cruising time was 8 hours. Figure 19 also shows an acoustic image of the mud volcano based on data obtained by the side scan sonar. The resolution is very high so that the details at the top of the mud volcano can be observed.

Sampling Rov Propulsion

Start

Fig. 20. Track of the vehicle during the survey of the mud volcano (left) and an acoustic image of a mud volcano obtained by the side scan sonar (right).

Start

Fig. 20. Track of the vehicle during the survey of the mud volcano (left) and an acoustic image of a mud volcano obtained by the side scan sonar (right).

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Responses

  • Amparo Ingraham
    What underwater sediment sampling?
    6 years ago

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