• Journal of Ocean Engineering and Technology
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• v.13 no.4 s.35
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• pp.82-97
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• 1999

A deep sea vehicle must be designed to ensure its safety under ultra-high pressure circumstances. If a pressure housing of a deepsea vehicle is collapsed by ultra-high pressure, the deepsea vehicle may be lost. The objective of this paper is to introduce a design collapse pressure for the deep sea pressure vessel which is composed of one cylinder and two hemispheres. Especially the collapse pressure of hemispherical shell with a hole at top is analyzed by a variational approach (weighted residual method). And for the purpose of design, the salty factor of collapse pressure is presented which is analyzed by interpolation method.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.351-354
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• 2006

In underwater environment, the control of AUV is difficult, because of the existence of parameter uncertainties and disturbances as well as highly nonlinear and coupled system dynamics. The requirement for the simple and robust controller which works satisfactorily in those dynamical uncertainties, call for a design using the PD or sliding mode controller. The PD controller is very popular controller in the industrial field and the sliding mode controller has been used successfully for the AUV controller design. In this paper, the two controllers arc designed for ISiMI(Integrated Submergible Intelligent Mission Implementation) AUV and the performances are compared by numerical simulation under the modeling uncertainty and disturbances. The design process of PD and sliding mode controller for ISiMI AUV and simulation results are included to compare the performances of the two controllers.

• Journal of Ocean Engineering and Technology
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• v.23 no.1
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• pp.48-53
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• 2009

Autonomous Underwater Vehicles (AUV's) provide an important means for collecting detailed scientific information from the ocean depths. The hull resistance of an AUV is an important factor in determining the power requirements and range of the vehicle. This paper describes a design method that uses Computational Fluid Dynamics (CFD) to determine the hull resistance of an AUV under development. The CFD results reveal the distribution of the hydrodynamic values (velocity, pressure, etc.) of an AUV with a ducted propeller. This paper also discusses the optimization of the AUV hull profile to reduce the total resistance. This paper demonstrates that shape optimization in a conceptual design is possible by using a commercial CFD package. Optimum design work to minimize the drag force of an AUV was carried out, for a given object function and constraints.

• Journal of Ocean Engineering and Technology
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• v.24 no.3
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• pp.46-51
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• 2010

This paper describes the implementation of a precise underwater navigation solution using a multi-sensor fusion technique based on USBL, DVL, and IMU measurements. To implement this precise underwater navigation solution, three strategies are chosen. The first involves heading alignment angle identification to enhance the performance of a standalone dead-reckoning algorithm. In the second, the absolute position is found quickly to prevent the accumulation of integration error. The third one is the introduction of an effective outlier rejection algorithm. The performance of the developed algorithm was verified with experimental data acquired by the deep-sea ROV, Hemire, in the East-sea during a survey of a methane gas seepage area at a 1,500 m depth.

• Journal of Ocean Engineering and Technology
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• v.19 no.2 s.63
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• pp.67-73
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• 2005

This paper describes depth, heading and speed control of an underwater vehicle that has four stern thrusters of which forces are coupled in the diving and, steering motion, as well as the speed of the vehicle. The optimal linear quadratic controller is designed based on a linearized- state space model, developed by combining the dynamic equations of speed, steering and diving motion. The designed controller gives provides an optimal thrust distribution, minimizing the given performance index to control speed, depth and heading simultaneously. To validate the performance of the controller, a simulation and tank-test are carried out with DUSAUV (Dual Use Semi-Autonomous Underwater Vehicle), developed by KORDI as a test-bed for testing new underwater technologies. Optimal gains of the controller are tuned, using a computer simulation environment with a nonlinear 6-DOF numerical DUSAUV model, developed by PMM (Planner Motion Mechanism) test. To verify the performance of the presented controller in experiment, a tank-test with DUSAUV is carried out in the ocean engineering basin in KORDI. The experimental results are also compared with the simulation results to investigate the accordance of the numerical and the real mode.

• Journal of Ocean Engineering and Technology
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• v.32 no.4
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• pp.287-295
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• 2018

This paper presents the results of an exploration of the ferromanganese crusts of Western Pacific Seamount registered by the Korean government. This area has been surveyed with a deep-sea camera and crust samples have been acquired by deep-sea dredging since 2013. On October 18-19, 2017, a united research team from KIOST and KRISO explored two blocks, OSM11 and OSM07, on the seamount using Hemire ROV. A precise survey was conducted on the ferromanganese crusts and sediments covering the slope/top of OSM11 and the middle flat area of OSM07. Rock samples were collected with precise positioning, and HD videos were recorded for 7 hours. This paper discusses the technical issues of this exploration in terms of (1) how to deal with an emergency situation during an electric power blackout, (2) the improvement of the thruster power by adding cooling plugs to the housings of the thruster amplifiers, (3) the relative motion of the depressor by changing the fixing method of the cable terminator, which affects the service life of the cable, (4) a sampling technique for the steep slope of the seamount, (5) integrated navigation under a USBL blackout, and (6) a 3-dimensional image mosaic for visualizing the distribution state of the crusts.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.1
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• pp.18-29
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• 2019

ROV surveys were conducted using 500 meter mini class ROV with HD video camera, 2 LED lights, a simple manipulator and 8 thrusters near the Dokdo and Simheungtaek seamount. Total six dives have been conducted using the ROV "V8 SII" from Sweden and ROV's support ship, "KOSAL V" at 4 stations between 45 and 370 meters with diving time ranged from 30 to 120 minutes. Dense communities of sea anemone (Actinostolidae sp.) and ophiuroids (Ophiuridae sp.) on the surface of rocky bottom and snow crab on the soft bottom with muddy-sand were observed at northwestern part of Simheungtaek seamount. We obtained the following results 1) habitats information for snow crab, one of the major fisheries resources, and deep-sea fauna, 2) observation on the specific topography and sediment conditions, 3) observation of the seabed surface covered with the discarded fishing gears. This study represents the first report of in situ visual observation of deep-sea organisms and their habitats near the Dokdo slopes and flat top of the Simheungtaek seamount in the East Sea. These results indicated that immediate oceanographic survey using the mini class ROV is available in the East Sea.