• Journal of Advanced Marine Engineering and Technology
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• v.33 no.8
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• pp.1203-1211
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• 2009

The dynamics of underwater vehicles can be greatly influenced by the dynamics of the vehicle thrusters. The control of the state of the hovering or very slow motion of the underwater vehicle is most important for automatic docking or control of the manipulator of the vehicle. The dynamics of the thruster based on the electric motor is nonlinear and has uncertain parameters. Since the dynamics of the vehicle coupled with the dynamics of the thruster is nonlinear and has uncertain parameters, a robust control is very effective for a desired motion tracking of the uncertain and nonlinear vehicle. In this paper a study was performed on the robust control scheme of the very slow motion or hovering motion of the underwater vehicle actuated by the electric motor. Also, a concurrent control on the state of the vehicle with nonlinearity and uncertain parameters was performed. A sliding mode control algorithm out of robust controllers was designed and applied, which compensates the nonlinear forces and uncertain parameters of the vehicle and actuator. Through a computer simulation, the proposed control scheme was compared with a linear PD controller and its superior performance was validated.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.6 s.150
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• pp.647-655
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• 2006

In this paper, submerged body dynamics model in vertical plane which can include the effect of free surface and wave is suggested to simulate the motions of submerged body moving beneath free surface precisely. A controller is designed, which can maintain a constant depth below the mean sea level and minimize the pitch angle. Numerical simulations show that the designed controller is effective on depth keeping and minimizing pitch angle in regular waves and irregular waves.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.2
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• pp.11-20
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• 2003

In this paper, the high-order spectral/boundary-element method is developed to calculate the 3-dimensional water waves generated by a submerged body. This method is one of the most efficient numerical methods by which the nonlinear gravity waves can be simulated Tn time-domain. Three-dimensional free-surface flows generated by a submerged sphere which is moving under the free-surface are calculated. Through example calculations, nonlinear effects on free-surface profiles and hydrodynamic forces are shown. Comparisons with others' results show good agreements.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.2
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• pp.148-153
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• 2014

Submerged bodies such as autonomous underwater vehicles (AUV) or remotely operated vehicles (ROV) are widely used in various fields of exploring underseas. Those bodies keep ballasting and deballasting for stable navigation and operation. Identifying the internal volumetric spaces of the bodies is a primary step for such an operation. Unfortunately, most CAD models given to the engineer do not properly represent the compartments since each face of a compartment exists as an independent entity rather than as a face that belongs to the compartment. In this paper, an algorithm that automatically identify the faces as a group that forms a closed volumetric space, i.e., a compartment is presented. A submerged body is sliced into a number of cross sections. Each sliced section is analyzed to yield closed loops that are sections of the compartment. Then, the associated closed loops are gathered along the longitudinal direction to form a compartment. The algorithm presented is shown to provide a practical and reasonable solution that can readily be used in various applications.

• The Journal of the Acoustical Society of Korea
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• v.27 no.6
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• pp.279-285
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• 2008

This study includes the efficiency assessment of a multiple access protocol for UUV (Underwater unmanned vehicle) control. Most of UUVs are controled by wire now; however, wireless control is demanded because of the demerit of the wire control that limits the place and activity. This study simulates efficiency of a standardization multiple access protocol (Pure ALOHA, Slotted ALOHA, Nonpersistent CSMA, Slotted Nonpersistent ISMA) formed for the purpose of performing wireless communication controlled by the ship or communication buoy at the sea surface and by the under water communication node at the bottom in order to efficiently control the UUV's. Results show that no significant changes occur related to changing type of the mother ship and the communication node; In addition, the Non-persistent CSMA and the Slotted Non-persistent ISMA show relatively high efficiency for underwater acoustic communication.

• Proceedings of the KAIS Fall Conference
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• 2009.05a
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• pp.240-243
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• 2009

본 논문에서는 수중에서 이동하는 무인잠수정 및 수중이동체의 위치를 측정하는 방법 중의 하나인 동적 단기선 방식(SBL)에 의한 무인잠수정의 위치측정에 대한 방법을 하이드로폰과 DAQ(Data Aquisition) 시스템을 이용하여 수조에서 테스트를 수행하였고, 실 해역에서의 실험을 실시하였다. 실험을 위해서 4개의 센서가 수조의 벽면에 고정이 되어 있으며, 이동체와 고정된 4개의 센서가 신호를 송수신함으로써 상호간의 위치추적이 가능하게 하는 시뮬레이션을 실시하였으며, 제안하는 SBL시스템과 장기선 방식(Long baseline)을 비교하기위한 시뮬레이션을 실시하여 두 시스템을 비교하였다. 측정된 신호는 DAQ 시스템을 이용하여 데이터를 취득하였고, Labview 프로그램을 이용하여 실시간으로 무인잠수정의 위치를 추정하였다. 위치추정에 사용된 알고리즘은 삼각측량법에 의한 방법을 사용하였으며, X, Y방향에 대해서는 비교적 오차가 적은 추정 결과를 나타내었으나 Z방향에 대하여서는 큰 오차를 보여 데이터로 사용할 수 가 없었다. 이는 수중이동체의 수심측정 센서를 이용하여 보완할 수 있을 것으로 본다. 향후 연구로는 위치추정 알고리즘을 보완하여 실제 선박 선저부에 센서가 부착되었을 경우에 대한 적용연구를 진행할 예정이며, 위치추정 알고리즘을 발전시켜 3차원에서의 정확한 위치 추적을 가능하게 할 예정이다.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.711-712
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• 2015

잠수함은 운행 중 수압에 따라 자화 특성이 변하므로 자기정숙화에 어려움이 있다. 본 논문은 잠수함 운행 중 수압에 따른 압력선체의 B-H Curve 특성 변화를 측정하였다. 잠수함의 압력선체는 강자성체 재질로 모델링 하여 제작하고 비자성체인 스테인리스로 보빈을 만들어 나사를 조이는 형태로 압축응력을 모사했다. 그 결과 응력이 가해지면 투자율이 작아지고 최대 자속밀도 또한 감소하였다.

• 한국전기화학회:학술대회논문집
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• 2001.10a
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• pp.27-27
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• 2001

• Journal of the Society of Naval Architects of Korea
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• v.29 no.4
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• pp.66-74
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• 1992

A panel method in the spirit of Hess & Smith(1962), and also of Dawson(1977) was developed to compute the wave resistance of a submerged, or a surface piercing, body moving in the water of finite depth. As a boundary condition on the free surface what is called the Poisson equation is used, while Yasukawa(1989) chose the Dawson equation for which the double-body flow is regarded as the basic one. In order to satisfy the boundary condition on the bottom surface automatically, the sum of a Rankine source and its image with respect to the bottom surface is chosen as the Green function, and hence the singularity is distributed only on the body and on the free surface thereby decreasing the required number of panels dramatically, compared to that of Yasukawa, without the consequential loss of accuracy. Calculations were done for a submerged sphere and for the Wigley hull, and the results are compared with other existing analytical and numerical data.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.2
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• pp.56-67
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• 1995

In this paper, a ship-cable-vehicle system's static configuration is shown obtained by solving cable nonlinear statics. Eigenfrequencies of the cable were calculated by the frequency domain analysis application of the linearized cable dynamic equations. Also extreme tensions in a slack-and-snapping long vertical cable were calculated by the clip-ping-off model.