• Special Issue of the Society of Naval Architects of Korea
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• 2006.09a
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• pp.112-121
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• 2006

The vertical displacement of a ship on the basis of the sea level is an important parameter for its stability and control. To indicate the displacement on operating conditions, "draft marks" are carved on the hull of the ship in various ways. One of the methods is welding. The position, shape and size of the marks are specified on the shipbuilding rules by classification societies to be checked by shipbuilders. In most cases, high-skilled workers do the welding along the drawing for the marks and welding bead becomes the marks. But the inaccuracies due to human errors and high labor cost increase the needs for automating the work process of the draft marks. In the preceding work, an indoor robot was developed for automatic marking system on flat surfaces and the work proved that the robot welding was more effective and accurate than manual welding. However, many parts of the hull structure constructed at the outdoor are cowed shapes, which is beyond the capability of the robot developed for the indoor works on the flat surface. The marking on the curved steel surface requiring the 25m elevations is one of the main challenges to the conventional robots. In the present paper, the robot capable of climbing vertical curved steel surfaces and performing the welding at the marked position by effectively solving the problems mentioned earlier is presented.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.5
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• pp.26-35
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• 2003

Propellers operating in a given nonuniform ship wake generate unsteady loads leading to undesirable stern vibration problems. The skew is known to be the most proper and effective geometric parameter to control or reduce the fluctuating forces on the shaft. This paper assumes the skew profile as either a quadratic or a cubic function of the radius and determines the coefficients of the polynomial function by applying the simplex method. The method uses the converted unconstrained algorithm to solve the constrained minimization problem of 6-component shaft excitation forces. The propeller excitation was computed either by applying the two-dimensional gust theory for quick estimation or by the fully three-dimensional unsteady lifting surface theory in time domain for an accurate solution. A sample result demonstrates that the shaft forces can be further reduced through optimization from the original design.

• 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.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.2
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• pp.53-61
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• 2001

A cutting machine for freeform hull surfaces of ship models is developed and a servo system is employed for tool path control. The servo system consists of BLDC(Blushless DC) motor, control driver and host controller. Also PI controller is applied for precision processing. GUI(Graphic User Interface) was realized by visual c++ for the convenience of users. Free form surfaces are formed by the cutting machine developed in the Ocean Engineering Wide Tank of the University of Ulsan.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2643-2645
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• 2004

The underwater system autonomously is navigated by using the wireless communication system, which receives the control signal from surface ship. The study proposes the new media access control protocol for underwater vehicles network in the view of communication distance and as CSMA(Carrier Sense Multiple Access) for the existing networks is intended to communication network using the high speed media such as electric signal or microwave signal, and thus it may introduce the reduction in throughput when applying the protocols to underwater communication network.

• Journal of Ship and Ocean Technology
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• v.8 no.2
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• pp.1-12
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• 2004

To keep the ocean environment from pollutions, strict international requirements on the controllability are arisen to the VLCC. Especially in low speed operations near the harbor, the VLCC is often supported by tug to replenish the insufficient rudder force. When water jet is blown to the flapped rudder, the Coanda effect induces a high-lift force by delaying stall and re-enforcing circulation in a large angle of attack (Lachmann 1961, Ahn 2003). Based on numerous research efforts, the rudder system supported by the Coanda effect was devised and its performances were evaluated in the towing tank for a large VLCC model. Hydrodynamic forces acting on the rudder system were measured with a water jet blowing on the rudder surface and compared with those acting on a conventional rudder. The effectiveness of the new rudder system was proven through an experimental evaluation.

• Journal of Navigation and Port Research
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• v.32 no.10
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• pp.771-776
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• 2008

The main purpose in having a control surface on a ship is to control the motion of it. It is the important element to determine the maneuvering characteristics of the ship. In this paper, the measured results has been compared with each other to predict the performance characteristics of flapped rudder's 2-dimensional section at $Re=3.0{\times}10^4$ using 2-frame grey level cross correlation PIV method. The side force of the rudder could be mainly improved by the lift force at 10 degrees angle of attack and the drag force at 20 degrees angle of attack. The separation point and boundary layer could be controlled by the change of the only flap's angle at 10 degrees angle of attack.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.5
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• pp.487-494
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• 2008

An experimental assessment has been made of the drag reducing efficiency of the outer-layer vertical blades, which were first devised by Hutchins (2003). The drag reduction efficiency of the blades was reported to reach as much as 30%. The assessment of the drag reducing efficiency is mainly restricted to the downstream region of the blades. Indeed, sufficient care has not been taken to such adverse effects as the increase in the wetted surface area and the flow disturbances due to the presence of the blades. In the present study, a series of drag force measurements in towing tank and circulating water channel has been performed toward the assessments of the total drag reduction efficiency of the outer-layer vertical blades.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.11a
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• pp.184-185
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• 2022

국제해사기구(IMO)에서는 2017년 미래선박으로서 자율운항선박(MASS)의 개념을 채택한 바 있으며, 실해역 운항을 위한 국제법규 및 규정 검토를 진행하고 있다. 무인선은 악천후시 유인선이 수행하기 힘든 임무를 대체하거나 지원하기 위하여 원격 혹은 자율적으로 운용되는 일종의 소형 자율운항선박을 의미한다. 선박해양플랜트연구소에서는 2011년부터 해양수산부 연구개발사업을 통하여, 무인선 아라곤호 시리즈를 개발하였으며, 아라곤1호, 2호, 3호 등 총 3척을 운용하고 있다. 해당 선박은 길이 8미터, 배수량 약 3톤급의 활주선형으로 원격운항, 경로추종 및 충돌회피 등 자율운항 기능이 적용되어 있다. 한편, 무인선은 공중 드론과 달리 탑재중량이 크고, 항속시간이 길어 해상에서 감시,첩보, 정찰 등에 효용성이 높으며, 최근 한척보다는 여러 척을 운용하는 것이 효과적이어서 무인선 군집(USV Swarm)으로 해상임무를 수행하려는 연구가 다양하게 진행되고 있다. 선박해양플랜트연구소에서는 2019년부터, 기존의 아라곤호 시리즈 무인선들을 활용하여, 무인선 군집 자율운항 시스템 개발을 위한 "인공지능 기반 무인선 상황인식 및 자율운항 기술 개발" 과제를 진행하고 있다. 해상에서 불법선박이 출현시 이를 효과적으로 단속하기 위하여 추적 기동이 필요한데, 본 연구에서는 무인선 3척을 활용하여 불법선박을 추적하는 해상 감시 실해역 시험을 수행하였다. 본 논문에서는 무인선 군집 자율운항 시스템에 대하여 소개하고, 무인선 군집을 활용한 불법선 추적에 관한 실해역 시험결과에 대해 소개한다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.05a
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• pp.200-201
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• 2023

Digital twin technology is used in various fields as a method of creating a virtual world to minimize the cost of solving problems in the real world, and is also actively used in the maritime field, such as large-scale systems such as ships and offshore plants. In this paper, we tried to build a digital twin of coastal waters using a ship-handling simulator. The digital twin of the coastal waters developed in this way can be used to safely manage Korea's coastal waters, where maritime traffic is complicated, by providing a actual maritime traffic data. It can be usefully used to develop and advance technologies related to maritime autonomous surface ships and intelligent maritime traffic information services in coastal waters. In addition, it can be used as a 3D-based monitoring equipment for areas where physical monitoring is difficult but real-time maritime traffic monitoring is necessary, and can provide functions to safely manage maritime traffic situations such as aerial views of ports/control areas, bridge views/blind sector views of ships in operation.