• The Journal of the Acoustical Society of Korea
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• v.30 no.1
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• pp.9-16
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• 2011

When a hydrofoil ship plies at high speed, there exist possibilities of collision with ocean mammals dwelling near the surface. An active sonar located within the immersed hydrofoil structure that provides the lift for the vessel, can be used for early warning of their presence. The proper functioning of the active sonar system depends on its ability to reject noise and pick up the target signal. In this article, we measured the noise on a hydrofoil of an operating ship with two flush-mounted hydrophones. The measurements were conducted for the purpose of (1) identifying the effect of operating state of machinery likes engine, cooler and generator (2) observing the change of noise depending on the measuring position (3) observing the change of noise with increasing ship speed. To verify our experiment, experiments were performed three times and the measured results are compared with other investigations and they show similarity to each other. The results are analyzed with frequency domain in order to apply to operating active sonar detecting system and focus on high frequency band within sonar's operating frequency region. Through these experiments and analysis, it is expected that we can identify the generated noise around hydrofoil where active sonar is installed and these results lead us to design active sonar that could distinguish target signal from noise more effectively.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.5
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• pp.369-377
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• 2014

In this paper, to recognize the collision behavior between a submerged floating tunnel(SFT) and underwater navigation vessel(UNV), both structures are modeled and analyzed. The SFT of collision point is modeled tubular section using concrete with steel lining. The other part of SFT is modeled elastic beam elements. Mooring lines are modeled as cable elements with tension. The under water navigation vessel is assumed 1800DT submarine and its total mass at collision is obtained with hydrodynamic added mass. The buoyancy force on SFT is included in initial condition using dynamic relaxation method. The buoyancy ratio (B/W) and the collision speed are considered as the collision conditions. As results, energy dissipation is concentrated on the SFT and that of the UNV is minor. Additionally, the collision behaviors are greatly affected by B/W and the tension of mooring lines. Especially, the collision forces are shown different tendency compare to vessel collision force of current design code.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.1
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• pp.83-88
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• 2011

There are various environmental conditions under which ship may navigate over ocean or in harbor. Ship's torque and speed change frequently under the voyage conditions. In this case, harmonics is created in the electrical power systems. The major adverse impacts of voltage and current harmonics in the electrical power systems on generator, transformer, converter, inverter and propulsion motor lead to the increase of machine heating caused by iron and copper losses which are dependent on frequency. In this paper, an analysis of THD(total harmonic distortion) for currents and voltages in the propulsion equipment was carried out. The THD and torque ripple in the input currents of the propulsion motor have been confirmed by the simulation results.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.4
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• pp.87-97
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• 1998

One of good ways to make a ship perform well in rough seas is to reduce its waterplane area and accordingly is subject to a reduced wave exciting forties. However, a great reduction of the waterplane area may create a penalty in speed performance due to the increased ratio of the wetted area to the displacement volume. This paper suggests a new catamaran hull form which compromises the speed and seakeeping quality by increasing the waterplane area somehow compared with that of the conventional SWATH ship. A 350 passenger carrying SWATH ship with a cruising speed of 30 knots in sea state of 4 has been developed and its performance was validated by the model tests. The design concept resistance performance and seakeeping dualities of the design craft are presented together with its comparative performance comparison with other high speed crafts.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.1
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• pp.276-284
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• 2013

This paper considers the transfer alignment in the inertial navigation system and the observability analysis is performed for velocity matching. The state variable of the Kalman filter is modeled including the lever arm error and the measurement equation is obtained. The SOM(Stripped Observability Matrix) method is used for the observability analysis for various maneuvering conditions of the vehicle, which gives the full state observability condition as a specific maneuver sequence of the vehicle. While the observability analysis of a lever arm effect in the existing papers is mainly performed by simulations, we performed it analytically by the observability analysis method. The analysis result is verified using the computer simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3B
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• pp.248-253
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• 2011

Collision avoidance algorithm of vessels have been studied to avoid collision and grounding of a vessel due to human error. In this paper, We propose a collision avoidance algorithm using bayesian estimation theory for safety sailing and reduced risk of collision accident. We calculate collision risk for efficient collision avoidance using bayesian algorithm and determined the safest and most effective collision risk is predicted by using re-planned with re-evaluated collision risk in the future(t=t'). Others ship position is assumed to be informed from AIS. Experimental results show that we estimate the safest and most effective collision risk.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.1
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• pp.15-20
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• 2017

The International Maritime Organization(IMO) has adopted and implemented compulsory regulation for reducing greenhouse gas emission that cause global warming. However, with global warming underway, the IMO plans to enforce voluntary carbon dioxide emissions reduction based on the Ship Energy Efficient Management Plan and the Energy Efficiency Operational Indicator(EEOI) in the near future. Large container ships sail at low speeds in order to save fuel and reduce carbon dioxide emissions. However, bulbous bows designed for high-speed ships decrease fuel efficiency by acting as resistance when reduced speeds are adopted by large container ships. In order to adopt low-speed operations and increase fuel savings, the bulbous bow of a large container ship was modified into the proper shape and size. Fuel consumption was compared for checking the result of EEOI before and after modifying the bulbous bow adopted on low speed operation of large high-speed ships. The results confirmed much larger carbon dioxide emissions reduction than expected. If EEOI would be implemented as compulsory regulation for reducing carbon dioxide emissions, bulbous bow modification can be considered as one of the fuel saving methods for the high-speed ships.

• Journal of the Korean Society for Marine Environment & Energy
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• v.2 no.1
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• pp.90-101
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• 1999

This paper is concerned with the design of automatic ship maneuvering system including automatic path tracking controller and automatic berthing controller. The optimal control technique is employed to design the automatic path tracking controller, which is based on the linearized equations of ship motion. The numerical example shows that the automatic path tracking controller is capable of tracking the line between way points which are determined by pilot a priori. The decentralized control technique is employed to design the automatic berthing controller. In addition to the automatic path tracking controller, the fuzzy logic controller is used to control the forward speed. The numerical example shows that the automatic berthing controller can be successfully implemented.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2017.11a
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• pp.124-127
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• 2017

선박에서 배출되는 환경오염 물질 및 온실가스에 대한 규제가 강화됨에 따라, 환경오염 물질 및 온실가스의 배출과 직접적으로 관련있는 연료 소모량을 줄이려는 다양한 연구가 진행되고 있다. 연료 소모량을 줄이기 위한 방안 중 하나는 환경 및 기상 예보를 이용하여 연료가 가장 적게 소모되는 항로를 찾는 것이다. 기존 연구에서는 연료 소모량을 주된 목적함수로 최소화 하되, 도착 시간에 대한 조건을 평가하기 위해 도착 시간의 기댓값을 계산하고 추가적인 목적함수로 고려하는 경우가 많았다. 그러나 선박 운항 예측 시 적용되는 환경 외란 정보는 상당한 불확실성을 포함하고, 이로 인해 발생하는 운항 속도 및 도착 시간에 대한 불확실성도 상당히 클 수 있기 때문에, 도착 시간의 기댓값뿐만 아니라 도착 시간에 대한 불확실성을 기반으로 제한 시간 내에 선박이 도착할 확률을 정량적으로 평가하는 것이 필요하다. 본 연구에서는 다목적 최적화 기법을 이용해 도착 시간의 기댓값과 연료 소모량에 대한 Pareto set을 구하되, 환경 외란으로부터 발생하는 도착 시간의 불확실성을 계산하여, 제한 시간 내에 선박이 도착할 확률을 계산하고 이를 항로 최적화 시 적용한다. 제안하는 방법의 유용성을 검증하기 위해 실제 환경에 가까운 맵을 기반으로 부산-도쿄 간의 항로를 최적화하고, 그 결과에 대해 논의한다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.6
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• pp.784-789
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• 2015

It was carried out a review of operating limit analysis for small high-speed boat by author. In general, a review of ship's seakeeping performance is performed in the step of ship design, but this study was carried out in the state of completion of boat. Motion performance of Pitch, Vertical and Lateral acceleration and Slamming were satisfied in some encounter angle but deck wetness was not satisfied in all it does the analysis. As a result, sea state rather than the speed and encounter angle of vessel have a greater effect on the seakeeping performance of target vessel. It seems to be due to the size of the target ship.