• Journal of Positioning, Navigation, and Timing
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• v.6 no.4
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• pp.149-157
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• 2017

In this study, a system that precisely determines the heave of ship hull was designed using time-differenced GNSS carrier phase measurement, and the performance was examined. First, a technique that calculates precise position relative to the original position based on TDCP measurement for point positioning using only one receiver was implemented. Second, to eliminate the long-cycle drift error occurring due to the measurement error that has not been completely removed by time-differencing, an easily implementable high-pass filter was designed, and the optimum coefficient was determined through an experiment. In a static experiment based on the precise heave measurement system implemented using low-cost commercial GNSS receiver and PC, the heave could be measured with a precision of 2 cm standard deviation. In addition, in a dynamic experiment where it moved up and down with an amplitude of 48 cm and a cycle of 20 seconds, precise heave without drift error could be determined. The system proposed in this study can be easily used for many applications, such as the altitude correction of fish detection radar.

• Journal of the Korean Institute of Navigation
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• v.12 no.2
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• pp.1-22
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• 1988

The transportations of most of cargoes in world trade have been fulfilled through sea lanes and it seems this trend will not change in near future. Nowadays, inview of the technical aspects of merchant vessels, they are continuously enlarged in hull size and greatly specialized in structure for the cargo spaces and dramatically automatized in navigating, piloting, cargo operating and various other operations, which unavoidably require high technicals in operating the modern merchant vessels. On the contrary to the trend of requiring of operating high technicals, the capabilities of crew on board have been gradually declining in technical competence and their morale for accomplishing their duties on board vessels has greatly falled won compared with that of old days. The above result inevitably brings many problems in operating modern vessels and causes accidents which are avoidable through good competence and high morale of the crew. We intend to analyze the causes of several great sea accident with which it seems some human errors are connected more or less directly or indirectly. We hope that this study could suggest some measures which help to prevent the recurrence of similar accidents by Korean ship's crews.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.504-508
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• 2009

To obtain high power, diesel engines continuously increase combustion pressure and mean effective pressure each cylinder, and the excitation sources and noisy sources are increased, too. Moreover, to reduce the costs, shipyards make hull structures weaker than before. As above reasons, it is more difficult to control the vibration phenomenon nowadays. In this study, it was investigated why diesel generator sets reached the vibration allowable limits during the FAT and heavy vibration phenomenon of diesel generator sets using ODS test during onboard tests. Also, it is found out the stiffness of deck and common bed using the test result of their structural impedance. To find out the vibratory characteristics of diesel generator sets, MODAL tests were carried out. From the sensitivity analysis after above tests, it was selected points to be reinforced and studied troubleshooting to solve heavy vibration phenomenon of diesel generator sets.

• International Journal of CAD/CAM
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• v.6 no.1
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• pp.3-8
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• 2006

The application of three-dimensional (3-D) CAD has been popularized for design and production and digital manufacturing has been spreading in many industrial fields. By simulation of the production process using 3-D digital models, which are the core of CIM (Computer Integrated Manufacturing) system, the efficiency and safety of production are improved at each stage of work, and optimization of manufacturing can be achieved. This paper firstly describes the concept of "simulation based production" in shipbuilding and also digital manufacturing; the 3-D CAD system is indispensable for effective simulation because ship structure is three dimensionally complex. By simulation, "computer optimized manufacturing" can be possible. The most effective fields of simulation in shipbuilding are in jobs where many parties have to cooperate, while existing two-dimensional drawings are hardly observed the whole structures due to interference between structures or equipment of complex shape. In this paper some examples of the successful application in IHIMU (IHI Marine United Inc.) are shown: assembly of a pipe unit, erection of a complex hull block, carriage of equipment, installation of a propeller, and access in an engine room.

• Journal of Ocean Engineering and Technology
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• v.23 no.1
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• pp.81-88
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• 2009

An evaluation of the structural integrity of an oceanographic buoy subjected to extreme loads was carried out in this study. Load components, such as the current, waves, and wind load, which were required for the sea's environmental conditions, were calculated precisely. A non linear finite element analysis was conducted to elucidate the structural response of the buoy under extreme environmental conditions. Based on the surface drift velocity scheme, a dynamic impact analysis was also carried out for the case of collision accidents. The proposed numerical technique would be a useful and cost effective tool for design scheme evaluation in the field of oceanographic buoys.

• Journal of Ocean Engineering and Technology
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• v.23 no.1
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• pp.135-139
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• 2009

In the line heating for the plate forming of a ship's hull, an in line assessment of completion is necessary for an automated production system. In the current curved plate forming process, a fabricated plate is compared to a template that is made in the mold loft and is used for the determination of the heating line for the next step. In this paper, a new method is presented for the in line assessment of completion for curved plate forming. This method uses a 3-D scanner. For the registration of the scanned data for a surface and the target surface, the ICP (Iterative Closest Points) method was adopted. A computer program was developed to carry out the registration, check for similarities, visualize the surface, and control the results. This program was applied to a sample curved plate forming process.

• Ocean Systems Engineering
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• v.6 no.4
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• pp.305-324
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• 2016

Wave load prediction at zero forward speed using finite depth Green function is a well-established method regularly used in the offshore and marine industry. The forward speed approximation in deep water condition, although with limitations, is also found to be quite useful for engineering applications. However, analysis of vessels with forward speed in finite water depth still requires efficient computing methods. In this paper, a method for analysis of wave induced forces and corresponding motion on freely floating three-dimensional bodies with low to moderate forward speed is presented. A finite depth Green function is developed and incorporated in a 3D frequency domain potential flow based tool to allow consideration of finite (or shallow) water depth conditions. First order forces and moments and mean second order forces and moments in six degree of freedom are obtained. The effect of hull flare angle in predicting added resistance is incorporated. This implementation provides the unique capability of predicting added resistance in finite water depth with flare angle effect using a Green function approach. The results are validated using a half immersed sphere and S-175 ship. Finally, the effect of finite depth on a tanker with forward speed is presented.

• 한국전산유체공학회:학술대회논문집
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• 1996.05a
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• pp.85-92
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• 1996

Numerical simulations are made for the three-dimensional flow around a wing in ground effect craft haying the complex geometry. A numerical tool is developed for the primary design of hull and wing shape of practical Wing-In-Ground effect(WIG) stop. The finite-difference method is utilized to descretize the governing equations and pressure field is obtained by using Marker-And-Cell(MAC) method. The air and water flows are simultaneously simulated in the time-marching solution procedure for the Navier-Stokes equation. The porosity technique and the density function are devised for the implementation of the three-dimensional body-boundary and the free-surface conditions, respectively. In this paper, a craft is modeled simply by three blocks containing a wing mounted on a main body horizontally, with the endplate. The numerical calculations of a WIG advancing in a calm water are performed and the WIG-generated wave profiles are also obtained. In the final paper, details of the numerical methods employed for the present study and calculated results are discussed.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.1
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• pp.48-58
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• 2002

There is a purpose of this study for the proposal of the optimum technique utilized for the vibration design initial step. The stiffened plate structure for the ship hull is made for analysis model. To begin with, dynamic characteristics of stiffened plate structure is analysed using FEM. Main vibrational mode of the structure is decided in the analytical result of FEM. The simplified equation on the natural frequency of the main vibrational mode is induced. Next, sensitivity analysis is carried out using the simplified equation, and rate of change of dynamic characteristics is calculated. Then, amount of design variable is calculated using this sensitivity value and optimum structural modification method. The change of natural frequency is made to be an objective function. Thickness of panel, cross section moment of stiffener and girder become a design variable. The validity of the optimization method using simplified equation is examined. It is shown that the result effective in the optimum modification for natural frequency of the stiffened plate structure.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.768-772
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• 2008

Various scanning systems have been studied in many industrial areas to acquire a range data or to reconstruct an explicit 3D model. Currently optical technology has been used widely by virtue of noncontactness and high-accuracy. In this paper, we describe a 3D laser scanning system developped to reconstruct the 3D surface of a large-scale object such as a curved-plate of ship-hull. Our scanning system comprises of 4ch-parallel laser vision modules using a triangulation technique. For multi laser vision, calibration method based on least square technique is applied. In global scanning, an effective method without solving difficulty of matching problem among the scanning results of each camera is presented. Also minimal image processing algorithm and robot-based calibration technique are applied. A prototype had been implemented for testing.