• Journal of the Korean Institute of Navigation
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• v.15 no.4
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• pp.1-11
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• 1991

Since it is very important for an ocean-going vessel to transmit information quickly and accurately to her owner or charterer not only for the ship's safety but for economic operation of the ship, some newly-built automated vessels equipped with automatic information transmission system which consists of INMARSAT-C and specially-designed computer. This system, however, is not applicable to the existing vessel without chaging her equipments and, furthermore, is too expensive for small shipping companies to fit out such a system on their vessels. Therefore, we propose a low-priced information transmission system which consists of a personal computer and communication equipments in the existing vessel, and in this paper, as the groundwork of the proposed system, we have made up the ship's position transmission system which is composed of and IBM AT-compatible, PC, INMARSAT-A and a GPS receiver. As the test result of the system through sea trial on the training ship 'HANBADA', we confirmed that transmission of the ship's position was achieved succesfully and consequently there could be high possibility of cost-effectiveness of the proposed system.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.2
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• pp.133-138
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• 2016

This paper describes the track initiation and target-tracking filter for ship tracking in a marine environment by using Light Detection And Ranging (LiDAR). LiDAR with three-dimensional scanning capability is more useful for target tracking in the short to medium range compared to RADAR. LiDAR has rotating multi-beams that return point clouds reflected from targets. Through preprocessing the cluster of the point cloud, the center point can be obtained from the cloud. Target tracking is carried out by using the center points of targets. The track of the target is initiated by investigating the normalized distance between the center points and connecting the points. The regular track obtained from the track initiation can be maintained by the target-tracking filter, which is commonly used in radar target tracking. The target-tracking filter is constructed to track a maneuvering target in a cluttered environment. The target-tracking algorithm including track initiation is experimentally evaluated in a sea-trial test with several boats.

• The Journal of the Acoustical Society of Korea
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• v.21 no.6
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• pp.576-584
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• 2002

This paper proposes a new denosing method using wavelet packet, to reject unknown external noise and white gaussian ambient noise for measuring the transient noise which is one of the important elements for ship classification. The previous denosing method applied the same wavelet threshold at each node of multi-single sensors for rejecting white noise is not adequate in the underwater environment existing lots of external noises. The proposed algorithm of this paper applies a modified soft-threshold to each node according to the discriminated threshold so as to reject unknown external noise and white gaussian ambient noise. It is verified by numerical simulation that the SNR is increased more than 25㏈. And the simulation results are confirmed through sea-trial using multi-single sensors.

• The Journal of the Acoustical Society of Korea
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• v.32 no.4
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• pp.354-360
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• 2013

In this paper, it is discussed that the detection and tracking performance of the piecewise linear path underwater target is improved using clutter reduction algorithm in heavy clutter density environment. Through clutter reduction algorithm using Hough Transform, measurements which represent clutter features are removed and the performance of target tracking on the remaining measurements is demonstrated applying CMKF-L(Converted Measurement Kalman Filter with Linearization) as tracking filter. Algorithm performance test is conducted using simulation data and real sea-trial data and by applying the proposed algorithm in heavy clutter density environment, it is confirmed that the target is tracked consistently and stably with clutter rejected measurements.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.3
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• pp.204-214
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• 2017

Recently, ship owners have been requiring the assessment of the maneuverability of a twin-screw ship under machinery failures. In this paper, we are only focused on the propulsion failure among propulsion failure, power supply failure, steering system failure etc. First of all, the mathematical model for the twin-screw 174K LNGC is verified by comparing the simulated results for $35^{\circ}$ turning test, $10^{\circ}/10^{\circ}$ zigzag test and $20^{\circ}/20^{\circ}$ zigzag test under normal operating condition and those obtained from free running model tests. And, sea trial results of 216K LNGC under single propeller failure are compared with those of 174K LNGC under identical condition to verify the proposed method to predict maneuverability under single propeller failure. After the straight line maneuver is simulated under the single propeller failure, the speed and equilibrated heading and rudder deflection angles at steady state are predicted. After the IMO maneuvering tests are simulated under the single propeller failure, the results are reviewed to investigate the maneuvering characteristics due to the failure.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.1
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• pp.63-71
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• 2017

During the sea trial test, we discovered EMI(Electromagnetic Interference) between MIL-SATCOM parabolic antenna and ES(Electronic Warfare Support) omni antenna. Emitted side lobe of CW(Continuous Wave) from MIL-SATCOM raises the threshold level of ES omni antenna. Therefore detection rate of ES is decreased. To solve this problem, the path of side lobe of CW from MIL-SATCOM should be blocked using EMI shield. This paper presents the method how to calculate the size of EMI shield, material, and optimized deployment. The test of the EMI shield effect was performed on a surface ship. After installing EMI shield, EMI has been decreased significantly. This paper will provide a method how to design EMI shield and a way to verify the result.

• International Journal of Ocean System Engineering
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• v.3 no.1
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• pp.10-15
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• 2013

A ship cruising in the ocean oscillates continuously due to wave action. In order to reduce the ship's roll, we developed a fin stabilizer as an anti-rolling device for a 500-ton-class high-speed marine vessel. During the development phase, it was necessary to set up control gains for the motion and hydraulic systems and assess the effectiveness of the anti-rolling performance on the ground. For this reason, a Target Simulator, which simulated the ship's motion, was given operator inputs such as the engine telegraph and waterjet deflection angle, and generated roll using a one-degree-of-freedom motion base. Hardware-In-the-Loop Simulation (HILS) was performed using the Target Simulator in order to confirm the various logics of the developed fin stabilizer, select initial control gains, and estimate the anti-rolling performance. In conclusion, it was confirmed that HILS was very helpful to develop the fin stabilizer because it could reduce the number of sea trial tests that were needed and could find many malfunctions in the factory a priori.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.7
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• pp.801-807
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• 2005

Any failure of intake and exhaust valves of marine diesel engine must be regarded as serious, and any steps which can be taken to prevent such failure are desirable. The purposes of this study is to investigate and to analyse the failure causes of intake and exhaust valves for marine diesel engine during sea trial after completion of overhauling. In this study, to analyse the failure causes, we have carried out on board inspection, fractography test and discussion based on the specimen and repairing report provided by the ship owner. From the results of above inspection, test and discussion, it has been considered reasonable to conclude that the causes of damaged valves of the ship are as follow ; 1) During operation, the stick or seizure of valve spindle occurred and hence the movement of exhaust valve spindle was to be resisted and subsequently the engine was to be operated under an unappropriated valve timing and the exhaust valve sustained the repeated loads exceeding the fatigue strength of valve material. 2) By the loads above described, the fatigue fracture was initiated at the structural noncontinuous part of exhaust valve spindle, and then the valve head was finally fractured and dropped in the cylinder. 3) The fractured exhaust valve head impacted the intake valve at various direction to be bent or damaged.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.54 no.3
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• pp.239-245
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• 2018

International Maritime Organization (IMO) has established standards for ship manoeuvrability and applied these standards for vessels over 100 meters in length that built since 2004 (IMO, resolution MSC.137[76]). These standards are no exception to fishing vessels. In this study we carried out a manoeuvring simulation of the new model ship (Stern trawler) of fisheries training ship of Pukyong National University based on Kijima's empirical formula. The formula takes into account of the effect of stern shape or does not take into account of the effect of stern shape. Also we checked whether the simulation results of turning motion of model ship meet IMO manoeuvrability criteria and then compared trajectories between the simulation results of model ship and the results of real sea trial test of the existing ship. In conclusion, Kijima's empirical formulas can estimate the manoeuvrability of fishing vessels at design stage approximately, it needs more parameters of fishing vessel own in case of expressing the manoeuvrability of fishing vessel accurately.

• Special Issue of the Society of Naval Architects of Korea
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• 2009.09a
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• pp.93-96
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• 2009

Foundation structure for the main engine heavy spare parts in the engine room is susceptible to resonance problem due to outfitting weight. In addition the deck floor has a large opening for the main engine installation and maintenance, which further weakens the foundation structure. To reinforce the weak structure, two types of approaches have been used; 1) insert an H-pillar below or above the floor and 2) increase the stiffener size. In this paper, the H-pillar approach is used to solve the vibration problem of the foundation structure in the engine room opening area. A commercial program is used to analyze the vibration problem ad to find the location and the size of the H-pillar. Modal test at the quay and on-board vibration measurement during the sea trial have confirmed the validity of inserting an H-pillar below the floor.