• Journal of the Korean Society of Industry Convergence
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• v.23 no.4_2
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• pp.661-667
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• 2020

The optimal shape modeling of core parts through 3D modeling and structural analysis for the development of small and medium-sized ships. The goal is to improve the efficient structure of the hydraulic system for controlling the rudder among the core steering parts in small and medium-sized ships. Through 3D modeling and structural analysis, a new concept of tiller parts and a double-acting hydraulic cylinder control system were proposed and operational structural stability was evaluated. Structural analysis of the three different tiller designs that can be replaceable onto existing fishing vessels was conducted to derive the final shapes. The emphasis was placed on evaluating the structural stability of the key drive components, the tiller, pin, and cylinder rodin the maximum torque condition of the hydraulic cylinder.

• Journal of the Korea Safety Management & Science
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• v.19 no.4
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• pp.309-316
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• 2017

Recently, the outboard engine system of internal combustion engine is widely used in the field of small ship propulsion. However, the internal combustion engine has serious problems of energy depletion and environmental problems, so electric propulsion methods are being studied. In this paper, we have developed important motors and controllers of electric propulsion system for small marine outboard motors. The motor design was performed through the motor characteristics analysis method, and the 30Kw system was developed through the BEMF processing circuit and the power conversion circuit by the embedded microprocessor. This study was carried out through government supported projects and achieved quantitative targets through accredited institutions.

• Journal of Korea Ship Safrty Technology Authority
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• s.23
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• pp.2-13
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• 2007

With the effectuation of the amendment of MARPOL 73/78 on 5 April 2005, enforcement regulations of Marine Pollution Prevention Act were revised in domestic on 12 March 2005 that double hull structure was required to the small single bottom oil tankers under DWT(deadweight tonnage) 500 ton for the protection of the marine pollution casualties. The objective of this study is to develop the double bottom structure of small oil tanker under DWT 500 ton with superior crashworthiness and to establish its suitable standard to double bottom structure. The promoting strategy of this R&D is classified into the crashworthy structural analysis of small oil tankers using LS/DYNA3D code and the examination of their damage stabilities according to tonnage. It could be thought that the desirable inner bottom height should be above the B/7.5 and its minimum height 0.65m for the domestic small oil tanker under DWT 500ton.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.15 no.4
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• pp.251-259
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• 2015

In this paper, a ship detection method is proposed; this method uses edge-based segmentation and histogram of oriented gradient (HOG) with the ship size ratio. The proposed method can prevent a marine collision accident by detecting ships at close range. Furthermore, unlike radar, the method can detect ships that have small size and absorb radio waves because it involves the use of a vision-based system. This system performs three operations. First, the foreground is separated from the background and candidates are detected using Sobel edge detection and morphological operations in the edge-based segmentation part. Second, features are extracted by employing HOG descriptors with the ship size ratio from the detected candidate. Finally, a support vector machine (SVM) verifies whether the candidates are ships. The performance of these methods is demonstrated by comparing their results with the results of other segmentation methods using eight-fold cross validation for the experimental results.

• Journal of Navigation and Port Research
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• v.42 no.2
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• pp.87-96
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• 2018

A trajectory control system plays an important role in controlling motions of marine vehicle when a series of way points or a path is given. In this paper, a sliding mode control (SMC)-based trajectory tracking controller for marine vehicles is presented. A small-sized unmanned ship is considered as a control object. Both speed and heading angle of a ship should be controlled for tracking control. The common point of related researches was to separate ship's speed and heading angle in control methods. In this research, a new control law from a general sliding mode theory that can be applied to MIMO (multi input multi output) system is derived and both speed and heading angle of a ship can be controlled simultaneously. The propulsion force and rudder force are also applied in modeling stage to achieve accurate simulation. Disturbance induced by wind is also tackled in the dynamics considering robustness of the proposed control scheme. In the simulation, we employed a way-point method to generate ship's trajectory and applied the proposed control scheme to ship's trajectory tracking control. Our results confirmed that the tracking error was converged to zero, thus demonstrating the effectiveness of the proposed method.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.364-379
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• 2019

Wave-induced ship motion and load responses are usually investigated on the assumption that the incident waves are long-crested. The realistic sea waves are however short-crested irregular waves. Real practice reveals that the ship motion and load responses induced by short-crested waves are different from those induced by long-crested waves. This paper aims to conduct a comprehensive study on ship motions and loads in different wave fields. For this purpose, comparative studies by small-scale model towing tank test and large-scale model sea trial are conducted to experimentally identify the difference between ship motions and loads in long-crested and short-crested irregular waves. Moreover, the influences of directional spreading function of short-crested waves on ship motions and loads are analyzed by numerical seakeeping calculation. The results and conclusions obtained from this study are of great significance for the further extrapolation and estimation of ship motions and loads in short-crested waves based on long-crested wave response results.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.30 no.4
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• pp.299-311
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• 1994

The new course distances of a ship are one of the important factors of the safety handling as the indices to indicate directly her abilities of course alteration. Recently, International Maritime Organization (IMO) exhorts that all vessels should use maneuvering booklets in which are drawn the curves of new course distances obtained from the test of measuring them and noted other maneuvering performance standard in various navigation conditions. This paper describes the method to calculate many new course distances for many rudder angles by turning circle test without observation or using other calculating methods. The main results are as follows: 1) The mean difference of the distances between two new course distances by the turning circle test and heading test of the experimental ship was about 7.7% vaules of the ones by the heading test. when her altering angles were $48^{\circ}$, $63^{\circ}$and $70^{\circ}$, using the rudder angle of $35^{\circ}$ . These new course distances were therefore found to be small in difference of those. 2) The mean difference of the distance between two new course distances by the turning circle test and the maneuvering indices of the experimental ship was about 4.5% values of the ones by the maneuvering indices, when her altering angles were $48^{\circ}$, $63^{\circ}$and $70^{\circ}$, using the rudder angle of $35^{\circ}$, these new course distances were therefore found to be small in difference of those. 3) The mean difference of the distance between two new course distances by the turning circle test and the observation of the experimental ship was about 6.1% values of the ones by the observation, when her altering angles were $48^{\circ}$, $63^{\circ}$and $70^{\circ}$, using the rudder angle of $35^{\circ}$. These new course distances were therefore found to be small in difference of those. 4) It is confirmed that many new course distances for many angles can be calculated easily by using the method of ship's simple turning circle test, without observation or using the maneuvering indices and heading test method. 5) It is considered to be helpful for the safety of ship handling to draw curves of new course distances by turning circle test and $\phi_4$ - $\phi_2 by heading test, and utilize them at sea.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.1
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• pp.8-14
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• 2020

According to the statistics provided by Korean Maritime Safety Tribunal for the year 2018, the majority of marine accidents in the past four years have occurred in fishing boats and small-sized boats. Negligent behavior resulting from not looking outside and non-compliance with navigation laws are the primary reasons behind ship collisions. Although safety education and training are reinforced to prevent such accidents, they still occur frequently. Hence, technical methods are continuously being developed to reduce ship collisions caused by human cause. The objective of this study is to reduce ship collisions by employing the WAVE communication system, which has short transmitting and receiving periods that can be incorporated for high-speed small-sized vessels. In this study, the suitability of the communication range was examined, and the appropriate range and timing for avoidance motion were accordingly selected, and a control algorithm based on the same was thereby designed. Consequently normal operation of the collision avoidance system was verified by connecting and simulating the proposed WAVE communication router-controller-steering equipment.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.856-866
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• 2021

The increasing international awareness regarding air pollutant reduction has resulted in increasing demand for eco-friendly ships; hence, electric ships are being actively developed by various countries. Presently, studies on electric ships are mainly focused on electric propulsion systems and electric motors. However, from the ship perspective, there are no studies on conceptual designs for coastal car ferries powered by removable power supply systems. In the present study, the main research consideration is regarding the conceptual design of a fully electrified car ferry using a battery-based removable system as the main power source. By analyzing the dimensions of more than 100 domestic coastal car ferries, the main criteria satisfying the requirements for developing a suitable vessel were derived, and a study on intact/damage stability was conducted considering the application of a removable battery truck. Further analyses of the problems concerning the conceptual design were also performed to derive solutions.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.7
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• pp.1129-1139
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• 2022

Collision accidents happen frequently. The majority of ships involved in collisions in the coastal areas of Korea are middle and small size ships. The proportion of collision accidents is only 9% of all types of marine accidents; however, the number of casualties resulting from collisions is 34.4% of all human life damages. Generally, as reported by the people involved in these collisions, the navigation lights of the opponent ships were poor and invisible when the accident happened even though the weather and visibility were good. Furthermore, there are many insistences for poor navigation light conditions of the opponent ship in the bay or harbor. Therefore, it is necessary to analyze the present conditions and safety of navigation lights. Therefore, in this study, we examined the rules and books of navigation lights and compared it to that of other transportation systems, such as aircraft, trains, and road vehicles. Furthermore, we analyzed the current marine traf ic circumstances and ship collision accidents that happened in the past 5 years. Additionally, a questionnaire was prepared to gather the opinion of ship experts and secure the objectivity for improvement methods of navigation lights. Finally, methods to improve the navigation lights on ships were devised.