• Journal of the Korean Society of Fisheries and Ocean Technology
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• 제42권2호
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• pp.111-118
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• 2006

It is indispensable to grasp the turning ability of a ship to operate her effectively. For this purpose, the author measured the turning ability of training ship, A-RA by use of bow thruster and stem rudder. The turning ability of this ship, in case of using both of stem rudder and bow thruster at the same time, caused by increase of steering angle provides more influence to the size of tactical diameter than it caused by the power of bow thruster. But the influence of bow thruster on the turning ability is available only within rudder angle $5^{\circ}\;-\;10^{\circ}$, so it is possible to grasp that the effect of bow truster is reduced as rudder angle become bigger. In case of the influence of bow thruster by her speed, the ability of bow thruster is very effective at low speed, but it is almost not available in normal turning speed. Therefore, the using both of stem rudder and bow thruster can be useful in case of low speed proceeding at entrance or departure of the narrow waterway or inside port which sea traffic is congest for collision avoidance.

• Journal of the Institute of Convergence Signal Processing
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• 제21권4호
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• pp.170-176
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• 2020

In this study, the lift, drag and moments of the rudder that influences on the maneuvering ships directly has been investigated using CFD(Computational Fluid Dynamics). One of typical ship rudders effecting on the forces and moments is the bow rudders during maneuvering on the sea. Thus, the forces and moments should be investigated for the bow of ship rudder. Among the IFS bow rudder series, the balance IFS 54 BR 15 is used for study. As a turbulent model, standard k-epsilon is applied to this study. The hydrodynamic of the bow rudder, especially lift, drag and moment coefficients are calculated for the different angles of attack. The angles of attack between water flow and rudder are presented in cases including 0°, 5°, 10°, 15°, 20°, 25°, 30° and 35°. The results of calculation for those influences on maneuvering performance of ships are compared with the relevant results of the previous experimental studies.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• 제47권4호
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• pp.435-442
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• 2011

In an attempt to respond to the increase in international oil prices and reduce operating expenses, ship remodeling was carried out on a 740ton class tuna purse seiner. To strengthen the competitiveness of the fisheries industry by improving vessel performance, a bulbous bow was newly equipped. The slipway and rudder area were also lengthened and enlarged with the propeller and main engine remained unchanged. To reduce the hull resistance, a circle type bulbous bow was attached on the hull behind bow thruster and thus the cost for exchanging electrical equipment for bow thruster was reduced. The new rudder area was expanded 15% more than the old one within the extent that the existing mechanical control part and rudder stock were not changed. To prevent fishing net damage and stabilize wake field, slipway was lengthened to the optimal position. All of the new design of remodeling parts went through the model tests in towing tank and CWC. Besides resistance test, all of necessary model test results were delivered for hydrodynamic character for the modified ship. The maneuvering simulation to verify that the remodeled ship satisfies the IMO rules was performed in both zigzag and turning tests. The estimated resistance with new bulbous bow and lengthened stern was reduced by 4.8% in the 2-dimensional analysis and 17.4% in the 3-dimensional analysis in comparison of conventional ship. The average reduction of resistance was estimated about 10%. Maneuvering character of modified hull form was found to satisfy all regulations under IMO. The remodeling of tuna purse seiner can not only improve fishing performance but also contribute to reduction of operating cost by saving energy for the fisheries industry.

• Journal of the Korean Institute of Navigation
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• 제10권2호
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• pp.83-96
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• 1986

In the restricted sea way such as fair way in harbor, narrow channel etc, the safe ship-handling is a very important problem, which is greatly related with turning ability of ships. It is of great importance that ship-handlers can grasp the position of pivoting point varying with time increase at any moment for relevant steering activities. Mean while, in advanced ship-building countries they study and investigated pivoting point related with turning characteristics, hut their main interest lies in ship design, not in safe ship controlling and maneuvering. In this regards it is the purpose of this paper to provide ship-handlers better under standing of pivoting point location together with turning characteristics and then to help them in safe ship-handling by presenting fact that pivoting points vary according to configuration of ships. The author calculated the variation of pivoting point as per time increase for various type of vessels, based on the hydrodynamic derivatives obtained at test of Davidson Laboratory of Stevens Institutes of Technology , New Jersey, U.S.A. The results were classified and investigated according to the magnitude of block coefficient , length-beam ratio, length-draft ratio, rudder area ratio ete, and undermentioned results were obtained. (1) The trajectory of pivoting point due to variation of rudder angle are all the same at any time, though the magenitude of turning circle are changed variously. (2) The moving of pivoting point is affected by the magnitude of block coefficient, length-beam ratio, length-draft ratio, however the effect by rudder area ratio might be disregarded. (3) In controlling and maneuvering of vessels in harbor, ship-handlers might regard that the pivoting point would be placed on 0.2~0.3L forward from center of gravity at initial stage. (4) The pivoting point of VLCC or container feeder vessels which have block coefficient more than 0.8 and length-beam ratio less than 6.5 are located on or over bow in the steady turning. (5) When a vessel intends to avoid some floating obstruction such as buoy forward around her eourse, the ship-handler might consider that the pivoting point would be close by bow in ballast condition and cloase by center of gravity in full-loaded condition.

• Journal of Navigation and Port Research
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• 제32권8호
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• pp.597-602
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• 2008

T.S. HANBADA has a relatively large hull and superstructures above the water line, so she has much of leeway or turning of bow with the effect of winds. Especially on berthing, unberthing and/or sailing on low speed, these effects take place more significant. Therefore, it was carried out the numerical calculation of the wind force and moments acting on the T.S. HANBADA, and then calculated the leeway angle and counter rudder angle with the relative wind direction and velocity. Also, it was suggested the maximum wind velocity which could be berthed or unberthed used by bow thruster and the tugboat operations in strong winds. These results will be great helpful to the vessels with large superstructures on ship's handling in harbour or tugboat operations.

• Journal of the Society of Naval Architects of Korea
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• 제41권1호
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• pp.40-46
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• 2004

In this paper, one of the harbour manoeuvring tests is described. its goal is to investigate the so-called crabbing performance of ships. By crabbing is meant the ability of the vessel to move sideways with the use of her own manoeuvring devices like propellers, rudders, transverse thruster, etc. The crabbing model tests were carried out in the Ocean Engineering Wide Tank, University of Ulsan(UOU) to measure the transverse forces and yawing moments by the transverse thruster alone and the propeller-rudder arrangement in combination with the bow thruster. The comparison between UOU crabbing test results and data measured at one of foreign research institutes showed a little gap due to different rotating conditions of controllable pitch propellers.

• International Journal of Naval Architecture and Ocean Engineering
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• 제4권3호
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• pp.199-210
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• 2012

The recent researches on the automatic berthing control problems have used various kinds of tools as a control method such as expert system, fuzzy logic controllers and artificial neural network (ANN). Among them, ANN has proved to be one of the most effective and attractive options. In a marine context, the berthing maneuver is a complicated procedure in which both human experience and intensive control operations are involved. Nowadays, in most cases of berthing operation, auxiliary devices are used to make the schedule safer and faster but none of above researches has taken into account. In this study, ANN is applied to design the controllers for automatic ship berthing using assistant devices such as bow thruster and tug. Using back-propagation algorithm, we trained ANN with set of teaching data to get a minimal error between output values and desired values of four control outputs including rudder, propeller revolution, bow thruster and tug. Then, computer simulations of automatic berthing were carried out to verify the effectiveness of the system. The results of the simulations showed good performance for the proposed berthing control system.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.720-723
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• 2005

Ship motion is a complex controlled process with several hydrodynamic parameters that vary in wide ranges with respect to ship load condition, speed and surrounding conditions (such as wind, current, tide, etc.). Therefore, to effectively control ships in a designed track is always an important task for ship masters. This paper presents an effective adaptive autopilot ships that ensure the optimal accuracy, economy and stability characteristics. The PID control methodology is modified and parameters of a PID controller is designed to satisfy conditions for an optimal objective function that comprised by heading error, resistance and drift during changing course, and loss of surge velocity or fuel consumption. Designing of the controller for course changing process is based on the Model Reference Adaptive System (MRAS) control theory, while as designing of the automatic course keeping process is based on the Self Tuning Regulator (STR) control theory. Simulation (using MATLAB software) in various disturbance conditions shows that in comparison with conventional PID autopilots, the designed autopilot has several notable advantages: higher course turning speed, lower swing of ship bow even in strong waves and winds, high accuracy of course keeping, shorter time of rudder actions smaller times of changing rudder direction.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.359-362
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• 2006

This study develops an automatic berthing control algorithm for ships with a bow thruster and a stern thruster as well as a rudder. A nonlinear mathematical model for low speed maneuvering of ships is used to develop a MIMO(multi-input multi-output) nonlinear control algorithm. The algorithm consists of two parts, which are forward velocity control and heading angle control. The control algorithm is designed based on the longitudinal and yaw dynamic models of ships. The desired heading angle is obtained by the so called "Line of Sight" method. An optimal control force allocation method of the rudder and the thrusters is suggested. The nonlinear control algorithms are tested by numerical simulations using MATLAB, and shows good tracking performances.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• 제51권1호
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• pp.61-70
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• 2015

In an attempt to improve the maneuvering character of hull form renovated tuna purse seiner. A renovation was carried out on the 3 tuna purse seiner fishing vessel. To grasp the progress of maneuvering and resistance on ship B (730 ton class), new bulbous bow was only attached. The ship A (740 ton class) and C (600 ton class) were modified for new bulbous bow, enlarged slipway and rudder. And then the zigzag and the turning test were carried out. According to the turning test, the advance and the tactical diameter were improved very much for the modified ship. The sea trial was carried out for the original and modified ship A. It is showed that the results of sea trial corresponded with that of the tank test on the whole. In the result of the zigzag test on ship B, the turning ability was improved very much, but the yaw checking ability was deteriorated in just some degree. In the result of the zigzag test on ship C, the turning ability and yaw checking ability were remarkably improved. Ship C was greatly improved among the three ships for the maneuvering character of modified hull form.