• Journal of Ocean Engineering and Technology
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• v.33 no.5
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• pp.462-469
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• 2019

In this study, a motion control problem for the vessels towed by tugboats or towing ships on the sea is considered. The towed vessels, such as barge ships, are used for several purposes. Generally, these vessels have no power propulsion system and are towed using ropes and towing vessel (tugboats). The basic mathematical model of the towed vessel in which three active rudders are attached was introduced from a previous study. Owing to the dependency of the motions of the towed vessel to the towing ship, a method is suggested to cope with the undesirable disturbance and improve the tracking performance. For the simulation study, a model of the towed vessel with a towing ship is made, and necessary physical parameters are identified from the experiment. For the defined and linearized model, a control system is designed, and the control performance is also evaluated. A simulation study is conducted and the effectiveness of the proposed control strategy is verified.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.6
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• pp.637-642
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• 2013

In this paper, an analysis results of towing force and towing points which are dominating factors to determine the behavior of towed ship are introduced. The towing force and towing points to achive the desired posture and its position of the towed vessel are derived based on simplified dynamics and linearization method. LQR algorithm for posture control is applied to linearized system and numerical simulation is also executed. Force based on COG(cneter of gravity) and gain of controller to achieve desired posture for target vessel are obtained by using Riccati matrix equation and pseudo inverse matrix is applied to analyze the relation between the derived force and its towing point. Based on this analysis method, towing force need to move the towed vessel from its initial position to target position can be calculated. The towing method including towing point and direction is also considered on this method. Finally, the relation between towing force and towing point is confirmed from the analysis and the results can be applied to arrangement of tug boats during salvage works.

• Journal of the Korean Institute of Navigation
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• v.23 no.4
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• pp.21-28
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• 1999

In some cases a towing vessel and her tow, a fishing boat, and a vessel at anchor have a priority against a general power-driven vessel underway in the application of collision rule. This article aims at suggesting a practical guide for the construction of the meaning of a vessel engaging in fishing, a vessel engaged in towing operation such as severely restricts the towing vessel and her tow in their ability to deviate from their course and a vessel at anchor, which are permitted to have the above priority. The construction of the application of the collision rule on the above vessels is supported by the decisions of MAIA and the judgment of civil courts.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.12-23
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• 2021

In the conventional experiment to assess the towing operations, the towing stability of the towed vessel has been evaluated under the condition without lateral motion of the tug-boat. However, the tug-boats may have a lateral force to change the direction of the towed vessel. In this study, experiments have been conducted considering unsteady conditions in the towing system. First, a towing test system in a Circular Water Channel (CWC) using the conventional experimental method is built. Second, the towing characteristics of the towed vessel are investigated using the conventional method, and they are compared with other research results and stability discriminant criteria. Third, the lateral motion of the tug-boat was modeled as a sinusoidal motion using a forced oscillation device changing frequency and amplitude. Finally, the discussion is given in terms of both towing- and course-stability of the towed vessel according to the lateral motion of the tug-boat.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.943-956
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• 2020

In this study, the motion control problem of the vessel towed by a towing ship (tugboat) is considered. The non-powered towed ship is dragged by the towing ship. Even though the towed ship is equipped with propulsion systems, they cannot be used at low or constant speeds due to safety issues. In narrow canals, rivers, and busy harbor areas especially, where extreme tension is required during towing operation, the course stability of the towed vessel depends on the towing ship. Therefore, the authors propose a new control strategy in which the rudder system of the towed vessel is activated to provide its maneuverability. Based on the leader-follower system configuration, a nonlinear mathematical model is derived and a back-stepping control is designed. By simulation and experiment results with a comparison study, the usefulness and effectiveness of the proposed strategy are validated.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.56 no.3
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• pp.238-245
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• 2020

In this study, a motion control problem for the vessel towed by towing ship on the sea is considered. The towed vessel does not have self-control capabilities such that its course stability totally depends on the towing ship. Especially, in the narrow canal, river and congested harbor area, extreme tension is required during the towing operation. The authors, therefore, propose a new control system design method in which the rudder is activated to provide its maneuverability. Based on the leader following system configuration, a nonlinear mathematical model is derived and a backstepping control is designed. By experiment results with nonlinear control framework, the usefulness and effectiveness of the proposed strategy are presented.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.54 no.4
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• pp.343-352
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• 2018

In this study, a motion control problem for the vessels towed by tugboats or towing ships on the sea is considered. The towed vessel looks like the barge ship, which is used for many purposes. In these vessels, basically, the power propulsion system is not installed but just towed by a towing vessel such as tugboats with ropes and wires. It means that the motions of towed vessel are basically dependent on the tracking route of towing boat. Therefore, in some cases, undesirable and unpredictable motions may be made by environmental factors such as wave, wind attack and so on. As a result, a collision accident with others may occur during maneuvering situation. Based on these facts, the authors try to encourage the steering performance of the towed vessel by using controllable rudders without any propulsion system. In this study, especially, a controllable vessel with three rudders is considered, and a mathematical model is induced for the future study. The model is described as surge, sway motion and inertia moment by following the general representation method for the surface ship.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.2
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• pp.140-149
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• 2008

This study evaluated the efficiency of an oil fence and spreading devices for one vessel in a towing tank. A series of model experiments and numerical calculations were conducted using an existing oil fence for two vessels and a new method for one vessel. Models of the oil fence and spreading devices were constructed on $1/20^{th}$ scale from waterproofed nylon fabric and canvas. The tensions acting on the model of the oil fences and the horizontal distance between the spreading devices were calculated numerically while the oil fences were being towed. The results were extremely close to the results of the model experiments. The ratio of the opening width to the total length of the oil fence, which shows the efficiency of the oil fence for one vessel, was 49.7% in 0.4 m/sec. Therefore, the proposed oil fence system should be very useful for oil containment at sea. As the opening width of the oil fence is not proportional to the length of the towing rope, it may be reasonable to maintain the towing rope at approximately 100 m. Furthermore, a reasonable towing speed, when operating the oil fence for one vessel equipped with spreading devices, was within 0.4 m/sec.

• Journal of Navigation and Port Research
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• v.38 no.5
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• pp.463-470
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• 2014

In this paper, calculation of towing force required to tow the ship and experiments to verify its appropriacy are discussed. Friction, wind and wave-making resistance of vessel are considered to calculate towing force of specified vessel. Propeller resistance is also reflected and it is assumed that the propellers are locked. Node analysis to estimate additional resistance on towline is applied. Total towing force could be obtained by adding the ship's resistance and towline resistance. Experiments with training ship SAE YU DAL was executed to check the effectiveness of calculation methods and some comparison between experiments and calculation results was also done. From the comparative analysis, we confirmed that towing speed is primary terms in the calculation of towing force and propeller resistance is a major elements of ship's resistance with the increasing of towing speed. We can see that additional resistance induced by yawing of ship during towing have to be considered for total tow resistance.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.46 no.4
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• pp.476-486
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• 2010

Fishing efficiency of a trawl vessel can be enhanced by increasing the swept area per unit time, which can be attained either by increasing the mouth size of the net, or by increasing the towing speed. To improve fishing and fuel efficiency of trawl vessels targeting fishes of greater mobility, in which the towing speed is more critical in determining fishing efficiency, we conducted a series of model tests to evaluate the performance of the newly-designed nozzle propeller before installing it in a trawl vessel to verify its towing speed and fuel efficiency in the sea. By conducting further model tests in the experimental basin, we redesigned the propeller of stern trawler to improve the resistance and propulsion performance. Through actual fishing operations, we evaluated the improvement in fuel and fishing efficiency by installing the new nozzle propeller. The trawling speed increased by 0.6kts at the same engine power (RPM), while the engine margin increased by more than 20%. The increased towing speed by installing the redesigned propeller is expected to enhance fishing performance through increasing the number of hauling- and casting operations per unit times, while shortening the towing duration. Analysis of the Catch-Per-Unit-Effort (CPUE) data indicated that the mean CPUE of trawl fishery increased from 3.04kg/m in year 2007 to 6.15kg/m in year 2008, confirming enhanced fishing efficiency by adopting the redesigned propeller.