• Journal of the Society of Naval Architects of Korea
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• v.42 no.6 s.144
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• pp.666-672
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• 2005

Reduction of a ship's rolling is the most important performance requirement for improving the safety of the crew on board and preventing damage to cargos as well as improving the comfort of the ride. A mass driving anti-rolling system (MO-ARS) might be one candidate of several systems against the ship's rolling. In this paper, three types of MD-ARS, two passive and one active devices, are developed for small ships. After they are installed on the cabin of the small leisure boat, respectively, a series of performance test is conducted before and after operating them. Through the test, it is confirmed that the roll responses of the ship are pretty well reduced by the MO-ARS.

• Journal of Ocean Engineering and Technology
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• v.6 no.2
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• pp.41-45
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• 1992

In this paper an application technique of moment equation method to solution of nonlinear rolling equation of motion of ships is investigated. The exciting moment in the equation of rolling motion of ships is described as non-white noise. This non-white exciting moment is generated through use of a shaping filter. These coupled equations are used to generate moment equations. The nonstationary responses of the nonlinear system are obtained. The results are compared with those of a linear system.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.1 s.145
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• pp.22-31
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• 2006

Recent studies have shown that the short time solution of the equation of motion for the rolling of ships is important in deciding the possibility of capsize of ships due to the excessive heel. Since most of known solutions for nonlinear equations of motion are long time or steady periodic solutions, here a simple way is described to get the short time solutions of the Duffing equation, which was chosen for deriving a criterion for the capsize of the ship. With the small external rolling moment, we first assume the state of the small damping and near resonance. Then, for cases when the frequency of the external moment is higher than the resonant one, an inequality was derived as a criterion for the capsize. This gives the range of the initial condition and the magnitude of the external moment which should be avoided for a ship to be safe from capsize. Furthermore, from the linearized equation, it is also shown that a simple and self-explanatory solution can be obtained consistent with that for the case of no damping, which yields the well-known linear growth with time.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2009.10a
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• pp.239-240
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• 2009

Vessels stability problems need to resolve the nonlinear mathematical models of rolling motion. For nonlinear systems subjected to random excitations, there are very few special cases can obtain the exact solutions. In this paper, the specific differential equations of rolling motion for intact ship considering the restoring and damping moment have researched firstly. Then the partial stochastic linearization method is applied to study the response statistics of nonlinear ship rolling motion in beam seas. The ship rolling nonlinear stochastic differential equation is then solved approximately by keeping the equivalent damping coefficient as a parameter and nonlinear response of the ship is determined in the frequency domain by a linear analysis method finally.

• Journal of Navigation and Port Research
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• v.33 no.9
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• pp.629-634
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• 2009

Vessels stability problems need to resolve the nonlinear mathematical models of rolling motion. For nonlinear systems subjected to random excitations, there are very few special cases can obtain the exact solutions. In this paper, the specific differential equations of rolling motion for intact ship considering the restoring and damping moment have researched firstly. Then the partial stochastic linearization method is applied to study the response statistics of nonlinear ship rolling motion in beam seas. The ship rolling nonlinear stochastic differential equation is then solved approximately by keeping the equivalent damping coefficient as a parameter and nonlinear response of the ship is determined in the frequency domain by a linear analysis method finally.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.727-730
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• 2004

Reduction of a ship's rolling is the most important performance requirement for improving the safety of the crew on board and preventing damage to cargos as well as improving the comfort of the ride. A mass driving anti-rolling system (MD-ARS) might be one candidate of several systems against the ship's rolling. In this paper, three types of MD-ARS, two passive and one active devices, are developed for small ships. After they are installed on the cabin of the small leisure boat, respectively, a series of test is conducted before and after operating them. Through the test, it is confirmed that the roll responses of the ship are pretty well reduced by the system.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.4
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• pp.1014-1023
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• 2014

In this paper the real life operation of ULCS (Ultra Large Container Ships) is presented from the point of view of shipmasters. The paper provides interpretation of results of questionnaire filled by masters of large container ships during Tools for Ultra Large Container Ships (TULC) EUI FP7 project. This is done in a way that results of questionnaire are further reviewed and commented by experienced master of ULCS. Following phenomena are subject of questionnaire and further discussed in the paper: parametric rolling, slamming, whipping, springing, green water and rogue waves. Special attention is given to the definition of rough sea states as well as to measures that ship masters take to avoid them as well as to the manoeuvring in heavy seas. The role of the wave forecast and weather routing software is also discussed.

• Journal of Fisheries and Marine Sciences Education
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• v.9 no.2
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• pp.167-178
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• 1997

It has been expected not only for crew but also for passengers to realize a ship whose rolling and other motions are small as much as possible. Restricting our consideration to the roll reduction, the conventional roll stabilization system, fins or anti-rolling tanks hve been utiized as the actuator. Excessive motions would interfere with the recreational activities of passengers on a cruise ship. Often more than half of the load of a containership is stowed above deck where it is subjected to large acclerations due to rolling. In some situations this may cause some internal damage to the contents of the containers; in more severe situations failure of the lashing can occur and containers may be lost over-board. Underdeck cargo in ordinary cargo ships and bulk commodities in colliers, ore ships and grain ships can shift if the motions become too severe. The purpose of this study is to concentrate on the additions. either internal or external to the hull, that reduce or otherwise improve the motion responses of the hull. It is assumed that the additions are such that their benefit to the motions of the ship outweights any impact on the ability of the ship to perform its assigned task. It is particularly challenging to obtain large improvements in the motion characteristics of existing ships that are being rebuilt or modified for some task not anticipated in their original design. Further the authors will statistically analyze the influence of ruder-roll-yaw coupling motion in the case of application of this advanced control method to various kinds of ship.

• Journal of Mechanical Science and Technology
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• v.18 no.8
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• pp.1312-1318
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• 2004

Roll stabilization systems for ships are employed to increase comfort for passengers, maintain full working capabilities for members of the crew and prevent cargo damage. In this paper, we have investigated the usefulness of active stabilizing system to reduce ship rolling under disturbances, using varied reaction of the flaps. In the proposed anti-rolling system for a ship, the flaps as the actuator are installed on the stern to reject rolling motion induced by disturbances such as wave. The action induced by flaps depends on power of disturbances and can take the ship balance. Especially, in this study we define the system parameters under the given system structure and design the controller to evaluate the usefulness of the proposed system.

• Ocean Systems Engineering
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• v.1 no.3
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• pp.249-261
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• 2011

The stochastic nonlinear dynamic behavior and probability density function of ship rolling are studied using the nonlinear dynamical systems approach and probability theory. The probability density function of the rolling response is evaluated through solving the Fokker Planck Equation using the path integral method based on a Gauss-Legendre interpolation scheme. The time-dependent probability of ship rolling restricted to within the safe domain is provided and capsizing is investigated from the probability point of view. The random differential equation of ships' rolling motion is established considering the nonlinear damping, nonlinear restoring moment, white noise and colored noise wave excitation.