• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.2
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• pp.329-339
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• 2002

In ship operation the consequency of roll motions can seriously degrade the performance of mechanical and personnel effectiveness. So many studies for the roll stabilization control system design have been performed and very good results have been achieved. In many studies, the stabilizing fins are used. Recently rudders, which have been extensively modified, have been used to exclusively to stabilize the roll. This paper examines the two-degree-of-freedom servosystem design technique to synthesize the yaw control system which achieves the course keeping object of the ship and the H$_{\infty}$ control approach to suppress the roll motion, respectively.

• Journal of the Society of Naval Architects of Korea
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• v.61 no.5
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• pp.297-311
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• 2024

In this study, a combined seakeeping performance evaluation method has been developed for the design purpose of the light aircraft carrier CVX of Korean Navy. A frequency domain analysis method was developed for evaluation of safe operating envelope up to sea state 6, while a time domain analysis method was developed for survival condition of sea state 7 and higher. The frequency-domain solver AdFLOW-Navy was developed by adding empirical formula of roll damping and fin-stabilizer to the existing AdFLOW by KRISO, which was based on the three-dimensional higher order boundary element method (HOBEM). For the estimation of the roll damping coefficient, a two-dimensional cross-section was automatically extracted from the three-dimensional panel, and the roll damping coefficient was analyzed for the two-dimensional cross-section. As for the time domain analysis method, KIMAPS-Navy was developed by improving and expanding the KIMAPS series developed by KRISO which is based on the impulse response function by utilizing the hydrodynamic coefficients obtained from the AdFLOW-Navy. In addition, a weakly nonlinear analysis approach was applied to analyze highly nonlinear motion under heavy sea states. Finally numeraical analysis results were compared with model tests, which showed practical usefulness of the present combined seakeeping analysis approach.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.11a
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• pp.33-39
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• 2004

A ship runs with various modes of motion due to waves. Among the modes, roll mainly influences on the safety of cargos and crew's fatigue. Therefore a ship equipped with anti-rolling devices are on an increasing trend. In this research, we developed a free running model ship to evaluate the performances of fin stabilizer and moving weight stabilizer. Also those performance tests were carried out through the proposed test procedure.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.8
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• pp.975-983
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• 2011

A microfin on a heated surface and its effects of the heat transfer has been investigated. The thickness of the fin is about 8 micrometer to allow the flexible up-down motion of the fin. Two-way complete FSI (Fluid-Structure Interaction) method has been applied for the analysis. Firstly, the deformation of a microfin due to the pulsating flow is evaluated using structure analysis. The flow and temperature patterns are predicted by CFD (Computational Fluid Dynamics) method. At each time step, using the pressure force and temperature distribution from CFD, the deformation of the wing is evaluated by FEM. Also in order to estimate the resonance probability, the natural frequency of the wing structure is calculated by modal analysis. The proposed numerical procedure was validated through experiment using a single fin. Through this work, we show that the increase of 40% in heat transfer capacity using the microfin has been compared with that of flat plate case.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.6
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• pp.644-652
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• 2013

This paper describes the development and field experiments of Manta-type Unmanned Underwater Vehicle (UUV). Various simulations for Manta UUV are performed by using the nonlinear 6-DOF motion of equations. Through this simulation we verified the motion performances of Manta UUV. To acquire the blueprint of Manta UUV, it was designed with the simulation results. The Manta UUV uses a Doppler Velocity Log (DVL), gyrocompass, GPS, pressure sensor and other minor sensors, applied to measure the motion, position and path of Manta UUV. For its propulsion and changing a direction in the underwater, one vertical fin and four horizontal fins are installed at the hull of UUV. The Manta UUV system was verified with motion and autonomous navigation test at field.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.416-423
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• 2004

This paper presents the thermal characteristic analysis of a high-speed horizontal machining center with spindle speed of 50,000rpm and feedrate of 120m/fin. The spindle system is designed based on the built-in motor, angular contact ceramic ball bearings, oil-air lubrication and oil-jacket cooling method. The X-axis and Y-axis feeding systems are composed of the linear motors and linear motion guides, and the Z-axis feeding system is composed of the servo-motor, ball screw and linear motion guides. The thermal characteristics such as the temperature distribution, temperature rise, thermal deformation and step response, are estimated based on the finite element model of machining center and the heat generation rates of heat sources related to the machine operation conditions. Especially, the thermal time constant assessed from the step response function is introduced as an index of thermal response characteristics.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.3
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• pp.361-368
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• 2012

This paper presents an approach on the design of a nonlinear controller to track a reference velocity for an air-breathing supersonic vehicle. The nonlinear control scheme involves an adaptation of propulsive and aerodynamic characteristics in the equations of motion. In this paper, the coefficients of given thrust and drag functions are estimated and they are used to approximate the equations of motion under varying flight conditions. The form of the function of propulsive thrust is extracted from a thrust database which is given by preliminary engine input/output performance analysis. The aerodynamic drag is approximated as a function of angle of attack and fin deflection. The nonlinear controller, designed by using the approximated nonlinear control model equations, provides engine fuel supply command to follow the desired velocity varying with time. On the other hand, the stabilization of altitude, separated from the velocity control scheme, is done by a classical altitude hold autopilot design. Finally, several simulations are performed in order to demonstrate the relevance of the controller design regarding the vehicle.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2016.05a
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• pp.106-107
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• 2016

Rolling motion of floating body might upset the body, make crews and passengers exhausted and/or apply forces to the structure to cause damage. Therefore for almost ships bilge keels are equipped, in special case fin stabilizer or gyroscope may be installed. This paper suggests the Anti-rolling pendulum to reduce roll motion to act the similar role with anti-rolling tank. The device suggested has more effective than the anti-rolling tank with 1/6 volume of the tank.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.6
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• pp.796-807
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• 2009

The swimming abilities of aquatic-animals are of vital importance to their ecology. The relationship between outer shapes and the swimming ability has been focused just a few centuries ago by engineering community. Present paper surveys the recent studies of the aquatic-animals' swimming performance in the morphological point of view. Also an experimental study is performed in order to investigate the effect of the tail fin's shape on the propulsive performance. The result showed that the morphological study provided valuable data for exploring the secrets of the aquatic-animals' swimming performance.

• Bulletin of the Society of Naval Architects of Korea
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• v.24 no.4
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• pp.71-83
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• 1987

There is at present a growing interest in the use of SWATH(Small Waterplane Area Twin Hull )ship for a variety of purposes due to their good seakeeping characteristics, small speed reduction in wave, and large deck area. Highly sophisticated design technology is requested to develop the SWATH ship. This paper describes the design technology for high speed coastal passenger SWATH ship which includes feasibility study, general arrangement and hull form design, resistance and propulsion test, motion test in regular waves, control fin design, and structural design.