• Journal of the Korean Society for Precision Engineering
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• v.28 no.1
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• pp.40-47
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• 2011

Mobile harbor which is a novel concept of ocean transportation to bring the containers from the cargo ship waiting on the ocean away is being focused now. To provide the mobile harbor with the stable loading/unloading condition, it is necessary to develop the oscillation mitigation technologies such as anti-rolling system. Anti-rolling system using AMD(Active Mass Driving) has merits that it can handle the disturbances more actively and mitigate the rolling oscillation faster than other type anti-rolling system. However, rack-and-pinion type AMD has problems such as big friction noise from gears and motor, wear and tear, and continuous maintenance. In this paper, novel anti-rolling system using Maglev type AMD for mobile harbor is suggested in order to resolve the problems caused by the friction. This novel anti-rolling system doesn't make any friction because it supports the moving mass by using magnetic levitation force and moves it by using propulsion force from the linear motor. The demo system of the novel anti-rolling system using maglev type AMD has been developed in order to investigate its feasibility. This paper presents the procedures and results of development of this demo system.

• Journal of the Korean Society for Railway
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• v.18 no.2
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• pp.87-93
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• 2015

The uneven reaction surface profile facing the lift magnets in attractive Maglev vehicles naturally brings about pitch motion of the bogie. In particular, in the placement configuration of the long stator of the linear synchronous motor (LSM) on the track for high-speed propulsion, surface irregularities and the offsets between the stator packs create measurable airgaps, i.e., the clearance between the magnet and the stator, with discontinuously extreme values, resulting in bogie pitch motion. This occurs because the airgap velocities and accelerations derived by the differentiations of the measured air-gaps are used to determine the voltages applied to the magnets. This paper incorporates bogie pitch motion into a control law for each magnet controller to reduce the variations in both the airgap and the pitch angle. The effectiveness of the proposed method is analyzed using a full-scale Maglev vehicle running over a test track.

• Journal of Aerospace System Engineering
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• v.11 no.5
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• pp.42-49
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• 2017

The solid rocket motor(SRM) consists of a motor case, igniter, propellants, nozzle, insulation, controller, and driving device. The liquid rocket propulsion systems(LRPSs) cools the nozzle by the fuel and oxidizer but SRM does not cool the nozzle. The nozzle of SRM is high temperature condition and high velocity condition so occurs the erosion by combustion gas. This erosion occurs the change of nozzle throat and reduces thrust performance of rocket. The material of Rocket nozzle is minimization of erosion and insulation effect and endure the shear force, high temperature and high pressure. The purpose of this study is to investigate the erosion characteristics of solid rocket nozzles by each combustion time. Through the structure inspection of Graphite and C-C composite, identify the characteristics of the microstructure before and after erosion.

• Journal of Navigation and Port Research
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• v.33 no.1
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• pp.35-41
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• 2009

A waypoint tracking algorithm(WTA) is designed for Unmanned Surface Vehicle(USV) in which water-jet system is installed for propulsion To control the heading of USV for waypoint tracking, the steering nozzle of water-jet need, to be controlled. Firstly, target heading is calculated by using the position information of waypoints input from the land control center. Secondly, the command for the steering nozzle of water-jet is calculated in real time by using the heading and the rate-of-turn( ROT) from magnetic compass, In this study, in order to consider the drift angle due to external disturbance such as wind and wave, the course of ground( COG) can be used instead of heading at higher speed than a certain value, To test the performance of newly-designed WTA, the tests were carried out in actual sea area near Gwang-an bridge of Busan. In this paper, the sea trial test results from WTA are analyzed and compared with those from manual control and those from commercial controller.