• Journal of Navigation and Port Research
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• v.27 no.2
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• pp.193-198
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• 2003

The slew motion of a single point moored ship by the external forces is considered to control itself. The maneuvering equations of motion are derived to express the motion of a ship. The wind forces and the wave forces are considered as the external forces of the single point moored ship in the simulation. The wave forces in the time domain analysis are generated from the frequency transfer function calculated by 3-D source distribution method. The wind forces are used the results from OCIMF(1994). To control the slew motion, the bow thruster and the bridle anchoring with 2nd anchor are used in the numerical simulation.

• Journal of Navigation and Port Research
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• v.27 no.1
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• pp.55-61
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• 2003

The maneuvering equations of motion are derived to express the motion of a ship. The wave forces in the time domain analysis are generated from the frequency transfer function calculated by 3-D source distribution method. The linear wave forces whose periods are equal to those of incident waves and the nonlinear wave forces that make long period drift forces are computed for the simulation. The consideration of irregular waves and nonlinear wave force effects on the slew motion are carried on the analyzing the motion of ship in the regular and irregular waves.

• Journal of KSNVE
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• v.5 no.1
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• pp.59-65
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• 1995

In this study, we investigated the operational limit of magnetic bearing-rotor system due to the maximum force limit and slew rjate limit of the electromagnetic actuator as a function of the time dependent control characteristics. The feedback gain of the controller varies the current of the electromagnet coil with the motion of the rotor. The distorsion of magnetic force due to the slew rate limit is not occurred jup to 30, 000 rpm in the magnetic bearing that we have a close relation with the rotational speed and vibration level of the rotor and the proportional gain of the controller. Therefore the maximum force limit determines the maximum allowable orbit radius of the magnetic bearing-rotor system. The maximum allowable vibration levels are exponentially decreased according to the increment of rotational speed and proportional gain of the controller.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.544-549
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• 2001

The effect of power supply voltage on the performance limits in a laboratory Magneto-rheological fluid based device was identified by experiments. It suggests that the frequency range of motion for control be limited by the voltage attenuation due to the coil inductance and the maximum power supply voltage set for practical use of MRF devices. In this work, the magnetic and electrical characteristics of MRF device are investigated and a design procedure is formulated to achieve the desired performance for a given power supply.

• International Journal of Aeronautical and Space Sciences
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• v.2 no.1
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• pp.78-92
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• 2001

In this paper, several dynamic systems are modeled using the time domain finite element method. Galerkins' Weak Principle is used to model the general second-order mechanical system, and is applied to a simple pendulum dynamics. Problems caused by approximating the final momentum are also investigated. Extending the research, some dynamic analysis methods are suggested for the hybrid coordinate systems that have both slew and flexible modes. The proposed methods are based on both Extended Hamilton's Principle and Galerkin's Weak Principle. The matrix wave equation is propagated in space domain, satisfying the geometric/natural boundary conditions. As a result, the flexible motion can be obtained compatible with the applied control input. Numerical example is shown to demonstrate the effectiveness of the proposed modeling methods for the hybrid coordinate systems.

• Journal of Mechanical Science and Technology
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• v.15 no.11
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• pp.1517-1523
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• 2001

The effect of power supply voltage on the performance limits in a laboratory magneto-rheological fluid based device was identified by experiments. It suggests that the frequency range of motion for control is limited by the voltage attenuation due to the coil inductance and the maximum power supply voltage set for practical use of an MRF devices. In this work, the magnetic and electrical characteristics of the MRF device are investigated and a design procedure is formulated to achieve the desired performance for a given power supply.

• Journal of Astronomy and Space Sciences
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• v.20 no.2
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• pp.153-162
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• 2003

Recently, we have reconstructed LX-200 12inch telescope system for tracking and observing man-made space object. Motor, motor driver and motion controller were up-graded for getting faster respond characteristic and active control available. Also, command signal was offered to the PID controller into motor driver as computed real orbiting information of objects using PC, and it's control period of command signal was reduced to the 20ms. As the result, slew speed of the mount system was in proved up to $18^{\circ}/sec$ and respond speed of the system was faster than that of commercial system. Also, flipping state of image observed could be minimized by the up-graded system.