• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1654-1659
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• 2003

This paper introduces a fast Fourier transform (FFT)-based spectral analysis method for the transient responses as well as the steady-state responses of linear discrete systems. The force vibration of a viscously damped three-DOF system is considered as the illustrative numerical example. The proposed spectral analysis method is evaluated by comparing with the exact analytical solutions as well as with the numerical solutions obtained by the Runge-Kutta method.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.1
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• pp.33-40
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• 2014

Reliability analysis of jacket type offshore wind turbine (OWT) support structure under extreme ocean environmental loads was performed. Limit state function (LSF) of OWF support structure is defined by using structural dynamic response at mud-line. Then, the dynamic response is expressed as the static response multiplied by dynamic response factor (DRF). Probabilistic distribution of DRF is found from response time history under design significant wave load. Band limited beta distribution is used for internal friction angle of ground soil. Wind load is obtained in the form of thrust force from commercial code called GH_Bladed and then, applied to tower hub as random load. In a numerical example, the response surface method (RSM) is used to express LSF of jacket type support structure for 5MW OWF. Reliability index is found using first order reliability method (FORM).

• Structural Engineering and Mechanics
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• v.43 no.5
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• pp.679-690
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• 2012

A new concept sea-floating port called mobile harbor has been introduced, in order to resolve the limitation of current above-ground port facilities against the continuous growth of worldwide marine transportation. One of important subjects in the design of a mobile harbor is to secure the dynamic stability against wave-induced excitation, because a relatively large-scale heavy crane system installed at the top of mobile harbor should load/unload containers at sea under the sea state up to level 3. In this context, this paper addresses a two-step sequential analytical-numerical method for analyzing the structural dynamic response of the mobile harbor crane system to the wave-induced rolling excitation. The rigid ship motion of mobile harbor by wave is analytically solved, and the flexible dynamic response of the crane system by the rigid ship motion is analyzed by the finite element method. The hydrodynamic effect between sea water and mobile harbor is reflected by means of the added moment of inertia.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.3
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• pp.386-396
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• 1996

The dynamic characteristics of a condenser are numerically studied for the control of air-conditioning systems. The important factors, such as the refrigerant flow rate and refrigerant temperature, air velocity and air temperature at the condenser inlet, are incorporated into the analysis. This study was focused on the analysis of dynamic responses by transfer function method in the condenser. Block diagrams were made through analytic transfer function, and dynamic responses are evaluated on Bode diagrams in the frequency response. These results may be used for determining an optimum design parameters in an actual component and total systems. Also, the mathematical models, frequency response and steady state response may be used to increase understanding, to obtain useful information for its commercialization, to evaluate the hardware and the optimum design parameters, the design control system and to determine the best controller setting for the refrigeration and air conditioning systems.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.5
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• pp.493-499
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• 2010

In the sea-floating logistics port called mobile harbor a crane system with the different structure from the conventional above-ground container crane is installed. And, the dynamic stability of whole mobile harbor by the wave excitation is definitely affected by the crane positioned at the top. This paper is concerned with the dynamic rolling analysis of the mobile harbor subject to sea state 3 wave excitation, for which two-step analysis procedure composed of theoretical and numerical approaches is employed. First, the rigid rolling of mobile harbor is obtained according to the linear wave theory. And then, the dynamic rolling response of the flexible crane system caused by the rolling excitation of mobile harbor is analyzed by finite element analysis. The coupled interaction effect between the sea wave and the mobile harbor is taken into consideration by the added mass technique.

• Structural Engineering and Mechanics
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• v.61 no.3
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• pp.419-426
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• 2017

Recently, the transportation of dangerous explosive goods is increasing, which makes vehicle blasting accidents a potential threat for the safety of bridge structures. In addition, blasting accidents happen more easily when earthquake occurs. Excessive dynamic response of bridges under extreme loads may cause local member damage, serviceability issues, or even failure of the whole structure. In this paper, a new explosion-proof and aseismic system is proposed including cable support damping bearing and steel-fiber reinforced concrete based on the existing researches. Then, considering one 40m-span simply supported concrete T-bridge as the prototype, through scale model test and numerical simulation, the dynamic response of the bridge under three conditions including only earthquake, only blast load and the combination of the two extreme loads is obtained and the applicability of this explosion-proof and aseismic system is explored. Results of the study show that this explosion-proof and aseismic system has good adaptability to seism and blast load at different level. The reducing vibration isolation efficiency of cable support damping bearing is pretty high. Increasing cables does not affect the good shock-absorption performance of the original bearing. The new system is good at shock absorption and displacement limitation. It works well in reducing the vertical dynamic response of beam body, and could limit the relative displacement between main girder and capping beam in different orientation so as to solve the problem of beam falling. The study also shows that the enhancement of steel fibers in concrete could significantly improve the blast resistance of main beam. Results of this paper can be used in the process of antiknock design, and provide strong theoretical basis for comprehensive protection and support of girder bridges.

• 제어로봇시스템학회:학술대회논문집
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• 1987.10b
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• pp.566-569
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• 1987

The primary difficulties encountered in the use of step motors are underdamped response when stopping at a specified position and dynamic instability during high-speed slewing. This paper proposes a speed and position detection scheme using the back EMF generated by the rotating permanent magnet field of a two-phase 1.8.deg. hybrid step motor, and presents its application to the state-variable feedback control of the hybrid step motor. All simulation results in a single step response show that the hybrid step motor performances such as peak overshoot and settling time are greatly improved.

• Transactions on Electrical and Electronic Materials
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• v.18 no.5
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• pp.265-272
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• 2017

This paper presents the dynamic modeling, analysis, and control of an AC/DC/AC-assisted, self-excited induction generator connected to the grid. The dynamic model includes wind turbine models with pitch control, gear boxes, self-excited induction generators, excitation capacitance, inductive load models, controlled six-pulse rectifiers, and novel state-space models of a grid-connected inverter. The system has been simulated to verify its capabilities of buildup voltage, stator flux response, stator phase current, electromagnetic torque, and magnetizing inductance variation during both the dynamic and steady states with a variable-speed prime mover. The complete setup of the above dynamic models was simulated using MATLAB/SIMULINK.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.1
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• pp.51-56
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• 2000

This paper presents the characteristics of the dynamic response and calibration technique on a linear variable differential transformer(LVDT). The linear error of the LVDT was proven $\pm$1% in the static calibration and $\pm$0.5% in the dynamic calibration. In this paper, the linearity error generated in the static and dynamic state of the core movement can be eliminated using the correction algorithem of the static and dynamic state derived from the least square linear approximation for the nonlinearity of the curves of direct data fitting and Lagrange polynomials. With the static and dynamic calibration method, the calibration accuracy of the LVDT can be reduced to within $\pm{0.5%.}$.

• Proceedings of the KIEE Conference
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• 1979.08a
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• pp.119-120
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• 1979

A linear state equation of the first order differential form relating the load-frequency dynamic characteristics of interconnected power systems was derived for use in computer simulation. A now solution of the algebraic matrix riccati equation for application in quadratic optimal controllor and least-square state estimator dermination was developed. The program for a dynamic state equation for two interconnected control areas was developed. The optimized load-frequency deviation was analysed and a numerical analysis was tried based on the computer simulation. It was shown that the dynamic response of th loed-frequency could be optimized with weighting factors IR and Q. The result was that the load-frequency and the tie-line deviation were visibly reduced.