• 한국자동차공학회논문집
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• 제11권4호
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• pp.144-150
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• 2003

Recently, the virtual test techniques using computer simulation play an important part in the vehicle development procedures in order to reduce the development time and cost by replacing the physical prototypes of the vehicle components or systems with the virtual prototypes. In this paper, virtual durability test procedures for the vehicle suspension module have been developed. Virtual durability test consists of dynamic simulation computing load history of suspension components, fatigue analysis computing the life of components. A vehicle suspension module for dynamic simulation are developed and validated by comparison with the measured data obtained from the field vehicle test. And on the basis of the validated vehicle suspension model, fatigue analysis has been performed for the virtual durability design of the suspension components.

• Wind and Structures
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• 제20권2호
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• pp.169-189
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• 2015

To investigate the effects of "sudden change" of wind fluctuations on vehicle running performance, which is caused by the artificial discrete simulation of wind field, a three-dimensional vehicle model is set up with multi-body dynamics theory and the vehicle dynamic responses in crosswind conditions are obtained in time domain. Based on Hilbert Huang Transform, the effects of simulation separations on time-frequency characteristics of wind field are discussed. In addition, the probability density distribution of "sudden change" of wind fluctuations is displayed, addressing the effects of simulation separation, mean wind speed and vehicle speed on the "sudden change" of wind fluctuations. The "sudden change" of vehicle dynamic responses, which is due to the discontinuity of wind fluctuations on moving vehicle, is also analyzed. With Principal Component Analysis, the comprehensive evaluation of vehicle running performance in crosswind conditions at different simulation separations of wind field is investigated. The results demonstrate that the artificial discrete simulation of wind field often causes "sudden change" in the wind fluctuations and the corresponding vehicle dynamic responses are noticeably affected. It provides a theoretical foundation for the choice of a suitable simulation separation of wind field in engineering application.

• 대한토목학회논문집
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• 제10권4호
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• pp.173-184
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• 1990

본 연구에서는 활성슬러지 하수처리장에 유입된 PAHs의 일종인 anthracene을 대상으로 이의 농도분포, 물리적 혹은 생물학적 변환을 예측하기 위한 수학적 모형을 제안하였다. 이 수학적 모형은 유입 anthracene의 volatilization, biodegradation 및 adsorption/desorption과 같은 반응을 고려한 5개의 연립미분방정식으로 구성되어 있으며, 이들에는 7개의 kinetic rate constants와 18개의 input variables를 포함하고 있다. Steady state simulation의 결과 유입된 anthracene은 1차 침전지에서의 슬러지 배출로 인하여 약 33%가 포기조에서 발생한 volatilization에 의하여 약 61%가 제거되어, 총괄적인 anthracene의 제거율은 약 97%정도이었다. Dynamic simulation의 결과로 본 연구대상 system의 경우에 system이 steady state에 도달하는 시간은 약 160시간 정도로 예측되었다. 이와 아울러 본 연구에서 제안된 수학적 모형의 활용 가능성이 각종 simulation의 결과로 비교적 구체적으로 규명되었다.

• 대한기계학회논문집A
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• 제36권9호
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• pp.1003-1008
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• 2012

실시간 차량동역학 해석을 위해서는 효율적인 차량 모델이 필요하게 된다. 효율성을 높이기 위해 집중질량모델로 가정하면 현가장치의 특성을 고려하기 어렵게 되며, 현가장치의 특성을 모두 고려한 다물체동역학 모델에서는 효율성이 떨어진다. 그러므로 본 논문에서는 다물체동역학 모델링을 사용하되 해석의 효율성을 저하시키는 현가장치의 각종 요소들의 효과는 기구정역학 실험으로 추출된 특성그래프로 대체함으로써 효율성도 기하고자 시도하였다. $6{\times}6$ 차량을 차체와 휠로 구성된 차량으로 모델을 정의하였고, 다물체동역학 모델인 ADAMS 결과와 비교하여 실험적 모델의 유용성을 검증하였다. 그리고 검증된 실험적 차량모델을 RT-LAB을 활용한 실시간 시뮬레이션 환경에 삽입하여, 실시간성 시뮬레이션의 가능성을 검증하였다.

• 상하수도학회지
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• 제26권5호
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• pp.609-617
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• 2012

A dynamic water quality model is presented in order to simulate water quality under slowly varying flow conditions over time. To improve numerical accuracy, the proposed model uses a lumped system approach instead of extended period simulation, unlike the other available models. This approach can achieve computational efficiency by assuming liquid and pipe walls to be rigid, unlike the method of characteristics, which has been successfully implemented in rapidly varying flows. The discrete volume method is applied to resolve the advection and reaction terms of the transport equation for water quality constituents in pipes. Numerical applications are implemented to the pipe network examples under steady and unsteady conditions as well as hydraulic and water quality simulations. The numerical results are compared with EPANET2, which is a widely used simulation model for a water distribution system. The model results are in good agreement with EPANET2 for steady-state simulation. However, the hydraulic simulation results under unsteady flows differ from those of EPANET2, which causes a deviation in water quality prediction. The proposed model is expected to be a component of an integrated operation model for a water distribution system if it is combined with a computational model for rapidly varying flows to estimate leakage, pipe roughness, and intensive water quality.

• 한국시뮬레이션학회논문지
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• 제21권1호
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• pp.27-34
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• 2012

본 논문의 목적은 복잡한 군수지원시스템의 모델링과 시뮬레이션을 위한 방법론을 제안하는 것이다. 제안하는 군수지원시스템 시뮬레이션 모델을 구성하는 요소들은 세 가지가 있다 : Logistics force agent(static model), Military supplies transport manager(function model), Military supplies state manager(dynamic model). Logistics force agent는 main function agent와function agent로 구성된다. Function agent가 다른 Logistics force agent에도 적용할 수 있도록 설계되었으며, 이는 에이전트의 높은 조합성과 재사용성을 가진다. Military supplies transport manager는 보급로에 대한 정보를 가지며 military supplies state manager로부터 받은 결정변수를 기반으로 보급로를 결정하고 군수품을 수송하는 역할을 하는 에이전트이다. Military supplies state manager는 군수품 보급을 요청받고 보급량, 우선순위 따위의 결정 변수를 military supplies transport manager에게 알려주는 역할을 한다. 본 논문에서는 군수 시뮬레이션 모델의 설계를 위해 Discrete Event Systems Specification(DEVS) formalism을 이용하였다.

• Journal of Power Electronics
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• 제1권1호
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• pp.48-55
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• 2001

This paper describes a switching-level simulation model and scaled hardware model for SSSC, which is useful for analyzing the dynamic interaction between the SSC and the power transmission system. A detailed simulation model with EMTP was developed to verity the SSSC operation with control system, and its increasing capability of power transmission through the line for a typical one-machine infinite-bus system. The simulation results of the developed model are compared with the experimental results froma scaled model fo 2KVA rating for evaluation the whole system operation.

• 한국전산유체공학회지
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• 제9권1호
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• pp.1-9
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• 2004

Large eddy simulation is used to investigate the compressible flow over a cavity with high aspect ratio. The sub-grid scale stresses are modeled using the dynamic model. The compressible Navier-Stokes equations are solved with the sixth order accurate compact finite difference scheme in the space and the 4th order Runge-Kutta scheme in the time. The buffer Bone techniques are used for non-reflecting boundary conditions. The results show the shear layer oscillation over the cavity. The votical disturbances, the roll-up of vorticity, and impingement and scattering of vorticity at the downstream cavity edge can be seen in the shear layer. Several peaks for the resonant frequencies are found in the spectra of the vertical velocity at the center-line. The most energetic Peak near the downstream edge is different from that at the center part of the cavity The pressure has its minimum value in the vortex core inside the cavity, and becomes very high at the downstream face of the cavity. The variation of the model coefficient predicted by the dynamic model is quite large between 0 and 0.3. The model coefficient increases in the stream-wise evolution of the shear layer and sharply decreases near the wall due to the wall effect.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.265-270
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• 2005

This paper presents a new attitude stabilization and control of an unmanned helicopter based on neural network compensation. A systematic derivation on the dynamics of an unmanned small-scale helicopter is performed. Combined rotor-fuselage-tail dynamics is derived in body-fixed reference frame with its origin at the C.G. of the helicopter. And the resulting nonlinear equation of motion consists of 6-DOF air vehicle dynamics as well as the rotor flapping and engine torque equations. A simulation model was modified using the existing simulator for an unmanned helicopter dynamic model, which reflects the unmanned test helicopter(CNUHELI). The dynamic response of the refined model was compared with the flight test data. It can be shown that a good coincidence was accomplished between the real unmanned helicopter system and the mathematical model. This dynamic model was linearized for classical controller design using small perturbation method. A Neuro-PD control system was designed for both longitudinal and lateral flight modes, and the results were compared with the PD-only control response. Simulation results show that the proposed Neuro-PD control system demonstrates better performance.

• The Journal of Asian Finance, Economics and Business
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• 제8권3호
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• pp.1-10
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• 2021

This study examines the dynamic pattern of the exchange rate volatilities of the ASEAN-5 currencies from January 2006 to August 2020. The exchange rates applied in this study comprise bilateral and effective exchange rates in order to investigate the influence of the US dollar on the stability of the ASEAN-5 currencies. Since a volatility model employed in this study is a natural cubic spline volatility model, the Monte Carlo simulation is consequently conducted to determine an appropriate criterion to select a number of quantile knots for this model. The simulation results reveal that, among four candidate criteria, Generalized Cross-Validation is a suitable criterion for modeling the ASEAN-5 exchange rate volatilities. The estimated volatilities showed the inconstant dynamic patterns reflecting the uncertain exchange rate risk arising in international transactions. The bilateral exchange rate volatilities of the ASEAN-5 currencies to the US dollar are more variable than their corresponding effective exchange rate volatilities, indicating the influence of the US dollar on the stability of the ASEAN-5 currencies. The findings of this study suggest that the natural cubic spline volatility model with the quantile knots selected by Generalized Cross-Validation is practical and can be used to examine the dynamic patterns of the financial volatility.