• Coupled systems mechanics
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• 제4권1호
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• pp.67-98
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• 2015

Numerical prediction of dynamic behavior of fully coupled saturated porous media is of great importance in many engineering problems. Specifically, static and dynamic response of soils - porous media with pores filled with fluid, such as air, water, etc. - can only be modeled properly using fully coupled approaches. Modeling and simulation of static and dynamic behavior of soils require significant Verification and Validation (V&V) procedures in order to build credibility and increase confidence in numerical results. By definition, Verification is essentially a mathematics issue and it provides evidence that the model is solved correctly, while Validation, being a physics issue, provides evidence that the right model is solved. This paper focuses on Verification procedure for fully coupled modeling and simulation of porous media. Therefore, a complete Solution Verification suite has been developed consisting of analytical solutions for both static and dynamic problems of porous media, in time domain. Verification for fully coupled modeling and simulation of porous media has been performed through comparison of the numerical solutions with the analytical ones. Modeling and simulation is based on the so called, u-p-U formulation. Of particular interest are numerical dispersion effects which determine the level of numerical accuracy. These effects are investigated in detail, in an effort to suggest a compromise between numerical error and computational cost.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.1441-1446
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• 2009

Numerical analysis is a powerful method in evaluating the soil-pile-structure interaction under the dynamic loading, and this approach has been applied to the practical area due to the development of computer technology. Finite Difference Method, one of the most popular numerical methods, is sensitive to the shape and the number of mesh. However, the trial and error approach is conducted to obtain the accurate results and the reasonable simulation time because of the lack of researches about mesh size and the number. In this study, FLAC 3D v3.1 program(FDM) is used to simulate the dynamic pile model tests, and the numerical results are compared with the 1G shaking table tests results. With the different size and shape of mesh, the responses of pile behavior and the simulation time are estimated, and the optimum mesh sizes in dynamic analysis of single pile is studied.

• 한국항해항만학회지
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• 제28권3호
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• pp.161-167
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• 2004

지금까지(1988∼2000년) 국내 해양안전심판원에서 재결한 선박충돌사고의 원인분류 통계데이터를 살펴보면 전체 2,290건의 인적과실(Human Error) 중에서 상대선박에 대한 경계의무소홀이 929건으로 약 40.6％나 되는 가장 많은 비중을 차지하고 있는 것으로 파악되고 있다. 선박충돌사고는 좌초사고와 더불어 인적과실로 기인한 수많은 인명피해와 재산피해 및 해양환경오염을 유발하는 심각한 해양사고로서 이에 대한 사고원인을 철저히 분석하고 그 예방대책 마련이 무엇보다 중요한 과제가 되고 있다. 따라서, 본 연구에서는 선박충돌사고의 인적과실을 분석하기 위한 목적으로 목포해양안전심판원에서 재결한 선박충돌사고(1990∼2002, 65건)에 대하여 상대선 경계의무소홀이나 동정감시 불충분으로 기인하여 발생한 충돌사고를 조사항목별로 분석하고, GEMS 동적모델을 이용하여 선박충돌사고의 인적과실 유형을 체계적으로 분류하였다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 춘계학술대회 논문집
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• pp.278-286
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• 2001

The purpose of this paper is to suggest an analytical technique for time history analysis of R/C frame structure using high-strength concrete under seismic loading. Current researches in hysteretic model of structral elements using high-strength concrete are not enough. It is the cause of error that apply hysteretic model of element using normal-strength concrete to the inelastic analysis of high-strength concrete R/C frame structures. In this paper time history analysis using IDARC and DRAIN programs was performed for a 2-bay, 20-story R/C frame structures. Particularly nonlinear dynamic analysis was performed by IDARC program that was applied hysteretic model of structural element using high-strength concrete. centro earthquake 1940 NS waves was used in the analysis and its peak ground accelerations are changed to be 0.12g, 0.25g

• 한국공작기계학회논문집
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• 제15권2호
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• pp.107-113
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• 2006

This paper presents an efficient dynamic modeling method for multi-stepped rotor system using effective spring elements to take into account the structural weakening effect due to the steps. This paper demonstrates that the Timoshenko shaft model give rise to a significant error in the case of multi-stepped rotors. An effective bending spring model is introduced to represent the structural weakening effect in the presence of steps. The proposed modeling method is validated through a series of simulations and experiments. Finally, a spindle is dealt with as an analysis example.

• 한국정보통신학회논문지
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• 제25권12호
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• pp.1826-1834
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• 2021

본 논문에서는 지상의 광학 관측 시스템에서 미지 우주물체를 짧은 주기로 촬영할 때의 연속 추적 가능성을 확인해 본다. 저궤도영역으로 한정된 대상 표적에 대해 모의 관측 데이터를 생성하였고, 표적특성을 고려하여 예측 오차의 성능지수를 설정하였다. 칼만 필터를 이용하여 표적의 다음 위치를 예측하였고, 등속도/등가속도 표적 기동 모델이 미지 우주물체의 방위각/고도각 두 축에 적용되었다. 몬테카를로 시뮬레이션을 수행한 결과, 최대 비선형구간의 최대 오차 비율이 2% 미만으로 나타나 연속적인 추적을 보장할 수 있다고 판단할 수 있었다. 등가속도 모델이 케이스별 예측 오차값의 변화가 적어서, 미지 우주물체의 추적에 더 적합하였다. 이러한 분석은 광학 관측을 이용한 미지 우주물체 궤도 결정의 기초를 제공할 수 있다.

• 한국통신학회논문지
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• 제18권9호
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• pp.1376-1385
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• 1993

본 연구에서는 고속운전 및 빈번한 부하의 변동에 대해서도 효과적인 과도응답 및 정상상태 응답특성을 갖도록 조작키(actuator)의 동특성방정식을 유도하여 매니퓰레이터의 동특성방정식과 결합시켜 2차 미분방정식으로 표현되는 새로운 매니퓰레이터의 모델 시스템 알고리즘을 제안하였다. 또한 비선형 궤환과 선형화 기법을 적용하여 변수들이 상호간에 심하게 결합되어 있는 시변 비선형 등특성모델을 감결합된 선형모델로 변환한다. 이럴 경구 모델의 제어기 구성시 시스템의 안정성을 얻기 위하여 극 재배치 법을 적용하였으며, 또한 경로오차를 최소화 시켜주기 위하여 오차방정식에 대한 최적제어를 적용하였다. 제안한 알고리즘을 조작키가 포함된 3관절 로보트 메니퓰레이터에 적용하여 컴퓨터 시뮬레이션한 결과 만족할만한 결과를 얻었다.

• International Journal of Control, Automation, and Systems
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• 제5권3호
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• pp.283-294
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• 2007

In this paper, a nonlinear controller based on adaptive sliding-mode method which has a sliding surface vector including new boundizing function is proposed and applied to a two-wheeled welding mobile robot (WMR). This controller makes the welding point of WMR achieve tracking a reference point which is moving on a smooth curved welding path with a desired constant velocity. The mobile robot is considered in view of a kinematic model and a dynamic model in Cartesian coordinates. The proposed controller can overcome uncertainties and external disturbances by adaptive sliding-mode technique. To design the controller, the tracking error vector is defined, and then the sliding surface vector including new boundizing function and the adaptation laws are chosen to guarantee that the error vector converges to zero asymptotically. The stability of the dynamic system is shown through the Lyapunov method. In addition, a simple way of measuring the errors by potentiometers is introduced. The simulations and experimental results are shown to prove the effectiveness of the proposed controller.

• 동아시아경상학회지
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• 제8권1호
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• pp.57-69
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• 2020

Purpose - This study examines what are the asset market fluctuations in Europe and how each economic variable affects major variables, and explore the dynamics of housing and stock market through Greece. The variables under consideration are balance on current account (BCA), index of stock (STOCK), gross domestic product (GDP), housing price indices (HOUSING), M3, real rate of interest (IR_REAL) and household credits (LOAN). We investigate the functional and causal relationships between housing and stock market. Research design, data, and methodology - Vector error correction model (VECM) is used to figure out the dynamic relationships among variables. This study also contains the augmented Dickey-Fuller unit root, cointegration, Granger causality test, and impulse response function and variance decomposition analysis by EViews 11.0. Results - The statistical tests show that all variables under consideration have one unit root and there is a longterm equilibrium relationship among variables for Greece. GDP, IR_REAL, M3, STOCK and LOAN can be considered as causal factors to affect real estate market, while GDP, LOAN, M3, BCA and HOUSING can bring direct effects to stock market in Greece. Conclusions - It can be judged that the policy that affects the lending policy of financial institutions may be more effective than the indirect variable such as monetary interest rate.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1292-1295
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• 1996

This paper proposes an adaptive control technique for the autopilot design of STT missile. Dynamics of the missile is highly nonlinear and the equilibrium point is vulnerable to change due to fast maneuvering. Therefore nonlinear control techniques are desirable for the autopilot design of the missile. The nonlinear controller requires the exact model to obtain satisfactory performance. Generally a look-up table is used for the dynamic coefficients of a missile, so there must be coefficients error during actual flight, and the performance of the nonlinear controller using these data can be degraded. The proposed adaptive control technique compensates the nonlinear controller with modeling error resulting from the error of aerodynamic data and disturbance. To investigate the usefulness, the proposed method is applied to autopilot design of STT missile through simulations.