• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1810-1815
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• 2003

Sliding mode control with nonlinear interpolation in the boundary layer is proposed. A modified sigmoid function is used for nonlinear interpolation in the boundary layer and its parameter is tuned by a fuzzy logic controller. The fuzzy logic controller that takes the distance between the system state and the sliding surface as its input guides the choice of parameter of the modified sigmoid function and the parameter is on-line tuned. Owing to the decreased thickness, the proposed method has better tracking performance than the conventional linear interpolation method. To demonstrate its performance, the proposed control algorithm is applied to a simple nonlinear system model.

• 제어로봇시스템학회논문지
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• 제7권12호
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• pp.1031-1035
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• 2001

In this paper, a robust recursive control approach for nonlinear system, which is based on Lyapunov stability, is proposed. The proposed method can apply to extended systems including cascaded systems and the stability is guaranteed in the sense of Lyapunov. The recursive design procedure so called “robust recursive control approach” is used to find a stabilizing robust controller and simultaneously estimate the uncertainty parameters. First, a nonlinear model with uncertainties whose bounds are unknown is derived. Then, unknown bounds of uncertainties are estimated. By using these estimates, the stabilizing robust controller is updated at each step. This approach is applied to the pitch autopilot design of a nonlinear missile system and simulation results indicate good performance.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.100-103
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• 2008

Recently Development of construction system that subjective operators share and control information efficiently based on the three-dimensional space and design information throughout life cycle of construction project is progressing dynamically. In case of civil structures which are infrastructure, Demand for structure of complex system which has multi-functions such as super and smart bridges and express rails is increasing and system development which computerizes and integrates process of structure design is in need. For that, research about link way between three dimensional modeling data and structure analysis programs should be preceded. In this research, therefore, research about interface design between three dimensional virtual modeling data to automate efficient civil-structure-design and nonlinear finite element analysis program which is made up of reinforced concrete material model that express material's character clearly.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.90-95
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• 2004

During the past 50 years methods for predicting wave overtopping of coastal structures have coastal structures have continuously been developed Wave overtopping is one of the most important processes for the design of seawalls. The term 'wave overtopping' is used here to refer to the processes where waves hit a sloping structure run up the slope and, if the crest level of the slope is lower than the highest run up level, overtop the structure. Wave overtopping is dependent on the processes associated with breaking wave. The Numerical model is based on Navier-Stokes equation and Marker-Density Function of method for nonlinear free-surface flow by Miyata & Park(1995). The influence of how the slopes of seawalls, wave type and crest freeboard affect overtopping discharges has been investigated. The research of study using the new development nonlinear free-surface flow numerical model SOLA-VOF are presented.

• 한국농공학회지
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• 제38권3호
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• pp.112-126
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• 1996

This study was conducted to develop an optimal runoff bydrograph model by comparison of the peak discharge and time to peak between observed and simulated flows derived by four different models, that is, linear time-invariant, linear time-variant, nonlinear time-invariant and nonlinear time-variant models under the conditions of heavy rainfalls with regionally uniform rainfall intensity in short durations at nine small watersheds. The results obtained through this study can be summarized as follows. 1. Parameters for four models including linear time-invariant, linear time-variant, nonlinear time-invariant and nonlinear time-variant models were calibrated using a trial and error method with rainfall and runoff data for the applied watersheds. Regression analysis among parameters, rainfall and watershed characteristics were established for both linear time-invariant and nonlinear time-invariant models. 2. Correlation coefficients of the simulated peak discharge of calibrated runoff hydrographs by using four models were shown to be a high significant to the peak of observed runoff graphs. Especially, it can be concluded that the simulated peak discharge of a linear time-variant model is approaching more closely to the observed runoff hydrograph in comparison with those of three models in the applied watersheds. 3. Correlation coefficients of the simulated time to peak of calibrated runoff hydrographs by using a linear time-variant model were shown to be a high significant to the time to peak of observed runoff hydrographs than those of the other models. 4. The peak discharge and time to peak of simulated runoff hydrogaphs by using linear time-variant model are verified to be approached more closely to those of observed runoff hydrographs than those of three models in the applied watersheds. 5. It can be generally concluded that the shape of simulated hydrograph based on a linear time-variant model is getting closer to the observed runoff hydrograph than those of three models in the applied watersheds. 6. Simulated hydrographs using the nonlinear time-variant model which is based on more closely to the theoritical background of the natural runoff process are not closer to the observed runoff hydrographs in comparison with those of three models in the applied watersheds. Consequently, it is to be desired that futher study for the nonlinear time-variant model should be continued with verification using rainfall-runoff data of the other watersheds in addition to the review of analyical techniques.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.133-140
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• 2006

When concrete is confined triaxially, its strength and toughness are enhanced. Hoop reinforcements or transverse reinforcements laterally confine concrete in the case of a RC member and an outer tube confines concrete in a CFT(Concrete Filled Tube) member. But biaxially confined concrete. such as concrete in a hollow R.C member, does not have much enhanced strength and toughness. In this study, a new-type member. which is a hollow CFT member named as an ICH(Internally Confined Hollow) CFT member, was developed to overcome the low ductility of the hollow member and the high cost of the CFT member. A material nonlinear model for the concrete in an CFT member or an ICH CFT member was developed and coded as a computer program based on Mander's concrete model. Analysis results were verified with experimental results and the developed analysis model showed reasonable and accurate results.

• 대한기계학회논문집A
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• 제41권7호
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• pp.591-597
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• 2017

이 논문은 횡방향 안정성 및 조향성능 개선을 위한 차량 통합운동제어시스템(IDCB)의 개발에 관한 것이다. IDCB의 개발을 위하여 8자유도의 차량 모델 및 비선형 관측기를 설계하였다. 퍼지 로직 제어 방법 및 슬라이딩 모드 제어 방법을 이용하여 전륜 및 후륜의 제동압력을 독립적으로 제어하여 차량의 요 속도 및 횡방향 미끄러짐 각이 목표값을 추종하도록 하였다. 결과를 살펴보면 비선형 관측기는 만족할 만한 수준의 관측 결과를 보여주었다. 개발된 IDBC는 다양한 노면 조건 및 운전 조건에서 요속도 및 횡방향 미끄러짐 각이 목표값을 잘 추종하도록 하여 차량의 횡방향 안정성 및 조향성을 개선시키는 것을 확인할 수 있다.

• 한국자동차공학회논문집
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• 제15권1호
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• pp.56-63
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• 2007

In case of bus rollover, the body structure of the bus should be designed to ensure the survival space for passengers. So, this study focuses on evaluating rollover strength through a computer simulation using the commercial code, LS-DYNA3D at the initial stage of vehicle development. For this study, section structure was modeled using a simple beam element, and impact boundary conditions required by ECE(Economic Commission for Europe) regulation No.66 were applied. In order to confirm the validity of the beam element bus model, the results compared with the test results and shell element bus model. The analysis errors from beam element bus model are due to the difference in strain energy of joint area between beam and shell model. In this study, a method for the joint modeling was suggested by using nonlinear springs to which the collapse mechanisms were applied.

• Computers and Concrete
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• 제4권5호
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• pp.363-376
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• 2007

The paper presents the development of an adaptable strut-and-tie model that can be applied to the design or analysis of four-pile caps that support axial compression and biaxial flexure from a supported rectangular column. Due to an absence of relevant test data, the model is validated using nonlinear finite element analyses (NLFEA). The results indicate that the use of the proposed model would lead to safe and economical designs. The proposed model can be easily extended to any number of piles, providing a rational procedure for the design of wide range of pile caps.

• 한국산학기술학회논문지
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• 제17권2호
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• pp.620-626
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• 2016

구조물의 비선형 지진응답을 평가하는 것은 내진공학에 있어서 중요한 요소로 인식되고 있다. 비선형 정적해석은 이를 위한 대표적인 방법론의 하나이며, 특정 해석단계에서의 구조물 강성추정을 위한 다양한 수치해석적 방법론들이 제시, 적용되고 있다. 하지만, 이러한 방법론들은 상당한 해석시간을 요하거나 부정확한 간편법에 그치고 있어 실무적용에 많은 어려움이 존재한다. 이러한 이유로 본 연구에서는 비선형 정적해석 시 정확하고 효과적인 구조물 강성추정 방법론을 제시하고자 한다. 이를 위하여, 기존의 단계해석법에 대한 이론적 연구를 수행하였으며, 이를 바탕으로 이선형 재료모델 특성을 가진 구조물의 강성구성 알고리즘을 제시하였다. 최종적으로, 제시된 알고리즘을 적용한 컴퓨터 프로그램 sNs를 개발하였다.