• Journal of the Society of Disaster Information
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• v.15 no.2
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• pp.186-197
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• 2019

Purpose: This study intends to develop a nonlinear cyclic plasticity damage model in the framework of finite element formulation, which is capable of taking large deformation effects into account, in order to accurately predict the hysteretic behavior of stainless steel structures. Method: The new cyclic constitutive equations that utilize the combined isotropic-kinematic hardening rule for plastic deformation is incorporated into the damage mechanic model in conjunction with the large strain formulation. The damage growth law is based on the experimental observations that the evolution of microvoids yields nonlinear damage accumulation with plastic deformation. The damage model parameters and the procedure for their identification are presented. Results and Conclusion: The proposed nonlinear damage model has been verified by simulating uniaxial strain-controlled monotonic and cyclic loading tests, and successfully applied to a thin-walled stainless steel pipe subjected to constant and alternating strain-controlled cyclic loadings.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.3
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• pp.63-70
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• 2010

We are able to find many materials of pendulum dynamic/analysis using linearized model. Usually, analysis of pendulum is to calculate for velocity, period and angle by linearized model on Newton's law. In this paper, analyzed periodical movement of pendulum using nonlinear load model. That is, analyzed load value according to location of moving pendulum at real time. And for the shake of maneuver for pendulum's location, found load control value and compared result of linearized mode with nonlinear model. The result makes know that it is possibility of nonlinear load control model to apply to various model of movement object including flight object, pendulum and etc.

• Journal of the Korean Institute of Intelligent Systems
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• v.9 no.6
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• pp.605-614
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• 1999

This paper addresses analysis and design of a class of complex single-input single-output fuzzy control systems. In the proposed method, the fuzzy model, which represents the local dynamic behavior of the given nonlinear system, is utilized to construct the controller. The overall controller consists of the local compensators which compensate the local dynamic linear model and the feed-forward controller which is designed via sliding mode control theory. Therefore, the globally stable fuzzy controller is designed without finding a common Lyapunov matrix. and shows improved perfonnance and tracking results by taking the advantages of fuzzy-model-based control theory and sliding mode control theory. Furthennore, stability analysis is conducted not Ibr the fuzzy model but for the real underlying nonlinear system. Two numerical examples are included to show the effcctiveness and feasibility of the proposed fuzzy control method.

• Journal of the Korean Geotechnical Society
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• v.33 no.12
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• pp.45-58
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• 2017

As many seismic codes for various facilities are changed into a performance based design code, demand for a reliable nonlinear response-history analysis (RHA) arises. However, the equivalent linear analysis has been used as a standard approach since 1970 in the field of site response analysis. So, the reliability of nonlinear RHA should be provided to be adopted in replace of equivalent linear analysis. In this paper, the reliability of nonlinear RHA is reviewed for a layered soil layer using Loma Prieta earthquake records in 1989. For this purpose, the appropriate way for selecting nonlinear soil models and the effect of base boundary condition for 3D analysis are evaluated. As a result, there is no significant differences between equivalent linear and nonlinear RHA. In case of 3D analysis, absorbing boundary condition should be applied at base to prevent rocking motion of the whole model.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.9
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• pp.45-52
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• 2006

In this study, a nonlinear control by feedback linearization method, one of nonlinear control schemes based on the nonlinear model, is proposed to suppress the flutter of a supersonic composite panel using piezoelectric materials. Most of the previous panel flutter controllers are the LQR(Linear Quadratic Regulator) which is based on the linear model. A nonlinear feedback linearizing controller proposed in this study considers the nonlinear characteristics of the system model. We use the actuator implemented by piezoceramic PZT. Using the principle of virtual displacements and a finite element discretization with the conforming four-node rectangular element, we first derive the discretized dynamic equations of motion, which are transformed into a nonlinear coupled-modal equations of motion of state space form. The effectiveness of the proposed method is also compared with the LQR based on the linear model through numerical simulations in the time domain using the Newmark method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.639-642
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• 2011

이 연구에서는 완전 조립식 교량 하부구조의 비선형해석을 위한 전산플랫폼을 개발하였다. 완전 조립식 교량 하부구조의 비선형거동을 정확하게 파악하고 합리적이면서 경제적인 설계기준의 개발을 위한 자료를 제공하는데 그 목적이 있다. 재료적 비선형성에 대해서는 균열콘크리트에 대한 인장, 압축, 전단모델과 콘크리트 속에 있는 철근모델을 조합하여 고려하였다. 사용된 부착 또는 비부착 텐던요소는 유한요소법에 근거하며 프리스트레스트 콘크리트 부재의 콘크리트와 텐던의 상호작용을 구현할 수 있다. 그리고 접합면요소는 세그먼트 접합부의 비탄성거동을 예측할 수 있다. 제안된 해석기법은 수치예제에 대하여 비선형거동을 비교적 정확하게 예측하였다.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2549-2551
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• 2005

본 논문은 제어 공정의 파라미터의 동정과 축소모델을 이용하여 선형 및 비선형 특성을 고려한 PID 제어기 설계를 제안하였다. 제어기 파라미터값은 2차의 지연시간을 갖는 축소 모델의 파라미터값에 의해 결정되며, 외란 및 제어 공정의 파라미터 값이 변할 때에는 실제 모델의 동정을 통해 구하며, 또한 실제 공정과 축소 모델의 관계식을 통해 제어 파라미터 값을 실시간으로 보정하여 제어한다. 시뮬레이션을 통하여 실시간 모델 동정 및 제어 파라미터 값이 보정됨을 확인 할 수 있다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.239-242
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• 2004

In this paper, the general mathematical model of LRE(Liquid Rocket Engine) is presented. For the analysis about the trend of dynamics and the stability of open type LRE, it is transformed to linear model by Laplace transform and synthesized to the linear complex model of LRE with Matlab/Simulink.

• Journal of the Korean Institute of Intelligent Systems
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• v.18 no.6
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• pp.762-767
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• 2008

This paper introduces a $L_{\infty}$-gain state feedback fuzzy controller design for the time delay nonlinear system represented by Takagi-Sugeno(T-S) fuzzy model. First, the T-S fuzzy model is employed to represent the time delay nonlinear system. Next based on the fuzzy model, a fuzzy state feedback controller is developed to achieve $L_{\infty}$-gain performance. Finally, sufficient conditions are derived for $L_{\infty}$-gain performance. The sufficient conditions are formulated in the format of linear matrix inequalities (LMIs). The effectiveness of the proposed controller design methonology is finally demonstrated through numerical simulations.

• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.569-579
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• 2011

Reinforced concrete walls subjected to cyclic loading show complicated inelastic behaviors varying with aspect ratio, re-bar detail, and loading condition. In the present study, a macro model for nonlinear analysis of reinforced concrete walls was developed. For exact prediction of inelastic flexure-compression and shear behaviors, the macro model of the wall was idealized with longitudinal and diagonal uniaxial elements. The uniaxial elements consist of concrete and re-bars. Simplified cyclic models for concrete and re-bars under uniaxial loading was used. For verification, the proposed model was applied to slender, lowrise, and coupled walls subjected to cyclic loading. The results showed that the proposed method predicted the nonlinear behaviors of the walls with reasonable precision.