• International Journal of Fuzzy Logic and Intelligent Systems
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• 제6권3호
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• pp.190-196
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• 2006

In this paper, the nonlinear damping force model is made to identify the properties of the ER damper using higher order spectrum. The higher order spectral analysis is used to investigate the nonlinear frequency coupling phenomena with the damping force signal according to the sinusoidal excitation of the damper. Also, this paper presents an inverse model of the ER damper, i.e., the model can predict the required voltage so that the ER damper can produce the desired force for the requirement of vibration control of vehicle suspension systems. The inverse model has been constructed by using piecewise linear damping force model. In this paper, the fuzzy logic control based on heuristic knowledge is combined with the skyhook control. And it is simulated for a quarter car model. The acceleration of the sprung mass is included in the premise part of the fuzzy rules to reduce the vertical acceleration RMS value of the sprung mass. Then scaling factors and membership functions are tuned using genetic algorithm to obtain optimal performance.

• 대한기계학회논문집A
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• 제38권11호
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• pp.1193-1199
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• 2014

서비스 로봇이 충돌안전성을 확보한 상태에서 고속 주행 임무를 수행하기 위해서는 동적 장애물의 속도를 고려한 궤적 계획이 필요하다. 정적 장애물만을 고려한 상태에서 궤적을 계획하는 경우 장애물과의 상대속도로 인해서 로봇이 장애물과 충돌할 수 있다. 본 연구에서는 동적 장애물의 속도를 고려한 궤적시간조정기법을 제안한다. 제안된 기법을 통해서 기존에 생성된 궤적의 시간을 조정해서 장애물 회피가 가능한지를 평가할 수 있다. 만일 회피가 불가능할 경우 생성된 경로가 아닌 다른 경로를 선택할 수 있다. 모의 시험 결과를 통해서 제안된 기법을 통해서 짧은 시간 내에 장애물 회피를 수행할 수 있음을 보였다.

• International Journal of Concrete Structures and Materials
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• 제9권1호
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• pp.89-118
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• 2015

The geometric nonlinearity of off-diagonal bracing system (ODBS) could be a complementary system to covering and extending the nonlinearity of reinforced concrete material. Finite element modeling is performed for flexural frame, x-braced frame and the ODBS braced frame system at the initial phase. Then the different models are investigated along various analyses. According to the experimental results of flexural and x-braced frame, the verification is done. Analytical assessments are performed in according to three dimensional finite element modeling. Nonlinear static analysis is considered to obtain performance level and seismic behaviour, and then the response modification factors calculated from each model's pushover curve. In the next phase, the evaluation of cracks observed in the finite element models, especially for RC members of all three systems is performed. The finite element assessment is performed on engendered cracks in ODBS braced frame for various time steps. The nonlinear dynamic time history analysis accomplished in different stories models for three records of Elcentro, Naghan and Tabas earthquake accelerograms. Dynamic analysis is performed after scaling accelerogram on each type of flexural frame, x-braced frame and ODBS braced frame one by one. The base-point on RC frame is considered to investigate proportional displacement under each record. Hysteresis curves are assessed along continuing this study. The equivalent viscous damping for ODBS system is estimated in according to references. Results in each section show the ODBS system has an acceptable seismic behaviour and their conclusions have been converged when the ODBS system is utilized in reinforced concrete frame.

• 전산구조공학
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• 제8권3호
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• pp.113-122
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• 1995

이 논문의 목적은 현행법규(Uniform Buidling Code, NEHRP 설계규준 등)에 따라 설계된 구조들의 성능 및 안정성을 평가하는데 있다. 구조물의 내진성능은 신뢰성으로 표현할 수 있다. 구조물의 그의 수명동안 내진에 대한 신뢰성 해석을 하기 위해서는 주어진 구조물들의 많은 양의 동적반응 해석을 요구하는 것이 일반적이다 따라서 구조물의 신뢰성 해석을 위하여 구조물이 위치한 지역에 많은 양의 지진기록들이 요구된다. 이 논문에서는 인위적인 지진들(artificial earthquakes)을 부정착 임계 파정법(nonstationary randon process)을 이용해 만들었고 구조물은 Uniform Building Code와 AISC 허용응력 설계지침서(AISC allowables stress design manual)에 따라서 설계하였다. 이 논문에서는 주어진 지진하중에 대한 구조물의 반응은 구조물의 비선형 반응해석과 반응변위수정계수들을 이용한 간략화된 동위 구조물 해석(ENS)으로 얻었다. 이 논문에서는 구조물의 내진성능을 평가하였다. 또한 동위구조물(Equivalent Nonlinear System (ENS))을 이용한 해석과 구조물의 비선형 반응해석의 결과들을 비교하여 동위구조물을 이용한 방법의 정확성도 령가하였다.

• Transactions on Control, Automation and Systems Engineering
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• 제2권1호
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• pp.13-18
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• 2000

In this paper, an Adaptive Evolutionary Computation(AEC) is proposed. AEC uses a genetic algorithm(GA) and an evolution strategy (ES) in an adaptive manner is order to take merits of two different evolutionary computations: global search capability of GA and local search capability of ES. In the reproduction procedure, proportions of the population by GA and ES are adaptively modulated according to the fitness. AEC is used to design the membership functions and the scaling factors of fuzzy logic controller (FLC). To evaluate the performances of the proposed FLC, we make an experiment on FLC for the speed control of an actual DC series motor system with nonlinear characteristics. Experimental results show that the proposed controller has better performance than that of PD controller.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국제학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.351-354
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• 1993

In this paper, reheat-fan engine is described as class of models constructed from nominal and uncertainty model for robust control. In this class of models, uncertainty model consists of structured and unstructured uncertainty, and each model is identified from nonlinear simulation using FFT and ML technique. Then, control requirements and augmented plant are specified. H$_{\infty}$ controller satisfying the control requirements is designed by using constant scaling matrix. Finally, efficacy of the H$_{\infty}$ controller is showed by computer simulation.n.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 1999년도 춘계종합학술대회
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• pp.355-360
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• 1999

본 논문에서는 퍼지 논리 제어기에서 전문가의 지식없이 시행 착오법에 의해 최적화 되지 않은 제어 규칙을 이용하는 경우에도, 소속 함수 관계와 스케일링 팩터를 유전자 알고리즘으로 최적화하여 우수한 제어 성능을 갖는 지능 제어 방식을 제안한다. 제안하는 제어 방식은 실제 플랜트는 퍼지 논리를 이용해서 제어를 하되 먼저 오프 라인상에서 퍼지 제어기의 소속 함수 초기 변수값과 스케일링 팩터의 초기값을 유전 알고리즘으로 최적화시킨후 제어를 하는 직접 적응 제어 방식이다. 제안된 제어 방식의 유용성을 확인하기 위하여 비선형 시스템을 제어 대상으로 기존의 퍼지 제어 방식과 시뮬레이션을 통하여 비교 및 검토를 한다.

• 대한전기학회논문지:전력기술부문A
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• 제54권2호
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• pp.51-60
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• 2005

In this paper, we design the GA-fuzzy precompensator of a Power System Stabilizer for Thyristor Controlled Series Capacitor(TCSC-PSS) for enhancement of power system stability. Here a fuzzy precompensator is designed as a fuzzy logic-based precompensation approach for TCSC-PSS. This scheme is easily implemented by adding a fuzzy precompensator to an existing TCSC-PSS. And we optimize the fuzzy precompensator with a genetic algorithm for complements the demerit such as the difficulty of the component selection of fuzzy controller, namely, scaling factor, membership function and control rules. Nonlinear simulation results show that the proposed control technique is superior to conventional TCSC-PSS in dynamic responses over the wide range of operating conditions and in convinced robust and reliable in view of structure.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.870-876
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• 1993

This paper presents a binary clustering network (BCN) and a heuristic algorithm to detect pitch for recognition of keywords in continuous speech. In order to classify nonlinear patterns, BCN separates patterns into binary clusters hierarchically and links same patterns at root level by using the supervised learning and the unsupervised learning. BCN has many desirable properties such as flexibility of dynamic structure, high classification accuracy, short learning time, and short recall time. Pitch Detection algorithm is a heuristic model that can solve the difficulties such as scaling invariance, time warping, time-shift invariance, and redundance. This recognition algorithm has shown recognition rates as high as 95% for speaker-dependent as well as multispeaker-dependent tests.

• 한국디지털건축인테리어학회논문집
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• 제9권3호
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• pp.15-23
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• 2009

Chaos theory, qualitative study of unstable aperiodic behavior in deterministic nonlinear dynamical systems, is dominant paradigm in the twenty first century. Fractal geometry, as an expressed form of chaos, now influences many areas such as architecture, art, music, economics, literature, etc. The purpose of this study is to analyze fractal geometry and fractal formative elements in architectural design. There are scaling, superimposition, distortion, deformation and repetition in the fractal form generator that can be applied to design concept and process in architecture. This study shows fractal geometry can be the architectural form creation method. Fractal geometry similar to nature's patterned order can be provided endless possibilities for design analysis and methodology in architecture. Therefore the further study of fractal geometry should progress synthetically through the basis of the study.