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대체모델의 정확성 및 강건성 향상을 위한 가중함수 기반 순차 최소거리최대화계획
장준용(Junyong Jang),조수길(Su-gil Cho),이태희(Tae Hee Lee) 대한기계학회 2015 大韓機械學會論文集A Vol.39 No.4
효율적인 최적설계를 위해 공학분야에 도입된 대체모델의 정확성은 표본점에 큰 영향을 받는다. 대체모델의 정확성을 높이는 방법으로 기 추출한 응답을 이용하는 순차실험계획이 제안되었다. 크리깅 대체모델의 상관계수를 가중치로 적용하여 대체모델의 정확성을 향상시킨 연구가 있었으나, 주어진 정보가 부족하거나 상관계수가 잘못 추정된 경우 표본점이 잘못 추출되어 대체모델의 강건성이 저하된다. 본 논문에서는 기존 순차실험계획의 여러 문제점을 제시하고, 이를 해결하기 위한 가중함수 기반 순차 최소거리최대화계획을 제안한다. 제안하는 순차실험계획의 효용성을 수학 함수에 적용하여 기존 순차실험계획들과 비교하여 정확성과 강건성이 향상됨을 예시한다. In order to efficiently optimize the problem involving complex computer codes or computationally expensive simulation, surrogate models are widely used. Because their accuracy significantly depends on sample points, many experimental designs have been proposed. One approach is the sequential design of experiments that consider existing information of responses. In earlier research, the correlation coefficients of the kriging surrogate model are introduced as weight parameters to define the scaled distance between sample points. However, if existing information is incorrect or lacking, new sample points can be misleading. Thus, our goal in this paper is to propose a weight function derived from correlation coefficients to generate new points robustly. To verify the performance of the proposed method, several existing sequential design methods are compared for use as mathematical examples.
제한된 정보를 이용한 로어컨트롤암의 신뢰성 기반 최적설계
장준용(Junyong Jang),나종호(Jongho Na),임우철(Woochul Lim),박상현(Sanghyun Park),최성식(Sungsik Choi),김정호(Jungho Kim),김용석(Yongsuk Kim),이태희(Tae Hee Lee) 한국자동차공학회 2013 한국자동차공학회 부문종합 학술대회 Vol.2013 No.5
Lower control arm (LCA)is a part of chassis in vehicles. Performances of LCA such as stiffness, durability and permanent displacement have to be considered in design optimization. However it is hard to consider different performances at once in optimization because these are measured by different tools like Radioss, Abaqus, etc. In this paper, firstly, we construct the integrated design automation system for LCA based on Matlab including Hypermesh, Radioss and Abaqus. Secondly, Akaike information criterion (AIC) is used for assessment of reliability of LCA. It can find the best estimated distribution of performance from limited stochastic information and then obtain the reliability from the distribution. Finally, we consider tolerances of design variables and variation of elastic modulus and obtain performances of target reliability by performing reliability-based design optimization (RBDO) with the integrated system.
시간-변화 동적 응답에 대한 통계적 공간-시간 메타모델링 기법의 비교 연구
장준용(Junyong Jang),이진민(Jin Min Lee),이태희(Tae Hee Lee) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Statistical metamodels have developed with a variety of design optimization techniques in structural engineering fields for the last decade because of efficient design and easy interconnection into design frameworks. However, they have only handled responses with respect to space (design) variables such as size and shape of structures. In this research, statistical space-time metamodeling techniques that can handle time-variant dynamic responses with respect to both space variables and a time variable are compared. The first, we compare spatiotemporal response approach (SRA) and multiple response approach (MRA) from the viewpoint for handling approaches of a time variable. The second, we compare MRA and double-loop MRA from the viewpoint for prediction of responses at time untried points. The last, we compare double-loop MRA and split time region (STR) double-loop MRA from the viewpoint for building time of kriging model.
장준용(Junyong Jang),조수길(Su-gil Cho),이민욱(Minuk Lee),이태희(Tae Hee Lee) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
Carrying out optimum design, in general, designer needs to set up ranges of design variables at the beginning. At this point, after we fulfil optimization by using metamodel and design of experiment, we need to modify the ranges of design variables or additional sample point if initial optimum point is located around boundary that designer set arbitrarily. In this study, through extrapolation of metamodel applied to initial design, we quantitatively evaluate accuracy of predicted responses outside of the boundary and propose ranges of extrapolation keeping accuracy without additional sample points. We select krigingmodel as the metamodel which gives Bayesian information and evaluates expanding performance after we examine the nonlinearity according to R-square of response surface model(RSM) through mathematical examples.
코깅 토크와 토크 리플 저감을 위한 800W급 소형 SPM 전동기 다중목적 최적 설계
장준용(Junyong Jang),조수길(Su-gil Cho),이수진(Su-Jin Lee),홍정표(Jung-Pyo Hong),이태희(Tae Hee Lee) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5
SPM(Surface-mounted permanent magnet) motor is widely used for variety of fields, but it is necessary for reducing torque ripple and cogging torque which result in noise and vibration. Since the configuration of the motor has great impact on these responses, study related shape optimization is proceeding actively. However, these responses cannot design easily for general optimization technique because of trade off relation. So, this paper presents multi-objective optimization of stator and rotor in a SPM motor. Also kriging metamodel and global optimization technique is applied, because multi-objective function is nonlinearity and has multiple local optimums.
장준용(Junyong Jang),조수길(Su-gil Cho),이태희(Tae Hee Lee) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
In order to efficiently optimize the problem involving complex computer codes or computationally expensive simulation, surrogate models are widely used. And because their accuracy significantly depends on sample points, a number of design methods are proposed. One approach is sequential design of experiments which can consider existing information of responses. In earlier research, correlation coefficients of kriging model are introduced as weight parameters to define scaled distance between sample points. However, if existing information is wrong or lacking, new sample points can be misleading. Thus, our goal in this paper is to generate new points robustly by adjusting the weighting parameters derived from correlation coefficients. To verify the performance of the proposed method, several existing design methods are compared by mathematical examples.
상관함수에 따른 분할영역 크리깅모델의 1차 미분연속 연구
장준용(Junyong Jang),이진민(Jin Min Lee),이태희(Tae Hee Lee) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.4
공학에서 효율적인 최적설계를 위하여 크리깅모델을 널리 사용하고 있다. 하지만 설계변수에 대한 표본점이 많아지면 크리깅모델을 구성할 때 상관계수를 결정하는 최우량추정과정이 오래 걸리는 어려움이 있다. 특히 시간-변화 동적 응답에 대한 이중순환 다중응답접근법 기반 통계적 공간-시간 메타모델에서 취급해야 할 시간변수에 대한 표본점이 상당히 많다. 따라서 시간변수를 효율적으로 다루기 위하여 시간분할영역 메타모델링 기법이 개발되었다. 본 논문에서는 분할영역의 경계점에서 크리깅모델의 1차 미분연속성과 분할영역 크리깅모델의 수치적 안정성을 검증한다. 그리고 수학예제를 통하여 상관함수에 따른 경계에서의 연속성에 대해 비교 분석한다. In engineering fields, Kriging model has been widely used to improve the efficiency of optimization. However, if the number of sample point of variables increase, it is time-consuming to build Kriging model because of maximum likelihood estimation(MLE) determining coπelation parameter. Especially in double-loop multiple response approach based statistical space-time metamodel for time-variant dynamic responses the number of time presampled point is much more than the number of space variable. Thus split time region(STR) metamodeling technique is developed for handling time-variable efficiently. In this research, we verify C1-continuty and numerical stability of split region Kriging model at boundary points. And we carry out some mathematical examples for comparing differential value according to coπelation functions at boundary point.