• Proceedings of the KIEE Conference
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• 2007.10c
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• pp.39-40
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• 2007

본 논문은 Slotless BLDCM의 발열특성에 고려하여 열 발생을 최소화 하고자 다중 반응표면법을 적용하여 모터의 형상 및 권선 사양의 최적 선정에 관한 연구이다. 본 연구에서는 전류밀도의 최소화를 목적함수로 하여 형상 및 권선 사양의 최적화를 실시하였다. 변수에 대한 영향도의 분석은 전자계 해석을 통한 결과값을 통하여 실시하였으며, 열적 특성을 파악하기 위해서 전자계-열계의 해석을 통해서 최적값의 열적 안정성을 파악하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.672-676
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• 2002

In this paper, a reliability-based design optimization method, which enables the determination of optimum design that incorporate confidence range for structures, is studied. Response surface method and Monte Carlo simulation are utilized to determine limit state function. The proposed method is applied to the I-type steel structure for reliability based optimal design.

• Journal of Aerospace System Engineering
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• v.11 no.4
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• pp.36-43
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• 2017

Blade design optimization of QTP-UAV prop-rotor was conducted using ModelCenter(R). Performance efficiency of the blade in hover and forward flight were adopted as the multi-objective function. Required power and pitch link force applied to constraint in each flight mode and limited lower than the value of the baseline blade. Design variables of root chord length of the blade, taper ratio, twist slope, twist angle at 0.5R of the blade, anhedral angle, parabolic coefficient of a tip shape and location of airfoil were used to generate the blade planform. CAMRAD-II, the comprehensive analysis program of rotorcraft, was used for performance analysis of prop-rotor blade in design process. Performance of the optimized blade improved 1.6% of figure of merit in hover and 13.6% of propulsive efficiency in forward flight. Pitch link force also reduced approximately 30% less than that of the baseline blade.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.432-436
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• 2007

본 연구의 목적은 3차원 풍력터빈 블레이드 최적형상설계를 위한 실용적이고 효율적인 설계 과정을 구현하는 것이다. 국내 연안의 해상풍력에 적용하기 위해서 통계적 모델을 이용하여 풍황 자료를 분석하였다. 설계에 관련된 많은 수의 설계변수를 효과적으로 관리하기 위해서 설계과정은 운용조건 최적화와 블레이드 형상설계의 2단계로 구성하였다. 실험계획법에 의해 추출된 각 운용조건점은 형상설계를 위한 입력값으로 제공된다. 형상설계 단계에서는 최소에너지손실 조건과 결합된 BEMT를 이용하여 각 블레이드 단면에서의 시위길이와 피치각 분포를 최적화하였다. 블레이드 단면 익형은 NREL S830을 이용하였고, 익형의 공력성능은 XFOIL을 이용하여 예측하였다. 설계된 블레이드 형상의 성능해석을 수행하고 그 결과를 바탕으로 반응면을 구성하였다. 좀 더 나은 성능을 가진 블레이드 형상을 찾기 위해서 초기설계공간에서 확률적 방법을 이용하여 타당성 있는 설계공간까지 운용조건 설계변수를 이동시키고 구배최적화 기법을 통해 각각의 제약함수를 만족하면서 연평균발생에너지를 최대로 하는 최적블레이드 형상을 구현하였다. 제시된 최적설계과정은 풍력터빈블레이드 개발에 실용적이고 신뢰성 있는 설계툴로서 사용이 가능하다.

• New & Renewable Energy
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• v.3 no.3
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• pp.63-71
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• 2007

본 연구의 목적은 3차원 풍력터빈 블레이드 최적형상설계를 위한 실용적이고 효율적인 설계과정을 구현하는 것이다. 국내 연안의 해상풍력에 적용하기 위해서 통계적 모델을 이용하여 풍황자료를 분석하였다. 설계에 관련된 많은 수의 설계변수를 효과적으로 관리하기 위해서 설계과정은 운용조건 최적화와 블레이드 형상설계의 2단계로 구성하였다. 실험계획법에 의해 추출된 각 운용조건 설계점은 형상설계를 위한 입력 값으로 제공된다. 형상설계 단계에서는 최소에너지손실 조건과 결합된 BEMT를 이용하여 각 블레이드 단면에서의 시위길이와 피치각 분포를 최적화하였다. 블레이드 단면 익형은 NREL S830을 이용하였고, 익형의 공력성능은 XFOIL을 이용하여 예측하였다. 설계된 블레이드 형상의 성능해석을 수행하고 그 결과를 바탕으로 반응면을 구성하였다. 좀 더 나은 성능을 가진 블레이드 형상을 찾기 위해서 초기설계공간에서 확률적 방법을 이용하여 타당성 있는 설계공간까지 운용조건 설계변수를 이동시키고 구배최적화 기법을 통해 각각의 제약함수를 만족하면서 연간에너지생산량을 최대로 하는 최적블레이드 형상을 구현하였다. 제시된 최적설계과정은 풍력터빈블레이드 개발에 실용적이고 신뢰성 있는 설계툴로서 사용이 가능하다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.7
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• pp.703-714
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• 2010

This paper describes the design optimization of a rotating rectangular channel with staggered arrays of pin-fins by Kriging metamodeling technique. Two non-dimensional variables, the ratio of the height to the diameter of the pin-fins and the ratio of the spacing between the pin-fins to the diameter of the pin-fins are chosen as the design variables. The objective function that is a linear combination of heat transfer and friction loss related terms with a weighting factor is selected for the optimization. To construct the Kriging model, objective function values at 20 training points generated by Latin hypercube sampling are evaluated by a three-dimensional Reynolds-averaged Navier-Stokes (RANS) analysis method with the SST turbulence model. The Kriging model predicts the objective function value that agrees well with the value calculated by the RANS analysis at the optimum point. The objective function is reduced by 11% by the optimization of the channel.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.82-85
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• 2006

A trapezoidal fin with various lateral surface slopes is designed optimally by using one-dimensional analytic method. For four different convection characteristic numbers, the trend of heat loss as a function of fin tip length is shown. The optimum heat loss is somewhat arbitrarily chosen as 92% of the maximum heat loss. The optimum fin length corresponding to this optimum heat loss versus convection characteristic number is presented. The optimum effectiveness and specific effectiveness is presented as a function fin shape factor.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.7
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• pp.821-826
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• 2011

CAE-based structural optimization techniques are applied for the design of a lightweight crane. The boom of the crane is designed by shape optimization with the shape of the cross section of the boom as the design variable. The design objective is mass minimization, and the static strength and dynamic stiffness of the system are set as the design constraints. Hyperworks, a commercial analysis and optimization software, is used for shape and topology optimization. In order to consistently change the shape of the elements of the boom with respect to the change in the shape of its cross section, the morphing function in Hyperworks is used. The support of the boom of the original model is simplified to model the design domain for topology optimization, which is discretized by using three-dimensional solid elements. The final result after shape and topology optimization is 19% and 17% reduction in the masses of the boom and support, respectively, without a deterioration in the system stiffness.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.3
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• pp.155-162
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• 2014

Using an isogeometric approach, a continuum-based shape design optimization method is developed for steady state power flow problems at high frequencies. In case the isogeometric method is employed to the shape design optimization, the NURBS basis functions used in CAD geometric modeling are directly utilized to embed the exact geometry into the computational framework so that the design parameterization for shape optimization is much easier than that in the finite element method and consequently provides the enhanced smoothness of design perturbations. Thus, exact geometric models can be used in both the response and the shape sensitivity analyses, where normal vector and curvature are continuous over the whole design space so that enhanced shape sensitivity can be expected. Through numerical examples, the developed isogeometric sensitivity is compared with finite difference one to provide excellent agreement. Also, it turns out that the proposed method works very well in the shape optimization problems.

• The Journal of the Acoustical Society of Korea
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• v.40 no.4
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• pp.347-358
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• 2021

The objective of this study is to optimize the shape of doubly curved surface where a conformal array is equipped. That surface is modeled with a double-ellipsoid solid controlled by four parameters. By analyzing the performance of the conformal array beams with the beam pattern synthesis, two design parameters are determined. Then, we define the weighted object function which is formulated as the sum of sharp indexes for directivity index, the elevation resolution, and the bearing resolution. The direct calculation on all grids is used to evaluate the weighted object function and seek the optimal value of two design parameters when the weightings are given. In the simulation, four kinds of weighting cases are respectively applied to evaluate the weighted object function. The optimal shapes of double-ellipsoid solid are shown in each case. Especially, when the uniform weightings are used, the double-ellipsoid solid with more smooth surface is obtained.