• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.306-311
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• 2017

This paper deals with the design optimization of the kinematic characteristics of an automotive suspension system. The kinematic characteristics of the suspension determine the attitude of the wheels, such as the toe and camber, which not only relates to tire wear during driving, but also greatly affects the control of the vehicle and its stability, which corresponds to the motion performance of the vehicle. Therefore, it is very important to determine the characteristics of the suspension mechanism at the initial stage of the design. In this study, a displacement analysis is performed to determine the kinematic properties of the suspension for the McPherson strut suspension. For this purpose, a set of constraint equations for the joints constituting the suspension mechanism was established and a program was developed to solve them. We also used ADS, a design optimization program, to obtain the desired kinematic characteristics of the suspension. As the design variables for optimization, we used the coordinates of the hard points, which are the points of attachment of the suspension to the vehicle body, and are defined as the summation of the toe-in for the up and down movement of the wheel as the objective function. As the constraint functions, the maximum camber angle and minimum roll center height, which are design requirements, are considered. As a result of this study, it was possible to determine the optimal locations of the hard points that satisfy both constraint functions and minimize the change of the toe-in.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2639-2641
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• 2003

유전자 알고리즘은 다윈의 자연선택설과 유전자의 진화 개념을 이용한 적응 탐색 알고리즘으로 적용하고자 하는 문제의 매개 변수를 유전자와 비슷한 데이터 구조로 부호화하고, 유전 연산자를 이용하여 문제의 해답을 찾는 알고리즘이다. 최근 유전자 알고리즘은 이러한 복수개의 목적 함수를 최적화 하기 위한 다중 최적화 문제를 위한 최적화 기술로서의 관심이 크게 다루어지고 있으며 전송 문제, 생산 공정 문제 계획 등과 같은 다목적 함수를 다루는 많은 응용 부분에 대해 적용되고 있다. 본 논문에서는 기본적인 다중 목적 함수용 예와 Gen과 Kim이 제안한 네트워크 신뢰도를 고려한 연결 비용과 메시지 지연을 고려한 이중 구속 통신망 설계 문제를 가지고 가중치 합과 여러 가지 파레토 방법들을 비교하고 연구 검토 하고자 한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.5
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• pp.56-64
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• 2006

Station collocation of closely placed multiple GEO spacecraft is required to avoid the problem of collision risk, attitude sensor interference and/or occultation. This paper presents the method of obtaining the orbit correction scheme for collocating two GEO spacecraft within a small station-keeping box. The relative motion of each spacecraft with respect to the virtual geostationary satellite is precisely expressed in terms of power and trigonometry functions. This closed-form orbit propagator is used to define the constraint conditions which meet the requirements for the station collocation. Finally, the technique of constrained optimization is used to find the orbit maneuver sequence. Nonlinear simulations are performed and their results are compared with those of the classical method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.870-875
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• 2004

Beam stiffeners have frequently been used for raising natural frequencies of base structures. In stiffener layout optimization problems, most of the previous researches considering the position and/or the length of the stiffener as design variables dealt with structures having just simple convex shapes such as a square or rectangle. The reason is concave shape structures have difficulties ill formulating geometry constraints. In this paper, a new geometry constraint handling technique, which can define both convex and concave feasible lesions and measure a degree of geometry constraint violation, is proposed. Evolution strategies (ESs) is utilized as an optimization tool. In addition, the constraint-handling technique of EVOSLINOC (EVOlution Strategy for scalar optimization with Lineal and Nonlinear Constraints) is utilized to solve constrained optimization problems. From a numerical example, the proposed geometry constraint handling technique is verified and proves that the technique can easily be applied to structures in net only convex but also concave shapes, even with a protrusion or interior holes.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.6
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• pp.37-46
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• 2001

In this research, a controller design method based on optimization is proposed that can satisfy constraints on maximum responses of building structures subject to around excitation modeled by partially stochastic process. The class of controllers to be optimized is restricted to LQR. Weighting matrix on controlled outputs is used as design variable. Objective function, constraint functions and their gradients are computed by the parameterization of control gain with Riccati matrix. Full state feedback controllers designed by proposed optimization method satisfy various design objectives and their necessary maximum control forces are computed for the production of actuator. LQG controllers composed of Kalman filter and LQR designed by proposed method perform well with little deterioration. So it is possible to design output feedback controllers satisfying constraints on various maximum responses of structures.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.2
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• pp.223-233
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• 2011

A design optimization problem was formulated to minimize the volume of an RC building structure while satisfying design constraints on structural displacements under vertical, wind and seismic loads. We employed metamodel-based design optimization using design of experiments, metamodeling and optimization algorithm to circumvent the difficulty of the automation of structural analysis procedure. Especially, we proposed a design approach of repetitive design optimizations by stages with changing the side constraint values on design variables and limit values on design constraints until a satisfactory design result was obtained. Using the proposed design approach, the volume of the RC building structure has been reduced by 53.3 % compared to the initial one while satisfying all the design constraints. This design result clearly shows the validity of the proposed design approach.

• Computational Structural Engineering
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• v.10 no.2
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• pp.225-232
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• 1997

Material properties of a new composite composed of components with known material properties are usually investigated through experiments. Elastic modulus and Poisson's ratio are measured at various volume fractions of mixed components and utilized as the base information on an analytical model for predicting the mechanical behaviors of a structure constructed by the composite. Elastic material properties of a composite at various volume fractions are numerically estimated by minimizing the error between the static displacements computed from a model for the composite and those computed from a model of homogeneous and isotropic material. A finite element model for a composite is proposed to distribute different types of material components easily into the model depending on the volume fraction. Then, the material properties of a composite filled with solid mircospheres are predicted numerically through a sample study and the estimated results are compared with experimental results and some theoretical equations.

• Journal of the Korean Magnetics Society
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• v.27 no.2
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• pp.63-69
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• 2017

Naval ships are particularly required to maintain acoustic and magnetic silence due to their operational characteristics. Among them, underwater magnetic field signals derived by ships are likely to be detected by threats such as surveillance systems and mine systems at close distance. In order to increase the survivability of the vessels, various techniques for reducing the magnetic field signal are being studied and it is necessary to consider not only the magnitude of the magnetic field signal but also the gradient of it. In this paper, we use the commercial electromagnetic finite element analysis tool to predict the induced magnetic field signal of ship's scaled model, and arrange the degaussing coil. And the optimum degaussing current of the coil was derived by applying the particle swarm optimization algorithm considering the gradient constraint. The validity of the optimal degaussing technique is verified analytically by comparing the magnetic field signals after the degaussing with or without gradient constraint.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.7
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• pp.745-750
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• 2012

This study extends the constraint force design method allowing topology optimization for planar rigid-link and string mechanisms. To our best knowledge, by applying conventional machine and mechanism design theories, it is likely that it is possible to find out optimal locations of joints and lengths of rigid-links but somewhat difficult to find out optimal topology of rigid-links. To achieve optimal topology of rigid links, there is our previous contribution so called the new constraint force design method with the binary design variables determining the existence of the auxiliary forces imposing apparent lengths among unit masses. By adding new binary design variables, this research extends the constraint force design method to find out optimal mechanism consisting of stringy links as well as rigid links that seems impossible in the conventional machine and mechanism design theories.

• Journal of Aerospace System Engineering
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• v.15 no.5
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• pp.8-15
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• 2021

This paper describes a design method using an optimization technique to satisfy the longitudinal handling quality of high maneuverable jet aircraft. The dynamic inversion technique was applied to the target aircraft, and the control gain optimization satisfied the longitudinal short-period handling quality, however, the stability margin was not considered. If the stability margin is not satisfied, it is necessary to directly readjust the gains through trial and error methods for improvement. To improve this, an additional compensator and an optimization constraint were added to the control gain optimization procedure. In addition, the degree of handling quality satisfaction with the optimization result was reevaluated, and additional control evaluation criteria for the convergence of the time response and the steady state error that the flight performance requirement set as the optimization constraint cannot be reflected, and the results are described.