• Bulletin of the Korean Space Science Society
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• 2010.04a
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• pp.31.2-31.2
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• 2010

편대비행 위성이 공동의 임무를 수행하기 위해서는 편대를 이루는 위성의 각기 다른 초기 오차와 다양한 외란 환경에서도 자세 동기화를 이룰 수 있는 기법이 필요하다. 이 연구에서는 편대비행위성의 자세 동기화를 위하여 비선형 시스템에 대한 준최적 제어기법인 SDRE(State-Dependent Riccati Equation)에 기반한 추적 제어기가 사용되었다. 반작용 휠이 포함된 위성의 자세 동역학이 SDRE 추적 제어기를 구성하는데 이용된다. 이를 Leader/Follower 편대비행 시스템에 적용하며, 기준 자세를 추적하는 Leader 위성의 자세를 Follower 위성이 추적하여 자세 동기화를 이룰 수 있다. MATLAB과 SIMULINK를 이용한 수치해석적 시뮬레이션으로 추적 제어기의 성능을 검증하였으며, 이에 대한 실시간 HIL(Hardware-In-the-Loop) 시뮬레이션이 수행되었다. 무중력 환경을 모사하는 에어베어링시스템과 세 개의 반작용 휠을 장착한 자세제어 HILS(Hardware-In-the-Loop Simulator)는 PC104 타입의 임베디드 컴퓨터에서 SIMULINK의 xPC Target을 이용한 실시간 시뮬레이션 환경을 제공하며, 이에 적용되는 SDRE 추적 제어기는 이산화되어 설계되었다. 또한 SDRE 추적 제어기에 대한 안정성을 보장하는 영역이 추정되어 위 추적 제어기가 위성 편대비행에 적합한 자세 동기화 기법임을 보였다.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.199-206
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• 2005

In paper the discrete optimum design program was developed using the continuous and discrete optimum algorithms based on the SUMT and genetic algorithms. In this paper, the objective function is the weight of structures and the constraints are limits state design limits method. The design variables are diameter and thick of steel pipe. Design examples are given to show the applicability of the optimum design using the continuous and discrete optimum algorithms based on the SUMT and genetic algorithms of this study.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.6
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• pp.241-248
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• 2008

The objective of sensitivity analyses is to identify critical variables of structural models and how their variability impacts mechanical response results. The sensitivity analyses have been used as significant basis data for practical applications of measuring and reinforcing fragile building structures. This study presents several sensitivity analysis methods for topological optimum designs of linear elastostatic structural systems. Numerical examples for structural analyses and topological optimum modeling demonstrate the reliability of sensitivities formulated in the present study.

• Proceeding of KASS Symposium
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• 2005.05a
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• pp.236-245
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• 2005

This paper was developed the discrete optimum design program by the refined fuzzy-genetic algorithms based on the genetic algorithms and fuzzy theory. The optimum design of this paper can perform both size and shape optimum design for planar and spacial steel structures. In this paper, the objective function is the weight of steel structures and the constraints are the design limits defined by design and buckling strengths, displacements and thicknesses. The design variables are dimensions and coordinates of steel sections. Design examples are given to show the applicability of the discrete optimum design program of this paper.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.1
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• pp.118-126
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• 2000

An optimum structural design system for double hull oil tankers is developed based on the generalized slope deflection method which was previously proposed by the authors. For the optimization technique, the Hooke & Jeeves direct search method is applied to the minimum weight design problems with discrete design variables. A minimum weight design program is developed for the longitudinal members by the classification rules and for the transverse frames and the bulkhead members by the generalized slope deflection method. By this program, a minimum hull weight design of double hull oil tankers considering tank arrangement is performed and the design results are compared with existing ship. It is possible to find optimum tank arrangement and efficient types of hull structures for the minimum weight design of double hull oil tankers.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.3
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• pp.231-238
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• 2004

This paper presents the high speed noise reduction processing system using the modified discrete fourier transform(MDFT) on the frequency domain. The proposed filter uses the linear prediction coefficients of the adaptive line enhance(ALE) method based on the Sign algorithm The signals with a random noise tracking performance are examined through computer simulations. It is confirmed that the fast adaptive digital filter is realized by the high speed adaptive noise reduction(HANR) algorithm with rapid convergence on the frequency domain(FD).

• Proceedings of the KIEE Conference
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• 1999.11c
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• pp.591-593
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• 1999

The finite time optimum regulation problem of a discrete time bilinear system with a quadratic performance criterion is obtained in terms of a sequence discrete algebraic Lyapunov equations. Our new method is based on the successive approximations. This algorithm saves the computation time to solve the optimal problem, and the design procedure is illustrated for an example.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.4
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• pp.53-58
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• 2003

Design of the corrugated watertight bulkhead for a bulk carrier is principally determined by the permissible limit of Classification requirements. As the weight of upper and lower stool has considerable portion of the total weight of the transverse bulkhead, optimum design including the stool geometry and size will play an important role on economic shipbuilding. The purpose of this study is focused on the minimization of steel weight using the design variables, which are the shape and the size of the corrugation as well as the upper and lower stools. Discrete variables are used as design variables for the practical design. In this study, the evolution strategies (ES), which can highly improve the possibility of leaching the global minimum point, are selected as an optimization method. Usefulness of this study is verified by comparison with the proven type ship design. As objective function, total weight of the transverse bulkhead including the upper and lower stools is used.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.6
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• pp.559-567
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• 2012

A level set based topological shape optimization method for nonlinear structure considering hyper-elastic problems is developed. To relieve significant convergence difficulty in topology optimization of nonlinear structure due to inaccurate tangent stiffness which comes from material penalization of whole domain, explicit boundary for exact tangent stiffness is used by taking advantage of level set function for arbitrary boundary shape. For given arbitrary boundary which is represented by level set function, a Delaunay triangulation scheme is used for current structure discretization instead of using implicit fixed grid. The required velocity field in the actual domain to update the level set equation is determined from the descent direction of Lagrangian derived from optimality conditions. The velocity field outside the actual domain is determined through a velocity extension scheme based on the method suggested by Adalsteinsson and Sethian(1999). The topological derivatives are incorporated into the level set based framework to enable to create holes whenever and wherever necessary during the optimization.

• Journal of the Korean Society of Industry Convergence
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• v.11 no.3
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• pp.127-134
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• 2008

This study is to develop the structure analysis and optimization algorithm of the strut supported temporary structure for underground constructions. Developed algorithm performs the analysis and the optimization of each strut, wale, and H pile of temporary structures separately. The design variables of nonlinear optimization consist of the cross-sections of temporary structures such as strut, wale, and H pile and the solution of the nonlinear programming is searched using for the method of successive unconstranint minimization technique. The weight of the structure is used for the object function of nonlinear programming. the constraints are derived from the specification of the temporary structures as compressive axial, bending, shear, composite stress and serviceability. The structural analysis is performed based on the elastoplastic beam theory. This developed program can be used to evaluate the applicability, convergence, and effectiveness of the temporary structures.