• 항공우주시스템공학회지
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• 제10권1호
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• pp.29-34
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• 2016

Flutter wind-tunnel test is an expensive and complicated process. Also, the test model may has discrepancy in the structural characteristics when compared to those of the real model. "Dry Wind-Tunnel" (DWT) is an innovative testing system which consists of the ground vibration test (GVT) hardware system and software which computationally can be operated and feedback in real-time to yield rapidly the unsteady aerodynamic forces. In this paper, we study on the aerodynamic forces of DWT system to feedback in time domain. The aerodynamic forces in the reduced-frequency domain are approximated by Minimum-state approximation. And we present a state-space equation of the aerodynamic forces. With the two simulation model, we compare the results of the flutter analysis.

• 한국항공우주학회지
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• 제30권7호
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• pp.29-35
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• 2002

접는 미사일 조종날개의 공력탄성학적 특성을 조사하였다. 접는 미사일 조종날개는 2차원 익형 모델로 가정하였다. 초음속 DPM을 이용하여 초음속 비정상 공기력을 계산하였으며, 최소 상태 변수 근사법을 이용하여 비정상 공기력을 근사화하였다. 선형 및 비선형 플러터 해석을 위해 근궤적법과 시간적분법을 사용하였다. 비선형 플러터 해석을 위해 전개부의 힌지는 비대칭 이선형 스프링으로 가정하였으며, 기술함수를 이용하여 선형화하였다. 플러터 해석으로부터, 비선형 파라미터가 공력탄성학적 특성에 미치는 영향을 조사하였다.

• 대한전기학회논문지
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• 제33권10호
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• pp.396-401
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• 1984

This paper present a method of using simplified models for deriving suboptimal controllers to the original higher-order systems. Routh approximation method is a very useful technique for reducing the order of a linear systems. This method dose not require a knowlege of system eigenvalues and eigenvectors and possesses many desirable features such as preservation of reduced order model stability and minimum computational requirements. These properties are utilized to derive suboptimal controllers in this paper. In order to implement htese ocntrollers on the original system, the relationship between the state vectors of the original system and the reduced order models is required. A procedure fir evaluating an approximate aggregation matrix is also developed. A numerical example is given for the illustration of this method, shich is compared with the existing Model aggregation method in the resultant figures.

• 전자공학회논문지B
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• 제30B권8호
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• pp.54-63
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• 1993

This paper proposes a method for improving the performances of the neural network for optimization by an optimal estimation of initial states. The optimal initial state that leads to the global minimum is estimated by using the stochastic approximation. And then the update rule of Hopfield model, which is the high speed deterministic algorithm using the steepest descent rule, is applied to speed up the optimization. The proposed method has been applied to the tavelling salesman problems and an optimal task partition problems to evaluate the performances. The simulation results show that the convergence speed of the proposed method is higher than conventinal Hopfield model. Abe's method and Boltzmann machine with random initial neuron output setting, and the convergence rate to the global minimum is guaranteed with probability of 1. The proposed method gives better result as the problem size increases where it is more difficult for the randomized initial setting to give a good convergence.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.1359-1361
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• 1996

This paper describes a design of real time fuzzy controller using Minimum fuzzy control Rule Selection Method(MRSM). The control algorithm of dynamic systems needs less computation time and memory. To reduce the computation time of fuzzy logic controller, minimum number of rules are to be selected for the fuzzy input variable. The universe of discourse is divided by the number of linguistic labels to allocate the assigned membership function to the fuzzy input variables. In this case, since fuzzy input variables are continuous, scale factor SU is tuned independently. According to increment of SU control surface is improved to adapt the change of system parameter. At this, crisp control surface is increased. With the increament of crisp control surface, fuzzy control surface is reduced. When error state deviates from desirable error state, crisp control surface is more useful than fuzzy control surface for obtaining fast rising time.

• Environmental Engineering Research
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• 제25권3호
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• pp.439-445
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• 2020

In the estimation of the aerosol single fiber efficiency using fibrous filters, there is a size range, where the particles penetrate most effectively through the fibrous collectors, and corresponding minimum single fiber efficiency. For small particles in which the diffusion mechanism is dominant, the Cunningham slip correction factor (C_c) affects the single fiber efficiency and the most penetrating particle size (MPPS). Therefore, for accurate estimation, C_c is essential to be considered. However, many previous studies have neglected this factor because of its complexity and the associated difficulty in deriving the appropriate parameterization particularly for the MPPS. In this study, the expression for the MPPS, and the corresponding expression for the minimum single fiber efficiency are analytically derived, and the effects of C_c are determined. In order to accommodate the slip factor for all particle-size ranges, C_c is simplified and modified. Overall, the obtained analytical expression for the MPPS is in a good agreement with the exact solution.

• 항공우주시스템공학회지
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• 제14권5호
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• pp.1-8
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• 2020

구조적 특성 및 공력의 상호작용과 조종면 작동기의 제어 시스템의 영향을 고려한 서보공력탄성 해석을 수행하였다. 공탄성 안정성 해석을 위해서 선행되어야 하는 구조모델의 자유진동 해석은 유한요소 해석 프로그램 MSC Nastran을 사용하였다. 비정상 공기력 계산에 ZAERO를 사용하였다. 비정상 공기력 검증에 Doublet Hybrid Method를 사용하였다. Karpel의 최소상태근사법을 이용하여 주파수 영역의 공기력을 라플라스 영역으로 근사하였다. 공탄성 상태방정식을 구동기의 동역학 상태방정식과 결합하여 서보 공탄성 모델의 상태공간방정식을 구성하였다. 고세장비 모델의 승강타 입력에 따른 안정성 해석을 수행하였다. 근궤적법과 시간적분법을 사용하여 주파수영역과 시간영역에서의 서보공탄성 안정성 해석을 수행하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.1197-1201
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• 2001

Flutter suppression of a wing/store model is investigated. An aircraft wing with a store is modeled as a 2-D typical section. Unsteady aerodynamics of the wing/store model are computed by using Doublet Hybrid Method(DHM) in the frequency-domain, and are approximated by Minimum-state(MS) approximation. LQG controller is used to suppress the flutter of the wing/store model and the aeroelastic characteristics of the closed-loop system are investigated. The flutter characteristics of the wing/store model are improved and the flutter speed is increased up to about 16 ％.

• 항공우주기술
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• 제3권1호
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• pp.1-8
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• 2004

본 연구에서는 MSC/NASTRAN을 이용하여 플러터, 돌풍응답 등의 공탄성 현상에 대한 해석 및 제어에 필요한 일반화된 비정상 공기력 행렬들을 계산하고, 이를 외부 프로그램에서 활용하기 위해 MSC/NASTRAN의 DMAP ALTER를 이용하여 외부 파일로 추출하는 방법을 제시하였다. 또한, 공탄성 해석 및 제어를 위한 지배방정식 구성을 위해 추출된 일반화된 비정상 공기력 행렬들을 최소상태 근사법을 사용하여 근사화하는 방법을 제시하였으며, 이를 단순화된 항공기 날개 구조물 모델에 적용하여 검증하였다.

• Advances in aircraft and spacecraft science
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• 제6권5호
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• pp.391-407
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• 2019

Flight trajectory optimization has become an important factor not only to reduce the operational costs (e.g.,, fuel and time related costs) of the airliners but also to reduce the environmental impact (e.g.,, emissions, contrails and noise etc.) caused by the airliners. So far, these factors have been dealt with in the context of 2D and 3D trajectory optimization, which are no longer efficient. Presently, the 4D trajectory optimization is required in order to cope with the current air traffic management (ATM). This study deals with a cubic spline approximation method for solving 4D trajectory optimization problem (TOP). The state vector, its time derivative and control vector are parameterized using cubic spline interpolation (CSI). Consequently, the objective function and constraints are expressed as functions of the value of state and control at the temporal nodes, this representation transforms the TOP into nonlinear programming problem (NLP). The proposed method is successfully applied to the generation of a minimum length optimal trajectories along 4D waypoints, where the method generated smooth 4D optimal trajectories with very accurate results.