• 한국항공우주학회지
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• 제39권5호
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• pp.408-415
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• 2011

달착륙은 크게 궤도이탈 단계, 동력하강 단계로 구성되어지며, 동력하강단계는 Braking, Approach, Final landing phase의 세부 3단계로 나누어진다. 본 논문에서는 동력하강 세부 3단계의 최적경로를 통하여 달착륙선의 착륙 제어를 수행하기로 한다. 우선 Gauss pseudo-spectral 방법을 통하여 기준 궤적을 생성하였고, 고도와 각 방향의 속도오차를 이용하여 PID 제어기를 생성하였다. 마지막으로 Matlab의 Simulink를 이용하여 달착륙선의 착륙단계 시스템을 구성하고 이를 이용하여 시뮬레이션을 수행하였다.

• Industrial Engineering and Management Systems
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• 제4권1호
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• pp.94-101
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• 2005

This paper presents the first known application of a meta-heuristic algorithm, variable neighbourhood descent (VND), to the redundancy allocation problem (RAP). The RAP, a well-known NP-hard problem, has been the subject of much prior work, generally in a restricted form where each subsystem must consist of identical components. The newer meta-heuristic methods overcome this limitation and offer a practical way to solve large instances of the relaxed RAP where different components can be used in parallel. The variable neighbourhood descent method has not yet been used in reliability design, yet it is a method that fits perfectly in those combinatorial problems with potential neighbourhood structures, as in the case of the RAP. A variable neighbourhood descent algorithm for the RAP is developed and tested on a set of well-known benchmark problems from the literature. Results on 33 test problems ranging from less to severely constrained conditions show that the variable neighbourhood descent method provides comparable solution quality at a very moderate computational cost in comparison with the best-known heuristics. Results also indicate that the VND method performs with little variability over random number seeds.

• 한국항공운항학회지
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• 제31권1호
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• pp.79-91
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• 2023

In response to the recent surge in aviation demand, major airports and aviation authorities continue to make efforts to formulate arrival and approach procedures that take into account efficient aircraft separation, noise and environmental issues of carbon (CO2) emissions. In order to ensure efficient traffic control and environmental issues, as a result, a new concept Trombone, Point Merge, etc. have been introduced and widely used in the domestic airspace. However, these new concept procedures which do not properly reflect the characteristics of the aircraft operation performance and the FMS vertical descent guidance hinder flight efficiency as well as bring in turn negative factors such as level-off flight and the use of drag device at the busiest phase of the flight descent operation, like the Continuous Descent Operation (CDO). Accordingly, throughout modification the current Standard Terminal Arrival Route (STAR) and Instrument Approach Procedure(IAP) that reflect the aircraft descent performance and the FMS guidance, the flight operation safety and efficiency is expected to be improved eventually. We herewith analyze and propose the way of improving flight efficiency in the arrival operation procedure by supplementary modification which consequently contribute to the aviation industry international competitiveness.

• 한국항공우주학회지
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• 제38권12호
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• pp.1184-1194
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• 2010

달 착륙과 이륙은 착륙선의 자세 및 고도에 따라서 몇 가지 단계로 나누어져 있다. 따라서 최적의 착륙선 궤적을 생성하기 위해서는 각 단계에 맞는 구속 조건과 제어 값이 필요하다. 착륙과 이륙의 최적궤적생성은 연료소모 및 자세변화율을 최소화 하는 가격함수를 이용하여 최적화를 수행하였다. 본 논문에서는 궤적을 생성하는 최적제어 문제의 풀이 방법을 직접적인 접근방식중의 하나인 Gauss pseudo-spectral을 사용하였고, 이 문제로 착륙선의 기준 궤적과 상태 및 제어 값을 생성하였다.

• Journal of applied mathematics & informatics
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• 제5권3호
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• pp.701-716
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• 1998

In this paper we develop algorithms in programming lan-guage SCHEME for implementation of the main first order gradient techniques for unconstrained optimization. Implementation of the de-scent techniques which use non-optimal descent steps as well as imple-mentation of the optimal descent techniques are described. Also we investigate implementation of the global problem called optimization along a line. Developed programs are effective and simpler with re-spect to the corresponding in the procedural programming languages. Several numerical examples are reported.

• Advances in aircraft and spacecraft science
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• 제9권6호
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• pp.493-506
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• 2022

The study presents the results of the research of heat and heat exchange processes on the heat-stressed elements of the structure of an advanced TsAGI descent vehicle. The studies were carried out using a mathematical model based on solving discrete analogs of continuum mechanics equations. Conclusions were drawn about the correctness of the model and the dependence of the intensity of heat and mass transfer processes on the most heat-stressed sections of the apparatus surface on its geometry and the catalytic activity of the surface.

• 한국항공운항학회지
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• 제19권2호
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• pp.52-57
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• 2011

The procedures of Continuous Descent Approach(CDA) is designed to minimize the thrust required during landing, thereby reducing fuel consumption, noise and emissions compared to conventional approach procedures. Widespread implementation of CDA would result in significant reductions in the environmental impact and aircraft operation costs. This paper estimated the possible economic effects from the perspective of airliners through cost-benefit analysis, provided that the CDA is introduced. It is now proposed that a more comprehensive analysis model, which includes the reduced ATC communication burden between controllers and pilots, not to mention the economic aspect, should be established for the improvement.

• 전기학회논문지P
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• 제58권2호
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• pp.164-171
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• 2009

This paper presents new learning algorithm of dynamic Bayesian networks (DBN) by means of constrained least square (LS) estimation algorithm and gradient descent method. First, we propose constrained LS based parameter estimation for a Markov chain (MC) model given observation data sets. Next, a gradient descent optimization is utilized for online estimation of a hidden Markov model (HMM), which is bi-linearly constructed by adding an observation variable to a MC model. We achieve numerical simulations to prove its reliability and superiority in which a series of non stationary random signal is applied for the DBN models respectively.

• 한국통신학회논문지
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• 제11권6호
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• pp.396-401
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• 1986

Steepest Descent Method를 정전계 문제의 해석에 적용하였다. 반복법과 moment method와 같은 direct method와의 차이점을 기술하였다. 반복법을 이용하여 정확한 해에 단조적으로 수렴하며 대형 system의 해석에 적합함을 보였다. 정전계 문제에 대해서 해석한 수치결과를 제시하였으며 moment solution과 잘 일치하고 있음을 보였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.823-828
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• 1992

A novel steepest descent adaptive filter algorithm, which uses the instantaneous stochastic gradient for the steepest descent direction, is derived from a newly devised performance index function. The performance function for the new algorithm is improved from that for the LMS in consideration that the stochastic steepest descent method is utilized to minimize the performance index iterativly. Through mathematical analysis and computer simulations, it is verified that there are substantial improvements in convergence and misadjustments even though the computational simplicity and the robustness of the LMS algorithm are hardly sacrificed. On the other hand, the new algorithm can be interpreted as a variable step size adaptive filter, and in this respect a heuristic method is proposed in order to reduce the noise caused by the step size fluctuation.