• 한국항공우주학회지
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• 제42권3호
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• pp.243-253
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• 2014

본 논문은 플랜트 파라미터의 불확실성에도 불구하고 강인성을 보장하는 정량적 궤환 이론에 대해 다루고 있다. 정량적 궤환 이론은 플랜트의 파라미터와 외란의 불확실성에 대해 주파수 영역에서 설계 사양의 강인성을 보장한다. 정량적 궤환 이론을 이용하기 위해 선정한 플랜트는 기동성이 뛰어나며 헬리콥터와 같이 수직 이착륙이 가능한 4-회전익 비행체를 이용하였으며, 4개의 블레이드를 구동하는 모터의 파라미터 불확실성을 설정하여 요구사양에 맞는 자세 제어가 가능함을 실험하였다. 또한, 자세 제어에는 4-회전익 비행체의 파라미터 변동 범위와 동작 범위를 고려한 전필터를 사용하였다. 이를 위해 MATLAB에서 정량적 궤환 이론에 의해 제어기를 설계할 수 있는 QFT control toolbox인 QFTCT를 사용하여 각 설계 단계에 대해 소개하고 있다.

• Structural Engineering and Mechanics
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• 제49권1호
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• pp.41-64
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• 2014

The main objective of this article is the exploitation of a stochastic hybrid mesh-free method based on stochastic generalized finite difference (SGFD), Newmark finite difference (NFD) methods and Monte Carlo simulation for thermoelastic wave propagation and coupled thermoelasticity analysis based on GN theory (without energy dissipation). A thick hollow cylinder with Gaussian uncertainty in mechanical properties is considered as an analyzed domain for the problem. The effects of uncertainty in mechanical properties with various coefficients of variations on thermo-elastic wave propagation are studied in details. Also, the time histories and distribution on thickness of cylinder of maximum, mean and variance values of temperature and radial displacement are studied for various coefficients of variations (COVs).

• Asia pacific journal of information systems
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• 제12권4호
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• pp.101-120
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• 2002

Risk management or risk-based approach of software project management was developed to explain the effects of requirement uncertainty, control standardization, interactions on software quality. Based on a prior theory, five hypotheses were derived and empirically tested using a survey design. Data from 117 members in 3 SI companies support for the path model, and three of five hypotheses. The results showed that decreases in requirement uncertainty and increases in control standardization were directly associated with increases in the interactions between user and project teams, which, in turn, led to increases software quality. The findings suggested that the direct effect on software quality is primarily due to the interactions between user and project teams, rather than requirement uncertainty and control standardization.

• 대한전기학회논문지:시스템및제어부문D
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• 제49권4호
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• pp.183-190
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• 2000

It is well-known that the poles of a system are closely related with the dynamics of the systems, and the pole assignment problem, which locates the poles in the desired regions, in one of the major problem in control theory. Also, it is always possible to assign poles to specific points for exactly known linear systems. But, it is impossible for the uncertain linear systems because of the uncertainties that originate from modeling error, system variations, sensing error and disturbances, so we must consider some regions instead of points. In this paper, we consider both the analysis and the design of robust pole assignment problem of linear system with time-varying uncertainty. The considered uncertainties are the unstructured uncertainty and the structured uncertainty, and the considered region is the circular region. Based on Lyapunov stability theorem and linear matrix inequality(LMI), we first present the analysis result for robust pole assignment, and then we present the design result for robust pole assignment. Finally, we give some numerical examples to show the applicability and usefulness of our presented results.

• 전산구조공학
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• 제7권3호
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• pp.153-166
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• 1994

구조물의 손상예측정확도를 모델불확실성의 함수로 산정하는 방법론이 제시되었다. 먼저, 구조물의 손상발생위치과 크기를 결정할 수 있는 알고리즘의 요약되고 모델불확실성과 손상발견정확도를 측정하는 방법들이 제시되었다. 다음으로, 실존구조물의 손상발견정확도에 미치는 모델불확실성의 영향을 산정하는 방법론이 제시되었다. 마지막으로, 한개의 진동모드가 측정된 Plate-Girder교량을 사용하여 이같은 산정방법론의 적합성이 예증되었다.

• Structural Engineering and Mechanics
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• 제46권4호
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• pp.447-458
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• 2013

Splitting tensile strength (STS) is a respectable mechanical property reflecting ability of the concrete. The STS of concrete is mainly related to compressive strength (CS), water/binder (W/B) ratio and concrete age. In this study, the assessment of STS is made by a novel uncertainty-oriented method which uses least square optimization and then predicts STS of concrete by uncertain (fuzzy) numbers. The approximation method addresses a novel integration of fuzzy set theory and multivariate statistics. The numerical examples showed that the method is applicable with relatively limited data. In addition, the prediction of uncertainty at various levels of possibility can be described. In conclusion, the uncertainty-oriented interval analysis can be suggested an effective tool for appraising the uncertainties in concrete technology.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.95.3-95
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• 2001

This paper investigates the simultaneous use of mixed H2/H_inf and mu-synthesis design methodology to design a robust controller for flexible link. We adopt four steps to design control system as follows: Step 1 : Generally, there are differences between the nominal and real model, so we consider the plant as a combination of parametric model uncertainty and unstructured uncertainty represents real structural uncertainties associated with the damping ratios of the flexible modes retained in the nominal model without payload. denotes the uncertainty which is due to the payload added at the tip. Step 2 : We adopt the mixed H2/H_inf theory to design a feedback controller K(s) by using the model uncertainty ...

• 전기학회논문지
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• 제67권2호
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• pp.314-324
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• 2018

This paper proposes a linear distributed target tracking filter for multiple unmanned aerial vehicles(UAVs) sharing their passive sensor measurements through communication channels. Different from the conventional nonlinear filtering schemes, the distributed passive target tracking problem is newly formulated within the framework of a linear robust state estimation theory incorporated with a linear uncertain measurement equation including the coordinate transform uncertainty. To effectively cope with the performance degradation due to the coordinate transform uncertainty, a linear consistent robust Kalman filter(CRKF) theory is devised and applied for designing a distributed passive target tracking filter. Through the simulations for typical UAV surveillance mission, the superior performance of the proposed method over the existing schemes of distributed passive target tracking are demonstrated.

• 성인간호학회지
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• 제14권4호
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• pp.635-644
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• 2002

Purpose: This research was done to establish a theoretical foundation for the adjustment process of patients with hemophilia. Method: For this study, 14 patients with hemophilia participated. The data was collected through the in-depth interviews and analysed in terms of Strauss and Corbin's grounded theory methodology. Result: The core category was identified with "uncertainty". The adjustment process was classified into two stages: the 'unstable stage' before the moment they learn about the Hemophilia Foundation and the 'stable stage' since then. The two stages were further divided into four groups, namely 'the stage of isolation ', 'the stage of maintaining survival', 'the stage of pursuing hope', 'the stage of ambivalence'. The categories of these stages include a series of subcategories to describe the adjustment of patients. The quality of life for these patients has increasingly improved based on support from hemophiliac organizations. But due to the uncertainty of disease, the patients have four stages of adjustment process from the stage of isolation to that of ambivalence and might turn to feedback. Conclusion: Therefore the nursing interventions reflecting adjustment process of patients with hemophilia should be developed.

• 한국추진공학회지
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• 제22권5호
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• pp.73-80
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• 2018

고속 추진체계의 개발 초기는 자료의 부족, 비용 제약, 지상에서 실제 비행환경 모사의 어려움 등으로 불확실 요소들을 확률분포의 형태로 모델링하기 어려운 실정이다. 이러한 이유로 본 연구에서는 이중연소 램제트를 대상으로 전문가들의 경험에 의한 연소효율 정보를 수집하여 이를 에비던스 이론으로 모델링하여 불확실성을 정량화 하였다. 정량화한 불확실성 정보를 이용하여 흡입구와 연소기의 출구면적에 대하여 추력여유와 열질식의 불확실성을 고려한 신뢰성 최적설계를 수행하였다. 한정된 불확실 정보를 가지고 엔진의 개념설계가 가능함을 확인할 수 있었다.