• 한국시뮬레이션학회논문지
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• 제20권4호
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• pp.67-79
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• 2011

본 연구에서는 시계열 공정데이터 관리를 위한 모델모수 기반 이상 탐지방법을 제안한다. 일반적인 공정관리에 널리 쓰이는 전통적인 통계적 관리기법의 관리도(SPC chart)는 측정되는 데이터가 특정 분포를 따르며 상관관계가 없는 상황을 가정한다. 따라서 공정데이터 형태가 시계열데이터와 같이 특정분포를 따르지 않고, 자기상관관계를 갖는다면 전통적인 관리도로는 관리에 한계를 보인다. 본 연구는 시계열을 따르는 공정의 이상을 탐지를 위한 MPBC(Model Parameter Based Control-chart) 방법을 제안한다. 제안된 MPBC는 시계열공정을 모델링하고, 모델모수의 변화를 감지하여 공정의 이상을 탐지하는 방법이다. 시계열 공정은 ARMA(p,q) 모델을 가정하며, RLS(Recursive Least Square)를 이용하여 시계열 모델의 모수를 추정하고, 추정된 모수를 $K^2$관리도로 관리한다. 제안된 방법은 기존 알고리즘과 비교하여 시계열 공정 변화 탐지에 우수한 성능을 보였으며 시계열 데이터에 있어서 보다 효율적인 공정관리 방향을 제시한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 A
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• pp.305-307
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• 1992

This paper presents a technique, which identifies both process noise covariance and sensor noise covariance by using innovation correlation test. A correlation test, which checks whether the square root Kalman filter is workingly optimal or not, is given. The system is stochastic autoregressive moving-average model with auxiliary white noise Input. The linear quadratic Gaussian control is used for minimizing stochastic cost function. This paper indentifies Q, R, and estimates parametric matrics $A(q^{-1}),B(q^{-1}),C(q^{-1})$ by means of extended recursive least squares and model reference control. And The proposed technique has been validated in simulation results on the fourth order system.

• 한국전자파학회논문지
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• 제12권5호
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• pp.802-809
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• 2001

이 논문에서는 VHF 대역에서 동작하는 주파수도약 송신기의 전력증폭기를 선형화한다. 적응 전치왜곡기(adaptive predistorter)를 사용하여 애널리그 다항식 선형화기를 전치왜곡기로 사용한다. 수렴 소도를 높이기 위하여 전치왜곡기의 출력신호와 후처리기의 출력신호 사이의 오차가 글로벌 최소치에 접근하도록 RLS(recursive least square) 적응 앨거리듬을 적용한다. 실험결과 설계된 선형 전력증폭기의 ACP(Adjacent Channel Power)는 10 dB 개선된다.

• 한국전자파학회논문지
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• 제12권7호
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• pp.1102-1109
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• 2001

다항식형 전치왜곡기를 이용한 적응 전치왜곡 선형화기의 새로운 구조를 제안한다. 제안된 선형화기에서는 전치왜곡을 포함한 대부분의 연산이 DSP(digital signal processor)로 수행된다. 전치 왜곡기의 출력신호와 후처리기 의 출력 신호 사이 의 오차를 최소화하기 위하여 RLS(recursive least squares) 앨거리즘을 적용한다. 씨뮬레이션 결과 ACPR(adjacent channel power ratio)이 대역 가장자리에서 40 dB 이상 개선된다. 선형화기의 수렴 및 재수렴 특성 역시 만족스러운 성능을 보인다.

• 지능정보연구
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• 제1권1호
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• pp.61-72
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• 1995

Dynamic and explicit ordering of strategies is a key process in modeling knowledge-level problem-solving behavior. This paper addressed the important problem of howl to make the scheduler more knowledge-intensive in a way that facilitates the acquisition, integration, and maintenance of the scheduler control knowledge. The solution a, pp.oach described in this paper involved formulating the scheduler task as a heuristic classification problem, and then implementing it as a classification expert system. By doing this, the wide spectrum of known methods of acquiring, refining, and maintaining the knowledge of a classification expert system are a, pp.icable to the scheduler control knowledge. One important innovation of this research is that of recursive heuristic classification : this paper demonstrates that it is possible to formulate and solve a key subcomponent of heuristic classification as heuristic classification problem. Another key innovation is the creation of a method of dynamic heuristic classification : the classification alternatives that are selected among are dynamically generated in real-time and then evidence is gathered for and aginst these alternatives. In contrast, the normal model of heuristic classification is that of structured selection between a set of preenumerated fixed alternatives.

• Journal of Welding and Joining
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• 제27권5호
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• pp.81-87
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• 2009

Recently, extruded aluminium-alloy panels have been used in the car bodies for the purpose of the light-weight of railway vehicles and FSW(Friction Stir Welding), which is superior to the arc weldings, has been applied in the railway vehicles. This paper presents the optimum design of the FSW process on A6005 extruded alloy for railway vehicles to improve its mechanical properties. Rotational speed, welding speed and tilting angle of the tool tip were chosen as design parameters. Three objective functions were determined; maximizing the tensile strength, minimizing the hardness and maximizing the difference between the normalized tensile strength and hardness. The tensile tests and the hardness tests for fifteen FSW experiments were carried out according to the central composite design table. Recursive model functions on three characteristic values, such as the tensile strength, the hardness difference(${\Delta}Hv$) and the difference of normalized tensile strength and ${\Delta}Hv$, were estimated according to the classical response surface analysis methodology. The reliability of each recursive function was verified by F-test using the analysis of variance table. Sensitivity analysis on each characteristic value was done. Finally, the optimum values of three design parameters were found using Sequential Quadratic Programming algorithm.

• 한국기계가공학회지
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• 제12권4호
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• pp.114-122
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• 2013

This study introduces an optimization methodology for the determination of gate location that ensures the melt flow balance within a part cavity of injection mold. A new sequential direct-search scheme based on the recursive reduction of the designer-specified gate design area is developed, and it is integrated with a commercial flow simulation tool for optimization. To quantify the level of melt flow balance, we employ the maximum difference among the fill times for the melt fronts to reach the boundary elements of part cavity as objective function. The proposed methodology is successfully applied in the case study of melt flow balancing in molding of a bar code scanner model. The result shows that the melt flow balance at the optimized gate positions is significantly improved from that for the initial gate position.

• 대한산업공학회지
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• 제20권4호
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• pp.113-134
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• 1994

A radial basis hybrid neural network (RHNN) is presented for an on-line detection of machine condition change. Two-phase modeling by RHNN is designed for describing a machine condition process and for predicting future signal. A moving block procedure is also designed for detecting a process change. A fast on-line learning algorithm, the recursive least square estimation, is introduced. Experimental results showed the RHNN could be utilized efficiently for on-line machine condition monitoring.

• Journal of the Korean Statistical Society
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• 제26권1호
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• pp.47-56
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• 1997

The asymptotic distribution of the extended Yule-Walker estimates of a mixed ARMA process is derived. Also, a recursive algorithm is derived to calculate the extended Yule-Walker estimates recursively, which is a generalization of the Levinson-Durbin algorithm.

• 한국경영과학회지
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• 제8권1호
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• pp.31-40
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• 1983

An uncertain dynamic evolving process has been a continuing challenge to decision problems. The dynamic random variable (drv) changes which characterize such a process are very important for the decision-maker in selecting a course of action in a world that is perceived as uncertain, complex, and dynamic. Using this subjective point prediction algorithm based on a modified recursive filter, the decision-maker becomes to have periodically changing plausible points with the passage of time.