• 한국군사과학기술학회지
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• 제3권1호
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• pp.138-145
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• 2000

This paper presents a robust fault diagnosis and fault tolerant control method for the control systems in closed-loop affected by unknown inputs or disturbances. The fault diagnostic scheme is based on the disturbance-decoupled state estimation using a 2-stage state observer for state, actuator bias and sensor bias. The estimated bias show the occurrence time, location and type of the faults directly. The estimated state is used for state feedback to achieve fault tolerant control against the faults. Simulation results show that the method has definite fault tolerant ability against actuator and sensor faults, moreover, the faults can be detected on-line, isolated and estimated simultaneously.

• Journal of the Korean Statistical Society
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• 제19권2호
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• pp.151-159
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• 1990

Regression diagnostics often involves assesment of the changes that result from deleting multiple cases. Diagnostic mehtodology based on global influence measure, however, needs prohibitive computing time. As an alternative, Cook (1986) developed influence approach in which it is checked whether a minor modification of specifiation influences key results of an analysis. In line with Cook's development, we propose and study an inflence derivative method that yields both the magnitude and direction of case influences. The utility of our methodology is highlighted when case influence derivatives are plotted in a lower demensional space. Such plots are especially effective in unmasking "masked" observations in least squares regression and in robust regression also. We give several illustrations.strations.

• Structural Engineering and Mechanics
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• 제25권6호
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• pp.691-716
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• 2007

The purpose of the present work is to establish a method for predicting the location and depth of a crack in a circular cross section beam by only considering the frequencies of the cracked beam. An accurate knowledge of the material properties is not required. The crack location and size is identified by finding the point of intersection of pulsation ratio contour lines of lower vertical and horizontal modes. This process is presented and numerically validated in the case of a simply supported beam with various crack locations and sizes. If the beam has structural symmetry, the identification of crack location is performed by adding an off-center placed mass to the simply supported beam. In order to avoid worse diagnostic, it was demonstrated that a robust identification of crack size and location is possible if two tests are undertaken by adding the mass at the left and then right end of the simply supported beam. Finally, the pulsation ratio contour lines method is generalized in order to be extended to the case of rectangular cross section beams or more complex structures.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1463-1467
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• 2005

This paper proposes an analytical redundancy technique for fault diagnostics of the sensor in steer-by-wire system. We use incorporating vehicle dynamics modeling into the design of a diagnostic system for steer-by-wire system. The use of a model of vehicle dynamics improves the speed and accuracy of the diagnoses. The proposed fault diagnostics algorithm is based on parity-space methods to generate residuals. To reduce the effects of modeling uncertainty and dynamic transients, the residuals are subject to filtering. We construct diagnostic system consisting residual threshold for detection and isolator with using the directional residual vector.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1989년도 한국자동제어학술회의논문집; Seoul, Korea; 27-28 Oct. 1989
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• pp.805-812
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• 1989

An efficient diagnostic approach for real-time operation aiding expert system in chemical process plants is discussed. The approach is based on the hybrid of the simplified symptom tree(SST) and the fault consequence digraph(FCD), representation of propagation patterns of fault states. The SST generates fault hypothesis efficiently and the FCD resolve the real fault accurately. Frame based knowledge representation and object-oriented programming make diagnostic system general and efficient. Truth maintenance system enables robust pattern matching and provides enhanced explain facilities. A prototype expert system for supports operation of naphtha furnaces process, called OASYS, has been built and tested to demonstrate this methodology. Utilization of diversified process symbolic data, produced using dynamic normal standards, overcomes the problem of qualitative Boolean reasoning and enhance the applicability.

• 자원ㆍ환경경제연구
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• 제9권2호
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• pp.373-391
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• 2000

This paper investigates the existence of a long-run relationship between world oil price and consumer price index for Korea during 1983~1999. The cointegration and error correction modelling approaches have been applied. Empirical results suggest that there exists a long-run relationship among world oil prices. consumer prices, M2 and a production gap variable. The dynamic behavior of the relationship has been investigated by estimating a error correction model, in which the error correction term have been found significant. The error correction model has also been found to be robust as it satisfy almost all relevant diagnostic tests.

• 한국수자원학회논문집
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• 제35권4호
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• pp.425-442
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• 2002

새만금간척지역은 동경 $126^{\circ}10'{\sim}126^{\circ}50'$와 북위 $35^{\circ}35'{\sim}36^{\circ}05'$ 위치하고 있다. 새만금간척지역은 대조차가 5.6m 이고 최대 조유속은 $1.41m\;s^{-1}$ 이다. 조간대 침전물의 대부분은 금강, 만경, 동진강으로부터 유입되고 있다. 이 지역의 저질은 실트질 모래로 구성되어 있다. 동절기의 바람은 북서풍이 우세하다. 새만금간척면적은 40,100ha 이고 방조제의 길이는 33km이다. 본 연구의 목적은 강 진단모델과 예보모델에 의하여 간척전 후의 잔차류의 계절변화를 규명하는 것이다.

• 전기학회논문지
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• 제62권7호
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• pp.987-993
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• 2013

Integrity of the control and instrumental cables in nuclear power plant is important to maintain the stability of the nuclear power plants. In order to diagnose the integrity of the cables, the diagnostic methods based on reflectometry have been studied. The reflectometry is a non-destructive method and it is applicable to diagnose the live cables. We introduce a Gaussian enveloped linear chirp reflectometry to diagnose the cables in the nuclear power plants. In this paper, we estimate the instantaneous frequency of the Gaussian enveloped linear chirp signal by using the weighted robust least squares filtering to localize the impedance discontinuities in the class 1E instrumental cable.

• Journal of Information Processing Systems
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• 제15권4호
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• pp.820-832
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• 2019

Estimation of accurate blood volume flow in ultrasound Doppler blood flow spectrograms is extremely important for clinical diagnostic purposes. Blood volume flow measurements require the assessment of both the velocity distribution and the cross-sectional area of the vessel. Unfortunately, the existing volume flow estimation algorithms by ultrasound lack the velocity space distribution information in cross-sections of a vessel and have the problems of low accuracy and poor stability. In this paper, a new robust ultrasound volume flow estimation method based on multigate (RMG) is proposed and the multigate technology provides detail information on the local velocity distribution. In this method, an accurate double iterative flow velocity estimation algorithm (DIV) is used to estimate the mean velocity and it has been tested on in vivo data from carotid. The results from experiments indicate a mean standard deviation of less than 6% in flow velocities when estimated for a range of SNR levels. The RMG method is validated in a custom-designed experimental setup, Doppler phantom and imitation blood flow control system. In vitro experimental results show that the mean error of the RMG algorithm is 4.81%. Low errors in blood volume flow estimation make the prospect of using the RMG algorithm for real-time blood volume flow estimation possible.

• Ocean and Polar Research
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• 제23권3호
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• pp.223-242
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• 2001

This paper presents the depth-mean monthly variation in the circulation of the Yellow Sea and the East China Sea computed using a robust diagnostic model. The mixed three-dimensional finite-difference Galerkin function model developed by Lee et at. (2000, 2001) has been extended to take into account baroclinic effects and then used to calculate the depth-mean flow fields as part of the results. In addition to M2 tide and oceanic flows previously considered, the model has been driven by the monthly mean wind stresses from Na and Seo (1998), the density gradient calculated based on by GDEM data set released by US Navy. Model results are very encouraging in that many of observed features including Jeju Cyclonic Gyre and frontal eddies along the shelfside of the Kuroshio main stream and west of Kyushu, are satisfactorily reproduced and are expected to be of value in interpreting observations in various oceanograhic disciplines.