• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1996년도 Proceedings of the Korea Automatic Control Conference, 11th (KACC); Pohang, Korea; 24-26 Oct. 1996
• /
• pp.283-286
• /
• 1996

This study suggests a new methodology for the fault diagnosis based on the signed digraph in developing the fault diagnosis system of a boiler plant. The suggested methodology uses the new model, fault-effect tree. The SDG has the advantage, which is simple and graphical to represent the causal relationship between process variables, and therefore is easy to understand. However, it cannot handle the broken path cases arisen from data uncertainty as it assumes consistent path. The FET is based on the SDG to utilize the advantages of the SDG, and also covers the above problem. The proposed FET model is constructed by clustering of measured variables, decomposing knowledge base and searching the fault propagation path from the possible faults. The search is performed automatically. The fault diagnosis system for a boiler plant, ENDS was constructed using the expert system shell G2 and the advantages of the presented method were confirmed through case studies.

• Ocean Systems Engineering
• /
• 제2권1호
• /
• pp.1-16
• /
• 2012

Offshore wind turbines are complex structural and mechanical systems located in a highly demanding environment. This paper proposes a multi-level system approach for studying the structural behavior of the support structure of an offshore wind turbine. In accordance with this approach, a proper numerical modeling requires the adoption of a suitable technique in order to organize the qualitative and quantitative assessment in various sub-problems, which can be solved by means of sub-models at different levels of detail, both for the structural behavior and for the simulation of loads. Consequently, in a first place, the effects on the structural response induced by the uncertainty of the parameters used to describe the environmental actions and the finite element model of the structure are inquired. After that, a meso-level FEM model of the blade is adopted in order to obtain the detailed load stress on the blade/hub connection.

• International Journal of Aeronautical and Space Sciences
• /
• 제16권4호
• /
• pp.510-519
• /
• 2015

Concerning the issue of high-dimensions, hybrid uncertainties of randomness and intervals including implicit and highly nonlinear limit state function, reliability analysis based on the hybrid uncertainty reliability mode combining with back propagation neural network (HU-BP neural network) is proposed in this paper. Random variables and interval variables are as input layer of the neural network, after the training and approximation of the neural network, the response variables are obtained through the output layer. Reliability index is calculated by solving the optimization model of the most probable point (MPP) searching in the limit state band. Two numerical cases are used to demonstrate the method proposed in this paper, and finally the method is employed to solving an engineering problem of the aerospace friction plate. For this high nonlinear, small failure probability problem with interval variables, this method could achieve a good analysis result.

• Nuclear Engineering and Technology
• /
• 제50권2호
• /
• pp.280-291
• /
• 2018

In the framework of OECD/NEA Working Group on Fuel Safety, a RIA fuel-rod-code Benchmark Phase I was organized in 2010-2013. It consisted of four experiments on highly irradiated fuel rodlets tested under different experimental conditions. This benchmark revealed the need to better understand the basic models incorporated in each code for realistic simulation of the complicated integral RIA tests with high burnup fuel rods. A second phase of the benchmark (Phase II) was thus launched early in 2014, which has been organized in two complementary activities: (1) comparison of the results of different simulations on simplified cases in order to provide additional bases for understanding the differences in modelling of the concerned phenomena; (2) assessment of the uncertainty of the results. The present paper provides a summary and conclusions of the second activity of the Benchmark Phase II, which is based on the input uncertainty propagation methodology. The main conclusion is that uncertainties cannot fully explain the difference between the code predictions. Finally, based on the RIA benchmark Phase-I and Phase-II conclusions, some recommendations are made.

• 한국광학회지
• /
• 제20권2호
• /
• pp.110-117
• /
• 2009

본 논문은 광원 및 디스플레이 기기의 중요한 품질 지표 중 하나인 색특성 측정과 관련하여 대표적인 측정량인 CIE 1931(x, y) 색좌표, CIE 1960(u, v) 색좌표, 상관색온도(correlated color temperature, CCT), 분포온도(distribution temperature)에 대한 측정불확도 평가방법과 그 산출 예를 소개한다. 분광복사계를 사용하여 광원의 상대분광분포를 측정하고 이로부터 위의 색특성 측정량을 계산하는 경우에 대하여 표준소급체계를 소개하고, 상대분광분포의 불확도가 각 색특성 측정량의 불확도로 전파되는 과정을 파장간 상관관계를 고려한 행렬식을 이용하여 일관되게 유도한 후, CIE A 표준광원, LED 백색광, LCD 백색광에 대해 측정불확도 산출 예를 보였다.

• 한국과학교육학회지
• /
• 제26권7호
• /
• pp.826-834
• /
• 2006

본 연구의 목적은 예비교사를 대상으로 하여 측정 자료의 불확실도 개념을 조사하는 것이다. 연구의 대상은 서울시내 소재한 대학의 예비교사 27명이었다. 예비교사들에게 개방적인 탐구과제를 수행하게 하고 이것을 관찰 분석하는 방법을 사용하였다. 예비교사들의 개념을 조사하기 위해 2차례의 질문지를 제시하였으며, 일부에 대해서는 면담을 실시하였다. 응답한 자료를 분석하여 불확실도의 개념요소인 대표값의 표현, 정밀과 정확, 오차의 분석, 불확실도의 전파 등으로 나누어 예비교사들의 개념을 정리하였다. 연구결과에 의하면 예비교사들은 대표값의 표현에서 과학자들의 개념과 다른 개념을 가지고 있었으며, 정밀과 정확을 혼돈하여 사용하고 정밀한 실험을 실시하는데 소홀하였다. 또한 오차를 나열할 뿐 그 원인이나 실험에 영향을 미치는 정도를 분석하는 경우는 거의 없었다. 이러한 연구결과는 예비교사와 학생들이 올바른 개념을 가지게 하기 위한 교육과정이나 교수 학습 자료 개발에 활용될 수 있을 것이다.

• ETRI Journal
• /
• 제42권1호
• /
• pp.108-117
• /
• 2020

This study proposes a robust range-only beacon mapping method for registering the locations of range-only beacons automatically. The proposed method deals with the multipath propagation of signals from range-only beacons using the range-only measurement association (RoMA) and an unscented Kalman filter (UKF). The RoMA initially predicts the candidate positions of a range-only beacon. The location of the range-only beacon is then updated using the UKF. With the proposed method, the locations of range-only beacons are accurately estimated in a multipath environment. The proposed method also provides the location uncertainty of each range-only beacon. Simulation results using the model for multipath propagation and experimental results in a real indoor environment verify the performance of the proposed method.

• 한국지능시스템학회논문지
• /
• 제8권5호
• /
• pp.39-44
• /
• 1998

이동 로봇의 운행을 위해서 이동 로봇의 절대 위치를 결정하는 것이 중요하다. 본 논문에서는 신경회로망을 이용하여 랜드마크의 영상을 통해 이동 로봇의 위치를 결정하는 방법을 제안한다. 픽셀의 불확시한 값, 부정확한 카메라 조정과 렌즈의 왜곡으로 인해 이동 로봇의 위치를 결정에 있어서 위치 오차가 생기게 된다. 이러한 오차를 줄이기 위해서 BPNN(Back Propagation Neural Network)를 사용하는 방법을 제안한다. 기존의 방법과 비교하여 우수성을 보여주기 위해서 실험결과를 보여준다.

• 대한전기학회논문지:시스템및제어부문D
• /
• 제52권8호
• /
• pp.482-491
• /
• 2003

In this paper are presented kinematic and dynamic modeling and path-tracking of four-wheeled mobile robots with 2 d.o.f haying the limited drive-torques. Controllability of wheeled-mobile robots is revealed by the kinematic model. Instantaneously coincident coordinate system, force/torque propagation and Newton's equilibrium law are used to drive the dynamic model. When drive-torques generated by inverse dynamics exceed the limitation, we make wheeled-mobile robots follow the reference path by modifying the planned reference trajectory with time-scaling. The controller is introduced to compensate for error owing to modeling uncertainty and measurement noise. And simulation results prove that method proposed by this paper is efficient.

• 대한조선학회논문집
• /
• 제57권1호
• /
• pp.1-7
• /
• 2020

In general, an inspection schedule is established based on the long-term fatigue life during the design stage. However, in the design stage, it is difficult to clearly identify the uncertainty factors affecting long-term fatigue life. In this study, the probabilistic fatigue life assessment was conducted in accordance with the methodology of DNV-GL. Firstly, The initial crack distribution estimated through the initial crack propagation analysis was updated by reflecting the results of crack inspection. Secondly, the updated crack distribution was compared with the initial crack distribution, and the probability of failure was updated with the effect of crack inspection.