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합성곱 신경망 알고리즘을 활용한 베어링 다중 고장 진단 모델 개발
이상원(S. W. Lee),이창호(C. H. Lee),김진우(J. W. Kim),김수종(S. J. Kim) Korean Society for Precision Engineering 2021 한국정밀공학회 학술발표대회 논문집 Vol.2021 No.11월
회전 기계에서 베어링은 전체 기계시스템의 구동 및 제어에 핵심적인 역할을 하므로 장비의 안전하고 지속적인 작동을 위해서는 베어링의 유지 보수 및 상태 모니터링이 필수적이다. 본 연구에서는 베어링의 예상치 못한 파손으로 인한 기계시스템의 손상에 대비하기 위해, 대표적인 딥러닝 알고리즘인 Convolutional Neural Networks (CNN)을 활용한 베어링의 고장 상태 및 고장 종류 진단 모델을 개발하였다. 베어링 시뮬레이터를 사용하여, 정상 및 고장 상태의 베어링의 회전운동을 구현하였으며, 각 베어링 상태에서의 신호 데이터는 2 개의 가속도 센서를 X, Y 축에 고정시켜 수집하였다. 고장 상태는 4 종류로 볼, 케이지, 외륜, 내륜 고장을 부품에 모사하였으며, 정상 및 고장 상태의 데이터 세트는 각각 500 개씩 수집하였다. 베어링 상태의 시계열 데이터 신호는 Short Time Fourier Transform (STFT) 기법으로 전처리 하였고 두 단계의 CNN 알고리즘을 활용하여 진단 모델을 개발하였다. 첫 번째 단계에서는 정상 및 고장 상태를 분류할 수 있는 모델로 설계하였고 두 번째 단계에서는 고상 상태로 분류된 데이터 세트에 대해서 4가지의 고장 종류를 분류할 수 있는 모델로 설계하였다. 각 단계에서 사용된 CNN 알고리즘 설계는 동일하며, K-fold Cross Validation 을 통해 개발된 모델에 대한 검증을 수행하였다.
경사냉각면에 따른 함수정방형내의 동결현상에 관한 실험적 연구
이춘희,김종준,김병철,Lee, C.H.,Kim, J.J.,Kim, B.C. 대한설비공학회 1997 설비공학 논문집 Vol.9 No.4
It was studied the phenomena of transient freezing of an inclined water-saturated enclosure. One side of the test section was cooled and the other sides were insulated. The effects of the initial temperature, the inclination angle on the temperature field and the shape of the ice-water interface were observed. In the beginning of freezing, with increasing the inclination angle the freezing rate was increased and in the stable density layer centered $4^{\circ}C$, the freezing was fast as the convective fluid flow became small. When the initial temperature was above the $4^{\circ}C$, the frozen thickness in the upper part of inclined surface was thinner than that in the lower part, but with time the frozen thickness of upper part was thicker than that of lower part, below the $4^{\circ}C$, the frozen thickness in the upper part was thicker than that of lower part from the begining, and above the $8^{\circ}C$ in the beginning upper part was thinner with concave, but with time thicker the upper part, vanishing concave.
최병철(B.C.Choi),이춘희(C.H.Lee),박희주(H.J.Park),정명근(M.G.Jung),신병선(B.S.Shin) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Recently, as people pay attention to the environmental pollution, the emission of diesel engine has become a serious problem. We carried out the performance evaluation test of Diesel Oxidation Catalysts (DOC) for Diesel Engine equipped Vehicles. DOC that was basically coated with Pt catalyst was manufactured with various washcoat materials. It was found that CO conversion efficiency depends on temperature, but THC conversion is dominated by temperature and space velocity. THC and CO conversion efficiency of aged catalysts increased with addition of Zr03 and Zeolite B in the washcoat. We found that DOC performance changes by coating technique even if it is same washcoat materials. DOC that the durability performance coats in suitable washcoat coating technology in high temperature was superior.<br/>
점화플러그 중심전극의 극성이 전극마모 및 천연가스 엔진성능에 미치는 영향
김영민(Y.M.Kim),이장희(J.H.Lee),이춘희(C.H.Lee),신동성(D.S.Shin),정익재(I.J.Chung) 한국자동차공학회 1998 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1998 No.11_1
In the present work, a durability test has been performed to investigate the effects of different polarities of plug central electrode on the electrode wear with gasoline engine which electronic characteristics of spark plug is similar to natural gas engine. And a series of experiments have been performed to investigate the effects of different polarities on the ignition pattern and the performance of natuarl gas engine in lean regions.<br/> The results show that electrode wear of positive central polarity is much less than conventional negative polarity and different central polarities have very little effects on the engine performance such as lean limit and IMEP in lean regions.<br/>
김영민(Y.M.Kim),이장희(J.H.Lee),이춘희(C.H.Lee),신동성(D.S.Shin),정익재(I.J.Chung) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.11_1
Natural gas is an attractive fuel in view of abundant resources and low emission. So in order to meet stricter cmission regulation on smoke and particulate matter from Diesel engine with lower CO₂ emission. natural gas has been applicated to heavy duty Diesel engine.<br/> This study describes the contents of the conversion of Diesel engine to spark ignited engine and effect of ignition timing. air fuel ratio and injection timing. For ease of experimental variable applications. IIL six cylinder engine was converted to experimental single cylinder engine.<br/>