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김태진(Taejin Kim),윤병동(Byeng D. Youn),우시형(Sihyeong Woo) 대한기계학회 2015 大韓機械學會論文集A Vol.39 No.3
시간영역반사계(time domain reflectometry, TDR)는 한 쌍의 도선에 입력한 파동의 진행 및 반사 현상을 분석하여 도선의 상태를 감시하는 기술이다. 이를 이용하여 본 논문에서는 파이프 연결부의 누수감지 시스템을 개발하였다. 파이프 표면에 설치된 도선을 통해 TDR 신호를 송신하면, 누수에 의해 도선의 특성 임피던스가 달라지는 지점에서는 반사가 일어나게 되고 이를 기반으로 누수의 발생지점을 추론할 수 있다. 이를 위해, 유한차분 시간영역법(finite difference time domain, FDTD)을 이용한 전진 모델을 만들고, 이의 역문제를 풀어 누수 위치를 추론하였다. Time domain reflectometry (TDR) is widely used for wire failure detection. It transmits a pulse that is reflected at the boundaries of different characteristic impedances. By analyzing the reflected signal, TDR makes it possible to locate the failure. In this study, TDR was used to detect the water leakage at a pipe joint. A wire attached to the pipe surface was soaked by water when a leak occurred, which affected the characteristic impedance of the wet part, resulting in a change in the reflected signal. To infer the leakage from the TDR signal, we first developed a finite difference time domain-based forward model that provided the output of the TDR signal given the configuration of the transmission line. Then, by solving the inverse problem, the locations of the leaks were found.
Jesnen-Shannon Divergence를 이용한 PHM 실험 디자인
김태진(Taejin Kim),윤병동(Byeng D. Youn) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
The most critical aspect in system condition diagnosis is to be aware of the signal change as the system degrades and to classify the signal into a proper state. Most condition diagnosis studies to date have focused on accurate classification of the tangled data set; these studies have paid less attention to experimental design, which could determine the quality of the signal. This study deals with experimental design for condition diagnosis that allows data separation between different health conditions in the sensing step. For this purpose, an experimental design method is proposed from an information theoretic point of view to find the sensing locations that give the best information for data separation. To measure the goodness of the design point, the Jensen-Shannon (JS) divergence is adopted as the utility function. The JS divergence is relevant to condition diagnosis in three ways. First, the JS divergence is good at measuring the separation of two distributions. Second, the boundedness of the JS divergence enables balanced separation between the states. Third, the symmetric property of the JS divergence is relevant for measurement of the overall separation of the distance between states. With the JS divergence as the utility function, the greedy algorithm with a Gaussian process is used for efficient optimization of the design criterion. Finally, the proposed method is validated through the case study of the gearbox condition diagnosis.
TDR 신호와 베이지안 추론을 이용한 파이프 누수 감지 시스템 개발
김태진(Taejin Kim),우시형(Sihyung Woo),윤병동(Byeng D. Youn) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
Time domain reflectometry (TDR) is widely used wire fault detection device. It sends pulse reflecting at the boundary of different characteristic impedances. By analyzing the reflected signal, TDR allows to locate the fault. In this paper, TDR is used to detect the water leakage at pipe joint. A wire attached on the pipe surface is soaked by water when the leakage occurs and it affects the characteristic impedance of the wet part, resulting in the change of the reflected signal. To infer the leakage from the TDR signal, we first develop FDTD based forward model which provides output of the TDR signal given the configuration of the transmission line. Then we adopt Bayesian inference scheme to solve the inverse problem. The Bayesian inference gives the probability of the fault location and the resistance at fault.
고전압 리튬이온 배터리의 동적 발열량 측정을 위한 열량계 개발
김현재(Hyunjae Kim),김태진(Taejin Kim),윤병동(Byeng D. Youn) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
Lithium-ion battery that applied to high power application such as electric vehicle produce large amount of heat that can causes poor performance or damage to lithium-ion battery. To prevent the adverse effects related to heat from the battery, several thermal model and its variations are developed and applied for prediction of temperature behavior. The thermal models based on theoretical approach generally can approximate heat generation rate at steady current state and semi -transient current state. However, in fully dynamic current state such as real driving condition, charging and discharging operations are quickly repeated then theoretical based thermal models give unfavorable approximation of temperature behavior. In this research, we introduce a hardware and software of a calorimeter for heat generation measurement in dynamic current state. For this purpose, we build a specialized calorimeter using thermoelectric module and control algorithm. This apparatus developed considering two a spects, hardware and software. First, the characteristics of thermoelectric module is figured through the calibration using electric heater. The algorithm for battery temperature is devised. The combining technique of feed-forward and PID control logic is proposed here. The performance of proposed calorimeter is evaluated using 5Ah pouch type lithium-ion battery and theoretical thermal model, and heat generation rate of the battery in dynamic current state is measured and compared with theoretical result.