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Performance Evaluation of an Entropy-Based Structural Health Monitoring System Utilizing Composite Multiscale Cross-Sample Entropy
(2019-01-01)
Lin, Tzu-Kang
;
Chien, Yi-Hsiu
;
土木工程學系
;
Department of Civil Engineering
The aim of this study was to develop an entropy-based structural health monitoring system for solving the problem of unstable entropy values observed when multiscale cross-sample entropy (MSCE) is employed to assess damage in real structures. Composite MSCE was utilized to enhance the reliability of entropy values on every scale. Additionally, the first mode of a structure was extracted using ensemble empirical mode decomposition to conduct entropy analysis and evaluate the accuracy of damage assessment. A seven-story model was created to validate the efficiency of the proposed method and the damage index. Subsequently, an experiment was conducted on a seven-story steel benchmark structure including 15 damaged cases to compare the numerical and experimental models. A confusion matrix was applied to classify the results and evaluate the performance over three indices: accuracy, precision, and recall. The results revealed the feasibility of the modified structural health monitoring system and demonstrated its potential in the field of long-term monitoring.
Entropy-Based Structural Health Monitoring System for Damage Detection in Multi-Bay Three-Dimensional Structures
(2018-01-01)
Lin, Tzu-Kang
;
Lainez, Ana Gabriela
;
土木工程學系
;
Department of Civil Engineering
In this paper, a structural health monitoring (SHM) system based on multi-scale cross-sample entropy (MSCE) is proposed for detecting damage locations in multi-bay three-dimensional structures. The location of damage is evaluated for each bay through MSCE analysis by examining the degree of dissimilarity between the response signals of vertically-adjacent floors. Subsequently, the results are quantified using the damage index (DI). The performance of the proposed SHM system was determined in this study by performing a finite element analysis of a multi-bay seven-story structure. The derived results revealed that the SHM system successfully detected the damaged floors and their respective directions for several cases. The proposed system provides a preliminary assessment of which bay has been more severely affected. Thus, the effectiveness and high potential of the SHM system for locating damage in large and complex structures rapidly and at low cost are demonstrated.
Application of multi-scale (cross-) sample entropy for structural health monitoring
(2015-08-01)
Lin, Tzu-Kang
;
Liang, Jui-Chang
;
土木工程學系
;
Department of Civil Engineering
This study proposes an information-theoretic structural health monitoring (SHM) system based on multi-scale entropy (MSE) and multi-scale cross-sample entropy (MSCE). By measuring the ambient vibration signal from a structure, the damage condition can be rapidly evaluated via MSE analysis. The damage location can then be detected by analyzing the signals of different floors under the same damage condition via MSCE analysis. Moreover, a damage index is proposed to efficiently quantify the SHM process. Unlike some existing SHM methods, no experimental database or numerical model is required. Instead, a reference measurement of the current stage can initiate and launch the SHM system. A numerical simulation of a four-story steel structure is used to verify that the damage location and condition can be detected by the proposed SHM algorithm, and the location can be efficiently quantified by the damage index. A seven-story scaled-down benchmark structure is then employed for experimental verification. Based on the results, the damage condition can be correctly assessed, and average accuracy rates of 63.4 and 86.6% for the damage location can be achieved using the MSCE and damage index methods, respectively. As only the ambient vibration signal is required with a set of initial reference measurements, the proposed SHM system can be implemented practically with low cost.
直流磁控電漿濺鍍腔體中多重尺度及物理現象之模擬及實驗研究(I)
(2004)
吳宗信
;
WU JONG-SHINN
;
交通大學機械工程研究所
工業界的應用以及學術界的研究中，有許多實用的系統涉及多重物理現象的交互作用(例如紊流、熱流、化學、機械、濺鍍、稀薄氣體、電磁或電漿製程)。在一些系統中，其時間及長度尺寸會相差數個次方。而這些跨物理量以及多重尺寸的數值模擬需要發展出具有經驗的模型以及方法來模擬這些交互作用。而且根據適當的軟硬體技術來發展有效率的數值演算法以及先進的計算技術。因為這些模擬需要相當大的計算量，因此通常需要有效率的平行化運算來滿足需求。本計畫為三年期計畫，將會詳細地模擬利用氬氣為工作氣體及銅為靶材的DC magnetron電漿濺鍍腔體之多尺寸及跨物理模擬；並建置一座標準(model)電漿濺鍍腔體，進行電漿參數的量測，以為模擬之比對標準。本研究的重要性與關聯性與現今工業界常用的物理氣相沉積等類似製程設備有極大的相關性。這些現象包括氬氣在稀薄氣體環境下放電所產生的電漿、帶能量的離子從氬氣電漿轟擊靶材所產生的濺鍍現象、被濺鍍出的原子在腔體中的傳輸以及被濺鍍出的原子在晶片上的沉積。模擬這些物理的相關方法包括流場解(靜電的Poisson方程式及靜磁的vector potential Poisson equation)，加上因在微量離子化的稀薄氣體，模擬非平衡現象之的電漿模擬法PIC/MC (Particle-In-Cell/Monte Carlo)、模擬靶材濺鍍的分子動力法MD (Molecular Dynamics)以及計算被濺鍍原子傳輸的直接模擬蒙地卡羅法 DSMC (Direct Simulation Monte Carlo)。而上述以分子及解統御方程式等模擬法需要藉由平行化來克服大量的計算時間。而各個領域的模擬必需經由本計畫之實驗結果或文獻上相關的模擬結果來驗證。本計畫的最後目標是結合上述的模擬法，以得到DC-magnetron 電漿濺鍍腔體內多重尺寸及多重物理之進一步瞭解。簡言之，所提出的計畫包括：第一年，發展並驗證二個分子模擬法之程式，包括電漿模擬程式以及靶材濺鍍的分子動力法等等。此外，設計並建置一座DC-magnetron濺鍍系統。第二年，開始發展相關上述相關模擬程式之平行化版本，並利用本實驗室架設的叢集式電腦進行測試。我們將會測試幾個不同領域的大尺寸計算。此外，利用量子化學法推導出銅原子團簇與背景氣體(氬氣)之間的碰撞行為參數，此參數在接下來的DSMC模擬中會使用到。接下來完整的平行化分子動力法將會得到濺鍍的資料並轉化成濺鍍的產生率。此外，我們將會安裝一個Langmuir探針系統來量測相關的電漿參數以便未來程式的驗證。第三年，繼續擴大電漿的量測。最後經由靶材表面相關的濺鍍資料來結合平行化的電漿模擬模組以及平行化的直接模擬蒙地卡羅法。

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