臺灣博碩士論文加值系統

結構系統的動態特性可藉由其自然頻率、阻尼比及模態振形加以描述，而一般模態參數識別法須同時利用激勵資料及響應資料來識別模態參數。但有許多工程結構在環境振動作用下，僅能獲得其響應資料。因此無需激勵信號的量測而直接由響應資料識別模態參數，為本文探討之重點。
本文考慮當線性結構系統在非白訊環境振動下，若激勵信號可假想由平穩白訊經一「濾波系統」所產生，則可將原結構之響應信號視為平穩白訊激勵信號經過一「合成系統」所產生的響應信號。因此可用相關函數方法求出相對應於自由振動衰減的信號，並利用Ibrahim時域模態參數法求出「合成系統」之模態參數。再利用結構模態的正交性及結構參數的穩定性，來區分「合成系統」中所含的結構參數和激勵參數。

Dynamical systems can be characterized by their modal parameters, which include natural frequencies, damping ratios and mode shapes. Identification of system characteristics is usually accomplished using both input and output data from the structural system. In many cases, however, only output measurements are available for structures under ambient conditions. It can be shown that if the input signals can be modeled as white noise the theoretical auto- and cross-correlation functions of structural response have the same mathematical form as free vibration of the structure. This thesis is considered modal parameter identification using ambient data. This is accomplished via adding, in cascade, a pseudo-force system to the structure’s system under consideration. The input to the pseudo-force system is white noise and the output of which is the actual force(s) applied to the structure. The structure’s responses solely are then used to identify the combined system. Structural parameters are then sorted out from identification result by using stability property of structural modes or orthogonality property of mode shapes.

目錄：
中文摘要……………………………………………………………….....i
英文摘要………………………………………………………………....ii
誌謝……………………………………………………………………...iii
目錄……………………………………………………………………...iv
表目錄…………………………………………………………………...vi
圖目錄………………………………………………………………….viii
第一章 緒論……………………………………………………………1
1-1 引言………………………………………………………….…1
1-2 文獻回顧…………………………………………………….…3
1-3 研究目的及方法…………………………………………….…4
1-4 論文內容…………………………………………………….…5
第二章 Ibrahim時域法之理論………………………………………...7
2-1 引言………………………………………………………… …7
2-2 Ibrahim時域法…………………………………………………7
2-3 Ibrahim時域法之探討………………………………………..13
第三章 一般環境振動下之模態參數識別…………………………..16
3-1 引言…………………………………………………………...16
3-2 NExT方法之應用……………………………………………17
3-3 受非白訊激勵信號理論推導………………………………...19
第四章 區分結構模態與激勵信號模態……………………………..22
4-1 引言………………………………………………………… ..22
4-2 利用結構模態正交性………………………………………. .22
4-3 利用模型縮減………………………………………………...26
4-4 利用結構模態穩定性…………………………………… ..…30
第五章 數值模擬結果與討論………………………………………..32
5-1 引言…………………………………………………………...32
5-2 比例阻尼系統………………………………………………...33
5-3 非比例阻尼系統……………………………………………...35
第六章 結論………………………………………………………..…38
參考文獻……………………………………………………………..…40
表目錄:
表 5-1 六個自由度(比例阻尼)結構受非白訊激勵信號之
識別結果(噪訊比:0%)…………...…………………………..42
表 5-2 六個自由度(比例阻尼)結構受非白訊激勵信號之
識別結果(噪訊比:20%)………...……………………………43
表 5-3 六個自由度(比例阻尼)結構受非白訊激勵信號對
質量矩陣正交性……………………………………………..44
表 5-4 六個自由度(比例阻尼)結構受非白訊激勵信號模
勁度矩陣正交性……………………………………………..44
表 5-5 六個自由度(比例阻尼)結構受非白訊激勵信號模
型縮減後對質量矩陣正交性………………………………..45
表 5-6 六個自由度(比例阻尼)結構受非白訊激勵信號模
型縮減後對勁度矩陣正交性………………………………..45
表 5-7 六個自由度(比例阻尼)結構受非白訊激勵信號結
構模態定性…………………………………………………..46
表 5-8 雙自由度(非比例阻尼)結構受非白訊激勵信號識
別結果與Ibrahim[14]結果比較(噪訊比:0%)……………….47
表 5-9 雙自由度(非比例阻尼)結構受非白訊激勵信號之
識別結果(噪訊比:20%)……………………………………...48
表 5-10 雙自由度(非比例阻尼)結構受非白訊激勵信號對
質量矩正交性………………………………………………..49
表 5-11 雙自由度(非比例阻尼)結構受非白訊激勵信號對
勁度矩正交性…………...…………………………………...49
表 5-12 雙自由度(非比例阻尼)結構受非白訊激勵信號
結構模態穩定性…………………………………...……….50
圖目錄:
圖 3-1 合成系統圖…………………………………………………...51
圖 5-1 白訊激勵之樣本函數圖…………………………….………..51
圖 5-2 白訊樣本之能量頻譜圖……………………………………...51
圖 5-3 六個自由度結構系統圖……………………………………...52
圖 5-4 六個自由度(比例阻尼)結構所考慮之激勵樣本函
數圖…………………………………………………………..53
圖 5-5 六個自由度(比例阻尼)結構假想激勵信號之系統
圖……………………………………………………………..53
圖 5-6 六個自由度(比例阻尼)結構受非白訊激勵結構第
1、3、6個自由度之響應圖(噪訊比:0%)……………………..54
圖 5-7 六個自由度(比例阻尼)結構受非白訊激勵結構第
1、3、6個自由度之響應相關函數圖(噪訊比:0%)…………...55
圖 5-8 六個自由度(比例阻尼)結構受非白訊激勵結構第
1、3、6個自由度之響應圖(噪訊比:20%)…………………….56
圖 5-9 六個自由度(比例阻尼) 結構受非白訊激勵結構第
1、3、6個自由度之響應相關函數圖(噪訊比:20%)………….57
圖 5-10 六個自由度(比例阻尼) 結構受非白訊激勵結構
之模態振形圖………………………………………………58
圖 5-11 雙自由度結構系統圖……………………………………….59
圖 5-12 雙自由度結構所考慮之激勵樣本函數圖………………….59
圖 5-13 雙自由度(非比例阻尼)結構假想激勵信號之系
統圖……...………………………………………………….59
圖 5-14 雙自由度(非比例阻尼)結構受非白訊激勵結構
響應圖(噪訊比:0%)………………………………………...60
圖 5-15 雙自由度(非比例阻尼)結構受非白訊激勵結構
響應之響應相關含數圖圖(噪訊比:0%)…………………...61
圖 5-16 雙自由度(非比例阻尼)結構受非白訊激勵結構
響應圖(噪訊比:20%)……………………………………….62
圖 5-17 雙自由度(非比例阻尼)結構受非白訊激勵結構
響應之響應相關含數圖圖(噪訊比:20%)………………….63

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