改良隨機遞減法於非定常環境振動之系統模態參數識別

Modal Identification from Nonstationary Ambient Vibration Data Using Improved Random Decrement Technique

江達雲(Dar-Yun Chiang) ； 林章生(Chang-Sheng Lin) ； 甄和宏(Ho-Hung Chen)

《航空太空及民航學刊.系列B》 44卷2期 (2012/12) Pp. 67-74

https://doi.org/10.6124/12-0803-699

摘要

隨機遞減法於模態參數識別之應用在過去僅限於激勵信號為定常白訊，且此法的有效性往往受限於時域信號的長度不足。本文針對隨機遞減法之樣本擷取提出改良方法，使得吾人可以在有限的時域信號內，獲得更多的樣本進行平均分析，以獲致更好的識別結果。此外，考慮激勵信號為零均值之非定常過程，其響應信號經改良隨機遞減法處理後可證明與脈衝響應或自由振動衰減響應有相同的數學形式，可進而利用Ibrahim時域模態參數識別法進行模態參數的識別。經數值模擬結果顯示，在適當的非定常環境振動情況下，本文所提出之改良方法可獲得良好的模態參數識別結果。

關鍵字

改良隨機遞減法 ； 非定常環境振動 ； 模態參數識別 ； Ibrahim時域法

並列摘要

An effective identification method is developed for determining the modal parameters of a structure from its measured nonstationary ambient vibration data. The conventional Random Decrement Technique (RDD) is applicable to linear systems excited by stationary white inputs only, and its effectiveness is usually limited by the length of measurement records available. It is shown that if the ambient excitation can be modeled as a zero-mean nonstationary process, then the nonstationary cross random decrement signatures of structural response are in the same mathematical form as that of free vibration of the structure, from which modal parameters of a system can then be identified. To improve the accuracy of identification, a modification of the sampling procedure in RDD is presented such that more response samples can be obtained to perform averaging analysis. Numerical simulations confirm the validity of the proposed modal-identification method from nonstationary ambient response data.

並列關鍵字

Modified random decrement technique ； Nonstationary ambient vibration ； Modal-Parameter identification ； Ibrahim time-domain method

參考文獻

Vandiver, J. K., Dunwoody, A. B., Campbell, R. B., and Cook, M. F., “A Mathematical Basis for the Random Decrement Vibration Signature Analysis Technique,” Journal of Mechanical Design, Vol. 104, April 1982, pp. 307-313.

Chiang, D.Y. and Cheng, M. S., “Modal parameter identification from ambient response,” AIAA Journal, Vol. 37, 1999, pp. 513-515.

Chiang, D. Y. and Lin, C. S., “Identification of Modal Parameters from Nonstationary Ambient Vibration Data Using Correlation Technique,” AIAA Journal, Vol. 46, No. 11, 2008, pp. 2752-2759.

Lin, C. S. and Chiang, D. Y., “A modified Random Decrement Technique for Modal Identification from Nonstationary Ambient Response Data Only,” Journal of Mechanical Science and Technology, Vol.26, No.6, 2012, pp. 1687-1696.

Chiang, D. Y. and Lin, C. S., “Identification of Modal Parameters from Nonstationary Ambient Vibration Data Using the Channel-expansion Technique,” Journal of Mechanical Science and Technology, Vol.25, No.5, 2011, pp. 1307-1315.