Based On Wavelet Transform Method Of Operating Modal Parameter Identification

Nowadays, based on modal analysis of vibration more and more scientific research institutions and enterprises of great importance, and modal parameter identification is one of the most important part of the foundation. Owing to the signals by practical testing could more objectively represent the intrinsic properties and boundary conditions of structures, the operational modal parameters identification become the latest research and developing direction in the field of modal parameters identification.Based on the reasons mentioned above, the operational modal parameters identification using wavelet analysis method is presented in this paper, the main content of which could be summarized as following:The accomplishments about operational modal parameters identification, both home and abroad, in the past resent years are systematically summarized here, and thus the research contents which to be later analyzed in this paper are determined.The basic theory of wavelet analysis is summarized systematically in the view of operational modal parameters identification. The property of wavelet time-frequency localization is deduced theoretically, and the relationship between wavelet resolution in time domain and that of frequency is analyzed. On the condition that the basic requirement of parameters identification is met, the Morlet wavelet is chosen as the mother wavelet to be used for system modal parameters identification based on wavelet selection principle after the various properties of several types of wavelets are analyzed and compared.Wavelet ridge extraction method is deeply analyzed in this paper that lays the foundation for exhibiting the method of modal parameters identification using wavelet method. The basic method for extracting wavelet ridge is exhibited on basis of the stationary phase theory. After analysis the differences among the various wavelet ridge extraction methods, the ant colony algorithm is chosen for extracting wavelet ridge. The simulation test turn out that ant colony algorithm not only could extract the wavelet ridge well, but also has a high noise resistance.The wavelet transformation used for identifying operational modal is established in this paper. A simulation example of 3DOFs system is presented which verifies the validity of modal parameters identification method using wavelet transformation of which precision is validated by comparing the results of experiment with that of theoretical calculation.In this paper, the operational vibration of cantilever is simulated by stimulating it using stochastic white noise. The modal parameters is identified by means of Polymax, Wavelet transformation, ITD (the Ibrahim Time Domain Techniques), and ARMA (Auto Regressive Moving Average) time-series modal methods. The modal parameters that identified using wavelet transformation, ITD, and ARMA are compared based on the results of Polymax, which furthermore verifies the validity and reliability of wavelet transformation method.