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Investigation on Modal Identification at Ambient Excitation

Author: ShaoYanQiu
Tutor: YueLin
School: Nanjing University of Aeronautics and Astronautics
Course: Mechanical Design and Theory
Keywords: Environmental incentives Random decrement technique Morlet wavelet Experimental Modal Analysis Modal Analysis Is only output
CLC: X321
Type: Master's thesis
Year: 2008
Downloads: 274
Quote: 2
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Abstract


Ambient excitation ( Ambient Excitation ) is a natural incentives, it does not have the valuable incentives equipment , without interrupting the normal use of the structure , convenience , and in recent years has been a great development . Incentive system under vibration in the environment generally have a small amplitude , randomness , the characteristics of the noise impact and the large amount of data , and the input is unknown , so bring some difficulties to the identification of the modal parameters . Wavelet analysis method can be time-domain and frequency-domain combination of joint time-frequency characteristics describing the observed signal , a signal when the spectrum is nearly 10 years of rapid development of the emerging discipline . In this paper, the complex-valued Morlet wavelet - frequency analysis, wavelet function to be identified signal the degree of similarity , modal parameter identification . The full text including the following : (1) learning the traditional modal parameter identification method , through literature review to understand the development of the system identification of modal parameters under ambient excitation , frequency domain and time domain methods are reviewed . For environmental incentives only output of the system in the modal parameter identification by random decrement technique to obtain the free response of the system , and improved methods of random decrement technique , the same data sample points , increasing the average number of times to get good free system response function , improved Morlet wavelet time-frequency analysis , decomposition of multi - degree-of-freedom system is a combination of a number of single - degree - of - freedom system , based on the relationship between wavelet coefficients and the system natural frequency and damping identify environmental incentives under the modal parameters of the system , application GARTEUR model numerical simulation shows the effectiveness of the method , the identification of its modal parameters to achieve better accuracy . ( 2 ) using the finite element method to confront - pole model analysis to obtain the natural frequencies of the model ; confrontation - rod model experimental modal analysis , modal parameters ; comparing the above results of the two methods ; Finally, the wavelet transform the hammering quality - Rod model response signal , the method of analysis of modal frequency and damping ratio of the model to verify the effectiveness of the wavelet transform vibration system modal parameter identification .

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CLC: > Environmental science, safety science > Administration of Environmental Protection > Environmental planning and environmental management > Regional environmental planning and management
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