Research On Structure Modal Parameter Identification Of The Varying Temperature

In recent years, the study of structural modal parameter identification method is a hot topic,which plays an important role in the model updating, health monitoring, vibration control andstructural damage identification and other aspects. For the present the study is mainly focused onlinear time invariant system, and a relatively mature theory and methods have been formed, whichhave been widely used in various engineering fields. Currently, the research on linear time varyingmodal parameter identification method is still in its infancy, and there are many issues that needfurther research.Through studying of the numerical simulation and experimental data analysis, the main contentof this paper is the time varying system modal parameter identification based on the empirical modedecomposition and Hilbert transform.Firstly, the theory and implementation of EMD decomposition method are introduced, and thendescribe the latest developments of EMD decomposition process, end effects and their improvementmethods. By comparing the characteristics and simulation Hilbert spectrum and short time Fourierspectral analysis of the signal, which indicates that Hilbert spectral analysis is more conducive tonon-stationary signals. Secondly, the modal parameter identification of the linear time invariantsystems based on Hilbert transform is introduced, and through the cantilever model, analysis andcompare of the results of the Hilbert transform identification method and wavelet transform method,the result shows that modal parameter identification method based on Hilbert transform can identifythe structural modal parameters under ambient excitation better. Thirdly, the instantaneous frequencyand damping ratio of linear time varying systems are defined, and then their recognition methods areintroduced. Through the numerical simulation analysis of time varying single freedom andmulti-degree of freedom system, we can illustrates that the method of Hilbert transform can identifythe instantaneous modal parameters of variable structure. Finally, the vibration test data is analyzedand compared with the theoretical value, which shows that Hilbert transform has some accuracy andfeasibility in modal parameter identification with temperature varying.