Modal Parameter Identification Method Of Structure Based On Power-Exponential Window

The modal parameters reflect the inherent vibration characteristics of structures.Accurate identification of structural modal parameters provides an important basis for structural optimization design,damage detection and safety assessment.The frequency domain modal parameter identification method based on Fourier transform is very convenient and fast,so it is widely used in engineering.However,such factors as spectrum leakage and the interaction between modes affect the accuracy of the results of the peak picking method,leading to a large error in the identification of structural modal parameters.In this paper,a Power-Exponential window suitable for the free response of structures is proposed,which can not only suppress the spectrum leakage to improve the spectrum smoothness,but also sharpen the spectrum of heavily damped structures.In addition,the explicit relationship between the amplitude-frequency characteristic curve and the frequency and damping ratio of the structure after adding the Power-Exponential window is established in this paper,which can effectively reduce the error of the identification frequency and damping ratio by the peak picking method.Firstly,based on the spectrum sharpening characteristics of structural frequency response function differentiation,the specific effect of spectrum sharpening on improving the identification accuracy of frequency and damping ratio is analyzed.Then the frequency domain direct realization method of frequency domain differential is studied,and based on the calculus characteristics of Fourier transform,the realization method of adding power function window in time domain is proposed.Then,a new window function,Power-Exponential window,which is suitable for peak picking is designed by combining power function window and exponential window.Through analysis,the optimal parameter value formula and general value suggestion are given.Then,the specific effect of the free response adding Power-Exponential window on frequency and damping ratio identification is studied,and a simple formula for modifying modal parameters is given.Finally,through several numerical simulation and experimental verification,the Power-Exponential window is applied to the parameter identification process of a variety of structures,and compared with the other five window functions.The results show that the modal parameter identification method based on the Power-Exponential window can effectively improve the quality of the spectrum after Fourier transform,so as to improve the identification accuracy of the frequency and damping ratio of the peak picking method,and broaden the application range of the peak picking method to the damping ratio.