A STUDY OF IMPULSE EXCITATION AND THE MODAL PARAMETERS IDENTIFICATIONFOR MECHANICAL STRUCTURE

摘要

A procedure including impulse excitation and identification of structural modal parameters is presented in this paper. Through Fast Fourier Transform of force and response signals, their cross-spectral density and auto-spectral density can be obtained and their ratio shows the transfer function. The main attention was given to accuracy of identification. It was found that a better results can be obtained when the whole expression of the transfer function instead of its imaginary or real part was used as the basic equation for curve-fitting. Moreover, for decreasing the leakage caused by the truncation, force and response signals in time domain are treated with an exponential window function, thus a more smooth transfer function is obtained. By using multi-group averaging technique in frequency domain, the influence of some random factors and noise is cleared away.