基于复解析带通滤波的自由衰减振动信号的频谱校正法

A method of spectrum correction for a damped free vibration signal based on complex analytic band-pass filtering

通过复解析带通滤波构造时域信号的解析信号,消除因时域实信号作FFT时由于时域截断产生的负频率成分能量泄露对正频率成分的干扰,从而提高自由衰减振动信号频谱校正精度。仿真分析及工程实测结果表明,当各个固有频率相隔较远时,校正精度很高。但在各阶固有频率靠得很近时不能直接使用这种方法。

A new method was proposed to improve the precision of spectrum correction for a damped free vibration signal based on frequency-domain.The principle of this method was that a continuous,and damped free vibration signal was sampled and its analytical signal was constructed,then N points fast Fourier transformation(FFT) was performed to the analytical signal from its starting data point to the(N + 1)-th data point.Finally,the modal parameters were calculated using the parameters of two corresponding peaks of amplitude spectra.This method could reduce the spectral leakage of negative frequency component caused from FFT.Simulation results showed that the precision of spectrum correction can be rather high when natural frequencies are far from each other;however,the method cannot be used if natural frequencys are very close to each other or the modal coupling is very serious.