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根据所测动态响应信号拟合系统模型时,一个重要的问题是:在低信噪比的情况下如何提高系统参数的估计精度。采用线性平均方法能适当提高信噪比,但在一般试验条件下,据此所获得的部分系统参数仍具有较大的误差。本文采用了时域广义维纳滤波方法对测取的动态信号进行预处理,以尽可能少的激励次数,从较高的背底噪声中检测出真实信号。文中还说明了适用于工程系统测试中噪声功率估计的滤波器分组方法。以悬臂梁的模态测试及分析为例,检验了该方法的有效性。试验表明,作振型分析时,因测点信号信噪比低而导致数据误差大的问题得以解决,这对实验模态分析是具有重要意义的。所完成的计算机-FFT 谱分析器信号预处理程序有很大的实用价值。
An important issue when fitting the system model to the measured dynamic response signal is how to improve the estimation accuracy of the system parameters at low signal-to-noise ratios. The linear average method can improve the signal-noise ratio properly, but under the general experimental conditions, some of the system parameters obtained therewith still have large errors. In this paper, the time-domain Wiener filter is used to preprocess the measured dynamic signal to detect the real signal from the high background noise with as few excitation times as possible. The paper also describes the filter grouping method suitable for noise power estimation in engineering system testing. Taking the cantilever modal test and analysis as an example, the validity of this method is verified. Experiments show that for the vibration mode analysis, the problem of large data error due to the low signal-to-noise ratio of the point signal is solved, which is of great significance for the experimental modal analysis. The completed computer-FFT spectrum analyzer signal pre-processing program has great practical value.