在頻率域中的模態參數識別，量測訊號大部分透過快速傅立葉轉換，將時間訊號轉至頻率域做進一步的分析，可能會遇到頻譜洩漏效應(Leakage phenomenon)，造成後續識別模態參數的誤差。故本文利用計算功率頻譜密度函數的方法－Welch s method，得到抑制洩漏現象後之功率頻譜密度函數。針對前人提出的多參考點最小二乘複頻域法進行研究，由於本識別法是藉由提高多項階數來增加模態參數的識別精度，然而在實際識別模態參數時，並無法選擇何階的多項式解所得到識別結果最精確，故在此引入盒形圖以利提取模態參數。

In frequency domain, the response signal in the modal parameter identification must be converted to the frequency domain by a fast Fourier transform. There may be a leakage phenomenon, which causes errors in identifying modal parameters. Therefore, this thesis uses the method of calculating the power spectral density function-Welch's method to obtain the power spectral density function that reduces the leakage phenomenon. We mainly study the poly -reference least squares complex frequency domain method to apply ambient vibra-tion situation. This identification method increases the Identified accuracy of modal parame-ters by increasing the order of multiple orders. When we identify under realistic ambient vi-bration, the polynomial solution of which order cannot be selected to obtain the most pre-cisely identified result, apply the box plot in this thesis. Therefore, this thesis uses the box plot which is a statistical method to obtain identification result.

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