在模態識別的過程中，當系統具有高阻尼比及相近模態時，會因模態干涉而影響識別精度。本文主要探討頻域之模態參數識別，針對前人提出的多參考點最小二乘複頻域法進行研究，並在作法上進行改良。根據結構動力學的理論，頻響函數可以表示成有理分式的型式；利用響應資料曲線擬合成有理分式形式，再以擬合之有理分式係數計算出模態參數。由於傳統純量模型只對單一頻響函數識別，無法獲得振型資訊；因此本文使用矩陣係數之有理分式建構系統的頻響函數矩陣進行模態識別，取代純量係數表示的有理分式模型。此外，為了避免在模態干涉下進行系統識別發生模態遺漏，吾人提高有理分式模型中分子及分母項的階數進行計算；然而卻衍生出虛假模態。吾人藉由不同階數計算的模態建立穩定圖，可從數值的穩定性來區分結構與虛假模態。數值模擬結果顯示，本文所提出方法在系統具有模態干涉與含雜訊的情況下仍具有良好精確性與強健性。

In the process of modal identification, when a system has close modes or high damping, the accuracy of results of identification may be poor due to modal interference. In this thesis, we mainly study the modal identification in frequency domain and improve polyreference least squares complex frequency domain method. According to the theory of structural dynamics, frequency response function can be expressed as a rational function form. By using the curve fitting technique, the response data can be expressed in rational fraction form, the modal parameters can be obtained from rational fractional coefficients. The conventional common denominator model only indicates the SDOF frequency response function, so it cannot acquire the mode shape information. In this thesis, we proposed the matrix-fractional coefficients model to perform modal identification through MDOF frequency response functions simultaneously. To avoid the phenomenon of omitted modes during the process of modal identification of systems with modal interference, we employ a higher-order model to perform modal identification, but fictitious modes may be caused by the numerical computation. The system and fictitious modes can be separated by using the different-order constructed stabilization diagram. Numerical simulations confirm the validity and robustness of the proposed modal-identification method for a system with modal interference under noisy conditions.

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