倒频谱编辑法在含转子结构运行模态参数辨识中的应用

Cepstrum editing method used in operational modal analysis of rotor structures

工况模态分析或称运行模态分析,通常假设结构所受载荷为白噪声,响应谱中峰值皆由结构模态导致。然而机械系统通常含有转子部件,在运行状态下测量响应中周期性谐波或其倍频响应占据主导,加剧了工况下模态参数辨识的难度。针对上述问题,该文提出了基于倒频谱编辑的工况模态参数辨识方法,识别测量响应中的谐波及其倍频响应并在参数辨识前去除其对模态参数提取的影响。所提方法适用于多谐波激励、谐波频率与结构模态频率重叠、慢变谐波等情况,通过三自由系统算例、自由边界钢梁试验和某型航空发动机试车实测数据验证了方法的可靠性。

Operational modal analysis technique,or output only modal analysis,commonly holds the assumption that the excitations acting on the structure are white noise,and therefore the peaks in the response spectrum all correspond to the modes of the structure.However,mechanical systems usually have rotor parts,and the periodic harmonics and their super-harmonics will dominate the measured responses at the operating states,which adds the difficulty in the identification of modal parameters.To solve the aforementioned problem,a modal parameter identification method was proposed based on cepstrum editing,which was able to identify the harmonic frequency and remove the effect of harmonics on modal parameter identification.The proposed method can handle the cases of multiple harmonics,the overlapping of the harmonic frequency with the modal frequency,slow-varying harmonics,etc.The proposed method was verified through the calculation example of a three degree-of-freedom system,the experiment of a free-free steel beam,and the measured responses of an aircraft engine.