Abstract：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, the paper proposes a modal parameter identification method based on cepstrum editing, which is 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 and the modal frequency, slow-varying harmonics, etc. The proposed method is verified through a three degree-of-freedom system, a free-free steel beam, and the measured responses of an aircraft engine.
[1] JAMES G H, CARNE T G, LAUFFER J P. The natural excitation technique (next) for modal parameter extraction from operating structures [J]. Modal Analysis-the International Journal of Analytical and Experimental Modal Analysis, 1995, 10(4): 260-77.
[2] 续秀忠, 华宏星, 陈兆能. 基于环境激励的模态参数辨识方法综述[J].振动与冲击,2002,21(3):1-5.
XU Xiu-zhong, HUA Hong-xing, CHEN Zhao-neng. Review of Modal Identification Method Based on Ambient Excitation [J]. Journal of Vibration and Shock, 2002, 21(3):1-5.
[3] 张济淳, 宋汉文. 环境激励下基于相关函数的脉冲响应函数重构[J]. 振动与冲击, 2020, 39(10).
Zhang Ji-chun, SONG Han-wen. Reconstruction of impulse response function based on correlation function under ambient excitation [J]. Journal of Vibration and Shock, 2020, 39(10).
[4] 廖明夫, 于潇, 王四季等. 双转子系统的振动[J]. 机械科学与技术, 2013, 32(4).
LIAO Ming-fu, YU Xiao, WANG Si-ji, et al. The Vibration Features of a Twin Spool Rotor System [J]. Mechanical Science and Technology for Aerospace Engineering, 2013, 32(4).
[5] 于亮亮，宋汉文. 激励中含有谐波成分时的工况模态参数辨识[J]. 振动工程学报, 2018, 31(01).
YU Liang-liang, SONG Han-wen. Operational modal analysis in the presence of harmonic excitation [J]. Journal of Vibration Engineering, 2018, 31(01).
[6] 张义民，李鹤，闻邦椿. 运行模态分析中谐波模态识别方法研究及应用[J]. 振动,测试与诊断, 2008, 28 (3).
ZHANG Yi-min, LI He, WEN Bang-chun. Harmonic Mode Identification in the Operational Modal Analysis and Its Application[J]. Journal of Vibration Measurement & Diagnosis, 2008, 28 (3).
[7] 夏遵平，王彤. 基于谱峭度的谐波模态检测方法[J]. 工程力学, 2013, 30(12).
XIA Zun-ping, WANG Tong. Detection Of Harmonic Modes With Spectral Kurtosis[J]. Engineering Mechanics, 2013, 30(12).
[8] PINTELON R., PEETERS B., GUILLAUME P. Continuous-time operational modal analysis in the presence of harmonic disturbances [J]. Mechanical Systems and Signal Processing, 2008, 22(5): 1017-35.
[9] CHEN W, JIN M, HUANG J, et al. A method to distinguish harmonic frequencies and remove the harmonic effect in operational modal analysis of rotating structures [J]. Mechanical Systems and Signal Processing, 2021,161.
[10] BOGERT B. P., HEALY M. J., TUKEY J. W. The quefrency alanysis of time series for echoes: cepstrum, pseudo-autocovariance, cross-cepstrum and saphe cracking [M]. Proceedings of the Symposium on Time Series Analysis. 1963.
[11] RANDALL R. B. A history of cepstrum analysis and its application to mechanical problems [J]. Mechanical Systems and Signal Processing, 2017, 97(3).
[12] 陈伟, 宋汉文. 非自伴随动力学系统的工况模态分析[J]. 振动工程学报, 2018, 31(5).
CHEN Wei, SONG Han-wen. Operational modal analysis of non-self-adjoint dynamic system [J]. Journal of Vibration Engineering, 2018, 31(5).
[13] 于亮亮, 宋汉文. 环境激励下脉冲响应函数与相关函数的关系[J]. 噪声与振动控制, 2017, 37(03): 14-18.
YU Liang-liang, SONG Han-wen. Discussion on the Relation between Correlation Functions and Impulse Response Functions under Ambient Excitation [J]. Noise and Vibration Control, 2017, 37(03):14-18.
