Abstract:The frequency domain decomposition (FDD) method is a common method for structural operational modal analysis ( OMA ) under ambient excitation. However, the existing FDD methods have some shortcomings : (1) spurious modes caused by non-white excitation and harmonic excitation cannot be eliminated ; (2) It is impossible to distinguish between structurally closely-spaced modes and spurious modes generated by uncorrelated non-white excitations. It is found that the rank of power spectral density ( PSD ) matrix is the decisive factor for the performance of FDD method. On this basis, a new OMA method is proposed. This method combines the response PSD function matrix under different excitation conditions, and performs singular value decomposition on the response PSD matrix under a single excitation condition and the augmented response PSD matrix under multiple excitation conditions. By comparing the rank changes of the single-case PSD matrix and the augmented PSD matrix at the peak of the singular value, the structural modal parameters including the closely-spaced mode are identified, and the spurious mode generated by the non-white excitation is eliminated. The effectiveness of the proposed method is verified by a truss structure simulation example and the engineering data set of Guangzhou Tower.
[1] REYNDERS E,HOUBRECHTS J,ROECK G D. Fully automated (operational) modal analysis[J]. Mechanical Systems and Signal Processing, 2012, 29: 228–250.
[2] 董霄峰 ,练继建 ,杨敏 ,等.谐波干扰下海上风机结构工作模态识别 [J]. 振动与冲击, 2015, 34(10): 152-156.
Dong Xiaofeng, Lian Jijian, Yang Min, et al. Modal identification of offshore wind turbine structures under harmonic interference [ J ]. Vibration and shock, 2015,34 ( 10 ) : 152-156.
[3] 秦仙蓉, 余传强, 孙远韬, 等. 基于监测数据的岸桥模态参数识别 [J]. 振动与冲击, 2019, 38(20): 216-221.
Qin Xianrong, Yu Chuanqiang, Sun Yuantao, et al. Modal parameter identification of quay crane based on monitoring data [ J ]. Vibration and shock, 2019, 38 ( 20 ) : 216-221.
[4] 宋明亮, 苏亮, 董石麟, 等. 模态参数自动识别的虚假模态剔除方法综述 [J]. 振动与冲击, 2017, 36(13): 1-10.
Song Mingliang, Su Liang, Dong Shilin, et al. Review of false modal elimination methods for automatic identification of modal parameters [ J ]. Vibration and shock, 2017, 36 ( 13 ) : 1-10.
[5] BRINCKER R, ZHANG L, ANDERSEN P. Modal Identification from Ambient Responses using Frequency Domain Decomposition[C]// Proceedings of the International Modal Analysis Conference, San Antonio, USA, 2000:625-630.
[6] 李青,王天舒, 等. 充液航天器液体晃动和液固耦合动力学的研究与应用 [J]. 力学进展, 2012, 42(4):472-481.
Li Qing, Wang Tianshu et al. Research and application of liquid sloshing and liquid-solid coupling dynamics of liquid-filled spacecraft [ J ].Mechanical progress, 2012, 42 ( 4 ) : 472-481.
[7] Jacob E, Flandro G. Thrust oscillations in large solid rocket boosters[C]//44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit. 2008: 4601.
[8] Hirsch H G, Pearce D. The Aurora experimental framework for the performance evaluation of speech recognition systems under noisy conditions[C]//ASR2000-Automatic speech recognition: challenges for the new Millenium ISCA tutorial and research workshop (ITRW). 2000.
[9] ZHANG Z, HUA H, XU X, et al. Modal parameter identification through Gabor expansion of response signals [J]. Journal of Sound and Vibration, 2003, 266(5): 943-955.
[10] BRINCKER R, ANDERSEN P, MøLLER N. An indicator for separation of structural and harmonic modes in output-only modal testing[C]// proceedings of the Proceedings of the European COST F3 Conference on System Identification & Structural Health Monitoring, Universidad Politécnica de Madrid, Spain, F, 2000. Universidad Politécnica de Madrid, 2000:265-272.
[11] GUILLAUME P, DEVRIENDT C, DE SITTER G. Identification of modal parameters from transmissibility measurements[C]// proceedings of the Finds and Results from the Swedish Cyprus Expedition: A Gender Perspective at the Medelhavsmuseet, F, 2005.
[12] YAN W-J, REN W-X. Operational Modal Parameter Identification from Power Spectrum Density Transmissibility [J]. Computer-Aided Civil and Infrastructure Engineering, 2012, 27(3): 202-217.
[13] YAN W-J, REN W-X. An Enhanced Power Spectral Density Transmissibility (EPSDT) approach for operational modal analysis: theoretical and experimental investigation [J]. Engineering Structures, 2015, 102: 108-119.
[14] ARAúJO I G, LAIER J E. Operational modal analysis approach based on multivariable transmissibility with different transferring outputs [J]. Journal of Sound and Vibration, 2015, 351: 90-105.
[15] 杭晓晨, 蒋令闻, 顾明华,等. 频域分解模态识别方法的阻尼识别精度研究 [J]. 振动工程学报, 2015, 28(4): 519-525.
Hang Xiaochen, Jiang Lingwen, Gu Minghua, et al.Research on damping identification accuracy of frequency domain decomposition modal identification method [ J ].Journal of Vibration Engineering, 2015,28 ( 4 ) : 519-525.
[16] 王彤, 张令弥. 运行模态分析的频域空间域分解法及其应用 [J]. 航空学报, 2006, 027(001): 62-66.
Wang Tong, Zhang Lingmi. Frequency domain Spatial domain Decomposition Method for Operational Modal Analysis and its application [J]. Acta Aeronautica et Astronautica Sinica, 2006, 027(001): 62-66.
[17] KANG J. Operational modal analysis method by combining power spectral density transmissibility functions under different load cases [J]. Mechanical Systems and Signal Processing, 2022, 180: 109433.
[18] BRANDT A. A signal processing framework for operational modal analysis in time and frequency domain [J]. Mechanical Systems & Signal Processing, 2019, 115(JAN.15): 380-393.
[19] KANG J, JU H, LIU L. Comparison of response transmissibility and power spectral density transmissibility on operational modal analysis [J]. Mechanical Systems and Signal Processing, 2021, 160: 107912.
[20] YAN W-J, ZHAO M-Y, SUN Q, et al. Transmissibility-based system identification for structural health Monitoring: Fundamentals, approaches, and applications [J]. Mechanical Systems and Signal Processing, 2019, 117: 453-482.
[21] QIN S, KANG J, WANG Q. Operational Modal Analysis Based on Subspace Algorithm with an Improved Stabilization Diagram Method [J]. Shock and Vibration,2016,(2016-1-5), 2016, 2016(pt.2): 1-10.
[22] TAO J, MU Y, JIA H, et al. A Novel Dominant Mode Estimation Method for Analyzing Inter-Area Oscillation in China Southern Power Grid [J]. IEEE Transactions on Smart Grid, 2016, 7(5): 2549-2560.
[23] ZHAO X, YE B. Selection of effective singular values using difference spectrum and its application to fault diagnosis of headstock [J]. Mechanical Systems & Signal Processing, 2011, 25(5): 1617-1631.
[24] ARAúJO I G, SáNCHEZ J A G, ANDERSEN P. Modal parameter identification based on combining transmissibility functions and blind source separation techniques [J]. Mechanical Systems and Signal Processing, 2018, 105: 276-293.
[25] CHEN W, LU Z, LIN W, et al. Theoretical and experimental modal analysis of the Guangzhou New TV Tower [J]. Engineering Structures, 2011, 33(12): 3628-3646.
[26] NI Y Q, XIA Y, LIAO W Y, et al. Technology innovation in developing the structural health monitoring system for Guangzhou New TV Tower [J]. Structural Control and Health Monitoring, 2009, 16(1): 73-98.
[27] GUO Y L, KAREEM A, NI Y Q, et al. Performance evaluation of Canton Tower under winds based on full-scale data [J]. Journal of WindEngineering and Industrial Aerodynamics, 2012, 104-106: 116-128.
[28] NI Y Q, WONG K Y, XIA Y. Health checks through landmark bridges to sky-high structures [J]. Advances in Structural Engineering, 2011, 14(1): 103-119.
[29] WANG, YOU-WU, NI, et al. Operational modal analysis of Canton Tower by a fast frequency domain Bayesian method [J]. Smart structures and systems, 2016.
[30] NI Y, XIA Y, LIN W, et al. SHM benchmark for high-rise structures: a reduced-order finite element model and field measurement data [J]. Smart Structures and Systems, 2012, 10(4_5): 411-426.
[31] CHEN W H, LU Z R, LIN W, et al. Theoretical and experimental modal analysis of the Guangzhou New TV Tower [J]. Engineering Structures, 2011, 33(12): 3628-3646.
[32] NI Y, XIA Y, LIN W, et al. SHM benchmark for high-rise structures: a reduced-order finite element model and field measurement data [J]. Smart Structures and Systems, 2012, 10(4-5): 411-426.
[33] ZHANG F-L, NI Y-Q, NI Y-C, et al. Operational modal analysis of Canton Tower by a fast frequency domain Bayesian method [J]. Smart Structures and Systems, 2016, 17(2): 209-230.