Operational Modal Analysis Method Based on the Pseudo Frequency Response Function Matrix

doi:10.3901/JME.2021.20.266

Abstract

Abstract: The operational modal analysis (OMA) technique based on the pseudo frequency response function (PFRF) method by the use of transmissibility measurements does not require the white noise excitation assumption, and has strong ability of harmonic modes rejection. However, its modal identification results depend on the selection of the PFRF to be analyzed, the stability needs to be improved. To solve this issue, an OMA method based on the pseudo frequency response function matrix (PFRFM) method is proposed. Firstly, the PFRFM with multiple reference measurement points and multiple reference loading conditions is constructed. Subsequently, the least squares complex frequency domain method is applied to the PFRFM to extract the modal frequencies and damping ratios, the transmissibility matrices are used to extract the modal shapes. Finally, the number of modes and the final modal results are determined by combing the stabilization diagram with the modal indicator function that is built on the arithmetic mean of the reciprocal of the second singular values about the transmissibility matrices with different references. The results of simulations for a 5 DOF mass-spring-damping system and experiments for a free beam demonstrate that the proposed method not only inherits the strong ability of harmonic modes rejection, but also can effectively solve the problem of insufficient stability of identification results of the PFRF method, obtain higher precision modal results to a certain extent, and is more conducive to automation.

Key words: operational modal analysis, transmissibility measurements, pseudo frequency response function matrix, harmonic modes

CLC Number:

TB123

CHEN Tao, CHU Zhigang, LI Peiran, PENG Chuan, YANG Liang. Operational Modal Analysis Method Based on the Pseudo Frequency Response Function Matrix[J]. Journal of Mechanical Engineering, 2021, 57(20): 266-276.

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