http://repositorio-aberto.up.pt/bitstream/10216/80233/2/94136.pdf

Explaining operational modal analysis with data from an arch bridge

An application of Structural Health Monitoring system based on FBG sensors to offshore wind turbine support structure model

Structural system identification based on variational mode decomposition

Operational modal parameter estimation of MIMO systems using transmissibility functions

Operational modal analysis using SVD of power spectral density transmissibility matrices

A frequency–spatial domain decomposition (FSDD) method for operational modal analysis

A frequency and spatial domain decomposition method (FSDD) for operational modal analysis (OMA) is presented in this paper, which is an extension of the complex mode indicator function (CMIF) method for experimental modal analysis (EMA). The theoretical background of the FSDD method is clarified. Singular value decomposition is adopted to separate the signal space from the noise space. Finally, an enhanced power spectrum density (PSD) is proposed to obtain more accurate modal parameters by curve fitting in the frequency domain. Moreover, a simulation case and an application case are used to validate this method.

An operational modal analysis method in frequency and spatial domain

A technique to extract real modes from the identified complex modes is presented in this paper, which enables the normalized real mode shapes, modal masses, and full or reduced mass and stiffness matrices to be obtained. The theoretical derivation of the method is provided in detail. An 11-DOF vibration system is used to validate the algorithm, and to analyze the effects of the number of modes utilized and measurement DOFs on the extraction results. Finally, the method is used to extract real modes from both experimental modal analysis and operational modal analysis.

Extraction of real modes and physical matrices from modal testing

Frequency domain polyreference (FDPR) and frequency domain direct parameter identification (FDDPI) methods developed in the middle of 1980 s has superior performance in selected frequency band, and become major MIMO modal identification techniques in frequency domain. However, the methods, as well as rational fraction polynomial (RFP) algorithm developed in late 1980 s, are not suitable for broadband application compared to their time domain counterparts, i.e. extended Ibrahim time domain (EITD) or eigensystem realization algorithm (ERA), and polyreference complex exponential (PRCE) methods, due to numerical issues. But all time domain modal identification algorithms have a serious drawback in discrimination structural (physical) modes from spurious (noise) ones. In this paper, a new frequency domain modal identification technique is presented based on left or right matrix fraction description (LMFD or RMFD) of MIMO FRF or half PSD matrix. Theoretical background of the two broadband modal identification procedures is discussed with relevant numerical issues. It is revealed that the RMFD-based procedure is actually z-domain implementation of the RFP algorithm. FDPR and FDDPI are actually special cases, i.e. first and second order of LMFD-based broadband modal identification procedure implementing in discrete z-domain, instead of continuous s-domain. It is also shown that both RMFD-based and LMFD-based broadband modal identification procedures are parallel to their time domain counterparts, i.e. PRCE and EITD algorithm. However, much easier and reliable structural mode discrimination can be obtained with much clearer stability diagram. Engineering applications of the two procedures, which make use of FRF measurements for EMA of an aircraft model and h-PSD measurements for OMA of a middle-raised office building, are presented with comparison with its counterparts in time and continuous frequency domain.

Tong Wang

Papers

A frequency–spatial domain decomposition (FSDD) method for operational modal analysis

An operational modal analysis method in frequency and spatial domain

Extraction of real modes and physical matrices from modal testing

A New Broadband Modal Identification Technique with Applications