Second-Order Blind Identification for Operational Modal Analysis

2007 ◽  
Author(s):  
F. Poncelet ◽  
G. Kerschen ◽  
J. C. Golinval ◽  
F. Marin
Keyword(s):  
Modal Analysis ◽  
Operational Modal Analysis ◽  
Blind Identification ◽  
Modal Parameter ◽  
Engineering Structures ◽  
Experimental Application ◽  
Large Structures ◽  
Output Only ◽  
Modal Parameter Estimation ◽  
Source Signals

For modal analysis of large structures, it is unpractical and expensive to use artificial excitation (e.g., shakers). However, engineering structures are most often subject to ambient loads (e.g., traffic and wind) that can be exploited for modal parameter estimation. One difficulty is that the actual loading conditions cannot generally be measured, and output-only measurements are available. This paper proposes to explore the utility of blind source separation (BSS) techniques for operational modal analysis. The basic idea of BSS is to recover unobserved source signals from their observed mixtures. The feasibility and practicality of the proposed method are demonstrated using an experimental application.

Operational Modal Analysis of Aluminum Beams

2007 ◽  
Vol 50 (1) ◽  
pp. 74-85 ◽  
Author(s):  
S. Rudroju ◽  
A. Gupta ◽  
S. Yandamuri
Keyword(s):  
Modal Analysis ◽  
Impact Test ◽  
Force Measurement ◽  
Operating Conditions ◽  
Impact Testing ◽  
Operational Modal Analysis ◽  
Normal Functioning ◽  
Large Structures ◽  
Output Only ◽  
Ambient Excitation

Natural frequencies obtained by modal analysis are important to engineers interested in predicting the dynamic behavior of structures. Traditional modal analysis involves impact testing or shaker testing, where response signal and input force are measured to obtain the transfer function. However, for large structures, input excitation force measurement may be difficult, if not impossible. Large structures may be subjected to ambient excitation; operational modal analysis (OMA), also known as output-only modal analysis, has been used for extracting modal parameters of these types of structures. The main advantage of operational modal analysis is that no artificial excitation is needed, and the analysis is based on measurements of only the output data of the system. Operational modal analysis tests are performed under the actual operating conditions of the system without any change of boundary conditions; the tests use the ambient loads as input and thus do not interfere with the normal functioning of the system. In this study, six aluminum beams of different configurations (beams with and without cuts of various lengths) were used for conducting experiments. Results based on impact test, shaker test, and operational modal analysis are presented.

scholarly journals Perspectives of Second-Order Blind Identification for Operational Modal Analysis of Civil Structures

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
C. Rainieri
Keyword(s):  
Modal Analysis ◽  
Second Order ◽  
Modal Identification ◽  
Computational Time ◽  
Parameter Estimates ◽  
Blind Identification ◽  
Modal Parameter ◽  
Civil Structures ◽  
Key Issues ◽  
Output Only

Innovative methods for output-only estimation of the modal properties of civil structures are based on blind source separation techniques. In the present paper attention is focused on the second-order blind identification (SOBI) algorithm and the influence of its analysis parameters on computational time and accuracy of modal parameter estimates. These represent key issues in view of the automation of the algorithm and its integration within vibration-based monitoring systems. The herein reported analyses and results provide useful hints for reduction of computational time and control of accuracy of estimates. The latter topic is of interest in the case of single modal identification tests, too. A criterion for extraction of accurate modal parameter estimates is identified and applied to selected experimental case studies. They are representative of the different levels of complexity that can be encountered during real modal tests. The obtained results point out that SOBI can provide accurate estimates and it can also be automated, confirming that it represents a profitable alternative for output-only modal analysis and vibration-based monitoring of civil structures.

Experimental Modal Analysis: Efficient Geometry Model Creation Using Optical Techniques

2006 ◽  
Vol 49 (2) ◽  
pp. 104-113 ◽  
Author(s):  
Steven Pauwels ◽  
Jan Debille ◽  
Jeff Komrower ◽  
Jenny Lau
Keyword(s):  
Modal Analysis ◽  
Numerical Models ◽  
Dynamic Properties ◽  
Real Life ◽  
Geometrical Model ◽  
Experimental Modal Analysis ◽  
Modal Parameter ◽  
Optical Techniques ◽  
Geometry Model ◽  
Modal Parameter Estimation

Experimental modal analysis (EMA) is widely used to characterize the dynamic properties of structures. Recently EMA is being used on more complex structures often involving hundreds of measurement points. Modal analysis results are frequently used in combination with numerical models, imposing higher standards on the quality of the modal parameter estimation and the accuracy of the geometry models. These requirements are often contradictory to the availability of test cells and prototypes. In order to solve this challenge, innovative solutions using optical techniques have been developed that simplify and accelerate the creation of a geometrical model of a test object, while at the same time increase the accuracy of measured coordinates. Industrial applicability of these techniques is proven by a number of benchmarks on real-life structures.

Modal Parameter Estimation for Underdamped Linear Dynamic Systems

2013 ◽  
Vol 486 ◽  
pp. 233-238
Author(s):  
Fillemon Nduvu Nangolo
Keyword(s):  
Parameter Estimation ◽  
Modal Analysis ◽  
Damping Ratio ◽  
Analytical Data ◽  
Modal Parameter ◽  
Classical Dynamic ◽  
Linear Dynamic Systems ◽  
Analysis Techniques ◽  
Vibration Parameters ◽  
Modal Parameter Estimation

Modal parameter estimation is the estimation of frequency, damping ratio, and modal coefficients from experimental data. Modal analysis techniques are a common method used to determine these properties. The Least-Squares Complex Exponential (LSCE) and the Eigensystem Realization Algorithm (ERA) are one of the popular methods of modal analysis techniques. This paper presents an experimental verification of the LSCE and ERA methods. The investigation focuses on the estimation of natural frequencies, damping ratio and modal coefficients. To investigate this, artificial analytical data were processed in MATLAB environment to estimate the modal parameters. The identified vibration parameters from the LSCE and ERA were compared with the values based on classical dynamic theory, and the natural frequency and damping ratios percent of error were calculated.

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