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Modal parameters identification using bilinear joint time-frequency analysis
, Article International Conference on Noise and Vibration Engineering 2006, ISMA 2006, Heverlee, 18 September 2006 through 20 September 2006 ; Volume 5 , 2006 , Pages 2907-2919 ; Mobed, M ; Shamsollahi, M. B ; Behzad, M ; Sharif University of Technology
Katholieke Universiteit Leuven
2006
Abstract
In this paper, a new method for modal parameter estimation using time-frequency representations is presented. Smoothed Pseudo Wigner-Ville representation which is a member of the Cohen's class distributions is used that reduces cross-terms in time-frequency plane dramatically and holds resolution as well. The method was applied to systems with high damping, and the results were superior to other conventional methods. © (2006) by the Katholieke Universiteit Leuven Department of Mechanical Engineering All rights reserved
Experimental Identification of Repeated Modes for a Plate Under Ambient Loading Using Time Domain Methods of Operational Modal Analysis
, M.Sc. Thesis Sharif University of Technology ; Hosseini Kordkhili, Ali (Supervisor)
Abstract
In this research, the reliability of time domain modal identification methods is studied. First three different MIMO time domain method are studied which are EITD, PRCE and ERA. The effectiveness and accuracy of the methods are evaluated for simulated mass-spring system and numerical cantilever beam in EMA (using time history data of impulse response directly) and OMA (using correlation function of random response of the structure) cases. Based on the results achived in this section, the most qualified method is identified (which was ERA) to continue the research. In order to evaluate the reliability of time domain OMA technique in case of repeated modes, first a numerical plate is studied...
Modal parameter identification of rotary systems based on power spectral density transmissibility functions
, Article 2018 SAE World Congress Experience, WCX 2018, 10 April 2018 through 12 April 2018 ; Volume 2018-April , 2018 ; 01487191 (ISSN) ; Sharif University of Technology
SAE International
2018
Abstract
Operational modal analysis based on power spectral density transmissibility functions (PSDT) is a powerful tool to identify the modal parameters with low sensitivity to excitations. The rotor systems may have the asymmetric damping or stiffness matrices which can lead to increase the difficulties of the identification procedure. In this paper, a new method is proposed to identify the modal parameters of the asymmetric rotary systems by the operational modal analysis based on the power spectral density transmissibility functions. For pole extraction from the PSDT function, a proper parametric identification method such as the Poly-reference Least Squares Complex Frequency-domain method...
A method for system identification in the presence of unknown harmonic excitations based on operational modal analysis
, Article 2019 SAE Automotive Technical Papers, WONLYAUTO 2019, 1 January 2019 through 1 January 2019 ; Volume 2019-January, Issue January , 2019 ; 01487191 (ISSN) ; Sharif University of Technology
SAE International
2019
Abstract
Operational modal analysis techniques classically have been developed based on the assumption that the input to the system is a stationary white noise. While, in many practical cases, the systems are excited by combination of white noise and colored noises (harmonic excitations). Consequently, in conditions where non-white noises are present, the existing OMA methods cannot completely distinguish between the system poles and the induced poles due to colored noises. In order to overcome this weakness of OMA methods, some researches have been conducted in the field. In this paper, a new method is proposed for identifying the modal parameters of the system under the unknown colored noises,...
Automatic System Identification Algorithm Including Uncertainty Estimation based on Operational Modal Analysis
, M.Sc. Thesis Sharif University of Technology ; Khodaygan, Saeed (Supervisor) ; Movahedi, Mohammad Reza (Supervisor)
Abstract
Modal analysis is very important in determining the physical properties of structures and mechanisms. This field is divided into two general parts: Experimental Modal Analysis (EMA) and Operational Modal Analysis (OMA). In the operational modal analysis, there are more challenges for the analyst due to the lack of inputs to identify the system. Many of the mechanical structures can not be analyzed experimentally and under specific loadings, but should be identified under actual operating conditions and in situations where the inputs of the system are not measurable. For this purpose, a modal analysis method called "Random Sub-Space Identification" (SSI) is intoduced, which uses only output...
Identification of dynamic properties of dams using system identification techniques and real earthquake excitations
, Article 9th US National and 10th Canadian Conference on Earthquake Engineering 2010, Including Papers from the 4th International Tsunami Symposium, Toronto, ON, 25 July 2010 through 29 July 2010 ; Volume 9 , 2010 , Pages 6985-6996 ; 9781617388446 (ISBN) ; Meshkat, A ; Sharif University of Technology
2010
Abstract
Investigation of the dynamic characteristics of an existing structure system based on field tests is of practical significance, since it can be employed in the field of examining construction quality, validating or improving analytical finite element structural models, or conducting damage assessment. The main purpose of this study is to investigate the dynamic characteristics of dams using the seismic response data. Whereas, in the process of frequency domain identification of dam properties, frequency response function (FRF) plays the most important role, evaluating the corresponding parameters with better accuracy has always been desirable. Therefore, a comparison was made between some...
Correlation between structural performance levels and damage indexes in steel frames subjected to earthquakes
, Article Scientia Iranica ; Volume 16, Issue 2 A , 2009 , Pages 147-155 ; 10263098 (ISSN) ; Estekanchi, H ; Vafai, A ; Sharif University of Technology
2009
Abstract
Various damage indexes have been introduced in recent years incorporating different parameters for estimating structural damage. Amongst these indexes, Plastic Ductility and Drift have been the center of attention of standards and building codes, like FEMA-356, because of their straightforward physical interpretation and ease of calculation. In this paper, several steel moment frames have been considered and their responses have been evaluated under a set of scaled earthquakes. A group of various damage indexes, which included cumulative and non cumulative, cyclic fatigue based, deformation based and modal parameter based, has been considered and the damage to structures has been evaluated...
Enhanced stabilization diagram for automated modal parameter identification based on power spectral density transmissibility functions
, Article Structural Control and Health Monitoring ; Volume 26, Issue 7 , 2019 ; 15452255 (ISSN) ; Khodaygan, S ; Sharif University of Technology
John Wiley and Sons Ltd
2019
Abstract
Operational modal analysis based on power spectral density transmissibility (PSDT) functions is a useful tool to identify the modal parameters with low sensitivity to excitations. For pole extraction from the PSDT function, a proper parametric identification method such as the polyreference least squares complex frequency-domain method or poly-Max method can be used. Then, the poles are selected from a stabilization diagram (SD) with overestimating the system model order. Therefore, spurious modes can be identified that must be distinguished and removed from the system poles. To reach this aim, many techniques have been proposed and applied. In this paper, a new algorithm is proposed to...