Calculation of Component Mode Synthesis Matrices From Measured Frequency Response Functions, Part 2: Application

1998 ◽  
Vol 120 (2) ◽  
pp. 509-516 ◽  
Author(s):  
J. A. Morgan ◽  
C. Pierre ◽  
G. M. Hulbert
Keyword(s):  
Frequency Response ◽  
Coupled System ◽  
Companion Paper ◽  
Component Mode Synthesis ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Measured Frequency ◽  
Measured Frequency Response ◽  
Coupled Beams ◽  
The Individual

This paper demonstrates how to calculate Craig-Bampton component mode synthesis matrices from measured frequency response functions. The procedure is based on a modified residual flexibility method, from which the Craig-Bampton CMS matrices are recovered, as presented in the companion paper, Part I (Morgan et al., 1998). A system of two coupled beams is analyzed using the experimentally-based method. The individual beams’ CMS matrices are calculated from measured frequency response functions. Then, the two beams are analytically coupled together using the test-derived matrices. Good agreement is obtained between the coupled system and the measured results.

Calculation of Component Mode Synthesis Matrices From Measured Frequency Response Functions, Part 1: Theory

1998 ◽  
Vol 120 (2) ◽  
pp. 503-508 ◽  
Author(s):  
J. A. Morgan ◽  
C. Pierre ◽  
G. M. Hulbert
Keyword(s):  
Frequency Response ◽  
Component Mode Synthesis ◽  
New Method ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Measured Frequency ◽  
Experimental Implementation ◽  
Measured Frequency Response ◽  
Expansion Coefficients ◽  
Theoretical Developments

This paper presents a new method to calculate the so-called Craig-Bampton component mode synthesis (CMS) matrices from measured frequency response functions. The procedure is based on a modified residual flexibility method, from which the Craig-Bampton CMS matrices are recovered. Experimental implementation of the method requires estimating the modal parameters corresponding to the measured free boundary modes and the Maclaurin series expansion coefficients corresponding to the omitted modes. Theoretical developments are presented in the present paper, Part 1. The performance of the new method is then demonstrated in Part 2 (Morgan et al., 1998) by comparison of experiment and analysis for a simple two-beam system.

Calculation of Component Mode Synthesis Matrices From Measured Frequency Response Functions

1995 ◽  
Author(s):  
Jeffrey A. Morgan ◽  
Christophe Pierre ◽  
Gregory M. Hulbert
Keyword(s):  
Frequency Response ◽  
Series Expansion ◽  
Dynamic Models ◽  
Component Mode Synthesis ◽  
Residual Effects ◽  
Response Functions ◽  
Maclaurin Series ◽  
Frequency Response Functions ◽  
Measured Frequency ◽  
Measured Frequency Response

Abstract This paper shows how to calculate Craig-Bampton component mode synthesis matrices from measured frequency response functions. The procedure is based on a modified residual flexibility method and the use of a Maclaurin series expansion to represent the residual effects of the omitted modes. It was developed as a base-band method for structures exhibiting normal modes of vibration determined from free boundary vibration tests. Of particular importance is the procedure developed for the estimation of the Maclaurin series expansion coefficients and for the recovery of the Craig-Bampton matrices from the residual flexibility formulation. This allows accurate dynamic models to be determined for measured systems that can be used to predict the effects of structural modifications and in substructure coupling analyses. The performance of the new method is demonstrated by comparison of experiment and analysis for two simple beams.

Detection of Local Damage of Flexural Member Using Measured Frequency Response Functions

2018 ◽  
Vol 23 (No 3, September 2018) ◽  
pp. 314-320
Author(s):  
Eun-Taik Lee ◽  
Hee-Chang Eun
Keyword(s):  
Damage Detection ◽  
Frequency Response ◽  
Damage Index ◽  
External Noise ◽  
Local Damage ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Measured Frequency ◽  
Measured Frequency Response ◽  
Proper Orthogonal

Measurements by sensors provide inaccurate information, including external noises. This study considers a method to reduce the influence of the external noise, and it presents a method to detect local damage transforming the measured frequency response functions (FRFs) to reduce the influence of the external noise. This study is conducted by collecting the FRFs in the first resonance frequency range from the responses in the frequency domain, taking the mean values at two adjacent nodes, and transforming the results to the proper orthogonal decomposition (POD). A damage detection method is provided. The curvature of the proper orthogonal mode (POM) corresponding to the first proper orthogonal value (POV) is utilized as the damage index to indicate the damage region. A numerical experiment and a floor test of truss bridge illustrate the validity of the proposed method for damage detection.

Fitting Discrete-Time Models to Frequency Responses for Systems With Transport Delay

2011 ◽  
Author(s):  
Jeffrey A. Butterworth ◽  
Lucy Y. Pao ◽  
Daniel Y. Abramovitch
Keyword(s):  
Frequency Response ◽  
Discrete Time ◽  
Response Functions ◽  
Time Model ◽  
Frequency Response Functions ◽  
Transport Delay ◽  
Discrete Time Model ◽  
Measured Frequency ◽  
Measured Frequency Response ◽  
Discrete Time Models

Fitting discrete-time models to frequency-response functions without addressing existing transport delay can yield higher-order models including additional non-physical nonminimum-phase (NMP) zeros beyond those that may appear as a result of sampling. These NMP zeros can be attributed to a discrete-time representation of a Pade´ approximation to account for the transport delay [1, 2]. Here, we explore this idea in greater detail and this discussion motivates the main contribution of this paper, the presentation of a procedure for fitting a discrete-time model to experimentally measured frequency response data. The appearance of NMP zeros in a system model can complicate controller design and limits the desired closed-loop performance. This discrete-time model-fitting procedure presents a technique that will help yield a model that reflects the measured frequency-response functions accurately, while minimizing the presence of non-physical NMP zeros. The key benefit being that, with respect to previous model fits, it may be possible to eliminate all NMP zeros in the discrete-time model. In the case of model-inverse-based control design, this will allow the stable inversion of the model without the use of approximation methods to account for NMP zeros.

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