Operational modal analysis of a rotating structure subject to random excitation using a tracking continuously scanning laser Doppler vibrometer via an improved demodulation method

2021 ◽  
pp. 1-30
Author(s):  
Linfeng Lyu ◽  
Weidong Zhu
Keyword(s):  
Image Processing ◽  
Laser Doppler Vibrometer ◽  
Random Excitation ◽  
Processing Method ◽  
Rotating Beam ◽  
Scanning Laser Doppler Vibrometer ◽  
Rotating Structure ◽  
Fan Blade ◽  
Measured Response ◽  
Demodulation Method

Abstract A new operational modal analysis (OMA) method that is based on a rigorous nonuniform rotating beam vibration theory and an image processing method is developed to estimate modal parameters (MPs) of a rotating structure (RS) under random excitation using an improved demodulation method. The solution to the governing equation of a nonuniform rotating beam is derived, which can be considered as the response of the beam measured by a continuously scanning laser Doppler vibrometer (CSLDV) system. A recently developed tracking CSLDV system can track and scan the RS. The image processing method determines the angular position of the RS so that the tracking CSLDV system can sweep its laser spot along a time-varying scan path on it. The improved demodulation method obtains undamped mode shapes (UMSs) of the RS by multiplying its measured response by sinusoidal signals with its damped natural frequencies (DNFs) obtained from the fast Fourier transform of the measured response. Experimental investigation of the OMA method using the tracking CSLDV system is conducted, and MPs of a rotating fan blade (RFB), including DNFs and UMSs, with different constant speeds and its instantaneous MPs with a non-constant speed are estimated. Estimated first DNFs and UMSs of the stationary fan blade and RFB are compared with those from the lifting method that was previously developed by the authors.

Operational Modal Analysis of a Rotating Structure Subject to Random Excitation Using a Tracking Continuously Scanning Laser Doppler Vibrometer via an Improved Demodulation Method

2021 ◽  
Author(s):  
Linfeng Lyu ◽  
Weidong Zhu
Keyword(s):  
Image Processing ◽  
Laser Doppler Vibrometer ◽  
Random Excitation ◽  
Processing Method ◽  
Rotating Beam ◽  
Scanning Laser Doppler Vibrometer ◽  
Rotating Structure ◽  
Fan Blade ◽  
Measured Response ◽  
Demodulation Method

Abstract A new operational modal analysis (OMA) method is developed for estimation of modal parameters (MPs) of a rotating structure (RS) subject to random excitation using a nonuniform rotating beam model, an image processing method, and an improved demodulation method. The solution to the governing equation of a nonuniform rotating beam is derived, which can be considered as the response of the beam measured by a continuously scanning laser Doppler vibrometer (CSLDV) system. A recently developed tracking CSLDV system can track and scan the RS. The image processing method determines the angular position of the RS so that the tracking CSLDV system can sweep its laser spot along a time-varying path on it. The improved demodulation method obtains undamped mode shapes (UMSs) of the RS by multiplying its measured response by sinusoids whose frequencies are its damped natural frequencies (DNFs) that are obtained from the fast Fourier transform of the measured response. Experimental investigation of the OMA method using the tracking CSLDV system is conducted, and MPs of a rotating fan blade (RFB), including DNFs and UMSs, with different constant speeds and its instantaneous MPs with a non-constant speed are estimated. Estimated first DNFs and UMSs of the stationary fan blade and RFB are compared with those from the lifting method that was previously developed by the authors.

Simulating and Measuring Structural Intensity Fields in Plates Induced by Spatially and Temporally Random Excitation

2004 ◽  
Author(s):  
Michael J. Daley ◽  
Stephen A. Hambric
Keyword(s):  
Pressure Fluctuations ◽  
Laser Doppler Vibrometer ◽  
Practical Interest ◽  
Analytical Techniques ◽  
Random Excitation ◽  
Plate Structures ◽  
Scanning Laser Doppler Vibrometer ◽  
Structural Intensity ◽  
Bending Waves ◽  
Pressure Fields

The structure-borne power in bending waves is well understood, and has been studied by many investigators in ideal beam and plate structures. All studies to date, however, have considered only the structural intensity induced by deterministic, localized drives. Since many structures of practical interest are excited by spatially random pressure fields, such as diffuse and turbulent boundary layer pressure fluctuations, techniques for measuring and predicting the structural intensity patterns in plates excited by such fields are presented here. The structural intensity at various frequencies in a simply-supported, baffled, flat plate driven by a diffuse pressure field is simulated using analytical techniques and measured by post-processing data from a scanning laser Doppler vibrometer and reference accelerometer using finite differencing techniques. The measured and simulated fields are similar, and show intensity patterns different from those caused by deterministic point drives.

scholarly journals Measurement of Translational and Angular Vibration Using a Scanning Laser Doppler Vibrometer

1996 ◽  
Vol 3 (2) ◽  
pp. 141-152 ◽  
Author(s):  
A.B. Stanbridge ◽  
D.J. Ewins
Keyword(s):  
Frequency Response ◽  
Laser Doppler Vibrometer ◽  
Random Excitation ◽  
Laser Doppler ◽  
Scanning Laser ◽  
Scanning Laser Doppler Vibrometer ◽  
Straight Line ◽  
Angular Vibration ◽  
Freely Suspended ◽  
Drive Signals

An experimental procedure for obtaining angular and translational vibration in one measurement, using a continuously scanning laser Doppler vibrometer, is described. Sinusoidal scanning, in a straight line, enables one angular vibration component to be measured, but by circular scanning, two principal angular vibrations and their directions can be derived directly from the frequency response sidebands. Examples of measurements on a rigid cube are given. Processes of narrow-band random excitation and modal analysis are illustrated with reference to measurements on a freely suspended beam. Sideband frequency response references are obtained by using multiplied excitation force and mirror-drive signals.

Simulating and Measuring Structural Intensity Fields in Plates Induced by Spatially and Temporally Random Excitation

2005 ◽  
Vol 127 (5) ◽  
pp. 451-457 ◽  
Author(s):  
Michael J. Daley ◽  
Stephen A. Hambric
Keyword(s):  
Pressure Fluctuations ◽  
Laser Doppler Vibrometer ◽  
Practical Interest ◽  
Analytical Techniques ◽  
Random Excitation ◽  
Flat Plates ◽  
Plate Structures ◽  
Scanning Laser Doppler Vibrometer ◽  
Structural Intensity ◽  
Bending Waves

The structure-borne power in bending waves is well understood, and has been studied by many investigators in ideal beam and plate structures. All studies to date, however, have considered only the structural intensity induced by deterministic, localized drives. Since many structures of practical interest are excited by spatially random pressure fields, such as diffuse and turbulent boundary layer pressure fluctuations, techniques for measuring and predicting the structural intensity patterns in flat plates excited by such fields are presented here. The structural intensity at various frequencies in a simply supported, baffled, flat plate driven by a diffuse pressure field is simulated using analytical techniques and measured by post-processing data from a scanning laser Doppler vibrometer and reference accelerometer using finite differencing techniques. The measured and simulated fields are similar, and show intensity patterns different from those caused by deterministic point drives. Specifically, no clear source regions are apparent in the randomly driven intensity fields, although the energy flow patterns do clearly converge toward a point damper attached to the plate.

Crosstalk Minimization Method for Eye-tracking-based 3D Display

2020 ◽  
Author(s):  
Seok Lee ◽  
Juyong Park ◽  
Dongkyung Nam
Keyword(s):  
Image Processing ◽  
Eye Tracking ◽  
Three Dimensional ◽  
Processing Method ◽  
Eye Position ◽  
Relative Location ◽  
3D Display ◽  
Minimization Method ◽  
3D Crosstalk ◽  
Pixel Value

In this article, the authors present an image processing method to reduce three-dimensional (3D) crosstalk for eye-tracking-based 3D display. Specifically, they considered 3D pixel crosstalk and offset crosstalk and applied different approaches based on its characteristics. For 3D pixel crosstalk which depends on the viewer’s relative location, they proposed output pixel value weighting scheme based on viewer’s eye position, and for offset crosstalk they subtracted luminance of crosstalk components according to the measured display crosstalk level in advance. By simulations and experiments using the 3D display prototypes, the authors evaluated the effectiveness of proposed method.

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