Download presentation

Presentation is loading. Please wait.

Published byBraden Winkley Modified over 2 years ago

1
Time-frequency-domain modal identification of ambient vibration structures using Wavelet Transform Numerical example

2
Natural frequency & damping Frequency Time Cutting slide Frequency domain Time domain Damping Ratios Identification Natural Frequencies Identification

3
Wavelet transform Continuous wavelet transform (CWT) is defined as convolution operator of signal X(t) and wavelet function : Wavelet function : Complex conjugate of wavelet function : Wavelet transform coefficient : Wavelet scale and translation parameters Info of time and frequency can be obtained. Relation of wavelet scale and Fourier frequency can be estimated s : Wavelet scale; f F : Fourier frequency f s : Sampling frequency; f : Central wavelet frequency

4
Wavelet function The complex Morlet wavelet is commonly used in the CWT: : Fourier transform of complex Morlet wavelet : Fourier frequency and central wavelet frequency

5
Damping & mode shapes Output displacements of the MDOF system can be decomposed in the structural normalized coordinates Wavelet transform coefficient of output response: Mode shape can be estimated via the wavelet coefficients of output displacements at point k and reference point: Decay envelope and logarithmic decrement can be extracted from this decay envelope and in tern of modulus: and

6
Damped natural frequencies Wavelet transform (Floor1) Frequency domain Wavelet transform (Floor5) =80s Frequency domain 5.91Hz 9.12Hz 14.02Hz Difficulties in identifying high-order low-dominant frequencnies Difficulties in identifying high-order low-dominant frequencnies due to inflexible resolutions & used smoothing due to inflexible resolutions & used smoothing

7
Refined by bandwidth filtering Filtered at frequency bandwidths Filtered at frequency bandwidths 1) 0-3.125Hz 1) 0-3.125Hz 2) 3.125-6.25Hz 2) 3.125-6.25Hz 3) 6.25-12.5Hz 3) 6.25-12.5Hz 4) 12.5-25Hz 4) 12.5-25Hz 5) 25-50Hz 5) 25-50Hz

8
Refined wavelet transform Bandwidth 0-20Hz [Bandwidth 0-3.125Hz] [Bandwidth 3.125-6.25Hz] [Bandwidth 6.25-12.5Hz] Only 1 st mode dominated f1=1.72Hz f2=5.37Hz f3=8.99Hz Refined and localized by Refined and localized by multiresolution analysis multiresolution analysis Filtered at frequency Filtered at frequency bandwidths bandwidths (0-3.125Hz; 3.125-6.25Hz (0-3.125Hz; 3.125-6.25Hz 6.25-12.5Hz; 12.5-25Hz; 6.25-12.5Hz; 12.5-25Hz; 25-50Hz) 25-50Hz) Dominant for mode 1 Dominant for mode 3 Dominant for mode 2

9
Refined wavelet transform [Bandwidth 0-3.125Hz] [Bandwidth 3.125-6.25Hz] [Bandwidth 6.25-12.5Hz] f1=1.72Hz f2=5.37Hz f3=8.99Hz Mode 1 Mode 2 Mode 3 [Slide 1] [Slide 2] [Slide 1] [Slide 2] [Slide 1] [Slide 2] 1.76Hz 5.49Hz 8.95Hz Amplitude envelope slop Damped Natural Frequencies (Hz) FEMFDDFDD-RDTWT mode 11.691.73 1.76 mode 25.225.355.345.47 mode 39.268.848.828.95 mode 413.613.6913.6713.72 mode 517.818.0518.0218.14

Similar presentations

Presentation is loading. Please wait....

OK

Wavelet Transform A Presentation

Wavelet Transform A Presentation

© 2018 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Download ppt on 3d printing Ppt on shell scripting interview Ppt on emerging technologies in computer science Ppt on stock market download Ppt on porter's five forces model analysis Ppt on success quotes Ppt on bresenham's line drawing algorithm Ppt on guru granth sahib ji Psychology ppt on motivation Convert doc file to ppt online templates