Combination of Fulcrum and FFT module

The com­bi­na­ti­on of the new Vic-3D FFT-Modu­le and the known syn­chro­ni­sa­ti­on / trig­ger device with Ful­crum modu­le of isi-sys GmbH / Cor­re­la­ted Solu­ti­ons INC for Vib­ro­cor­re­la­ti­on per­mits full modal and vibra­ti­on ana­ly­sis using con­ven­tio­nal low speed came­ras. It can be app­lied on objects with high fre­quen­cy exci­ta­ti­on, which can replace High-Speed (HS) came­ras, when con­ven­tio­nal shakers are used for excitation.

 

Excitation signal

A perio­dic vibra­ti­on signal with a wide fre­quen­cy spec­trum (e. g. chirp, fast sweep) is app­lies to a struc­tu­re via an elec­tro­dy­na­mic, hydrau­lic or pie­zo shaker. The came­ras of a ste­reo­scopic sys­tem are set to a short expo­sure dura­ti­on (we use 200μs here) and they are trig­ge­red though the Ful­crum modu­le of Vic-Snap.

The exci­ta­ti­on signal is shown in the images below. A pul­se is gene­ra­ted by the func­tion gene­ra­tor for each cycle of the exci­ta­ti­on (chirp) signal and con­nec­ted to the syn­chro­ni­sa­ti­on device below.

Anregungssignal

Image 1 — Fre­quen­cy spectrum

Anregungssignal 2

Image 2 — Exci­ta­ti­on signal

 

SynchronisationTrigger device

 

The came­ras are trig­ge­red through the stan­dard synchronisation/trigger device  DAQ-STD-8D con­trol­led by the Ful­crum Modu­le for Vic-Sna­p/ Vic-3D.

 

 

FFT Module Evaluation Examples

The fol­lowing results show the works­pace of the FFT Modu­le in Vic-3D with ampli­tu­de (left) and pha­se (right). Shif­ting the fre­quen­cy value in the graphs below (ampli­tu­de or pha­se vs fre­quen­cy) per­mits to select the cor­re­spon­ding mode shape for any ana­ly­sed fre­quen­cy. The ampli­tu­des (left) are dis­play­ed here as 3D plot, other opti­ons are e.g. genera­ti­on of ani­ma­ted vide­os of the mode shape vibration.

The results on a sqa­re pla­te 140 x 140mm of dif­fe­rent reso­nance fre­quen­ces are shown in the images below.

263Hz

Image 3 — Reso­nance at 263 Hz

 

707Hz

Image 4 — Reso­nance at 707 Hz

 

875Hz

Image 5 — Reso­nance at 875 Hz

 

 

Application example of the FFT module:

Ope­ra­ti­on mode ana­ly­sis on a mobi­le pho­ne during vibra­ti­on alert