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Vibration control of a Random Vibration test

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I have a PXI system with:

  1. PXI-4472B analog input module
  2. PXI-6221Multifunction DAQ
  3. PXI-6733 Analog output module

 

Additionally I have a vibration shaker along with its power amplifier.

 

I want to perform a random vibration test using these devices. This test is demonstrated here.

Briefly;

  1. I'm given a power spectral density (PSD) curve of the random vibration. This is called the (reference PSD)
  2. I need to create a time history of a random signal whose PSD coincides as close as possible to the given PSD
  3. This time signal should be output to the power amplifier of the shaker
  4. There is an accelerometer that measures the acceleration generated at the shaker table. This is called the (control accelerometer)
  5. The PSD of the measurements of this control accelerometer are calculated and compared with the reference PSD and the difference between them is used to construct a feedback control law that aims to minimize this difference so that the measured PSD is as close as possible to the reference PSD

So my questions are:

  • Is there any existing modules in LabView or LabVIEW Sound and Vibration Toolkit that accepts the reference PSD and generates the corresponding time history signal?
  • Is there any existing modules in LabView or LabVIEW Sound and Vibration Toolkit that performs the necessary feedback control to minimize the difference between the reference PSD and the measured PSD?

 

Thanks

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Not my field so pay close attention to other answers from actual experts.  Just trying to offer a couple thoughts in the meantime, FWIW.

 

- Prior to your control-loop work, I'd think you'd want to first do some open-loop work to characterize a freq domain transfer function of your power amp and shaker.  Then for a given desired accel, you'd know how to compensate the nominal control output so that the shaker produces the corresponding *actual* accel.

 

- I don't think a PSD converts unambiguously back into the time domain.  Other forms of FFT can (such as complex with Re/Im parts).   I'm not sure what the impact of this ambiguity will be on your efforts to construct a time domain signal from a PSD envelope.

 

- minimizing the difference between reference and measured PSD as a real-time control law sounds like a very advanced and specialized bit of work.  It sure doesn't sound like something that could exist as a pre-packaged module.  The fact you're hoping to find such an easy way out makes me suspect you may not yet have a sufficient understanding of the complexity of what you're trying to do.

   Just to set the right expectations - a project like this is gonna take very significant time and effort.

 

 

-Kevin P

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Solution
Accepted by topic author ahmedrashed

I have done acoustic tests with Sound and Vibration toolkit, but your requirement does not seem to fit into any of the available toolkit features.

 

Typically SVT covers the measurement aspect of sound and vibration and some level of sound generation aspects but nothing on vibration generation aspects. I am not experienced enough in vibration domain to provide any valuable thoughts but looking at the closed feedback loop requirement, it does not look simple to me. I would agree with Kevin's analysis, PSD may not be converted into a time-domain signal, even if you do it, when generated using a shaker may not result in the same exact PSD.

 

Interesting requirement, will follow this thread for insights from other experts in the field.

-Santhosh
Semiconductor Validation & Production Test
Soliton Technologies
NI CLD, CTD
LabVIEW + TestStand + TestStand Semiconductor Module (2013 - 2020)
NI STS for Mixed signal and RF
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