Modal Analysis

[upnickrogers]

Hello,

I am new to Labview and looking to do some modal testing. I have an impact hammer and accelerometer connected to my NI hardware (USB-6003).

Setup shown below:

In Labview, I have imported the voltage readouts from both the accelerometer and impact hammer using the DAQ Assistant as shown below:

I have looked at the VI's out there for doing this kind of analysis, and I do not have the understanding of Labview to adapt them to what I need. Can anyone lead me in the right direction or tell me how to modify my inputs to work with the existing VI's?

Also, I found a PDF showing exactly what I am looking for as far as functionality and output. I just want a graph of the frequency and the resonant frequency displayed like the one below:

Thanks,

Nick Rogers

Union Pacific Railroad

[Bob_Schor]

Nick,

     You have several choices.  Given that you've got a USB-6003 and are using it to get some data, I'm guessing that there are going to be more and other uses for this device, that you will want to use it to build a variety of Virtual Instruments to measure various things.

     The ideal way to do this, as I'm sure you already realize, is to use LabVIEW, which has "Virtual Instrument" as part of its name (the V and I in LabVIEW).  You can either (a) have your Company hire someone with LabVIEW skills to handle this, and other, projects, (b) contract out this Project, or (c) invest a little effort and learn how to do this yourself.  My recommendation would be the latter -- you've already demonstrated the necessary talent and "curiousity" that would make learning LabVIEW (for you) fun and relatively easy (in my opinion).

     Fortunately, there are a number of on-line Tutorials (I'll try to paste a link below) -- Google LabVIEW Tutorial.  This Forum is the place to return to when you have code that "doesn't quite work" or a concept that you don't understand.  Many students use it as a place to "Do My Homework For Me", and, for the most part, we successfully resist the impulse to do so, but encourage them to "keep trying, and Post Your Code".

http://www.ni.com/getting-started/labview-basics/

http://www.ni.com/academic/students/learn-labview/

http://www.ni.com/pdf/manuals/373427c.pdf

Bob Schor

[upnickrogers]

Thanks for the tip, Bob. I am struggling to figure out what to do, but I will keep at it. I'll check out those links you posted now.

Thanks,

Nick Rogers

Union Pacific Railroad

[CoastalMaineBird]

I've done impact testing before. More accurately, I've written the software that MechEngs have used to do the testing.

I still have the code, I remember Sxy * Sxx / (Sxx * Sxx) or something like that (I'd have to look up the code).

It provides a frequency domain transfer function between the point of impact and the point(s) of measurement.

There are not going to be "express" VIs that do exactly what you want, but the basics tools are there. 

I'm not able to just give you the code, but I can help out if you get stuck.

Like Bob said, we're not here to do the work for you (unless you want to contract it - that's what I do for a living), but we can provide a nudge or an idea here or there.

Search the NI site for "Transfer Function" and "Impact Testing" - you're bound to find something.