how do you track a levitated particle with labview vision

[ecantrell]

I am trying to track a 1 to 10 micron particle levitated in an electrodynamic balance.  Part of the method involves monitoring the dc voltage required to move the particle up and down to counter balance gravity (f = ma).  A high voltage AC field keeps the particle in the center but I'm not concerned with that.  I am watching the particle with vision acquisition.  What I can't figure out is how to take the observed position of the particle and use that information to automatically control a dc power supply.  That is, if the particle drifts too low, I need to increase the voltage to raise it.  If the particle rises to high, I have to decrease the voltage.  If the particle had an unchanging mass, it would not be a problem.  However, these particles loose mass which means that some kind of feedback acquisition control method has to be in place.  That's what I need help in.  I'm not a labview expert by any means.  In fact, I just started playing with the vision vi's.  Any help, suggestions or outright solutions would be greatly appreciated.

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Thank you,

Eric Cantrell 

[Richard_M]

Break the problem down into sections.

Work out how to detect the particle from the image (lots of image vi's for this).

Work out how to convert the position on the image to real world dimensions, mm or whatever.

Work out how to grap two images and work out the movement direction. You'll have to extract the vertical movement (assuming you don't care and have no control over left and right movement.)

Work out what voltage is required to change the position, and how the hardware works to apply the voltage.

Apply the voltage.

Easy!

(This is one way, I'm not saying it's the best. if you break it down you'll be able to learn Labview as you go on.)

[ecantrell]

I appreciate the speed reply.  I'm on a tight schedule here.   I had originally purchased the Machine Vision and Vision Aquisistion modules.  I was well on my way until this little icon called Vision Assisant died on me.  It seems the thirty das trial ran out.  Unfortunately I don't have another $4K so I have to find a different solution.  Had I known it was the Vision Development module I needed I would have bought that instead.  The project data collection will end in July so after that I am done with the vision part.  I did try to ask for an extension but that didn't work :^).  If you coud point me to a few of those vision vi's you metioned I would apprecieated it.  All the ones I ran across involved the Vision Assistant.

Thank you,

Eric

[Richard_M]

Have a look at the demos for how to detect and filter the particle. It's a few years since I used vision so I don't remember the exact names.