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jmwest

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Reply with quote  #1 
We were trying different approaches to calibrating our compass because it has always shown significant distortions.  I believe I may have found the problem.

The GPS antennas have very strong magnets in their bases.

I know we cannot modify the hardware, but removing the GPS antenna resulted in a tremendous improvement to our compass.  We are going to try to remove the magnet from one of the antennas to see if it improves our situation.
jjakenichol

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Reply with quote  #2 
Hi Jonathan,

Yes you're right about that.  Honestly I think that's a design flaw we've had since day 1, and you're not the first to bring it up.  It may be too late to make hardware modifications like that for this year, but I'd like to see it fixed.  

I think it would be pretty simple to disassemble the antennae and remove the magnet.  I'll investigate that solution myself and if it only requires new calibration, we may be able to make that change for this year's competition.  Making localization easier for everyone will go a long way.

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Jake Nichol
Swarming Technologies LLC - Swarmathon Hardware Support
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mfricke

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Reply with quote  #3 
Some teams this year have identified the GPS antenna as a significant source of soft iron interference for the IMU. So you are certainly not alone in your observation.

As Jake points out this may lead to a redesign in the future. Some teams have tried to develop software solutions in the meantime.

Let us know how your experiment goes with removing the magnet.

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Matthew Fricke
UNM Technical Lead, NASA Swarmathon

jmwest

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Reply with quote  #4 
We noticed how bad it was because the top broke off of one of our swarmies and we just set the gps antenna to the side and suddenly our compass cal was so bad that it was unusable.  We then removed the gps altogether and the compass was even worse without it.

I pried the magnet out of the gps antenna and then reattached the antenna to the swarmie with some velcro.  Did a new compass cal and the new cal values were remarkably different from the previous.  Haven't had a chance to test much to see if it is any better, but now we have one without the magnet and two with so we should be able to do a fair comparison.

I'll post our findings after some tests.
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