Quick question, motion detection

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Marcus Jaiclin

Jun 28, 2022, 12:25:49 AM6/28/22
to The Open Academic Robot Kit
I'm about to build the motion detection apparatus, but I can't find specs. 

What are the sizes of the moving dots? I remember two black squares, one smaller than the other, each on a white disc of paper, the disc about 10cm diameter, taking up one square of the sensor grid. Maybe 5mm and 2mm squares? Not sure. 

How fast (roughly) is it spinning?  I recall something in the neighborhood of 20 rpms, but that's a guess with a few years of memory haze in between me and that memory. 


Marcus Jaiclin

Jun 29, 2022, 11:36:22 PM6/29/22
to The Open Academic Robot Kit
I put together my version of the motion detection, roughly. Can somebody give it a quick check and let me know if it looks close enough to be considered standard?

I haven't gotten it into the sensor board yet, that will come tomorrow.  I've posted three short videos into our Google Drive folder of videos of them running, 'Movement_Test_Both.mp4' is probably most useful, it has both running side-by-side.  I ended up at about 15 rpm instead of 20, though it still seems a bit faster than my recollection even at 15 rpm.  I used 5mm for the larger square and 2mm for the smaller square, both 40mm from the center of a 90mm diameter disc.  I can easily move any of the values around, speed or distance.

Marcus Jaiclin, Ph.D. [he/him/his]
Wu Tsai Chair in Computer Science
7607 La Jolla Blvd.
La Jolla, CA 92037

Raymond Sheh

Jun 30, 2022, 12:04:55 AM6/30/22
to oar...@googlegroups.com, raymon...@georgetown.edu

Hi Marcus,

Sorry about taking so long to get back to you! We've been flat out running a high school drone competition over the past couple of days - piloting a model that we're hoping to roll out in RoboCupRescue and RMRC in upcoming years!

The moving dots in 2019 were 10mm and 5mm although at the range that we observe them at in RMRC, I don't know that it makes that much difference down to 2mm. Basically they're the "gap" in the corresponding Landolt-C. I've attached an PDF of the file (I'm pretty sure!) we used.

Similar with the speed, somewhere above 5rpm and below "motion blur is an issue" is where we tend to aim (nowadays we use those turntables they sell to display jewellery and other such things and they're generally in the 5-10rpm range).

I'm guessing you had an attachment that didn't survive the list. Did you want to maybe post a link instead?


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Georgetown University
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Marcus Jaiclin

Jun 30, 2022, 1:07:16 AM6/30/22
to Raymond Sheh, The Open Academic Robot Kit
The video link is now moot based on what you've said, so I won't bother adding it.

Thanks for the information about motion detection, this makes a lot of sense.

The drone event would be GREAT, I have talked to a number of students over the years who would love to compete in that.  And, clearly, I need an entirely new branch of robotics to learn because I have nothing better to do!  We have some challenges with aerial vehicles here in San Diego because of the enormous military presence in our area (the base where Top Gun was set is less than a mile from my house), but I'm sure something can be worked out.  


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