[Dprglist] ultrasonic positioning systems

[John Swindle]

Wow! The Marvelmind specs and videos look great! Looks like they've been incorporated since 2016. Specs are almost exactly what I am trying to do. Very neat. Thank you for pointing me to that!
They are doing 3D trilateration. Cool. 3D geometry always bumfuzzles me so I haven't even tried it.
They only require 2 beacons for 2D, and 3 beacons for 3D, so they are doing time-of-flight (as their website says) based on the radio synchronization. I'm doing difference in time-of-flight which does not use a radio and does not require synchronization but which requires 3 beacons for 2D. The radio idea is better and faster, but I never found a radio that had a communications stack with low jitter. Radio is not my thing, so I'm sure there are radios that can do the job that I don't know about.

Since their beacons are ultrasonic, they require line-of-hearing which is essentially line-of-sight between the beacons and the robot. The localizer I demonstrated operated at audible frequencies and was not affected by most obstacles, so my line-of-hearing is much more than line-of-sight. People rightly objected to my localizer's audible noise, so I switched to ultrasonics, which have all sorts of problems, such as line-of-sight requirements and absorption.
I am surprised that the range is 30 meters or more at ultrasonic frequencies. The absorption in air (not the 1/r spreading) is huge at those frequencies, far worse than the spreading. For one of the outdoor DPRG contests, I estimated I'd need powerful emitters (50 watts or more each) in order to cover a 150 foot square arena with ultrasonic frequencies. I abandoned the experiment. Neat that Marvelmind solved that problem.
I've been trying to keep the frequencies low to avoid both the line-of-sight and the absorption problems, and to make omnidirectionality easier. Maybe I will continue to work on that. Otherwise, it seems Marvelmind has solved the problem! Good stuff.
Later,John Swindle


-----Original Message-----
From: Karim Virani via DPRGlist <dprglist at lists.dprg.org>
To: dprglist <dprglist at dprg.org>
Sent: Thu, Feb 20, 2020 9:32 am
Subject: [Dprglist] ultrasonic positioning systems

Does anyone have any opinions about the MarvelMind Indoor Navigation system? 
https://www.superdroidrobots.com/shop/item.aspx/ips-indoor-navigation-positioning-system-dsp-starter-set-nia-v5-07/2664/_______________________________________________
DPRGlist mailing list
DPRGlist at lists.dprg.org
http://lists.dprg.org/listinfo.cgi/dprglist-dprg.org
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.dprg.org/pipermail/dprglist-dprg.org/attachments/20200220/2a95aa59/attachment.html>