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[DPRG] Mini-DARPA beacons, sonar

Subject: [DPRG] Mini-DARPA beacons, sonar
From: John Swindle swindle at compuserve.com
Date: Tue Jun 29 18:48:05 CDT 2010


Five years ago, several of you were interested in navigation 
beacons for your back yards to experiment with a mini-DARPA 
Challenge. Members suggested using sonar, lasers, infrared, or 
radio. I suggested using three loudspeakers (the beacons) and a 
microphone (on the robot), without any radio or laser 
synchronization. I couldn't get it to work then, but I have it 
working now. It's like LORAN, but using sound instead of radio.

I don't want to build a robot, so I wonder if one or more members 
would like to collaborate on adding the beacon receiver to his or 
her robot and then win Square Dance and Figure-8. In the arena, 
the beacons would probably be about 18 feet apart and the robot 
would drive a 12-foot square. When the robot needed to 
recalibrate its odometry, the robot would stop and listen. The 
navigation location data would come from a script running on my 
PC, but the robot would decide what to do with that data. The 
robot would need to stop for about 45 seconds for an accurate 
location. The robot might need to check its location several 
times (which would take a lot of time), or, since the nav data 
seem to be very repeatable, the robot could just check to see how 
close it is to its starting position when it thinks it is 
finished. Square Dance and Figure-8 are not timed, but I don't 
know if the 45-second delays are acceptible.

My PC could either be carried by the robot, or the robot could 
carry a wireless mic which would be self-powered (no interface to 
the robot). Somehow, the robot would be told where it is. I don't 
know what the best interface would be for giving the nav data 
back to the robot. Someone would have to help me with that part. 
If the robot doesn't carry my PC, then the interface would likely 
have to be WiFi. If several members are interested in using the 
beacons, then the beacons could be set up and left in place 
during several runs and my PC could send nav data to the robots 

I have a few questions for specific folks, such as:

Paul, Scott Sumner, and Will: I think you have robots that can 
carry a one-pound wireless microphone or maybe a three-pound PC, 
right? Are any of you interested in being the platform 
collaborator? (I mention these guys because they've expressed 
interest in beacons in the past, and I think they have robots 
that can carry a payload. I don't mean to play favorites. Anyone 
can use the beacons.)

Scott: May I borrow your wireless mic again?

Paul: If your Roomba platform were used, what does it take to 
communicate by WiFi to your robot? My script can launch and kill 

Ron and Dale: To be more real-world, the beacons need to be run 
as a separate gadget. I could use a second PC to do that, but it 
would be fun to use a handheld microcontroller instead. I know 
y'all both do that sort of thing.

Ed: About the contest rules: Is a contestant really allowed to 
win Square Dance and Figure-8 with a robot that listens to 
beacons? (If so, I predict nailing it to within a few inches.) 
And is there anything special about a collaborated entry? Any 
limit to the size of the team?

Ed: I've prepared a slide show. Let me know if you'd like me to 
present how the beacons work.

Best to y'all,
John Swindle

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