Subject:
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Re: Automatic feeding.
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Sat, 15 Feb 1997 00:28:33 GMT
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Original-From:
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Chuck McManis <cmcmanis@freegate#stopspammers#.net>
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Reply-To:
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CMCMANIS@FREEGATE.NETstopspammers
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Viewed:
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1254 times
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Barry Brouillette wrote:
>
> Has anyone worked up a system where a Hanyboard bot monitors it's
> battery level and then when it starts to get low it rolls over to
> a charging device and "plugs itself in"? It seems like this
> should be doable but I don't think I've seen any descriptions of
> workable systems.
One way that I did this was to steal an idea from the railroad
world.
> Two systems would seem to be needed:
>
> 1) A mechanical connector system which would allow the power
> connections to be made by simple driving up and pressing
> against it.
In my case I put a conductor (a wire) around the outside of my
two drive wheels. At the top of the wheels was a 'brush' (which
was a simple spring loaded contact) and on the floor were two
strips of aluminum foil the correct width apart to contact both
wheels. If you don't mind a bit of voltage loss, connect your
brushes to a fullwave bridge rectifier, then your robot can go
into the recharge bay in either direction.
> 2) A beacon system for finding the connector. Has anyone got a
> cheap, very simple beacon system that they are happy with?
In my case I used a light bulb at the bottom of a toilet paper
tube roll. This cheap collimator(sp?) allowed the robot to detect
when it was lined up with the beacon (it couldn't see it otherwise)
and the beacon and the detector were at a fixed height. In the
recharging bay area were two short panels which formed something
of a guiding gate (if you've seen a device for loading cattle you
can imagine this device)
Having a robot that can turn in place helps a lot.
This was the algorithm. :
drive along and wait for the beacon to be detected. (note
there was some dead reckoning going on in my case I knew
the basic room layout and my own general position.
When detected, turn in place until the beacon is right in
front of you.
If you loose the beacon wait, if you don't reacquire it in
3 seconds (ie someone was standing in front of it) then
turn 90 degrees (the detector was on a servo'd platform
so it could look full left or full right.) then move back
and forth in larger motions until the beacon is re-aqcuired.
When reacquired drive forward.
When power is detected on the wheels, stop.
First the joke part. So I showed this to some folks and one wise
cracker put some toilet paper back on the tube and suggested that
my robot did not want to be disturbed. And yes, it did look like a
small toilet for a robot :-)
Next a couple of times I lost the beacon just as I was driving into
the bay and tried to turn in place in the bay which was very
unsatisfying, not to mention hard on the bay walls. When I rebuild
it I will use sensors on the robot to tell it that it is close enough
to just ignore looking for the beacon. Finally, one time after the
robot had knocked one of the walls of the bay off, it managed a 90
degree turn which put the conductive wheel ACROSS the recharging
circuit. I blew out a chip when this happened (it was a MAXIM nicad
recharger chip). I think the spacing of the foil pads should be wide
enough so that you couldn't short them by driving over them sideways.
My current investigation is that I've taken apart an electronic
toothbrush that recharges inductively. It will probably appear a
bit outrageous but there is a lot of security in an inductively
coupled system (and you can use it outdoors which will be a big
win) I'm not sure about how much power I can easily get through
such a system (although Huges/GM has a patented system for recharging
electric cars this way.)
> If I could find a beacon that I could build for a few bucks that
> would identify itself to the Handyboard I
> could use it for this and a bunch of other navigation needs.
As with any 'few bucks' beacon system, it helps to have several
different types so that you can cross correlate them.
--
cmcmanis@netcom.com http://www.professionals.com/~cmcmanis
All opinions in the non-included text above are the sole opinions of
the author.
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Message is in Reply To:
 | | Automatic feeding.
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| Has anyone worked up a system where a Hanyboard bot monitors it's battery level and then when it starts to get low it rolls over to a charging device and "plugs itself in"? It seems like this should be doable but I don't think I've seen any (...) (27 years ago, 14-Feb-97, to lugnet.robotics.handyboard)
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