Newsgroups: comp.robotics
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From: gregc@ (Greg Campbell)
Subject: Project descriptions
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Message-ID: <CGpnDz.2y7@idacom.hp.com>
Date: Thu, 18 Nov 1993 23:17:59 GMT
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Organization: Hewlett-Packard
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Hello fellow robotics enthusiasts!

I have been reading this group religiously for about a year now. I have
used some of the ideas that I have read, but I have never posted anything
about my personal projects to the group.... I would now like to change that.

I think that one of the best ideas that has floated around the group for
some time now is the Tecnik LEGO sets. When this was suggested a while
ago, I went out and got a few sets of the stuff (my live-in girlfriend
at the time was worried that in a few months I would curl up into the
fetal position and start sucking my thumb!).

With the LEGO, I have build a small autonomous vehicle. It is built with
the motorcycle set (for the big wheels) and two motor sets. I kind of put
the two motors side-by-side with a set of gears on top of each. Each motor
drives one wheel. Having the motors below the axle plane creates a really
nice, LOW center of gravity - very stable. I built two bumpers with four
micro-switches each (using epoxy to attach the switches to a long [1x10]
LEGO block). I am controlling the whole rig with the M68HC11EVBU evaluation
board (good enough until I can get my hands on a sample 'HC11E9). I am
using two transistor H-bridge configurations to control the motors. I have
not PWM'ed the motors yet, but will do so in firmware in the near future.
As I said before, with the low center of gravity, slamming the motors full
on and full off is not much of a problem. I use two 9 volt batteries to
power the thing - the 6 AA battery pack that comes with the motor set does
not really hinder the movement of the vehicle in any way, but is just a
little too awkward for the size of it. One 9 volt is for the motors, the
other is for the computer.

This vehicle (which I call C.O.W. - Computer On Wheels) is used for
demonstration purposes. I belong to a group of scientists in Alberta called
"Science and Technology Hotline." Basically, the group serves the schools.
A teacher can call up the hotline with a question that they need answered,
or if they need a guest speaker, ect. The hotline forwards the request on
to qualified people....  So, I built the robot to use at robotic
presentations that I am asked to do in the schools around here. The robot
moves around the floor running into hockey pucks (I bring about a dozen
pucks with me to the school). When it hits a puck, it backs up a couple
of inches, pivots about 160 degrees, changes it head direction, and trucks
off missing the puck. The kids find the "about-face" portion really
interesting. I get all kinds of questions like "why doesn't it get confused
when it goes backwards like that?"



One of the other projects I was involved in was building a micro-mouse
for my final project in University (I am a Computer Engineer). This is
by far a much bigger project than the lego
toy. My partner and I worked on it for the entire school year, and never
quite compleated it (the hardware was all done, but the maze-solving
software never really got finished). We had the university machine shop
build us this amazing base structure that held the wheels, motors and
IR sensors that counted the gear teeth that rotated by on the wheels.
Above this was a metal plate that the computer was mounted on top of. The
plate acted as a very good ground plane to protect the computer section
from EMI from the motors. The computer was a MC68000 that we, believe it
or not, WIRE WRAPPED. It ran at 10MHz. We decided to build our own computer
because the CE department only had VME computer cards for us to work with.
The VME bus draws around 1 amp at steady state, which does not lend itself
well to being battery powered. We chose the MC68000 because that was what
the university used in it's labs, and they didn't have the tools for anything
else. It is a nice processor, but major overkill for what we got done (it
would have been nice when we got more heavily into the maze software).

The "ground plate" had plastic blocks with angled holes that IR LED emitter/
detector pairs sat in. The LED's were aimed downwards. There were 4 banks
of 5 LED pairs (one bank on each corner of the ground plate). These were used
for finding the wall. Ideally, each of the banks would ride over the the
walls - so we could tell where the mouse was in relation to the walls. The
whole unit was about 20 cm square, and about 25 cm tall (there were two
wire wrapped boards stacked on the ground plate - one for the computer,
and one for all the rest of the driver cct's).

The micro-mouse was a very complex project, and I would highly recommend
anyone interested in "giving it a shot" to do it.... I learned A LOT on
that project!


I am currently intrigued by the idea of a CNC drilling machine, and also
with the "CD jukebox." I am not sure what the near future hold for me as
far as projects go.... Maybe even a LEGO micromouse!!!


Please keep up the GREAT descriptions of YOUR projects. They inspire all
of us out here in net land!!!

Cheers!
Greg






-- 
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Greg Campbell      email: gregc@idacom.hp.com       HEWLETT-PACKARD
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"When you are up to your ass in alligators, it becomes awfully 
