[ale] robots

[Jeff Hubbs]

On Tue, 2002-05-21 at 14:32, Byron A Jeff wrote:
> > 
> > Byron A Jeff wrote:
> > 
> > > point that it'll be much simpler than my current problems. Here are some of
> > > the issues I have on the table with my current project: a useful robotic
> > > lawnmower:
> > 
> > Gee, why didn't you go with something like a robotic meat cleaver, at 
> > least then damage would be confined to a single building..
> 
> Safety is at the top of my list. I'm planning on using it in a secured
> enclosed yard that will idle the unit at the slightest detection of
> movement. The cutting blade is only 9 inches and will be located under the
> bot. Someone will have to work real hard to get to the dangerous stuff.
> That's why teenagers are the most dangerous. They think it would be funny
> to hop a fence, approach a dangerous item and see what it does. My hope is
> that if it does absolutely nothing when approached, that it'll fail to
> be interesting.
> 
> > 
> > So, the real question is, how far along are you?  Is it using embedded 
> > Linux, or some other OS?
> 
> Like I said in my post, I'm not even thinking about the brains right now.
> It'll be microcontroller controlled though, as I have a couple of dozen
> varieties of PIC controllers and the software expertise to make them sing.
> 
> Since it's a single purpose real-time system, there really isn't a need to
> carry an OS infrastructure.
> 
> I'm still doing component testing. The drive motor system works OK in my
> prototype wooden frame. I'll have to see how well it does once the gas
> powered generator is mounted. The cutting motor certainly cuts grass using
> a 9 inch edger blade. However the cuttings gets wrapped up in the motor, so
> a shield is the next priority.
> 
> As for the power system, I have the alternator and the battery, but I'm
> looking for a cheap working lawnmower engine. Free would be perfect.
> 
> BAJ
> 
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I'd like to respectfully submit that you're going about this all wrong. 
You appear to be trying to take the concept of the Snapper/Toro/Lawn Boy
and substitute human control with machine control.  In so doing, I think
you're losing sight of the fact that that concept is based around the
notion of a walking human operator.  Eliminate the human, and there's no
longer any need for the characteristics of the mower that are only there
for the sake of the mower operator.  

If I were going to try to solve the problem of robotic mowing, I
wouldn't concern myself with anything that was even remotely
lawnmower-like.  I would fashion a crude walker, six to eight inches in
length, that works its legs through analog tech and was fronted with a
kind of low-speed rotary scythe - a turning blade resembling that of a
food processor that turned against a stationary bypass blade.  I would
build several of these and make them solar powered.  I would consider
myself successful if I can drop these things in the yard in May and
gather them back up in November, having never had to actually go out and
mow the lawn in between.  

Reference http://www.solarbotics.com/.

The question to be answered is exactly how "smart" should the robots
be.  I would suspect that the robots needn't follow any preset orderly
path nor would it be necessary for them to specifically seek out high
grass to cut.  Rather, I think that if they simply wander around the
yard, snipping grass blades as they go, they will eventually go
everywhere they need to go and leave you with a decently attractive lawn
with the blades cut to an average height.  In order to make it possible
to solar-power these little guys, all motion should be very slow; I'd
say that these things ought to be able to creep maybe 10-12'/hour.  The
big problem that I think would need to be addressed is perimeter
containment; i.e., keeping the little buggers from wandering across the
street.  If the bots are set up to alter their gait when they hit an
obstacle (if you let a Bio-Bug loose in a room, you'll see what I mean)
then you're set for any fences or walls you might have, but if you've
got no boundary between your yard and the neighbor's, you may have to do
something special to keep the mowbots :-) hemmed in - unless, of course,
your neighbor wouldn't mind the idea of having these things buzz his
yard as well (have him kick in some $$$ for parts).  

One might also want to design these bots to handle inversion, either by
sensing the state and executing a flipover manuever, or by simply
designing them to be heads/tails insensitive (solar cells on top and
bottom, cuts the same either way).

I think if you go the high-speed whirling-blade route, you're going to
have more unintended consequences than you can stand (many being
safety-related) and you'll be spending all your time futzing about with
this thing instead of going about your other business while your yard is
slowly munched into submission all summer long.

- Jeff



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