[ale] robots

[Jeff Hubbs]

> That's kinda my point - if it's a fire-and-forget swarm of
> bots, then someone is going to stick a finger in the cutting
> area, and it *better not* do more than break the skin, or
> there will be legal problems (I'm assuming that it's reasonable
> for a blade to cut skin, and that an unsupervised toddler who
> gets a cut from a yard tool is not a problem, while one who loses
> a finger from a yard tool is)
> 
> -- 
> Pete Hardie                   |   Goalie, DVSG Dart Team

Depending on how the blades are shaped, I think it could be designed
such that you would have to try really hard to get a finger caught,
i.e., pick it up, jam a finger into the cutter, and wait a few seconds.

Jam correction would be very important because, whereas I think it is
reasonable that you should clear 1/2"- to 1"-thick branches out of your
yard by hand, I don't think it's reasonable to take that down to the
twig level.  My intuition tells me that a little twig would go into the
cutter just like grass would but would be too tough for the moving blade
to get through.  If the blade is a turning blade like I described
earlier, its motion could be easily detected and its motor could be made
to reverse for 1/2-1 rev.  The blades could be shaped such that when the
rotation is reversed, anything that's due to get cut will just get
ejected.  Follow that up with a bit of a maneuver to back away from the
offending object and resume operation and you have some robustness
there.

I don't know if you've had occasion to watch a Bio-Bug (~$30 at toy
stores) but they are based on Tildenesque concepts (although I think
it's realized in the digital domain instead of analog).  They have four
bent-paddle-shaped legs with two feelers in the front and one in the
back.  When they get blocked, they will change gait modes in an effort
to free themselves.  

I recall reading an article featuring Tilden and on the subject of
robots that go around the house doing things (not dissimilar from our
lawnmower problem here), he says that if you get up in the middle of the
night to go to the bathroom and trip over the dog, well, he's soft;
he'll heal - whereas if you trip over some very precise, highly
articulated robotic device and snap off a leg in so doing, you're
looking at a pretty hefty repair bill.  Tilden's robots deal in
"squishiness" and inexactitude, which is handled by its analog circuitry
much more readily than it could be in elaborate digital control systems.

- Jeff


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