After watching my bot crawl across the bumpy yard, sans brains at this
point, I can tell you that dead reconing will fail immediately.  The thing
doesn't even cut a straight path, kind of wanders back and forth, climbing
up and down the bumps and over cats, baseball bats molehills etc.

Standard GPS is not accurate enough for mowing control.  But it would be
accurate enough for theft control (see long thread March 2001)  to tell when
your bot had left the yard.  What's the cheapest GPS on the US side of the
water?

--Lawrence

----- Original Message -----
From: "Dan Michaels" <oricom@USWEST.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Friday, August 31, 2001 11:25 AM
Subject: Re: [EE]: - Botboard


> Madhu Annapragada wrote:
> >I have been toying with this idea for a while and I will throw it out
there
> >to see if it even holds up to the piclist scrutiny. What do you think
about
> >teaching the bot the first time? With heading information from a compass
and
> >wheel rotation information from encoders, the bot would build a table of
> >heading changes vs wheel rotations the first time (starting from a home
> >position). One would use a joystick to mow the lawn the first time. The
bot
> >records the wheel position every time the heading changes by a certain
> >amount. The second time around, the bot would head out in the first
heading
> >direction until it reaches the wheel rotation figure for the next heading
> >change, change to the new heading and so on.
> >Of course, the problems I see right away are wheel slippage and  noise
from
> >the compass. But for arguments sake, if I could solve those problems, do
you
> >see any other potential pitfalls for this method.
> .........
>
>
> Personally, I don't think that a dead reckoning system would work
> at all well in this case. Yards are never perfectly flat, and the
> moisture content - related to wheel slippage - is going to change
> daily. However, if you were to add "some" kind of fixed markers, I
> think a combination approach between marker sensing and dead
> reckoning based upon an internal representation would put you in
> business.
>
> Possibly a wire around the outer perimeter, as Quiet Joe mentioned,
> plus some low bricks at the edge of the flower beds, etc.
>
> - dan
> =============
>
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>

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