Re: [mowbot] Locomotion (was: Hello, and lots of ideas)

Dave Everett (Deverett nospam at
Tue, 24 Sep 1996 21:43:33 +1000

robin nospam at wrote:
> own, being prone to getting gummed up. I am still inclined to
> carry on the successful scheme I have used on the table-top: two
> drive wheels (D) with their axes on a diameter of a circular outline, and
> a third wheel on a swivel for support. On a smooth surface, this doesn't
> even have to be a wheel, just a rounded foot is adequate.
> ___
> .- S -.
> / c \
> | D D |
> \ /
> `-___-'

I was going to leave this till we were a bit closer to deciding a
chassis but,,
There is a flaw in using the diameter axled differential drive system.
Firstly I see you opted for only one skid, what happens when the robot
If you add another skid (or castor) this will cause problems in hills
valleys in the lawn, dips will cause the castors to lift the drive
off the ground and Mowbot will happily mow the air until the batteries
run out ;-)
Hill will cause violent slopping that could affect sensor readings.

I think as a minimum, a 3 wheel platform, where each wheel exerts equal
on the ground is the best compromise. This can still be done in a
circular base, I
have one here to prove that, just move the axle forward about half way
and place
the castor at the rear. Of course doing this negates the ability to
turns in the robots own diameter, and so I would suggest that a slightly
rectangular or square base would be more suitable as it will allow us to
the robot to the width of the axle base.

> Indulging my fantasies, I would really like a legged robot, but I
> think that is still a bit beyond the limits of technology we should
> try to adopt. Maybe in Son of Mowbot:-)

That appeals to me too :-) I've tried making legged robots that are
bigger than
those allowed using RC servos, but the motor and battery problems are
huge :-(

Dave Everett.