offset differential steering

Some people have reported trying it -- because the design of their robot
required it -- and it seems to work. I have not seen any scientific
studies on whether there are any advantages or disadvantages.

-- Gordon

Thanks for the input, Gordon. Logically it should work, but I'm far from
sure it will be that easy.

Marcus

    --FWIW during the heyday of Battlebots someone dreamed up the
"Meltybrain" controller for predictable steering regimes on spinning
two-wheeled robots. Maybe one of these would help?

--
        "Steamboat Ed" Haas         :  Before the last "election"          
        Hacking the Trailing Edge!  :  a fifty was a twenty...
                          www.nmpproducts.com
                   ---Decks a-wash in a sea of words---

You are asking about two wheels that are parallel, but not both
perpendicular to an imaginary line passing through their centers.  I
believe that this is essentially the same as the case where you have
crooked wheels.  So if one wheel is forward to the other and both
wheels turn at the same rate of speed, my guess is that the system
will tend to drift to the side of the forward wheel.  The wider the
bot, the less pronounced the effect.

Gary

Bronson Silva did it back in '03 at RoboMaxx with Bob, the micro sumo
bot. (http://www.robotdirectory.org/details.cfm?cat=1&id 8) As I
remember, Bob moved about just fine.

I have been trying it with Tiny, which measures smaller than micro-
but larger than nano-size. It does indeed turn to one side, but I
think one of my motors is slightly less powerful than the other:
http://robotguy.net/tiny1.jpg
http://robotguy.net/tiny2b.jpg
http://robotguy.net/tiny3b.jpg
http://robotguy.net/tiny4b.jpg

The biggest problem I have had is that every time someone looks at it
they ask "Did you know your wheels are crooked?"

I am molding several new chassis for Tiny this week and getting more
motors probably next week. I hope to build 5 of these for a
"swarmlet". If you are interested in the results, keep an eye on my
blog (http://robotguy.net/blog ).

-Robotguy
http://robotguy.net/blog

If mechanical system has center of (rotational) symmetry and both
wheels have the same velocity but opposite direction drift is
impossible: in symmetric system all directions are equals, no
preferred directions exists.

But both wheels MUST SLIDE relative to ground; the bigger wheel
axis eccentricity - the bigger sliding. It have at least two
negative effects:

   - more power consumed (because sliding required power)

   - rotating on the inclined ground accompanied by sliding down
     (inclination destroyed symmetry :-)

So big eccentricity is obviously harmful.

Nick