[Astronouth7303]

Originally Posted by gnormhurst

I'm not sure what formula you wish you had, but think about this: while the bot is turning the wheels will trace out two concentric circles. In general, when any wheeled vehicle is turning, you want the wheels to all travel in concentric circles, with each wheel tangent to the circle it traces out. If this is not the case, something will have to give, and that's why you see four-wheeled bots jumping around as they try to turn on the carpet.

I managed to figure that much out, fortumately. I just couldn't figure out how to solve for Radius.

Originally Posted by gnormhurst

If you think about it, the front wheels of a car are not always parallel -- during a turn the inside front wheel should be turned at a sharper angle.

So this note applies only to two-wheeled bots.

And Skid Steer/Tamk Dirve, right? just put the 'Left' and the 'right' at the average point of where the wheels touch the ground

Originally Posted by gnormhurst

If the two wheels are 30" apart, and the outer one runs at three times the RPMs of the inner one, the outer one will trace a circle with three times the circumference, and thus three times the radius. The difference between the outer and inner radii is always 30", so in this case the inner radius must be 15" and the outer, 15 + 30 = 45".

radiusInner = radiusOuter - 30;

wheelSpeedRatio = radiusInner / radiusOuter;

substituting ( radiusOuter - 30 ) for radiusInner:

wheelSpeedRatio = ( radiusOuter - 30 ) / radiusOuter ;

So if you want a certain turning radius, that is a formula for computing the ratio of wheel speeds that you need.

sI/sO = 1-W/rO? You're good.

sI*rO = (rO - W)sO
sI*rO = rO*sO - W*sO
sO*rO - sI*rO = W*sO
(sO-sI)*rO = W*sO
rO = (W*sO)/(sO-sI)
rI=W-rO

Thank you!