Hlp
How can we get the robot to move in a circle?

100- inch radius

Explanation:

The robot will drive towards the cylinder.

The robot should make 90 degree turn.

The robot should drive, with one wheel going slower as the other. (But it will be an constant). The robot will drive towards the cylinder.

The robot should make 90 degree turn.

The robot should drive, with one wheel going slower as the other. (But it will be an constant).

enter image description here

Between point 2 & 3 in the image, the displacement of the robot will be 90 degrees turned in 2*R*Pi/4 distance.

For the wheels, indeed: 2*(Radius-6)Pi/4 and 2(Radius+6)*Pi/4

The time of both wheels need to be the same. So, if you want to do this path in 10 seconds:

One wheel will set at (2*(Radius-6)Pi/4) inch/s. And the other wheel at (2(Radius+6)*Pi/4) inch/s.

But as Mactro mentions, the ratio should be the same.

(2 * (100 - 6) * Pi) / 4 = 147.654854719 (2 * (100 + 6) * Pi) / 4 = 166.50441064

So, 148/167 ratio for a 100 inch radius. I think this is going to help you?