I'm building a laptop robot based on a RAD base (see [1], though I've done more work since last updating that page). It actually goes forward and backward in a straight line quite nicely, thanks to a sort of clutch connection (not sure of the right term) between the two treads.
However, turning seems rather unreliable. Oh, it turns with enthusiasm, but exactly how much is it turning? I can never be quite sure. It turns by skidding, of course, and I think it's unlikely to skid exactly the same way twice. So, even adding encoders to the tracks wouldn't really tell me how it's moving in relation to the ground.
I've thought about getting some cheap optical mice and mounting them (or their guts) on the belly of the thing. One at the front and one at the back ought to do, giving me everything I need to measure linear motion and rotation. But mice seem to require very low clearance, which is likely to make it rather fiddly.
I understand that optical mice work via image-processing... I'm venturing into guess-land here, but I'd guess that the requirement to be right on top of the surface is a focus issue. Has anyone modified a mouse to work at a farther distance by adding or changing lenses?
(Hey, you hobby-robotics shops: if you could make a gadget that would provide X/Y speed data over nearly any surface from, 2-5 cm away, roboticists would beat a path to your door!)
Are there other good ways for tracked robots to turn reliably? Some simple solution I'm neglecting?
Thanks,
- Joe
[1]