Pololu produces the 3π robot, with two independently driven wheels plus ball caster, an ATmega 168 for smarts, and on-board power that allows it to autonomously move around. The 3pi comes pre-assembled, and is smaller and much more maneuverable than the Asuro kit I built recently.

There’s an impressive intro on the Pololu site:

The nice thing about the 3π is that it is fully Arduino-compatible and that it comes with two nice programs, for advanced line-following and maze searching, respectively.

So I set up a little track in a drawing program and printed it out, taping the 3 x 4 pages together to create a little track. Unfortunately, I couldn’t get 3π to successfully follow the line; perhaps the printed inkjet ink does not have sufficient contrast for its infrared eyes? The robot only barely follows the line, and goes off track into a spin all the time.

I will need to create a better track with black tape one day, as suggested on the Pololu site.

Still, this was very educational. I found out about proportional–integral–derivative (PID) controllers, and how they help create feedback-based control loops that push mechanical systems to their limits without overshoot or erratic behavior.

Update 2008-11-29 : indeed, with black masking tape 3π works just fine!