Of these challenges the only one I've attempted before at PiWars is 'Blast Off', utilising a line following sensor to stay on course. The challenge is a little trickier this time as its no longer a straight run, I'm guessing so the competing robots can't just zoom straight ahead, but actually have to track and follow the line (Or detect the walls).
Reading through the challenges Wall-E will need to be able to detect when he's close to a wall, check for colours (four colours for the Nebula, green alien faces for Mars) and track a line on the floor. So in theory a combination of a camera (With OpenCV for processing) and a distance sensor should be able to cover these combinations.
For the camera I'll be going with one that connects to the Raspberry Pi's camera port. This should ensure maximum performance and compatibility, along with enabling all the hardware image processing that the Raspberry Pi supports.
|A tiny camera!
For distance sensors the choice tends to be between ultrasonic and laser based modules. With the former being sound based, and less likely to be affected by the strong sunlight that often lights up the PiWars courses, and the later being light based and generally more accurate. Whilst I already own both, and the accuracy for these challenges doesn't have to be that precise, the ultrasonic sensors do require a lot of space to install.
|A little too bulky.
|The laser sensor installed low and out of sight.