My new robot can now follow a line pretty robust. Here is the first video of it:
This is what the robot "sees" when following the line:
The red and blue pixels marks the left and right edges of the line. I don't use that information yet and it is not tuned very well. The green pixels marks the center of the line. The yellow line is the result of the processing of the green pixels. This is the only information the robot uses to steer at the moment. It doesn't recognize intersections or forks on the line and doesn't even recognize that the line ends. More to come later...
A picture of the robot: