Desktop Line Following Robot

Recently many kind of robot contests have being opened and some interesting reports of the challenge are found on the web. The Line Following is a kind of the robot contests to vie running speed on the line. I build a tiny line following robot which can run on the desk, moving the key board aside will do. It is for only a personal toy reduced its size less than one fifth compared to typical line following robots, not in formura.
About Line Follower
The line follower is one of the self operating robot that follows a line that drawn on the floor. The basic operations of the line following are as follows:
1. Capture line position with optical sensors mounted at front end of the robot. Most are using several number of photo-reflectors, and some leading contestants are using an image sensor for image processing. The line sensing procss requires high resolution and high robustness.
2. Steear robot to track the line with any steearing mechanism. This is just a servo operation, any phase compensation will be required to stabilize tracking motion by applying digital PID filter or any other servo argolithm.
3. Control speed according to the lane condition. Running speed is limited during passing a curve due to friction of the tire and the floor.

There are two line styles, white line on the black floor and black line on the white floor. Most contest are adopting the first one in line width of between 15 and 25 millimeters.