Line tracking robots

Pls I am very new to this site but I beleive I can get the stuff I need here. I am doing a project on line tracking robot. I need to know the background, objective, scope, contraints and block diagram overview of the project. I realy don't know where to start and I am running out of time. Its urgent, please help me. pictures and diagrams will help a lot.

thanks.

I'll point you to my favourite site on this subject.

Here's a pic,
**broken link removed**

Mike.