Labyrinth maze solver

Screenshot-2.png (894311Bytes)

Hello All,

I am building an automatic maze solver using the following as an inspiration:

http://www.youtube.com/watch?v=Prq78ctJ2Rk&feature=related

I have built the maze control with steppers and I am using the following stepper motor control board:

http://www.sparkfun.com/products/10025

I am using a vision system to control the maze solver. I also found a link where this problem has been solved:

http://cse.logicol.org/?p=52

They have used template matching to identify the ball. The team mentioned in the above link also uploaded a video where it looks like they have canny edge detection for finding the path and executing a PID algorithm.

http://www.youtube.com/watch?v=8b5ARjT22bg&feature=player_embedded

Now, I have also established template matching and edge detection in opencv. I have also established controls of my stepper via USB serial port. How do I implement the navigation algorithm? How do I implement the PID control? I know the concept of PID control theoretically but I just don't know to implement it using the information from the camera. I am just clueless about making the ball follow the line.

Please find an attached image of the result I have obtained so far.

Sai