It's got just two motors: a servo motor to stick its nose to the line and a DC motor with a small gearbox to achieve the movement.
The control board is based on ATMega32 which is a very nice 8bit microcontroller equiped with 32KB of Flash and 2KB of SRAM memory.
The sensor board's got 8 infrared sensors and its acquisition is multiplexed to minimize the required IO pins. Also, an ambient light cancelation is performed so that the robot could be able to run in different light conditions and (almost) over any surfaces.
The picture on the right shows the simulator developed to test the algorithm in the PC. It helped me to tune the PID controller and to check all the computation done by the microcontroller. Basically I developed a tiny "RTOS" for the ATMega32 with a cyclic scheduler to achieve the acquisition, computation and PID task in Real-Time at the desired frequency.
At these competitions, the robots have to follow a black line over a white surface as fast as possible by taking the correct way in all the branches. The right way is indicated by a small black line located in the side to which the robot should take in the incoming branch. For this reason, the algorithm's got to be accurate enough in identifying the marks and branches as well as smooth enough to complete the track as fast as possible. Also, the track has got 90 degrees corners which usually become the headache of the competitors.
In this video you can watch Slayer in the Final round of Robolid 2006 competition. It got the fastest time and no penalties because it took all the branches correctly.
Hope you liked it.