Thank you for your reply (and Mastermime too, btw)
The sensors used for this robot are:
Light sensor (for turning on the leds when it's dark)
Electrec Mic (for detecting the whistle frequency)
2 Mid-Range Sharp sensors, like you said - http://www.sparkfun.com/products/242
2 Optical detector - http://www.sparkfun.com/products/246
These are used for line following, for area measurement and to avoid falling down from a table (for example) when in autonomous mode (represented by the black line in the bottom).
The sensors output an analog signal, that connects to the analog inputs of the microcontroller. So I get the distance value, instead of only 0v and 5v. So this is useful for hand controlling. If the hand is near the sensor, it moves backward, if is far away, it moves to front and if it doesn't detect anything, it stops.
I don't have any sensors in the wheels or in the motors. Just normal stepper motors.
Any question, please ask.