Two motors are defined, wheelL, wheelR. They are grouped in wheels for faster access when the given speed is the same for both wheels.

Wheels speed go from -500mm/s to 500mm/s.

Each motor is aliased to its .val attribute. This atribute gives the current wheel speed in mm/s:

  wheelL = 10; 

is equivalent to

  wheelL.val = 10;

The drop attribute holds the current state of the wheel. It is 0 if wheel is on the floor, 1 if the wheel has no ground contact.