Set the parameters for the movement (forward and backward) of the robot
The robot will use time as a parameter for movement (forward and backward) rather than distance (for example: centimeters).
The good news it that the underlying system of ev3 let us define a time or a position for the Motors: https://github.com/topikachu/python-ev3/wiki/Using-Motors
Concerning the position, it is not as easy as saying that: distance = speed * time
Indeed the distance will also depend of the texture of the floor and the charge of the battery.
This means that if the motors will run for a period of 5 seconds at a speed of 60 pulses per second, it is not easy to be sure of the traveled distance.