A motor assembly comprises an electric power train that is adapted to be connected to a power source and is also adapted to impart a torque to a wheel when the motor assembly is operating. The assembly further comprises a power determination means adapted to determine the amount of power supplied from the power source to the electric power train when the motor assembly is operating. In addition, the assembly comprises a rotational speed determination means adapted to determine a rotational speed of the wheel when the motor assembly is operating. Moreover, the assembly comprises a torque determination means adapted to determine a command torque value indicative of a requested torque to the wheel.