Motive power unit for a pedal vehicle, comprising a first and second motor, the latter being meshed on the bottom-bracket spindle and the first motor being connected to a sun gear, a planet holder being connected to an output sprocket of the motive power unit, which comprises a measuring element arranged to produce a measurement signal indicating a torque supplied by the first motor and a control unit producing a speed control signal to be supplied to the first motor and a torque control signal to be supplied to the second motor on the basis of the angular velocities of the motors.