Method for determining the torque of an electric motor

A method for determining a torque of an electric motor on a motor vehicle, the torque being generated by a rotor of the electric motor, and the torque being transmitted from a drivetrain to at least one drive wheel, the method comprising:

• measuring a rotation angle of the rotor of the electric motor;
• determining the torque generated by the rotor;
• wherein the at least one drive wheel driven by the rotor is fixed, the stationary rotor does not generate any torque, and a first rotation angle of the stationary rotor is measured, and subsequently,
• wherein a torque is applied by the rotor to the drivetrain, so that the rotor carries out a rotational movement due to the limited stiffness of the drivetrain, and subsequently
• in an equilibrium state between the torque generated by the rotor and a counter torque of the drivetrain, a second rotation angle of the rotor is measured, and
• wherein at least one of the torque generated by the rotor and the total stiffness of the drivetrain is ascertained from the measured values of a first rotation angle and a second rotation angle of the rotor.

A drive unit, which is a hybrid drive unit, for a motor vehicle, comprising:

• an electric motor having a sensor for detecting a rotation angle of a rotor of the electric motor;
• an internal combustion engine;
• a drivetrain;
• at least one drive wheel;
• a parking brake for the at least one drive wheel;
• and
• a control arrangement configured to perform the following:
• measuring a rotation angle of the rotor of the electric motor;
• determining the torque generated by the rotor;
• wherein the at least one drive wheel driven by the rotor is fixed, the stationary rotor does not generate any torque, and a first rotation angle of the stationary rotor is measured, and subsequently,
• wherein a torque is applied by the rotor to the drivetrain, so that the rotor carries out a rotational movement due to the limited stiffness of the drivetrain, and
• subsequently
• in an equilibrium state between the torque generated by the rotor and a counter torque of the drivetrain, a second rotation angle of the rotor is measured, and
• wherein at least one of the torque generated by the rotor and the total stiffness of the drivetrain is ascertained from the measured values of a first rotation angle and a second rotation angle of the rotor.