Method for ascertaining a characteristic variable of a clutch during generator operation

A method for ascertaining a characteristic variable of a clutch installed in a drive train of a vehicle for transmitting a transmission torque between a clutch input and a clutch output, wherein the drive train of the vehicle comprising:

• a first electric motor is connected to the clutch input and to an internal combustion engine and may assume a generator operation when it is driven by the internal combustion engine,
• a second electric motor is connected to the clutch output;
• the clutch input having a first rotational speed and the clutch output having a second rotational speed,
• wherein, in response to ascertaining that a speed difference between the first rotational speed and the second rotational speed is less than a threshold value, the transmission torque during the generator operation is ascertained by activating the clutch to adopt a slipping state and setting a predefined rotational speed difference between the first and second rotational speed,
• wherein, during the generator operation, the first electric motor causes a counter-torque opposing a drive torque from the internal combustion engine, wherein the transmission torque is ascertained to be equal to a torque difference between the drive torque and the counter-torque.