Methods and systems for operating a clutch of an axle are provided. In one example, the clutch may be characterized in static or dynamic conditions. The clutch characterization may be a basis for subsequently operating the clutch during gearbox shifting. In particular, an amount of torque that is transferred via the clutch may be controlled or adjusted according to the clutch characterization.

A friction engagement element control system is provided, which includes a friction engagement element including friction plates, which are an input-side friction plate and an output-side friction plate, and an actuation system configured to engage the input-side friction plate with the output-side friction plate with a pushing force, the friction plates having a characteristic in which a friction coefficient thereof decreases as a rotational difference between the friction plates increases. The device includes a controller configured to control the pushing force so that the negative slope characteristic becomes a positive slope characteristic in which a frictional force of the friction engagement element decreases as the rotational difference decreases, when engaging the friction engagement element.

A control method of a clutch for a vehicle may include determining whether or not learning of clutch characteristics is possible; learning the clutch characteristics when the learning of the clutch characteristics is possible; determining a clutch torque for controlling the clutch in consideration of a change amount in the clutch torque before and after the learning and controlling the clutch by the determined clutch torque; and determining whether or not it is difficult to continue to learn the clutch characteristics.

A clutch device has at least a multiplicity of clutch discs which are in frictional contact with one another, and a control unit which controls the clutch device. The clutch device is calibrated repeatedly during an operating time of the clutch device. A first calibration is performed at a first point in time. A second calibration is performed at a second point following the first calibration. The first point in time and the second point in time are within a first operating time of the clutch device and occur within a first time interval. At least a third calibration is performed in a subsequent second operating time at a third point in time. At least the second calibration is performed within a second interval of the third point in time. The first and second intervals are determined by the control unit based on a mileage of a vehicle or an energy input into the clutch device. The first interval is shorter than the second interval.

A method for operating a friction-locking shift element of a transmission of a motor vehicle includes actuating the friction-locking shift element for engagement according to a pressure versus torque characteristic curve. The pressure versus torque characteristic curve has a first characteristic point (a touch point) and a second characteristic point (a contact point), defines a first characteristic curve range between the touch point and the contact point having a first functional dependence, and defines a second characteristic curve range at or after the contact point having a second functional dependence. Once the touch point is reached, the friction-locking shift element begins to transmit torque mainly due to drag torques. Whereas, once the contact point is reached, the friction-locking shift element begins to transmit torque mainly due to friction between shift-element halves of the friction-locking shift element.

A clutch hydraulic control method and the double clutch transmission system may include performing a clutch pack flow rate control, which pre-fills a flow rate for clutch engage in a clutch pack of a clutch before shifting, when a shifting attempt is detected in a clutch controller.

A method for calibrating a characteristic diagram for a drive-train of a working machine, which contains a brake pedal characteristic of a brake system and a clutch characteristic of a drive clutch, in which an opening point at which the drive clutch is disengaged when a brake pedal of the brake system is actuated as a function of a pedal path, and/or a closing point at which the drive clutch is engaged when the brake pedal is released as a function of the pedal path, is calibrated. When the brake pedal is actuated and/or released an actual rotational speed profile of the drive-train is determined, the actual rotational speed profile determined is compared with a stored corresponding target rotational speed profile, and the opening point and/or closing point of the drive clutch is adapted to minimize deviation of the actual rotational speed profile from the target rotational speed profile.

Provided is a lock-up clutch control device of a vehicle in which a torque converter with a lock-up clutch is disposed between an engine and a transmission. This control device has a coasting capacity learning control section configured to decrease a LU differential pressure command value for the lock-up clutch during accelerator release operation and, when a slip of the lock-up clutch is detected during decrease of the LU differential pressure command value, update the LU differential pressure command value at the time of detection of the slip as a LU differential pressure learning value balanced with a coasting torque. The coasting capacity learning control section is further configured to, when operation of the PTC heater intervenes during coasting capacity learning control, correct the LU differential pressure command value by adding thereto a LU differential pressure correction value that corresponds to an increase of input torque to the lock-up clutch.

A method for operating an electrohydraulic transmission clutch of a motor vehicle, wherein, for a clutch operation, a hydraulic pressure is set by way of a regulating device of a controller as a function of a clutch signal, and, through the pressure, a disengagement element of the transmission clutch is moved through a soft region into a rigid region via a rigid point, or vice versa. The soft region is to be compensated for. Further, as a function of the clutch signal, the regulating device generates a preliminary target value signal for the pressure and a time derivative of the preliminary target value signal is generated as a movement signal, and a pilot control generates a pilot control signal as a function of the movement signal, and the preliminary target value signal and the pilot control signal are combined to give a final actuating value signal for the pressure.

A method for determining a service life of a friction clutch of a vehicle with a clutch actuation system includes setting a maximum torque at the friction clutch of the clutch actuation system. The method also includes incrementing a service life counter when an unintended slip at the friction clutch occurs, determining that wear has occurred on the friction clutch in response to reaching a specific counter value of the service life counter, and multiplying a weighted sensitivity factor by a first absolute vale which increments the counter in response to an unintended slip occurring.