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### DIWA adaptation

#### In order to achieve optimal shifting quality, the principle of adaptive control is used in the DIWA. This means manufacturing tolerances and ageing conditions that reduce the shifting quality are largely compensated by the controller itself. In short: The transmission software is optimized for low wear and high shifting comfort.

Working principle:

Shifting operations in the DIWA are always performed by engaging or disengaging the clutches. For this purpose, the clutch disks are pressurized with a control pressure that is controlled by solenoid valves. The control pressure profile thus determines when a disk is disengaged, slips (with what resistance) or is engaged. The ideal control pressure profile has been preset individually for each gear change (1-2, 2-3, 3-4, 4-3, etc.). The most important shifting quality feature is the slip time of the clutch disks. During the slip time, the drive shaft is synchronized with the output shaft. Due to manufacturing tolerances and ageing conditions, the actual disk slip time may be different from the ideal slip time. This is where adaptation becomes active. A correction factor is calculated for the difference between the ideal and the actual disk slip time, which adapts the control pressure profile for the next shifting operation.

The adaptation takes place in two stages: running in the vehicle (rough adaptation) and fine adjustment. Rough adaptation is carried out during the first five shifting operations (adaptation counter) where the control pressure profile is set with major correction values. This quickly compensates for greater deviations. Afterwards, fine adaptation is carried out. This includes only minor corrections. Due to this splitting into rough and fine adaptation, the adaptation data must be deleted after maintenance work has been carried out on the disks. Otherwise, the transmission controller would attempt to correct major changes on the disks in small steps using the fine adaptation feature.

PA and PR correction shifting adaptation:

The control pressure profile consists of a short controlled filling stroke and a pressure ramp for the solenoid valve to be switched on. The pressure ramp begins with the starting pressure PA and climbs during the delay time to reach the control pressure PR. The control pressure PR remains constant throughout the slip time. Once the slip time has elapsed, the control pressure will be set to maximum. This engages the clutch completely.

If the pressure PR is increased to PR' by means of adaptation, the slip time is reduced from tslip to tslip'. If the pressure PR is reduced to PR'', the slip time is increased from tslip to tslip''. The same principle is applied to the pressure PA and the delay time. The following generally applies to the relationship between times and control pressure:

Time | ΔPA ΔPR
Delay time too short | PA is reduced
Delay time too long | PA + PR are increased
Slip time and delay time too short | PA is reduced
Slip time too long | PR is increased

The correction values for PA and PR are divided into eight engine torque classes for each shifting operation. The engine torque class 0 is equivalent to zero load and the engine torque class 6 is equivalent to full load. The engine torque class 7 is used for kickdown shifts. Separate adaptation data are calculated for braking processes. The current adaptation data are displayed in the ALADIN report.

Influences on optimum shifting quality:

The optimum shifting quality is a compromise between shifting comfort and transmission load.

If the disk slip times are long, shifting becomes smooth but the load on the disks (especially the thermal load) is very high. In addition, very long slip times may interrupt the powerflow between the drive shaft and the output shaft, which results in jerky driving.

If the disk slip times are too short, shifting is also "jerky" but the load on the disks is minimized. Very short slip times would result in sudden loads on the disks, bearings and shafts.

For these reasons, slip time setpoints that represent a compromise between shifting comfort and transmission load have been defined for every gear change.

Entries in the early warning system:

Both the correction factor ΔPR and the maximum slip time are monitored by the early-warning system during adaptation. If maximum / minimum limits are exceeded, an entry is made in the early warning system.

Reporting Reset functions