Improved Comfort Analysis and Drivability Assessment by the Use of an Extended Power Train Model for Automatic Transmissions 2012-01-1529

The new generation of automatic transmissions is characterized by a compact and highly efficient design. By the use of a higher overall gear ratio and lightweight components combined with optimal gear set concepts it is possible to improve significantly fuel consumption and driving dynamics. Precise and efficient real time models of the whole power train including models for complex subsystems like the automatic transmission are needed to combine real hardware with virtual models on XiL test rigs. Thereby it's possible to achieve a more efficient product development process optimized towards low development costs by less needed prototypes and shorter development times by pushing front loading in the process.

In this paper a new real time model for automatic transmissions including approved models for the torque converter, the lock-up clutch and the torsional damper are introduced. At the current development stage the model can be used for comfort analysis and drivability assessment. Thereby various operating conditions including motored engine and an open, slipping or locked clutch condition can be simulated. For the torque converter a map based, an equivalent mechanical system model derived from the bond graph modeling method or a detailed physical model based on the energy and momentum equations can be used. The mechanical dampers can be varied in their positions and allow to model common used damper configurations including the conventional, TTD (Turbine Torsional Damper) and DTD (Double Torsional Damper) system arrangement.

Different simulation examples for various operation conditions and modeling approaches are analyzed to underline the broad range of application for comfort analysis and drivability assessment. Further an outlook is given how to include losses into the model to improve the efficiency of future power trains based on measurements and empirical equations.