Matteo Skull, Porsche Engineering Services
The requirements in terms of harmonizing disparate engine characteristics are ever more demanding. Power, efficiency, dynamic response, and exhaust emission quality are just four factors that need to be coordinated. To meet those requirements, engine functions and the associated calibration of the engine control system are increasingly complex. This applies in particular to one fundamental component of engine control: the air charge model. Without the use of powerful application tools, its exact calibration is no longer feasible. Porsche Engineering has developed an alternative method employing a Model-Based approach.
One of the great challenges of the air charge model is that the characteristics and maps have to be calibrated very precisely, although their outputs do not correspond to any directly measurable physical and thermodynamic values. Due to the interplay between the calculated values of the engine control unit and the complexity of calculation models, it has now become impossible to parameterize the air charge model—in other words, directly adjust the maps—during ongoing operations on the engine test bench. The basic calibration must therefore be conducted using special tools that enable correct calibration of maps using measurement data. The significance and use of such tools has risen enormously and their development is a core competence in the field of engine calibration at Porsche Engineering.
By inverting the logical path of a complete function whose outcome corresponds to a measurable physical variable, it is possible to derive the precise value of the map output for each executed operating point. As soon as the map outputs for all operating points are known, numerical models are created that calculate the relationships between the input and output values of the maps. Using these models, the respective maps are then calibrated.
This alternative approach has proven successful and is used for the calibration of almost all ECU models.
Recorded: 17 Apr 2018
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