Mean Value Modelling of a Diesel Engine with Turbo Compound
Over the last years, the emission and on board diagnostics legislations for
heavy duty trucks are getting more and more strict. An accurate engine model
that is possible to execute in the engine control system enables both better
diagnosis and lowered emissions by better control strategies.
The objective of this thesis is to extend an existing mean value diesel engine
model, to include turbo compound. The model should be physical, accurate,
modular and it should be possible to execute in real time. The calibration
procedure should be systematic, with some degree of automatization.
Four different turbo compound models have been evaluated and two models were
selected for further evaluation by integration with the existing model. The
extended model showed to be quite insensitive to small errors in the compound
turbine speed and hence, the small difference in accuracy of the tested models
did not affect the other output signals signi cantly. The extended models had
better accuracy and could be executed with longer step length than the
existing model, despite that more complexity were added to the model. For
example, the mean error of the intake manifold pressure at mixed driving was
approximately 3.0%, compared to 5.8% for the existing model. The reasons for
the improvements are probably the good performance of the added submodels and
the systematic and partly automatized calibration procedure including
optimization.
Oscar Flärd and Manne Gustafsson
2003
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