Air mass-flow measurement and estimation in diesel engines equipped with EGR and VGT
With stricter emission legislations and customer demands on low fuel
consumption, good control strategies are necessary. This may involve
control of variables that are hard, or even impossible, to measure
with real physical sensors. By applying estimators or observers, these
variables can be made available. The quality of a real sensor is
determined by e.g. accuracy, drift and aging, but assessing the
quality of an estimator is a more subtle task. An estimator is the
result of a design work and hence, connected to factors like
application, model, control error and robustness.
The air mass-flow in a diesel engine is a very important quantity that
has a direct impact on many control and diagnosis functions. The
quality of the air mass-flow sensor in a diesel engine is analyzed
with respect to day-to-day variations, aging, and differences in
engine configurations. The investigation highlights the necessity of
continuous monitoring and adaption of the air mass-flow. One way to do
this is to use an estimator. Nine estimators are designed for
estimation of the air mass-flow with the aim of assessing different
quality measures. In the study of the estimators and quality measures
it is evident that model accuracy is important and that special care
has to be taken, regarding what quality measure to use, when the
estimator performance is evaluated.
Erik Höckerdal, Lars Eriksson and Erik Frisk
SAE Technical paper series SP-2159,
2008
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