Black-Box Modeling of the Air Mass-Flow Through the Compressor in A Scania Diesel Engine
Stricter emission legislation for heavy trucks in combination with the
customers demand on low fuel consumption has resulted in intensive
technical development of engines and their control systems. To control
all these new solutions it is desirable to have reliable models for
important control variables. One of them is the air mass-flow, which
is important when controlling the amount of recirculated exhaust gases
in the EGR system and to make sure that the air to fuel ratio is
correct in the cylinders.
The purpose with this thesis was to use system identification theory
to develop a model for the air mass-flow through the compressor. First
linear black-box models were developed without any knowledge of the
physics behind. The collected data was preprocessed to work in the
modeling procedure and then models with one or more inputs where built
according to the ARX model structure. To further improve the models
performance, non-linear regressors was devel- oped from physical
relations for the air mass-flow and used to form grey-box models of
the air mass-flow.
In conclusion, the performance was evaluated through comparing the
estimated air mass-flow from the best model with the estimate that an
extended Kalman filter together with a physical model produced.
Oskar Törnqvist
2009
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