Model Based Control of Throttle, EGR and Wastegate
Due to governmental requirements on low exhaust gas emissions and the drivers
request of fast response, it is important to be able to control the gas flow in a
spark ignited engine accurately. The air into the cylinder is directly related to
the torque generated by the engine. The technique with recirculation of exhaust
gases (EGR) affect the air flow into the cylinder and increase the complexity of
the control problem. In this thesis a mean value model for a spark ignited engine
has been created. The basis was a diesel model from Linköping University that
has been modified and parameterized with data from a test cell. The model has
been used to study the gas exchange system with respect to the dynamic behaviors
and nonlinearities that occur when the three actuators (throttle, wastegate
and EGR-valve) are changed. Based on this analysis, some different control strategies
have been developed and tested on the model. The presented results show
that different control strategies give different behaviors and there is a trade-off
between fast torque response and high precision for controlling the EGR-ratio. A
control strategy is proposed containing two main feedback loops, prefiltering of
the reference signal and a feedforward part.
Henrik Andersson
2017
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Last updated: 2021-11-10
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