Control Oriented Modeling of Turbocharged (TC) Spark Ignition (SI) Engine

This paper proposes a new systematic procedure for model reduction of TC SI engines. The technique is based on the identification of time scale separation within the dynamics of various engine state variables. The model reduction is performed in two stages. First stage is to use dynamic properties of the engine states to obtain reduced order slow and fast time scale subsystems. Then in the second stage, physical characteristics are considered to isolate fast pressures. As a result a library of the control oriented engine models is obtained. The limitation of the reduced order models as a true representation of original model is first gauged qualitatively by the application of perturbation theory and then characterized quantitatively by means of simulations. Various assumptions under which these model reductions are applicable are presented and their validity in the context of the engine are discussed.