Modeling and control of the air-fuel ratio for GDI engines using ECU-1D Co-simulation tools

This report presents a control oriented model of the Air-Fuel Ratio (AFR) for a Gasoline Direct Injection (GDI) Spark Ignition (SI) engine, its validation and application to design model-based gain scheduling controllers. It is shown that a simple first order time delay system, whose parameters strongly depend on the in-cylinder air mass, reproduces accurately the dynamics involving in the closed loop control of the AFR. Such dynamics are mainly affected by the mixing of the exhaust gas streams and the transport delay between the injector location and the lambda-sensor located on exhaust pipe upstream the Three-Way Catalytic (TWC) converter. Since the dependency of the model parameters on the fresh air mass incoming into cylinders suggests such variable as the scheduling variable to develop simple adaptive controllers able to work effectively in the entire engine operating range, the in-cylinder air mass is predicted trough a regression model of the intake pressure and engine speed properly developed for this purposes. Model derivation and validation, the effectiveness of the control design as well as the comparison between different model based control strategies integrated with adaptive mechanisms, are carried out by means of numerical ECU coupled with an 1D Engine into a Co-Simulation environment developed for such purposes.