Control-Oriented “Crank-Angle” Based Modeling of Automotive Engines 2011-24-0144

It is well known that in automotive applications problems related to control and management are nowadays of paramount importance to improve engine performance and to reduce fuel consumption and pollutant emissions. In the design of control and diagnostics systems, the use of theoretical models proved to be very promising, also to reduce development time and costs, as widely documented in the open literature. From this point of view, the complexity of actual engines due both to the continuous enhancement of existing subsystems (e.g., turbochargers, exhaust gas recirculation systems, aftertreatment components, etc.) and to the introduction of specific devices (e.g., Variable Valve Actuation systems) give rise to challenging issues in modeling development and applications.

The paper describes a theoretical model of an automotive engine built up starting from the original library developed in Simulink® by the authors for the simulation of last generation automotive engines. The tool was used in former works to build up Mean Value Models (MVMs) of automotive engines for "real-time" simulations, which were used in Hardware-in-the-Loop (HiL) applications. The model proposed in this work is an enhancement of the mentioned ones to allow for "crank-angle" simulations of engine thermodynamic processes. To this extent several blocks were built up for the simulation of intake and exhaust valves (with user-defined lift curves and variable actuation) and of in-cylinder processes. Combustion process has been described following a classic single-zone approach based on a proper Heat Release Rate (HRR). Other components of the intake and exhaust systems were modeled by using the original library blocks.

Through a specific calibration procedure, the model was fitted on the typical layout of an automotive SI engine allowing for steady and transient simulations of the engine behavior. Calculated results are compared in the paper with available experimental data, showing a good agreement.