Experimental Validation of Model Predictive Charging Pressure and EGR Rate Control for an SI Engine

Abstract

Turbocharged spark-ignition (SI) engines with low pressure exhaust gas recirculation (EGR) offer a favorable potential to meet strict pollutant emission limits under real-driving conditions. While complex air path concepts with EGR are already state-of-the-art for diesel engines, the application for SI engines is still a topic of research. Due to the air-quantity-based engine load control as well as the potential occurrence of knocking combustion, a precise boost pressure and EGR rate control is decisive for a reliable operation. Within the scope of this paper, various model predictive control (MPC) concepts for turbocharged SI engines with EGR are proposed. For the evaluation, a prototype vehicle is equipped with a serial sequential turbocharging system as well as a low pressure EGR path. To control this overactuated multiple-input-multiple-output system with variable dead times, a linear as well as a nonlinear model predictive controller are developed. The benefit of utilizing a model of the EGR sensor dynamics within the observer is additionally examined. The control behavior is validated by performing tip-in tests with the vehicle on a test track. The results are evaluated considering overshoot, the time to reach the respective setpoints as well as steady-state accuracy.