Unburned Air Mass Fraction Estimation for Model-Based EGR Turbocharged Diesel Engine Unburned Air Mass Fraction Estimation

Intake unburned air mass fraction cannot be directly measured on production EGR turbocharged diesel engine. To deal with this problem, an innovative unburned air mass fraction estimation method for EGR turbocharged diesel engine was proposed in this paper, laying the foundation for the diesel air path control based on intake unburned air mass fraction. A dynamic model of the high pressure EGR turbocharged diesel engine was developed, and the EGR flow high gain observer was designed based on the dynamic model, to lay the foundation for the accurate estimation of the unburned air mass fraction. Based on the dynamic equations of the unburned air mass fraction in the intake and exhaust manifold, the full dimension state observer of the unburned air mass fraction was designed. The convergence stability of the observer was proved through a Lyapunov analysis. The results show that the observer can meet the stability requirements. It can be used for estimating the unburned air mass fraction. The EGR flow observer and the unburned air mass fraction observer were verified also using the GT-Power simulation data and the experimental data. The results show that the designed observers can accurately estimate the parameters, and the estimation error less than 3%, which meet the demand of diesel engine control system.