Design and experimental validation of a model-based injection pressure controller in a common rail system for GDI engine

Progressive reductions in vehicle emission requirements have forced the automotive industry to invest in research and development of alternative control strategies. All control features and resources are permanently active in an electronic control unit, ensuring the best performance in terms of pollutant emissions and power density, as well as driveability and diagnostics. A way to attain these goals is the adoption of Gasoline Direct Injection (GDI) engine technology. In order to assist the engine management system design, through a better performance of GDI engine and the Common Rail (CR) system, in this work an injection pressure regulation to stabilize the fuel pressure in the CR fuel line is proposed and validated via experiments. The resulting control strategy is composed by a feedback integral action and a static model-based feed-forward action whose gains are scheduled as function of fundamental plant parameters. The tuning of the closed loop performance is then supported by an analysis of the phase margin and the sensitivity function. Preliminary experimental results confirm the effectiveness of the control algorithm in regulating the mean value rail pressure independently from engine working conditions, i.e. engine speed and time of injection, with limited design effort.