Modeling and Control of the Fuel Injection System for Rail Pressure Regulation in GDI Engine

To obtain the precise injection in GDI engines, this paper presents a model-based rail pressure control scheme. First, a mathematical model is derived for the fuel rail injection system based on hydrodynamics and the bulk modulus of elasticity and simplified reasonably for the controller design. The system is uncontrollable at the point where the pump pressure is equal transiently to the rail pressure. A simple controller is designed for driving the system to the regular case where the pump pressure is larger than the rail pressure. In order to deal with system nonlinear, a nonlinear controller is derived and rearranged in the structure of feedforward feedback. The feedforward is related to the reference dynamics and the gain is state-dependent, while the feedback includes a state-dependent PD/PID error feedback and a state feedback related to the characteristics of the fuel rail system. The structure of the controller benefits potentially to the engineering-oriented implementation. Second, robustness is analyzed in the framework of input-to-state stability, where the error induced from the controller implementation, disturbances, and uncertainties are lumped as an additive input. Finally, the designed control scheme is tested in the more realistic simulation model established in the AMESim environment and the results are satisfying.