Transient fueling controller identification for spark ignition engines

Presented in this paper is a feedforward fueling controller identification methodology for the transient fueling control of spark ignition (SI) engines. The hypothesis of this work is that the feedforward fueling control of SI engines can be separated into steady state and transient phenomena and that the majority of the nonlinear behavior associated with engine fueling can be captured with nonlinear steady state models. The proposed transient controller identification process is built from standard nonparametric identification techniques followed by parametric model recovery. Crank angle serves as the independent variable for these models. Two separate system identification problems are solved to identify the air path dynamics and the fueling path dynamics. The transient feedforward controller is then calculated as the ratio of the air path-over-the fueling path dynamics thereby coordinating the engine fueling with the air path dynamics. It will be shown that a linear transient feedforward-fueling controller operating in tandem with a nonlinear steady state fueling controller can achieve air-fuel ratio regulation comparable to the production fueling controller without the extensive controller calibration process. The engine used in this investigation is a 1999 Ford 4.6L V-8 fuel injected engine.