Transient air/fuel ratio controller identification using repetitive control

Presented in this paper is a feedforward controller identification process for the transient fueling control of spark ignition (SI) engines. The objective of an SI fueling control system is to guarantee a prespecified air-fuel (A/F) ratio, despite changing driver demands commanded through the throttle. The controller identification process is based on standard system identification tools and is comprised of three steps. The first step involves the design and implementation of a repetitive feedback controller. Next, the engine is subjected to a prespecified periodic throttle motion for which the repetitive controller achieves precise A/F control as t → ∞. Finally, using the engine speed, the mass airflow, and the fuel pulsewidth information during precise fueling conditions, the feedforward fueling controller is identified using standard parametric system identification tools. This identification process can be performed during engine warm-up, thereby enabling a rapid determination of the fueling requirements as a function of temperature. Experimental validation is provided on a 1999 Ford 4.6L V-8 fuel injected engine with sequential port injection.