Air-Fuel Ratio Control with Respect to Oxygen Storage Dynamics

Reducing exhaust emissions is one of the biggest challenges facing the automotive engineering community today. In order to comply with future more stringent emission standards, the air-fuel ratio control must be improved. Commonly used control concepts do not account for the oxygen storage ability of the three-way catalyst, even though the storage state mainly influences post-catalyst exhaust emissions. In this paper a new air-fuel ratio control strategy based on the oxygen storage state is presented. Since the oxygen storage state can not be measured directly, a major component of the controller is a newly developed catalyst model that accounts for the spatial distribution of oxygen within the catalyst. The proposed control concept has been successfully tested on a vehicle equipped with a turbocharged, direct injection gasoline engine.