A reduced model of Three Ways Catalyst converter and stored oxygen rate estimation using switched observer

Pollutant emissions limitations ruled by the latest standards force car manufacturers to improve after treatment systems. This improvement is achieved by new systems on one hand, and by more efficient control strategies, on the other. This paper describes a 0-D model of Three Ways Catalyst converter (TWC) which is able to reproduce the transient dynamics of the converter although simple. A switched observer of stored oxygen rate is derived from this reduced model, and its convergence is proved. An estimation of the oxygen capacity of TWC provides precious information for on-board diagnosis or monitoring purpose. First, a description of the TWC dynamics and its reduced model will be described, then a discrete time switched observer of the stored oxygen rate and the free site capacity estimation by least squares method are presented.