Automotive emissions are strictly regulated by environmental legislation. To maximize exhaust gas conversion efficiencies under transient conditions the dynamics of the three-way catalyst (TWC) need to be considered. Oxygen-storage-dominated models are conventionally used to describe the non-linear dynamic behaviour of TWCs. In this paper, a non-linear identification method is applied to model the system, based on measurements of the upstream and downstream air-fuel ratios. The performance of the obtained non-linear autoregressive with exogenous inputs (NARX) models is directly compared with that of an oxygen storage model. The results highlight some of the limitations of the latter, while demonstrating the advantages of non-linear modelling.
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