Estimating the oxygen storage level of a three-way automotive catalyst

A moving horizon estimation strategy is developed for the determination of the oxygen storage level of a three-way automotive catalyst. The ability to store and release oxygen is a critical aspect to the operation of the three-way catalyst component in automotive emission control systems. Because the oxygen storage level cannot be measured directly, it must be estimated from pre-catalyst and post-catalyst air fuel ratio sensor measurements for model-based control and monitoring applications. However, these sensors are subject to distortion and the engine operating conditions that produce low tail-pipe emissions also result in the oxygen storage level becoming unobservable for a significant fraction of typical engine operation. The moving horizon estimator presented in this work, based on the use of a combined catalyst oxygen storage/sensor distortion model, is able to provide reliable estimates under these circumstances. The estimation algorithm is demonstrated using experimental engine operating data.