Modeling and diagnostics of three-way catalysts for advanced emissions control systems.

摘要

Automotive emissions are stringently regulated. Since 1980, a three-way catalyst (TWC) has been used to convert harmful emissions of hydrocarbons, carbon monoxide, and oxides of nitrogen into less harmful gases in order to meet these regulations. The TWC's efficiency of conversion of these gases is primarily dependent on the mass ratio of air to fuel (A/F) in the mixture leaving the exhaust manifold and entering the catalyst, the velocity of the exhaust mass, and the temperature of the catalyst. This dissertation develops a dynamic, phenomenological, control-oriented model of a TWC. The importance of developing such a model is explained, and the measurement capabilities needed to construct the model are detailed: medium bandwidth A/F measurements and low bandwidth temperature and emission measurements. In the second half of the dissertation, the dynamic TWC model is used for diagnostic purposes. Firstly, an extended Kalman filter is employed to monitor the status of a TWC using on-line parameter identification. Secondly, a more reliable diagnostic method is analyzed in the context of a hypothesis test that is based on the oxygen storage capacity of the TWC.