AN EVALUATION OF DETECTION METRICS FOR AN INTEGRATED CATALYST CONTROLLER AND DIAGNOSTIC MONITOR

An integrated, model-based methodology for three-way automotive catalyst control and diagnostic monitoring utilizing a limited integrator model with an adaptive integral gain is outlined in this work. This adaptive gain, which is a measure of the catalyst oxygen storage capacity, is used both by the controller to provide information on the dynamic catalyst behavior and by the diagnostic monitor to provide information on long-term catalyst deactivation and short-term emission control device failure. Nonparametric test statistics using various metrics computed from a moving window sample of the adaptive gain are compared to determine their ability to detect changes in catalyst system performance with a number of differently aged catalysts. These diagnostic monitoring metrics have been applied to 4.6 liter ULEV II gasoline engine data tested over an EPA Federal Test Procedure drive cycle.