Experimental Results on Dual-uego Active Catalyst Control

This paper describes active control of an aftertreatment system for a spark ignition engine equipped with a three-way catalyst and preand post-catalyst oxygen sensors. The control objective is to maximize the simultaneous conversion efficiencies of oxides of nitrogen and unburned hydrocarbons. Linear exhaust gas oxygen sensors are used to measure preand post-catalyst air-fuel ratio. A series controller configuration is adopted. The upstream controller provides relatively rapid response to disturbances on the basis of the pre-catalyst measurement, while the downstream controller uses the preand post-catalyst air-fuel ratio measurements to compensate for the bias corrupting the pre-catalyst air-fuel ratio measurement. The control strategy is tested on a 5.4L engine and compared with an existing proprietary controller that is based on the more common switching-type air-fuel ratio sensors.