A Pulse Width Modulation Control Scheme for Three-Way Catalyst Systems*

A closed-loop pulse width modulated control scheme for three-way automotive catalyst control utilizing feedback from a post-catalyst heated exhaust gas oxygen (HEGO) sensor is presented in this work. The controller manipulates the duty cycle of the pre-catalyst air fuel ratio target perturbations across stoichiometry to regulate the post-catalyst HEGO sensor voltage to a desired target. The controller is demonstrated using an experimental Ford 2.0l Duratec I4 engine with a dual-brick three-way catalyst configuration.