Control Considerations for an On-Line, Active Regeneration System for Diesel Particulate Traps

Garrett Automotive Group is developing an exhaust aftertreatment system aimed at particulate emissions reduction from commercial diesel engines. The system uses a ceramic wall flow filter to trap the particulates, and regeneration is effected by raising gas temperature by throttling the exhaust downstream of the turbocharger. Lab testing at steady conditions demonstrated good performance with both catalyzed and uncatalyzed traps. Road testing shows the regeneration must be accomplished under severe transient conditions created by the normal vehicle operating modes. Primary efforts are to accommodate those transients using advanced control and digital computational techniques. Some of those techniques are described and are shown to yield improved control performance.