Control of diesel engines using NOx-emission feedback

Abstract

Variations of engine-out emissions due to ageing, component drift or production tolerances pose serious problems to meet legislative restrictions on exhaust tailpipe pollutant emissions. This paper addresses feedback of the raw emissions for improved control of diesel engines. A discussion of issues regarding the inclusion of raw-emission feedback into the engine control structure is provided, and a novel control structure for combined feedback control of the air-path variables boost pressure and exhaust gas recirculation rate and of the NOx emissions is presented. The proposed control structure basically consists of an optimal linear output feedback controller and a setpoint-adaption loop on the exhaust gas recirculation rate. With this approach, a simple control structure is available requiring a marginal calibration effort to meet desired NOx-emission values. Unfavourable injection timing in connection with NOx control is minimized by adapting the exhaust gas recirculation rate setpoint. The performance of the proposed approach is demonstrated by experimental results.