A Real-time Control Framework for Integrated Diesel Engine and Selective Catalytic Reduction System 2019-01-1287
Integrated Diesel engine and aftertreatment system controls are very important for modern Diesel engines to achieve high fuel efficiency while facing the increasingly stringent NOx and particulate matter (PM) emission regulations. In this paper, a real-time implementable, integrated engine-aftertreatment control framework was proposed to coordinate a modern Diesel engine with the coupled urea-based selective catalytic reduction (SCR) system for achieving close-to-optimal engine efficiency as well as tight tailpipe NOx and NH3 slip requirements. With engine-out NOx emissions being considered as an additional active control input to the SCR system, other than urea solution injection rate, both engine fuel efficiency and tailpipe emissions were incorporated in the new SCR control problem formulation. Nonlinear backstepping-based control allocation algorithms were designed to intentionally increase engine-out NOx emission without sacrificing the tailpipe emission control performance. With the relaxed engine-out NOx emission constraint, start of injection (SOI) timing control was optimized for achieving higher engine efficiency. Simulation results based on experimentally calibrated Diesel engine and aftertreatment system models demonstrated significant fuel saving by 10.86% over the transient US06 cycle, with the proposed integrated control, compared to an isolated and more constrained Diesel engine control. In addition, the computationally-efficient integrated control algorithms can be implemented on the existing engine control units for realizing the fuel saving and emission control benefits in the near future.