Gain-scheduling Selective Catalytic Reduction Control in Diesel Engines with Switched H ∞ Controllers

This paper proposes a gain-scheduling (GS) control strategy for selective catalytic reduction (SCR) systems in diesel engines, to minimize both nitrogen oxides (NO x ) emissions and ammonia (NH 3 ) slip downstream of the SCR catalyst. The proposed GS controller switches among multiple linear time-invariant H ∞ controllers based on the engine’s operating condition, and adopts three measurable GS parameters, that is, the amount of NO x entering the SCR catalyst, exhaust gas temperature in the catalyst, and ammonia slip measurement. While switching surfaces for the first two GS parameters are determined by simply dividing their operating ranges, to find optimal switching surfaces for the ammonia slip GS parameter, a novel method called Violation-Time-based Decision method is proposed. The efficiency of the proposed GS SCR controller is validated in simulations using real experimental data obtained from a diesel engine in the Non-Road-Transient Cycle (NRTC).