Design of selective catalytic reduction systems controller for diesel engine using triple-step nonlinear method

Urea selective catalytic reduction (Urea-SCR) is well known for exhaust gas aftertreatment in diesel engines. In this paper, for simultaneously achieving high NO_x conversion efficiency and low ammonia slip, a ammonia storage controller is designed to track the desired coverage ratio along the axial direction of a SCR catalyst using the triple-step method. Different from the existing nonlinear controller design methods, the design procedure is formalized as a triple-step deduction, and the derived controller consists of 3 parts: steady-state-like control, feedforwad control based on reference dynamics, and statedependent feedback control. Simulations based on ECE driving cycle in the enDYNA diesel model are conducted to evaluate the effectiveness of the proposed control strategy. Furthermore, comparisons with PID controller are presented to show the advantage of the proposed triple-step method SCR control strategy.