This paper proposes a discrete-time preview-feedback controller capable of reducing nitrogen oxide (NOx) emissions with affordably low ammonia (NH3) slip downstream of a catalyst for selective catalytic reduction (SCR) systems. Because of the high NOx reduction rate, SCR systems are increasingly adopted in diesel engines. However, slow dynamics of the SCR system along with a time delay in the sensor result in a challenging control problem. To overcome the control challenges, the preview-feedback controller is proposed under the assumption that the NOx disturbance is previewed. To design the preview-feedback H∞ controller, a discrete-time generalized plant is derived by combining the linearized model of SCR system, the model for previewing disturbance signal, and the weighting function. Based on experimentally obtained data, the simulations show that the proposed controller can effectively reduce 34 % of NOx emissions and 6 % of NH3 slip more, compared to a non-preview controller. The robustness is then demonstrated using the uncertainties ranging from 10 to 40 %. This result shows that uncertainties of up to 30 % do not negatively affect the performance. Additionally, the result for the computational requirement shows that the proposed controller yields better performance with lower computation time than a model predictive controller does.
Discrete-Time Preview-Feedback H∞ Control for Selective Catalytic Reduction Systems
Int.J Automot. Technol.
International Journal of Automotive Technology ; 22 , 3 ; 811-821
2021-06-01
11 pages
Article (Journal)
Electronic Resource
English
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