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A control method for consistent performance of automotive selective catalytic reduction systems under variant aging conditions

This paper presents a novel control method for realizing consistent emission reduction performance of automotive selective catalytic reduction (SCR) systems under variant aging conditions. SCR systems have been widely recognized as one of the leading after treatment systems for reducing Diesel powertrain tailpipe NOx emissions in ground vehicle applications. While fresh SCRs are quite effective in reducing tailpipe NOx emissions, their NOx reduction capabilities and performances may substantially degrade with in-service aging. To ensure the emission control performance of a SCR system during the entire vehicle service life, it is thus critical for the SCR control system to be robust and adaptive against the SCR aging effects and strive to achieve the best possible and consistent tailpipe emission reductions even under the conditions that the SCR has been severely aged. A novel control method that combines a SCR ammonia coverage ratio reference generator and tracking controller with explicit consideration of SCR aging effects is analytically developed and verified in simulations. The simulation results under the US06 test cycle demonstrate high effectiveness of the proposed controller in achieving consistent tailpipe emission reductions against the system degradation derived from the catalyst aging.