Control of aged automotive selective catalytic reduction systems for consistent performances

This paper develops a consistent emission control method for automotive selective catalytic reduction (SCR) systems against variant aging conditions. SCR systems have been widely adopted on Diesel vehicles to reduce tailpipe NO_x emissions thanks to their superior performance compared with other aftertreatment technology. While fresh SCRs have a high NO_x removal efficiency, their NO_x reduction performances will be significantly impaired as they get aged. To maintain the consistent emission performance of a SCR system over its entire duty life, it is necessary to design a robust and adaptive control method of SCR against the aging effects and ensure the consistent NO_x reduction capability especially when SCR runs towards its end of life cycle. A control strategy that includes an ammonia coverage ratio tracking controller and a reference generator is derived and validated in simulation environment to account for various SCR aging conditions. The simulation results of US06 test cycle show that the proposed control strategy is able to maintain a consistent emission reduction performance under different aging conditions without generating excessive ammonia slip.