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.

[1]  Yisun Cheng,et al.  Modeling Study of Urea SCR Catalyst Aging Characteristics , 2007 .

[2]  Junmin Wang,et al.  Observer-Based Estimation of Air-Fractions for a Diesel Engine Coupled With Aftertreatment Systems , 2013, IEEE Transactions on Control Systems Technology.

[3]  Junmin Wang,et al.  Observer-based estimation of selective catalytic reduction catalyst ammonia storage , 2010 .

[4]  Frank Willems,et al.  Ammonia sensor for closed-loop SCR control , 2008 .

[5]  Young Sun Mok,et al.  Decomposition of Urea into NH3 for the SCR Process , 2004 .

[6]  Junmin Wang,et al.  A Two-Cell Backstepping-Based Control Strategy for Diesel Engine Selective Catalytic Reduction Systems , 2011, IEEE Transactions on Control Systems Technology.

[7]  Tan Feng,et al.  The characteristics of ammonia storage and the development of model-based control for diesel engine urea-SCR system , 2015 .

[8]  J. N. Chi,et al.  Modeling and Control of a Urea-SCR Aftertreatment System , 2005 .

[9]  M. Elsener,et al.  Urea-SCR: a promising technique to reduce NOx emissions from automotive diesel engines , 2000 .

[10]  Fengjun Yan,et al.  Design and Robustness Analysis of Discrete Observers for Diesel Engine In-Cylinder Oxygen Mass Fraction Cycle-by-Cycle Estimation , 2012, IEEE Transactions on Control Systems Technology.

[11]  Junmin Wang,et al.  Nonlinear and adaptive control of NO/NO2 ratio for improving selective catalytic reduction system performance , 2013, J. Frankl. Inst..

[12]  Hui Zhang,et al.  Robust Filtering for Ammonia Coverage Estimation in Diesel Engine Selective Catalytic Reduction Systems , 2013 .

[13]  C. Schär,et al.  Control-Oriented Model of an SCR Catalytic Converter System , 2004 .

[14]  Junmin Wang,et al.  Development and experimental studies of a control-oriented SCR model for a two-catalyst urea-SCR system , 2011 .

[15]  Gordon G. Parker,et al.  Model-Based Estimation and Control System Development in a Urea-SCR Aftertreatment System , 2008 .

[16]  Junmin Wang,et al.  Adaptive and Efficient Ammonia Storage Distribution Control for a Two-Catalyst Selective Catalytic Reduction System , 2012 .

[17]  Junmin Wang,et al.  Coordinated Active Thermal Management and Selective Catalytic Reduction Control for Simultaneous Fuel Economy Improvement and Emissions Reduction During Low-Temperature Operations , 2015 .

[18]  Junmin Wang,et al.  NO and NO2 Concentration Modeling and Observer-Based Estimation Across a Diesel Engine Aftertreatment System , 2011 .

[19]  Junmin Wang,et al.  Integrated diesel engine and selective catalytic reduction system active NOx control for fuel economy improvement , 2013, 2013 American Control Conference.

[20]  Fpt Frank Willems,et al.  Is Closed-Loop SCR Control Required to Meet Future Emission Targets? , 2007 .

[21]  Devesh Upadhyay,et al.  Modeling of a Urea SCR Catalyst With Automotive Applications , 2002 .

[22]  Christopher H. Onder,et al.  Control of an SCR catalytic converter system for a mobile heavy-duty application , 2006, IEEE Transactions on Control Systems Technology.