Compound Control Strategy Based on Active Disturbance Rejection for Selected Catalytic Reduction systems

Urea-based selected catalytic reduction (SCR) systems are effective ways in diesel engine after-treatment systems to meet increasingly stringent emission regulations. To achieve high NOx reduction efficiency and low NH3 slip, the control of the SCR system becomes more challenging, especially in transient operating conditions with model uncertainties. To effectively address this issue, this paper proposed a compound control strategy with a switching mechanism between an active disturbance rejection (ADR) controller and a zero-input controller. The ADR controller estimates and rejects the total (internal and external) disturbances from the SCR system when the exhaust gas temperature is high and its variation is small. The zero-input controller is used to lower ammonia surface coverage ratio to avoid high ammonia slip when exhaust gas temperature suddenly rises. The proposed control strategy is validated through a high-fidelity GT-Power simulation for a light-duty diesel engine over steady states and federal test procedure (FTP-75) test cycle. Its effectiveness is demonstrated especially in rapidly transient conditions with model uncertainties.

[1]  A. Wokaun,et al.  Isocyanic acid hydrolysis over Fe-ZSM5 in urea-SCR , 2006 .

[2]  E. Tronconi,et al.  The chemistry of the NO/NO2–NH3 “fast” SCR reaction over Fe-ZSM5 investigated by transient reaction analysis , 2008 .

[3]  Michiel J. Van Nieuwstadt,et al.  Model Based Analysis and Control Design of a Urea-SCR deNOx Aftertreatment System , 2006 .

[4]  J. Colson,et al.  Thermal decomposition (pyrolysis) of urea in an open reaction vessel , 2004 .

[5]  Frank Willems,et al.  Experimental Demonstration of a New Model-Based SCR Control Strategy for Cleaner Heavy-Duty Diesel Engines , 2011, IEEE Transactions on Control Systems Technology.

[6]  Yi Huang,et al.  An alternative paradigm for control system design , 2001 .

[7]  Enrico Tronconi,et al.  Study of a Fe–zeolite-based system as NH3-SCR catalyst for diesel exhaust aftertreatment , 2008 .

[8]  Junmin Wang,et al.  An extended Kalman filter for ammonia coverage ratio and capacity estimations in the application of Diesel engine SCR control and onboard diagnosis , 2010, Proceedings of the 2010 American Control Conference.

[9]  Timothy V. Johnson,et al.  Review of diesel emissions and control , 2009 .

[10]  Junmin Wang,et al.  Design and experimental validation of an extended Kalman filter-based NOx concentration estimator in selective catalytic reduction system applications , 2011 .

[11]  Andrew G. Alleyne,et al.  Adaptive Model Predictive Control of an SCR Catalytic Converter System for Automotive Applications , 2012, IEEE Transactions on Control Systems Technology.

[12]  Zhiqiang Gao,et al.  Active disturbance rejection control: a paradigm shift in feedback control system design , 2006, 2006 American Control Conference.

[13]  D. Murzin,et al.  Kinetic considerations of H2 assisted hydrocarbon selective catalytic reduction of NO over Ag/Al2O3: I. Kinetic behaviour , 2006 .

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

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

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

[17]  Ji-Soo Ha,et al.  Numerical Prediction on the Characteristics of Spray-Induced Mixing and Thermal Decomposition of Urea Solution in SCR System , 2004 .

[18]  Zhiqiang Gao,et al.  A Practical Approach to Disturbance Decoupling Control , 2009 .

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

[20]  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.

[21]  Jingqing Han,et al.  From PID to Active Disturbance Rejection Control , 2009, IEEE Trans. Ind. Electron..

[22]  Zhiqiang Gao,et al.  Scaling and bandwidth-parameterization based controller tuning , 2003, Proceedings of the 2003 American Control Conference, 2003..