Sliding-mode observer for urea-selective catalytic reduction (SCR) mid-catalyst ammonia concentration estimation

2011 ◽  
Vol 12 (3) ◽  
pp. 321-329 ◽  
Author(s):  
M.-F. Hsieh ◽  
J. Wang
Keyword(s):  
Selective Catalytic Reduction ◽  
Sliding Mode ◽  
Catalytic Reduction ◽  
Ammonia Concentration ◽  
Sliding Mode Observer ◽  
Concentration Estimation

Robust Filtering for Ammonia Coverage Estimation in Diesel Engine Selective Catalytic Reduction Systems

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Hui Zhang ◽  
Junmin Wang ◽  
Yue-Yun Wang
Keyword(s):  
Diesel Engine ◽  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Critical Role ◽  
Approximation Error ◽  
Ammonia Concentration ◽  
Nonlinear Observer ◽  
Coverage Ratio ◽  
Vehicle Simulation ◽  
Measurement Noises

In this paper, we investigate the nonlinear observer designs to estimate the ammonia coverage ratio in the diesel engine selective catalytic reduction (SCR) systems. The ammonia coverage ratio is an important variable due to its critical role in the SCR NOx conversion and the ammonia slip. However, the ammonia coverage ratio cannot be directly measured by onboard sensors. Therefore, it is necessary to develop effective observers to estimate the ammonia coverage ratio online. Based on a three-state SCR model, we develop two nonlinear observers. The first one only employs the dynamics of the ammonia concentration. The structure and the algorithm are simple. But it is sensitive to the measurement noises and the uncertainties in the system parameters. The second one is a discrete-time smooth variable structure estimator which is robust to the measurement noises, the approximation error, and the system uncertainties. Both estimators are implemented on a full-vehicle simulation of the FTP75 test cycle. The simulation results have verified the theoretical analysis.

Sliding-mode control of automotive selective catalytic reduction systems with state estimation

2019 ◽  
Vol 234 (2-3) ◽  
pp. 630-644
Author(s):  
Yao Ma ◽  
Junmin Wang
Keyword(s):  
Selective Catalytic Reduction ◽  
Surface Coverage ◽  
Sliding Mode ◽  
Catalytic Reduction ◽  
Tracking Error ◽  
Estimation Accuracy ◽  
Sliding Mode Controller ◽  
Coverage Ratio ◽  
Implementation Purpose ◽  
Ammonia Slip

A sliding-mode controller for an automotive selective catalytic reduction system is designed to drive its ammonia surface coverage ratio to the target level. The proposed controller only requires NOx, temperature and air flow sensor measurement installed on most mass production vehicles. Selective catalytic reduction systems have been widely equipped on diesel-powered ground vehicles to remove excessive NOx emissions. The tradeoff between NOx removal efficiency and ammonia slip poses a control challenge on regulating the ammonia surface coverage ratio to a proper level in the presence of disturbance. In this study, a sliding-mode controller is designed with explicit consideration of measurement noise and actuator saturation. The finite time convergence of tracking error is proved by a Lyapunov approach. For implementation purpose, an observer of ammonia surface coverage ratio and ammonia slip is also designed to provide states feedback and fault diagnostic information. The closed-loop controller performance is evaluated under an urban driving scenario based on an experimentally validated model. Results demonstrate the robust tracking performance and estimation accuracy against bounded uncertainties. The overall NOx efficiency is maintained with an acceptable ammonia slip level during the transient test cycle FTP75.

Smith control of SCR system based on sliding mode control

2021 ◽  
pp. 1-12
Author(s):  
Jie Ren ◽  
Cuiping Pu ◽  
An Yu
Keyword(s):  
Sliding Mode Control ◽  
Selective Catalytic Reduction ◽  
Sliding Mode ◽  
Catalytic Reduction ◽  
State Observer ◽  
Extended State Observer ◽  
Control Law ◽  
Extended State ◽  
Large Delay ◽  
Mode Control

The reaction process of selective catalytic reduction (SCR) denitrification system is complex, which has the characteristics of large inertia, large delay, strong interference and uncertainty. Traditional PID control can’t achieve accurate control of ammonia injection. Based on linear active disturbance rejection control (LADRC), Smith predictor is used to eliminate the delay output variables before entering extended state observer. The nonlinear state error feedback control law of ADRC structure is designed by using sliding mode control law, which improves the fast response and stability of the system. To solve the problem that the selective catalytic reduction denitrification system is difficult to achieve accurate modeling and large delay, Smith-SMC linear extended state observer (Smith-SMC-LESO) is designed. The simulation results of tracking characteristics, anti-jamming characteristics and robustness show that the set-point tracking performance and anti-jamming ability of Smith-LADRC and Smith-SMC-LESO are significantly improved.

Modeling Approach for a Hydrolysis Reactor for the Ammonia Production in Maritime Selective Catalytic Reduction Applications

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Katrin Johe ◽  
Thomas Sattelmayer
Keyword(s):  
Selective Catalytic Reduction ◽  
System Performance ◽  
Catalytic Reduction ◽  
Ammonia Concentration ◽  
Operating Conditions ◽  
Urea Solution ◽  
Step Method ◽  
Design And Optimization ◽  
Modeling Approach ◽  
Critical Process

The catalytic generation of ammonia from a liquid urea solution is a critical process determining the performance of selective catalytic reduction (SCR) systems. Solid deposits on the catalyst surface from the decomposition of urea have to be avoided, as this leads to reduced system performance or even failure. At present, reactor design is often empirical, which poses a risk for costly iterations due to insufficient system performance. The presented research project proposed a performance prediction and modeling approach for SCR hydrolysis reactors generating ammonia from urea. Different configurations of hydrolysis reactors were investigated experimentally. Ammonia concentration measurements provided information about parameters influencing the decomposition of urea and the system performance. The evaporation of urea between injection and interaction with the catalyst was identified as the critical process driving the susceptibility to deposit formation. The spray of urea solution was characterized in terms of velocity distribution by means of particle-image velocimetry. Results were compared with theoretical predictions and calculation options for processes in the reactor were determined. Numerical simulation was used as an additional design and optimization tool of the proposed model. The modeling approach is presented by a step-by-step method, which takes into account design constraints and operating conditions for hydrolysis reactors.

Investigation on the Control Strategy for Marine Selective Catalytic Reduction System

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Youhong Xiao ◽  
Hui Zhao ◽  
Xinna Tian ◽  
Wenyang Tan
Keyword(s):  
Optimal Control ◽  
Sliding Mode Control ◽  
Selective Catalytic Reduction ◽  
Control Strategy ◽  
Sliding Mode ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Operating Conditions ◽  
Model Based ◽  
Mode Control

Selective catalytic reduction (SCR) system has been proven to be an effective technology for the removal of NOx emitted from marine diesel engines. In order to comply with stringent International Maritime Organization (IMO) Tier III NOx emission regulations, a number of engine manufacturers have developed their own SCR systems. This paper focuses on modeling of an SCR reactor and developing model-based urea dosing control strategy. A mathematical model of SCR reactors has been established. Model-based control strategy relies on the three-state and one-state reactor models established to accomplish urea dosing algorithm and is promising in limiting excessive NH3 slip. The SCR reactor model is further used in a simulation for the purpose of developing model-based urea dosing control strategies. The simulation results show that the NO sliding mode control requires a massive prestudy of the NOx reduction capability of the catalyst in order to set an appropriate control objective for each operating condition. However, this calibration work can be omitted in the optimal control and NH3 sliding mode control, which mitigates the workload of the controller design. The optimal control strategy presents a satisfied control performance in limiting NH3 slip during transient state engine operating conditions.

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