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Journal Article

Model Based Control of SCR Dosing and OBD Strategies with Feedback from NH3 Sensors

2009-04-20
2009-01-0911
This paper presents a model-based control system for SCR urea dosing employing an embedded real-time SCR chemistry model and a NH3 sensor. The control algorithm consists of a number of control features designed to enhance ammonia storage control and closed-loop compensation using the mid-brick NH3 sensor. An adaptive control algorithm is developed to demonstrate robustness of the feedback control system to compensate for catalyst aging, urea injection malfunction, or dosing fluid concentration variation. Simulation and engine dynamometer testing following ESC and FTP emission cycles are used to demonstrate the advantages of this control approach for meeting both NOx emission requirements and NH3 slip targets. Furthermore this paper demonstrates potential of a NH3 sensor for on-board diagnostics. Additionally the feasibility of implementing model based algorithms in a 32-bit floating-point environment with an automotive controller is examined.
Technical Paper

Monitoring, Feedback and Control of Urea SCR Dosing Systems for NOx Reduction: Utilizing an Embedded Model and Ammonia Sensing

2008-04-14
2008-01-1325
This paper presents a monitoring, feedback and control system for SCR urea dosing utilizing an embedded model and NH3 sensing after the SCR for loop closing control. A one-dimensional SCR model was developed and embedded in a Simulink/Matlab environment. This embedded model is utilized for on-line, real time control of 32.5% aqueous urea dosing in the exhaust stream. Engine testing and simulation are used with the embedded SCR model and NH3 sensor closed loop feedback to demonstrate the advantages of this control approach for meeting both NOx emission requirements and NH3 slip targets. The paper explores these advantages under heavy duty FTP cycle conditions. The potential benefits include SCR size optimization and fuel consumption rate reduction under certain operating conditions.
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