Model Based Analysis and Control Design of a Urea-SCR deNOx Aftertreatment System

[+] Author and Article Information
Devesh Upadhyay

 Ford Research Laboratories, Dearborn, MI 48124dupadhya@ford.com

Michiel Van Nieuwstadt

 Ford Research Laboratories, Dearborn, MI 48124mvannie1@ford.com

J. Dyn. Sys., Meas., Control 128(3), 737-741 (Jun 02, 2005) (5 pages) doi:10.1115/1.2234494 History: Received January 29, 2004; Revised June 02, 2005

In this paper we tackle issues relevant to model based control design for a Urea based Selective Catalytic Reduction (SCR) process relevant to automotive applications. A three state, control oriented, lumped parameter model of the system is used to investigate essential controllability and observability properties of the Urea-SCR plant. Results from the controllability and observability analysis of both nonlinear and linearized models are shown to have realistic implications. Observer design for predicting gas phase ammonia slip is outlined and results presented. An altered definition of the catalyst efficiency is used in control design. It is shown that this altered definition lends itself readily to control synthesis in the Sliding Mode framework while satisfying the dual control objectives of maximizing NOx reduction and minimizing ammonia slip.

Copyright © 2006 by American Society of Mechanical Engineers
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Grahic Jump Location
Figure 1

Logarithm of the observability boundary: Cnox=R¯ox∕R¯red

Grahic Jump Location
Figure 2

Condition number of the observability Grammian at several operating points

Grahic Jump Location
Figure 3

Observer convergence resulting from a staircase profile in NOx and NH3 input. NOx levels are: 100, 200 and 300, ppm at intervals of 50s duration each. NH3 is injected stoichiometrically. Temperature is held constant at 300°C.

Grahic Jump Location
Figure 4

Simulated catalyst response under closed loop control




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