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Research Papers

Determining Model Accuracy Requirements for Automotive Engine Coldstart Hydrocarbon Emissions Control

[+] Author and Article Information
Nasser L. Azad

Department of Systems Design Engineering,  University of Waterloo, Waterloo, ON, N2L 3G1, Canadanlashgar@uwaterloo.ca

Pannag R. Sanketi

Google, Inc, Mountain View, CA 94043pannag@gmail.com

J. Karl Hedrick

Vehicle Dynamics and Control Lab, Etcheverry Hall,  University of California, Berkeley, CA 94720khedrick@me.berkeley.edu

J. Dyn. Sys., Meas., Control 134(5), 051002 (Jun 05, 2012) (11 pages) doi:10.1115/1.4006217 History: Received March 09, 2010; Revised January 30, 2012; Published June 05, 2012; Online June 05, 2012

In this work, a systematic method is introduced to determine the required accuracy of an automotive engine model used for real-time optimal control of coldstart hydrocarbon (HC) emissions. The engine model structure and development are briefly explained and the model predictions versus experimental results are presented. The control design problem is represented with a dynamic optimization formulation on the basis of the engine model and solved using the Pontryagin’s minimum principle (PMP). To relate the level of plant/model mismatch and the control performance degradation in practice, a sensitivity analysis using a computationally efficient method is employed. In this way, the sensitivities or the effects of small parameter variations on the optimal solution, which is the minimum of cumulative tailpipe HC emissions over the coldstart period, are calculated. There is a good agreement between the sensitivity analysis results and the experimental data. The sensitivities indicate the directions of the subsequent parameter estimation and model improvement tasks to enhance the control-relevant accuracy, and thus, the control performance. Furthermore, they provide some insights to simplify the engine model, which is critical for real-time implementation of the coldstart optimal control system.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 2

Comparison between the measured and computed Texh for a coldstart run

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Figure 3

Comparison between the measured and computed HCraw-c for a coldstart run

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Figure 4

Comparison between the measured and computed Texh for several coldstart runs

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Figure 5

Typical engine speed curves during coldstart period (known external inputs)

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Figure 6

The minimum value of the objective function in different iterations

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The optimal exhaust temperature trajectory

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The catalyst efficiency for the optimum solution

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Figure 9

The engine-out HC emissions rate for the optimum solution

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Figure 10

The profile of air/fuel ratio for the optimum solution

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Figure 17

Δ for a coldstart run

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Figure 18

AFR for a coldstart run

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Figure 19

ϖe for a coldstart run

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Figure 1

Block diagram models for Texh and HCraw-c

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Figure 11

The profile of spark timing for the optimum solution

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Figure 12

Texh for a coldstart experiment

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Figure 13

Δ for a coldstart experiment

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Figure 14

AFR for a coldstart experiment

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Figure 15

ϖe for a coldstart experiment

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Figure 16

HCraw-c for a coldstart run

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