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Research Papers

A Model Based Estimator for Cylinder Specific Air-to-Fuel Ratio Corrections

[+] Author and Article Information
Jason A. Meyer

Center for Automotive Research, Ohio State University, Columbus, OH 43212meyer.506@osu.edu

Stephen Yurkovich1

Center for Automotive Research, Ohio State University, Columbus, OH 43212yurkovich.1@osu.edu

Shawn Midlam-Mohler

Center for Automotive Research, Ohio State University, Columbus, OH 43212midlam-mohler.1@osu.edu

1

Corresponding author.

J. Dyn. Sys., Meas., Control 133(3), 031001 (Mar 23, 2011) (14 pages) doi:10.1115/1.4003379 History: Received March 01, 2010; Revised October 15, 2010; Published March 23, 2011; Online March 23, 2011

One of the most overlooked and oversimplified components of an engine model used for model based air-to-fuel ratio (AFR) control and/or diagnostics is the exhaust gas dynamics model. Without a proper model of the exhaust system, the mixing of exhaust gases and the dynamic transport delays are challenging to capture accurately, even with a meticulous experimental calibration. By representing the exhaust system with a finite impulse response (FIR) model whose coefficients are based on physical properties, these effects can be predicted accurately and smoothly across the complete range of operating conditions. Through on-line and off-line techniques, this model can markedly improve the performance of both open loop and closed loop AFR control. Because a FIR model has a linear relationship between the input and the output, the input error trajectory can be identified from a single precatalyst oxygen sensor measurement. This technique can be used to supplement the calibration of either the feed-forward or feedback portion of the AFR controller. Additionally, the FIR model can be used for on-line estimation of cylinder imbalance errors. This model based approach to cylinder imbalance estimation has several advantages over the current empirically based methods including robustness and ease of calibration.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Evolution of the input dependency vector

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Figure 2

Exhaust system separated into 100 cells

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Figure 3

Measured versus model predicted impulse response of cylinder-1 at idle

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Figure 4

Measured versus model predicted impulse response of cylinder-3 at idle

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Figure 5

Measured versus model predicted impulse response of cylinder-1 under moderate load

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Figure 6

Measured versus model predicted impulse response of cylinder-3 under moderate load

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Figure 7

Measured versus model predicted EGO response of a cylinder-1 imbalance error at idle

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Figure 8

Measured versus model predicted EGO response of a cylinder-3 imbalance error at idle

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Figure 9

Output dependencies: event prior to commanding fuel to cylinder-1 at idle

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Figure 10

Output dependencies: event when fuel is commanded to cylinder-1 at idle

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Figure 11

Influence on the output of a single AFR input from cylinder-1

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Figure 12

Influence on the output of a single AFR input from cylinder-3

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Figure 13

Summation of the input and output contributions during step changes in MAF with a fixed engine speed

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Figure 14

Summation of the input and output contributions during step changes in engine speed with a fixed MAF

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Figure 15

Prediction of the input EQR during a shifting transient

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Figure 16

Engine speed (solid line) and air flow (dashed line) during a shifting transient

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Figure 17

Identification of a cylinder-1 imbalance error applied at event 300 during idle (baseline)

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Figure 18

Identification of a cylinder-1 imbalance error applied at event 300 during idle, with first order filter (tuned)

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Figure 19

Condition number surface

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