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TECHNICAL PAPERS

Linear Parameter-Varying Lean Burn Air-Fuel Ratio Control for a Spark Ignition Engine

[+] Author and Article Information
Feng Zhang, Matthew A. Franchek

Department of Mechanical Engineering, University of Houston, 4800 Calhoun Rd. Houston, TX 77204

Karolos M. Grigoriadis1

Department of Mechanical Engineering, University of Houston, 4800 Calhoun Rd. Houston, TX 77204

Imad H. Makki

 Ford Motor Company, Powertrain Controls R&AE, Fairlane Program Center - B, 760 Town Center Drive, Dearborn, MI 48126

1

Corresponding author.

J. Dyn. Sys., Meas., Control 129(4), 404-414 (Jan 25, 2007) (11 pages) doi:10.1115/1.2745849 History: Received November 11, 2005; Revised January 25, 2007

Maximization of the fuel economy of the lean burn spark ignition (SI) engine strongly depends on precise air-fuel ratio control. A great challenge associated with the air-fuel ratio feedback control is the large variable time delay in the exhaust system. In this paper, a systematic development of an air-fuel ratio controller based on post lean NOx trap (LNT) oxygen sensor feedback using linear parameter-varying (LPV) control is presented. Satisfactory stability and disturbance rejection performance is obtained in the face of the variable time delay. The LPV controller is simplified to an explicit parameterized gain scheduled lead-lag controller form for the ease of implementation. A Ford F-150 truck with a V8 4.6 l lean burn engine was used to demonstrate the LPV air-fuel ratio control design. Both simulation and experimental results demonstrate that the designed controller regulates the tailpipe air-fuel ratio to the preset reference for the full engine operating range.

Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Aftertreatment system and “outer-feedback” loop AFR control system configuration in the lean burn mode

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Figure 2

System identification example (mean engine speed=1137rpm; mean air mass flow=3.0047lb∕min; mean air fuel ratio=1.1)

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Figure 3

Exhaust delay versus air mass flow

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Figure 4

Weighted control structure for LPV synthesis

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Figure 5

Weighted control structure

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Figure 6

LPV controller model reduction results

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Figure 7

Polynomial fitting for the coefficient of the LPV controller

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Figure 8

Bode diagrams of the loop transfer functions

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Figure 9

Nichols charts of the loop transfer functions

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Figure 10

Closed-loop step response (LPV controller)

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Figure 11

Closed-loop step responses (H∞ controller)

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Figure 12

Controller implementation block diagram

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Figure 13

Speed and air mass flow profile

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Figure 14

Variable time delay estimation

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Figure 15

Air-fuel ratio regulation simulation results

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Figure 16

Air-fuel ratio regulation simulation results (detailed view)

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Figure 17

Low engine speed driving experimental result (LPV controller)

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Figure 18

Highway driving experimental results (LPV controller)

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Figure 19

Highway driving experimental results (LPV controller)

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