Identification of the Twin Independent Variable Cam Timing Engines for AFR Control

[+] Author and Article Information
A. Umut Genç

 AVL Schrick, Avon House, Hartlebury Trading Estate, Worcestershire, DY10 4JB, UK

Keith Glover

Department of Engineering, University of Cambridge, Cambridge, CB2 1PZ, U.K.

J. Dyn. Sys., Meas., Control 127(4), 589-600 (Apr 12, 2005) (12 pages) doi:10.1115/1.2101849 History: Received August 02, 2003; Revised April 12, 2005

A control-oriented air-fuel ratio path model is developed to represent a spark-ignited, port-fuel-injected, twin-independent variable cam timing engine. Following a recent publication [Genç, SAE 2002-01-2752 (2002)] showing that cam timing not only affects the cylinder air flow but also the transient cylinder fuel flow, this paper constructs a mean value model that describes both air and fuel dynamics. While steady-state engine tests have been performed in order to identify the air path dynamics, a combination of linear and nonlinear identification methods have been used in order to identify the fuel path model including the wall-wetting dynamics. The resulting parameter-varying model has been validated with independent experimental data and can be used in powertrain controller design and development.

Copyright © 2005 by American Society of Mechanical Engineers
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Figure 1

Main sensors used in the AFR path identification

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Figure 2

Identified cylinder MAF surfaces

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Figure 3

Fuel path dynamics for a four-cylinder engine

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Figure 4

Identified frequency responses of the fuel path at different operating points

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Figure 5

Measured and predicted frequency responses at two different operating points

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Figure 6

Global identification framework for wall-wetting dynamics

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Figure 7

Global data for the identification of the wall-wetting dynamics

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Figure 8

Measured and predicted trajectories of dϕ∕dt, lambda and fuel flow

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Figure 9

(a) Variation of Xf (b) Variation of τf (c) Variation of Xs (d ) Variation of τs

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Figure 10

Variation of Xf∕τf during the identification experiment

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Figure 11

Transient validation of the AFR path model (IVO excitation)



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