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Research Papers

Transient Air-to-Fuel Ratio Control of an Spark Ignited Engine Using Linear Quadratic Tracking

[+] Author and Article Information
Stephen Pace

Mem. ASME
Electrical and Computer Engineering,
Michigan State University,
East Lansing, MI 48824
e-mail: paceste1@msu.edu

Guoming G. Zhu

Fellow ASME
Department of Mechanical Engineering,
Department of Electrical and
Computer Engineering,
Michigan State University,
1497 Engineering Research Court,
Room E148,
East Lansing, MI 48824
e-mail: zhug@egr.msu.edu

Contributed by the Dynamic Systems Division of ASME for publication in the JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT, AND CONTROL. Manuscript received April 20, 2012; final manuscript received October 24, 2013; published online December 9, 2013. Assoc. Editor: Eric J. Barth.

J. Dyn. Sys., Meas., Control 136(2), 021008 (Dec 09, 2013) (11 pages) Paper No: DS-12-1114; doi: 10.1115/1.4025858 History: Received April 20, 2012; Revised October 24, 2013

Modern spark ignited (SI) internal combustion engines maintain their air-to-fuel ratio (AFR) at a desired level to maximize the three-way catalyst conversion efficiency and durability. However, maintaining the engine AFR during its transient operation is quite challenging due to rapid changes of driver demand or engine throttle. Conventional transient AFR control is based upon the inverse dynamics of the engine fueling dynamics and the measured mass air flow (MAF) rate to obtain the desired AFR of the gas mixture trapped in the cylinder. This paper develops a linear quadratic (LQ) tracking controller to regulate the transient AFR based upon a control-oriented model of the engine port fuel injection (PFI) wall wetting dynamics and the air intake dynamics from the measured airflow to the manifold pressure. The LQ tracking controller is designed to optimally track the desired AFR by minimizing the error between the trapped in-cylinder air mass and the product of the desired AFR and fuel mass over a given time interval. The performance of the optimal LQ tracking controller was compared with the conventional transient fueling control based on the inverse fueling dynamics through simulations and showed improvement over the baseline conventional inverse fueling dynamics controller. To validate the control strategy on an actual engine, a 0.4 l single cylinder direct-injection (DI) engine was used. The PFI wall wetting dynamics were simulated in the engine controller after the DI injector control signal. Engine load transition tests for the simulated PFI case were conducted on an engine dynamometer, and the results showed improvement over the baseline transient fueling controller based on the inverse fueling dynamics.

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References

Figures

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Fig. 2

Schematic of AFR control problem

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Fig. 1

Mean-value engine model architecture

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Fig. 3

LQ tracking controller with state estimator

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Fig. 8

Single cylinder engine setup

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Fig. 9

Throttle dynamics model validation

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Fig. 4

Reference buffer formation

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Fig. 5

Schematic of baseline inverse fueling controller

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Fig. 6

Response of simulation 1

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Fig. 7

Response of simulation 2

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Fig. 10

Intake manifold filling dynamics model validation

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Fig. 11

Response of LQ tracking controller with state estimator

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Fig. 12

Response of LQ tracking controller with new wall wetting parameters

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Fig. 13

Response of inverse fueling dynamics feedforward controller

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Fig. 14

Response of LQ tracking with PID feedback control

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