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Research Papers

Simplified Decoupler-Based Multivariable Controller With a Gain Scheduling Strategy for the Exhaust Gas Recirculation and Variable Geometry Turbocharger Systems in Diesel Engines

[+] Author and Article Information
Seungwoo Hong

Automotive Research & Development Division,
Hyundai Motor Company,
Hwaseong-si, Gyeonggi-do 445-706, South Korea
e-mail: shsw0907@gmail.com

Inseok Park

Automotive Research & Development Division,
Hyundai Motor Company,
Hwaseong-si, Gyeonggi-do 445-706, South Korea
e-mail: gunbbang3@gmail.com

Jaewook Shin

Department of Automotive Engineering,
Hanyang University,
222 Wangsimni-ro,
Seongdong-gu, Seoul 133-791, South Korea
e-mail: jaeuk321@gmail.com

Myoungho Sunwoo

Professor
Department of Automotive Engineering,
Hanyang University,
222 Wangsimni-ro,
Seongdong-gu, Seoul 133-791, South Korea
e-mai: msunwoo@hanyang.ac.kr

1Corresponding author.

Contributed by the Dynamic Systems Division of ASME for publication in the JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT, AND CONTROL. Manuscript received December 2, 2015; final manuscript received November 7, 2016; published online March 13, 2017. Assoc. Editor: Junmin Wang.

J. Dyn. Sys., Meas., Control 139(5), 051006 (Mar 13, 2017) (17 pages) Paper No: DS-15-1610; doi: 10.1115/1.4035236 History: Received December 02, 2015; Revised November 07, 2016

This paper presents a simplified decoupler-based multivariable controller with a gain scheduling strategy in order to deal with strong nonlinearities and cross-coupled characteristics for exhaust gas recirculation (EGR) and variable geometry turbocharger (VGT) systems in diesel engines. A feedback controller is designed with the gain scheduling strategy, which updates control gains according to engine operating conditions. The gain scheduling strategy is implemented by using a proposed scheduling variable derived from indirect measurements of the EGR mass flow, such as the pressure ratio of the intake, exhaust manifolds, and the exhaust air-to-fuel ratio. The scheduling variable is utilized to estimate static gains of the EGR and VGT systems; it has a large dispersion in various engine operating conditions. Based on the estimated static gains of the plant, the Skogestad internal model control (SIMC) method determines appropriate control gains. The dynamic decoupler is designed to deal with the cross-coupled effects of the EGR and VGT systems by applying a simplified decoupler design method. The simplified decoupler is beneficial for compensating for the dynamics difference between two control loops of the EGR and VGT systems, for example, slow VGT dynamics and fast EGR dynamics. The proposed control algorithm is evaluated through engine experiments. Step test results of set points reveal that root-mean-square (RMS) error of the gain-scheduled feedback controller is reduced by 47% as compared to those of the fixed gain controller. Furthermore, the designed simplified decoupler decreased the tracking error under transients by 14–66% in various engine operating conditions.

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References

Figures

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Fig. 1

Air system schematic and definition of physical states

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Fig. 6

EGR system static gains according to the scheduling parameter

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Fig. 7

VGT system static gains according to the scheduling parameter

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Fig. 5

Static gains of EGR and VGT systems

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Fig. 4

Designed operating points and NEDC trajectory

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Fig. 3

Nonlinear characteristics of EGR and VGT systems: EGR valve lift (%, open) and VGT vane position (%,closed)

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Fig. 2

Correlation of reference variables for EGR control with NOx emissions

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Fig. 8

Static gains according to scheduling parameters in various operating conditions

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Fig. 9

Validation results of the proposed static gain model

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Fig. 10

Gain-scheduled single-input single-output controllers for EGR and VGT systems

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Fig. 11

Control structure of EGR and VGT systems

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Fig. 18

Nondiagonal elements of the decoupler at Ne = 2000 rpm, Wf = 25 mg/str

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Fig. 19

Step test results of desired intake pressure at Ne = 2000 rpm, Wf = 15 mg/str

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Fig. 12

Test bench and target engine

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Fig. 13

Experimental apparatus overview

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Fig. 17

Step test results of desired burned gas rate at Ne = 2000 rpm, Wf = 25 mg/str

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Fig. 14

EGR gain scheduling effect at Ne = 1750 rpm, Wf = 20 mg/str, uVGT = 85%

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Fig. 15

PI gains of the EGR controllers

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Fig. 16

Burned gas rate response between 38.5 and 43 s

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Fig. 21

Engine load step test results of the multivariable controller at 1750 rpm

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Fig. 22

Enlarged view of the transient period

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Fig. 20

NOx emission of the intake pressure step test at Ne = 2000 rpm, Wf = 15 mg/str

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