Introduction to Modeling and Control of Internal Combustion Engine Systems P1 potx

Introduction to Modeling and Control of Internal Combustion Engine Systems... OnderIntroduction to Modeling and Control of Internal Combustion Engine Systems ABC... This text is intended

Introduction to Modeling and Control of Internal Combustion Engine Systems

Lino Guzzella and Christopher H Onder

Introduction to Modeling and Control of Internal Combustion Engine

Systems

ABC

Prof Dr Lino Guzzella

2010 Springer-Verlag Berlin Heidelberg

This work is subject to copyright All rights are reserved, whether the whole or part of the rial is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks Dupli- cation of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always

mate-be obtained from Springer Violations are liable to prosecution under the German Copyright Law The use of general descriptive names, registered names, trademarks, etc in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.

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Who should read this text?

This text is intended for students interested in the design of classical and novel

IC engine control systems Its focus lies on the control-oriented mathematicaldescription of the physical processes involved and on the model-based controlsystem design and optimization

This text has evolved from a lecture series held during the last severalyears in the mechanical engineering (ME) department at ETH Zurich Thetarget readers are graduate ME students with a thorough understanding ofbasic thermodynamic and fluid dynamics processes in internal combustionengines (ICE) Other prerequisites are knowledge of general ME topics (cal-culus, mechanics, etc.) and a first course in control systems Students withlittle preparation in basic ICE modeling and design are referred to [64], [97],[194], and [206]

Why has this text been written?

Internal combustion engines represent one of the most important technologicalsuccess stories in the last 100 years These systems have become the mostfrequently used sources of propulsion energy in passenger cars One of themain reasons that this has occurred is the very high energy density of liquidhydrocarbon fuels As long as fossil fuel resources are used to fuel cars, thereare no foreseeable alternatives that offer the same benefits in terms of cost,safety, pollutant emission and fuel economy (always in a total cycle, or “well-to-wheel” sense, see e.g., [5] and [68])

Internal combustion engines still have a substantial potential for ments; Diesel (compression ignition) engines can be made much cleaner andOtto (spark ignition) engines still can be made much more fuel efficient Eachgoal can be achieved only with the help of control systems Moreover, withthe systems becoming increasingly complex, systematic and efficient system

improve-VI Preface

design procedures have become technological and commercial necessities Thistext addresses these issues by offering an introduction to model-based controlsystem design for ICE

What can be learned from this text?

The primary emphasis is put on the ICE (torque production, pollutant mation, etc.) and its auxiliary devices (air-charge control, mixture formation,pollutant abatement systems, etc.) Mathematical models for some of theseprocesses will be developed below Using these models, selected feedforwardand feedback control problems will then be discussed

for-A model-based approach is chosen because, even though more cumbersome

in the beginning, it after proves to be the most cost-effective in the long run.Especially the control system development and calibration processes benefitgreatly from mathematical models at early project stages

The appendix contains a brief summary of the most important controlleranalysis and design methods, and a case study that analyzes a simplified idle-speed control problem This includes some aspects of experimental parameteridentification and model validation

What cannot be learned from this text?

This text treats ICE systems, i.e., the load torque acting on the engine isassumed to be known and no drive-train or chassis problems will be discussed.Moreover, this text does not attempt to describe all control loops present

in engine systems The focus is on those problem areas in which the authorshave had the opportunity to work during earlier projects

Acknowledgments

Many people have implicitly helped us to prepare this text Specifically ourteachers, colleagues and students have helped to bring us to the point where

we felt ready to write this text Several people have helped us more explicitly

in preparing this manuscript: Alois Amstutz, with whom we work especially

in the area of Diesel engines, several of our doctoral students whose tations have been used as the nucleus of several sections (we reference theirwork at the appropriate places), Simon Frei, Marzio Locatelli and David Ger-mann who worked on the idle-speed case study and helped streamlining themanuscript, and, finally, Brigitte Rohrbach and Darla Peelle, who translatedour manuscripts from “Germlish” to English

Preface to the Second Edition

Why a second edition?

The discussions concerning pollutant emissions and fuel economy of passengercars constantly intensified since the first edition of this book was published.Concerns about the air quality, the limited resources of fossil fuels and thedetrimental effects of greenhouse gases further spurred the interest of boththe industry and academia to work towards improved internal-combustionengines for automotive applications Not surprisingly, the first edition of thismonograph rapidly sold out When the publisher inquired about a secondedition, we decided to seize this opportunity for revising the text, correctingseveral errors, and adding some new material The following list outlines themost important changes and additions included in this second edition:

• restructured and slightly extended section on superchargers, increasing thecomprehensibility;

• short subsection on rotational oscillations and their treatment on enginetest-benches, being a safety-relevant aspect;

• improved physical and chemical model for the three-way catalyst, ing the conception and realization of downstream air-to-fuel ratio control;

simplify-• complete section on modeling, detection, and control of engine knock;

• new methodology for the design of an air-to-fuel ratio controller exhibitingseveral advantages over the traditional H∞ approach;

• short introduction to thermodynamic engine-cycle calculation and somecorresponding control-oriented aspects

As in the first edition, the text is focused on those problems we were (orstill are) working on in our group at ETH Many exciting new ideas (HCCIcombustion, variable-compression engines, engines for high-octane fuels, etc.)have been proposed by other groups However, simply reporting those conceptswithout being able to round them off by first-hand experience would not addany benefit to the existing literature Therefore, they are not included in

VIII Preface to the Second Edition

this book, which should remain an introductory reference for students andengineers new to the topic of internal-combustion engines

1 Introduction 1

1.1 Notation 1

1.2 Control Systems for IC Engines 4

1.2.1 Relevance of Engine Control Systems 4

1.2.2 Electronic Engine Control Hardware and Software 5

1.3 Overview of SI Engine Control Problems 6

1.3.1 General Remarks 6

1.3.2 Main Control Loops in SI Engines 8

1.3.3 Future Developments 10

1.4 Overview of Control Problems in CI Engines 11

1.4.1 General Remarks 11

1.4.2 Main Control Loops in Diesel Engines 14

1.4.3 Future Developments 18

1.5 Structure of the Text 19

2 Mean-Value Models 21

2.1 Introduction 22

2.2 Cause and Effect Diagrams 24

2.2.1 Spark-Ignited Engines 25

2.2.2 Diesel Engines 28

2.3 Air System 30

2.3.1 Receivers 30

2.3.2 Valve Mass Flows 31

2.3.3 Engine Mass Flows 35

2.3.4 Exhaust Gas Recirculation 37

2.3.5 Supercharger 40

2.4 Fuel System 52

2.4.1 Introduction 52

2.4.2 Wall-Wetting Dynamics 53

2.4.3 Gas Mixing and Transport Delays 63

2.5 Mechanical System 64

X Contents

2.5.1 Torque Generation 64

2.5.2 Engine Speed 76

2.5.3 Rotational Vibration Dampers 81

2.6 Thermal Systems 85

2.6.1 Introduction 85

2.6.2 Engine Exhaust Gas Enthalpy 86

2.6.3 Thermal Model of the Exhaust Manifold 88

2.6.4 Simplified Thermal Model 89

2.6.5 Detailed Thermal Model 90

2.7 Pollutant Formation 98

2.7.1 Introduction 98

2.7.2 Stoichiometric Combustion 98

2.7.3 Non-Stoichiometric Combustion 100

2.7.4 Pollutant Formation in SI Engines 102

2.7.5 Pollutant Formation in Diesel Engines 108

2.7.6 Control-Oriented N O Model 110

2.8 Pollutant Abatement Systems 113

2.8.1 Introduction 113

2.8.2 Three-Way Catalytic Converters, Basic Principles 114

2.8.3 Modeling Three-Way Catalytic Converters 117

2.9 Pollution Abatement Systems for Diesel Engines 137

3 Discrete-Event Models 147

3.1 Introduction to DEM 148

3.1.1 When are DEM Required? 148

3.1.2 Discrete-Time Effects of the Combustion 148

3.1.3 Discrete Action of the ECU 150

3.1.4 DEM for Injection and Ignition 153

3.2 The Most Important DEM in Engine Systems 156

3.2.1 DEM of the Mean Torque Production 156

3.2.2 DEM of the Air Flow Dynamics 161

3.2.3 DEM of the Fuel-Flow Dynamics 164

3.2.4 DEM of the Back-Flow Dynamics of CNG Engines 173

3.2.5 DEM of the Residual Gas Dynamics 175

3.2.6 DEM of the Exhaust System 178

3.3 DEM Based on Cylinder Pressure Information 180

3.3.1 General Remarks 180

3.3.2 Estimation of Burned-Mass Fraction 181

3.3.3 Cylinder Charge Estimation 183

3.3.4 Torque Variations Due to Pressure Pulsations 188

Contents XI

4 Control of Engine Systems 191

4.1 Introduction 192

4.1.1 General Remarks 192

4.1.2 Software Structure 193

4.1.3 Engine Operating Point 196

4.1.4 Engine Calibration 197

4.2 Engine Knock 199

4.2.1 Autoignition Process 200

4.2.2 Knock Criteria 202

4.2.3 Knock Detection 204

4.2.4 Knock Controller 208

4.3 Air/Fuel-Ratio Control 210

4.3.1 Feedforward Control System 210

4.3.2 Feedback Control: Conventional Approach 215

4.3.3 Feedback Control: H∞ 217

4.3.4 Feedback Control: Internal-Model Control 229

4.3.5 Multivariable Control of Air/Fuel Ratio and Engine Speed 239

4.4 Control of an SCR System 244

4.5 Engine Thermomanagement 249

4.5.1 Introduction 249

4.5.2 Control Problem Formulation 250

4.5.3 Feedforward Control System 252

4.5.4 Experimental Results 255

A Basics of Modeling and Control-Systems Theory 261

A.1 Modeling of Dynamic Systems 261

A.2 System Description and System Properties 270

A.3 Model Uncertainty 276

A.4 Control-System Design for Nominal Plants 279

A.5 Control System Design for Uncertain Plants 288

A.6 Controller Discretization 291

A.7 Controller Realization 301

A.7.1 Gain Scheduling 301

A.7.2 Anti-Reset Windup 302

A.8 Further Reading 303

B Case Study: Idle Speed Control 305

B.1 Modeling of the Idle Speed System 306

B.1.1 Introduction 306

B.1.2 System Structure 307

B.1.3 Description of Subsystems 308

B.2 Parameter Identification and Model Validation 315

B.2.1 Static Behavior 315

B.2.2 Dynamic Behavior 319

XII Contents

B.2.3 Numerical Values of the Model Parameters 321

B.3 Description of Linear System 324

B.4 Control System Design and Implementation 326

C Combustion and Thermodynamic Cycle Calculation of ICEs 331

C.1 Fuels 331

C.2 Thermodynamic Cycles 333

C.2.1 Real Engine-Cycle 334

C.2.2 Approximations for the Heat Release 337

C.2.3 Csallner Functions 338

References 343

Introduction

In this chapter, first the notation used throughout this text is defined It ther contains some general remarks on electronic engine control systems andintroduces the most common control problems encountered in spark ignition(Otto or gasoline) and compression ignition (Diesel) engine systems The in-tention is to show the general motivation for using control systems and togive the reader an idea of the problems that can be tackled by feedforward andfeedback control systems for both SI and CI engines

fur-The emphasis in this chapter is on qualitative arguments fur-The cally precise formulation is deferred to subsequent chapters Those readers notfamiliar with modern electronic sensors, actuators, and control hardware forautomotive applications may want to consult either [7], [108], or [125]

˙x(t)

is used to indicate a flow of mass, energy, etc Both variables d

dtx(t) and ˙x(t)have the same units, but they are different objects No special distinction ismade between scalars, vectors and matrices The dimensions of a variable, ifnot a scalar, are explicitly defined in the context Input signals are usuallydenoted by u and output signals by y , whereas the index specifies whatphysical quantity is actuated or measured

Concentrations of chemical species C are denoted by [C], with unitsmol/mol, with respect to the reference substance The concentrations are

2 1 Introduction

therefore limited to the interval [0, 1] The concentration of pollutant speciesare often shown in plots or tables using ppm units (part per million), i.e., byusing a amplification factor of 106 For mass storage and transportation mod-els it is advantageous to use mass fractions, which are denoted by ξ havingunits [kg/kg]

In general, all variables are defined at that place in the text where theyare used for the first time To facilitate the reading, some symbols have beenreserved for special physical quantities:

m 2 K] heat-transfer coefficient

cx [kgKJ , -] specific heat capacities (x = p, v), concentration of x

ε [-] compression ratio, volume fraction

φ [◦, rad] crank angle

κ [-] ratio of specific heats

λ [-] air-to-fuel ratio, volumetric efficiency, Lagrange multiplier

M [molkg ] molar mass

N [-] number of engine revolutions per cycle

(1 for two-stroke, 2 for four-stroke engines)

molK] universal gas constant

σ0 [-] stoichiometric air-to-fuel ratio

ζ timing (e.g of ignition or injection)

In a turbocharged engine system, the four most important locations are ignated by the indices 1 for “before compressor,” 2 for “after compressor,” 3for “after engine,” and 4 for “after turbine.”

des-In general, all numerical values listed in this text are shown in SI units Afew exceptions are made where non-SI units are widely accepted These fewcases are explicitly mentioned in the text

The most commonly used acronyms are:

BDC (TDC) bottom (top) dead center (piston at lowest (topmost)

position)BMEP or pme (brake) mean-effective pressure

IVC (IVO) inlet-valve closing (opening)

EVC (EVO) exhaust-valve closing (opening)