Introduction to Modeling and Control of Internal Combustion Engine Systems

Transcription

1 Introduction to Modeling and Control of Internal Combustion Engine Systems

2 Lino Guzzella and Christopher H. Onder Introduction to Modeling and Control of Internal Combustion Engine Systems ABC

3 Prof. Dr. Lino Guzzella ETH Zürich Institute for Dynamic Systems & Control Sonneggstr Zürich ETH-Zentrum Switzerland lguzzella@ethz.ch Dr. Christopher H. Onder ETH Zürich Institute for Dynamic Systems & Control Sonneggstr Zürich ETH-Zentrum Switzerland onder@ethz.ch ISBN e-isbn DOI / Library of Congress Control Number: c 2010 Springer-Verlag Berlin Heidelberg This work is subject to copyright. All rights are reserved, whether the whole or part of the material 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. Duplication 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 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. Typesetting: Data supplied by the authors Production: Scientific Publishing Services Pvt. Ltd., Chennai, India Cover Design: WMX Design, Heidelberg, Germany Printed in acid-free paper springer.com

4 Preface 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 mathematical description of the physical processes involved and on the model-based control system design and optimization. This text has evolved from a lecture series held during the last several years in the mechanical engineering (ME) department at ETH Zurich. The target readers are graduate ME students with a thorough understanding of basic thermodynamic and fluid dynamics processes in internal combustion engines (ICE). Other prerequisites are knowledge of general ME topics (calculus, mechanics, etc.) and a first course in control systems. Students with little 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 technological success stories in the last 100 years. These systems have become the most frequently used sources of propulsion energy in passenger cars. One of the main reasons that this has occurred is the very high energy density of liquid hydrocarbon fuels. As long as fossil fuel resources are used to fuel cars, there are no foreseeable alternatives that offer the same benefits in terms of cost, safety, pollutant emission and fuel economy (always in a total cycle, or wellto-wheel sense, see e.g., [5] and [68]). Internal combustion engines still have a substantial potential for improvements; Diesel (compression ignition) engines can be made much cleaner and Otto (spark ignition) engines still can be made much more fuel efficient. Each goal can be achieved only with the help of control systems. Moreover, with the systems becoming increasingly complex, systematic and efficient system

5 VI Preface design procedures have become technological and commercial necessities. This text addresses these issues by offering an introduction to model-based control system design for ICE. What can be learned from this text? The primary emphasis is put on the ICE (torque production, pollutant formation, etc.) and its auxiliary devices (air-charge control, mixture formation, pollutant abatement systems, etc.). Mathematical models for some of these processes will be developed below. Using these models, selected feedforward and feedback control problems will then be discussed. 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 benefit greatly from mathematical models at early project stages. The appendix contains a brief summary of the most important controller analysis and design methods, and a case study that analyzes a simplified idlespeed control problem. This includes some aspects of experimental parameter identification and model validation. What cannot be learned from this text? This text treats ICE systems, i.e., the load torque acting on the engine is assumed 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 authors have had the opportunity to work during earlier projects. Acknowledgments Many people have implicitly helped us to prepare this text. Specifically our teachers, 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 dissertations have been used as the nucleus of several sections (we reference their work at the appropriate places), Simon Frei, Marzio Locatelli and David Germann who worked on the idle-speed case study and helped streamlining the manuscript, and, finally, Brigitte Rohrbach and Darla Peelle, who translated our manuscripts from Germlish to English. Zurich, May 2004 Lino Guzzella Christopher H. Onder

6 Preface to the Second Edition Why a second edition? The discussions concerning pollutant emissions and fuel economy of passenger cars constantly intensified since the first edition of this book was published. Concerns about the air quality, the limited resources of fossil fuels and the detrimental effects of greenhouse gases further spurred the interest of both the industry and academia to work towards improved internal-combustion engines for automotive applications. Not surprisingly, the first edition of this monograph rapidly sold out. When the publisher inquired about a second edition, we decided to seize this opportunity for revising the text, correcting several errors, and adding some new material. The following list outlines the most important changes and additions included in this second edition: restructured and slightly extended section on superchargers, increasing the comprehensibility; short subsection on rotational oscillations and their treatment on engine test-benches, being a safety-relevant aspect; improved physical and chemical model for the three-way catalyst, simplifying the conception and realization of downstream air-to-fuel ratio control; complete section on modeling, detection, and control of engine knock; new methodology for the design of an air-to-fuel ratio controller exhibiting several advantages over the traditional H approach; short introduction to thermodynamic engine-cycle calculation and some corresponding control-oriented aspects. As in the first edition, the text is focused on those problems we were (or still are) working on in our group at ETH. Many exciting new ideas (HCCI combustion, variable-compression engines, engines for high-octane fuels, etc.) have been proposed by other groups. However, simply reporting those concepts without being able to round them off by first-hand experience would not add any benefit to the existing literature. Therefore, they are not included in

7 VIII Preface to the Second Edition this book, which should remain an introductory reference for students and engineers new to the topic of internal-combustion engines. Acknowledgements We want to express our gratitude to the many colleagues and students who reported to us errors and omissions in the first edition of this text. Several people have helped us improving this monograph, in particular Daniel Rupp, Roman Möller and Jonas Asprion who helped preparing the manuscript. Zurich, September 2009 Lino Guzzella Christopher H. Onder

8 Contents 1 Introduction Notation Control Systems for IC Engines Relevance of Engine Control Systems Electronic Engine Control Hardware and Software Overview of SI Engine Control Problems General Remarks Main Control Loops in SI Engines Future Developments Overview of Control Problems in CI Engines General Remarks Main Control Loops in Diesel Engines Future Developments Structure of the Text Mean-Value Models Introduction Cause and Effect Diagrams Spark-Ignited Engines Diesel Engines Air System Receivers Valve Mass Flows Engine Mass Flows Exhaust Gas Recirculation Supercharger Fuel System Introduction Wall-Wetting Dynamics Gas Mixing and Transport Delays Mechanical System

9 X Contents Torque Generation Engine Speed Rotational Vibration Dampers Thermal Systems Introduction Engine Exhaust Gas Enthalpy Thermal Model of the Exhaust Manifold Simplified Thermal Model Detailed Thermal Model Pollutant Formation Introduction Stoichiometric Combustion Non-Stoichiometric Combustion Pollutant Formation in SI Engines Pollutant Formation in Diesel Engines Control-Oriented NO Model Pollutant Abatement Systems Introduction Three-Way Catalytic Converters, Basic Principles Modeling Three-Way Catalytic Converters Pollution Abatement Systems for Diesel Engines Discrete-Event Models Introduction to DEM When are DEM Required? Discrete-Time Effects of the Combustion Discrete Action of the ECU DEM for Injection and Ignition The Most Important DEM in Engine Systems DEM of the Mean Torque Production DEM of the Air Flow Dynamics DEM of the Fuel-Flow Dynamics DEM of the Back-Flow Dynamics of CNG Engines DEM of the Residual Gas Dynamics DEM of the Exhaust System DEM Based on Cylinder Pressure Information General Remarks Estimation of Burned-Mass Fraction Cylinder Charge Estimation Torque Variations Due to Pressure Pulsations

10 Contents XI 4 Control of Engine Systems Introduction General Remarks Software Structure Engine Operating Point Engine Calibration Engine Knock Autoignition Process Knock Criteria Knock Detection Knock Controller Air/Fuel-Ratio Control Feedforward Control System Feedback Control: Conventional Approach Feedback Control: H Feedback Control: Internal-Model Control Multivariable Control of Air/Fuel Ratio and Engine Speed Control of an SCR System Engine Thermomanagement Introduction Control Problem Formulation Feedforward Control System Experimental Results A Basics of Modeling and Control-Systems Theory A.1 Modeling of Dynamic Systems A.2 System Description and System Properties A.3 Model Uncertainty A.4 Control-System Design for Nominal Plants A.5 Control System Design for Uncertain Plants A.6 Controller Discretization A.7 Controller Realization A.7.1 Gain Scheduling A.7.2 Anti-Reset Windup A.8 Further Reading B Case Study: Idle Speed Control B.1 Modeling of the Idle Speed System B.1.1 Introduction B.1.2 System Structure B.1.3 Description of Subsystems B.2 Parameter Identification and Model Validation B.2.1 Static Behavior B.2.2 Dynamic Behavior

11 XII Contents B.2.3 Numerical Values of the Model Parameters B.3 Description of Linear System B.4 Control System Design and Implementation C Combustion and Thermodynamic Cycle Calculation of ICEs C.1 Fuels C.2 Thermodynamic Cycles C.2.1 Real Engine-Cycle C.2.2 Approximations for the Heat Release C.2.3 Csallner Functions References