1、Electronic CONTROL SYSTEMS Ross T. BannatyneElectronic Control Systems Ross T. Bannatyne Warrendale, Pa. Copyright 2003 SAE International eISBN: 978-0-7680-7124-5All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any me
2、ans, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. Illustrations are reprinted with permission from Motorola, Inc. For permission and licensing requests, contact: SAE Permissions 400 Commonwealth Drive Warrendale, PA 15096-0001 USA E-mail
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4、pyright 2003 SAE International Positions and opinions advanced in this book are those of the author(s) and not necessarily those of SAE. The author is solely responsible for the content of the book. SAE Order No. T-107 Printed in the United States of America.Contents Chapter 1 Types of Electronic Co
5、ntrol Systems 1 Chapter 2 Trends .5 Networks .6 Algorithm Complexity 6 Safety Critical/Fault-Tolerant Operation 7 Electronic Memory Types .8 Power Consumption 9 Electromagnetic Compatibility (EMC) 10 Smart Sensors 11 Microcontroller CPU Trends 11 Packaging Trends 13 Chapter 3 Technologies 15 Drivers
6、 of Technology Innovation 15 Semiconductor Technology 16 Electronic Control Unit (ECU) Technology 19 Technology Innovation Driving System Innovation 22 Automated Highway 24 Sensor Implementation 26 System Chips and Technology Partitioning 27 Chapter 4 Vehicular Networks 31 Motivation to Network 31 D
7、ifferent Types of Networks. 33 Fault-Tolerant Networking 37 Chapter 5 Challenges 43 Cost Reduction 43 Supplier Relationships 45 Custom Requirements of the Automotive Industry 46 Development Time 47 The Sensor Explosion .47 iiiChapter 6 Software 55 Cost 55 Reusability. 55 Electronic Design Automation
8、 57 Code Compression 60 Quality 61 Chapter 7 The Future 63 Changes in Systems: By-Wire. 63 Changes in Components: Digital Signal Controller (DSC)66 Competitive Advantage in Electronic Control Systems 76 References 79 Acronyms 81 About the Author 83 ivChapter 1 Types of Electronic Control Systems T h
9、is chapter describes the different categories of electronic control systems that are implemented in the automobile. The main character- istics of each category are discussed, as well as the recent level of growth for each category. The evolution of electronic control systems in the automobile since
10、the 1960s has been significant. The total value of such systems implemented in automo- biles in 2002 is estimated to be more than $13 billion. (Source: Motorola.) Figure 1.1 illustrates four broad categories of electronic control systems: (1) safety and convenience, (2) powertrain, (3) body controls
11、, and (4) entertain- ment and communications. Safety systems in automobiles have evolved considerably in the last 100 years. Around 1900, the round steering wheel was introduced, oil and gas powered lighting was replaced by electric lamps in 1912, and the 1920s saw the growth in popularity of the mu
12、ch safer “closed“ car, complete with roof. The last century also has seen hydraulic braking systems replace crude cable or rod- based systems, the introduction of seat belts (a major safety milestone in the 1950s), and the arrival of the Electronic Age in the 1960s and 1970s to herald a new revoluti
13、on in automotive safety system improvements. Today, safety systems is the fastest growing category of automotive electronic control systems. In general, electronically controlled safety systems optimize the interface between the driver and the road surface by using electronic controllers to assist t
14、he driver in “thinking quickly“ and taking specific actions quickly. For example, an antilock braking system (ABS) will continually measure the slip of the tires and “pump“ the brakes to avoid wheel lock-up if required. This 1Figure 1.1 Categories of electronic control systems. action can be perform
15、ed significantly faster by an electronically controlled system than by a human. Thus, it enhances safety. The powertrain category of electronic control systems has been around since the 1980s. These systems use microcontrollers and algorithmic software to monitor sensors and control the fuel mixture
16、 to the engine. In the 1990s, the complexity of these systems has increased dramatically due to regulatory emissions controls and concern for fuel economy. Cost reductions in compo- nents also has allowed more “processing power“ to be applied to the control system, resulting in engines with higher p
17、erformance. The entertainment and communications category (sometimes referred to as driver information systems) is the second fastest-growing category today. All sorts of devices are being added to the automobile to help “connect“ the driver to the external environment. For example, it is now common
18、 to have navigation systems in rental vehicles to help the driver locate particular 2places or streets. The interface between such systems and the driver has improved throughout the 1990s to ensure that the driver can access naviga- tional and general communications information easily and safely. On
19、e of the reasons that the entertainment and communications category of automotive electronic control systems is growing is because it allows drivers to “personalize“ their vehicles. (Drivers now can connect their cellular telephones and personal digital assistants (PDA) into docking stations on the
20、vehicle.) For this reason, not surprisingly, the interior space has become the new battleground for consumers. Features once reserved for high-end vehicles now appear in mid-tier vehicles and even in some low-tier products. The fourth category of electronic control systems in the modern automobile i
21、s body controls. Such systems are relatively basic but have become more robust and lower in cost in recent years. Examples are systems that control window lifting, door locks, seat and mirror controls, and sunroof controls. All these features are now regarded as unsurprising features of a low-cost a
22、utomobile. Figure 1.2 illustrates the growth in the four categories of electronic control systems between 1998 and 2002. The safety category has been growing the fastest at slightly more than an 80% increase in total value from 1998 to today. The main reason for this growth has been the adoption of
23、advanced safety Figure 1.2 Growth in electronic control systems by category. 3systems such as an “electronic stability program“ (an enhanced antilock brak- ing system that includes lateral stability features), collision warning and avoid- ance systems, and general global growth in adoption of system
24、s such as antilock braking and electronically controlled power steering. Powertrain control systems have the highest growth in dollar value but not in proportion to the overall market for automotive electronic controls (approxi- mately 60% growth in dollar value). The reason for this is that there i
25、s not much growth in the number of systems that are being installed, but the value of the systems is increasing because higher performance components are required to meet tighter specifications. Entertainment and communications systems have been growing at approxi- mately 70% from 1998 to today. The
26、 adoption of navigation systems and global positioning systems (GPS) that are becoming more affordable, plus increased implementation of higher-value systems such as compact disc play- ers, has helped this growth. This is expected to accelerate as automobiles are further developed to include feature
27、s such as Internet-based applications. Finally, the body controls category has exhibited the slowest growth recently. This is a result of nearing saturation in the implementation levels of basic body control features such as windows and locks. The types of components that are used in such systems ar
28、e the most basic (e.g., less processing power and software are required to move a sunroof than are required to control an engine). Therefore, lower-cost components are available, and there has been a great deal of cost-reduction work in this area. This is reflected in the growth of market size. 4Cha
29、pter 2 Trends T his chapter describes the most important trends in the development of automotive electronic control systems. The trend that most reflects the general growth in electronic control systems is the rising semiconductor content per vehicle. Figure 2.1 illustrates in U.S. dollars the growt
30、h of average semiconductor content per vehicle. In 1997, approximately $150 worth of semiconductors were in the average automo- bile. This is expected to increase to $250 in 2002. This chapter discusses the areas in which those increasing dollars are being spent. Figure 2.1 Growth in semiconductor v
31、alue per vehicle. 5Networks The networking trend is so important to automotive electronic control sys- tems that Chapter 4 has been devoted entirely to this subject. There are many benefits to networks in the automobile. From a control systems stand- point, it is advantageous because systems can sha
32、re data in real time, thus making more intelligent systems possible. For example, an integrated chassis control system may be implemented by coordinating the data generated by the braking, steering, and suspension systems. Another benefit of these networks is that “second guessing“ becomes easier. S
33、econd guessing is the practice of using data from one system to check the plausibility of the results of data from an independent system. This secondary data could be used as a backup under certain conditions. For example, the wheel speed and vehicle directional information used in a stability manag
34、ement system could be used to supplement a navigation system, especially in the event that the global positioning system (GPS) is lost. In general, networking has allowed the functionality of automotive control systems to increase significantly at a reasonable cost. Algorithm Complexity The increasi
35、ng complexity of automotive electronic control systems has had a dramatic effect on the throughput requirements and peripheral integration of automotive microcontrollers. Algorithms now are required to handle the inputs from many sensors and communications systems, execute real-time control cycles,
36、and control the outputs of many actuators. Figure 2.2 illustrates the effect of growing complexity on the physical charac- teristics of microcontrollers. Three generations of powertrain micro- controllers are shown. Within three generations, the microcontroller has become approximately 100 times mor
37、e powerful in terms of CPU through- put. Likewise, the program memory (holding the algorithm) has grown 40 times bigger, and the number of transistors on the chip has increased by a factor of 300. The powertrain application is by no means unique. Many controller systems in the vehicle have kept pace
38、 with these developments, and 32-bit RISC (Reduced Instruction Set Computer) processors are being used for new generations of airbags and ABS. 6Figure 2.2 The growing complexity of automotive microcontrollers. Algorithm complexity also is leading to the widespread implementation of operating systems
39、. Although many operating systems continue to be devel- oped in-house by application specialists, the industry will migrate quickly toward standardization of the operating system and network management. The OSEK/VDX operating system has been widely adopted as the open standard. (OSEK is a German acr
40、onym for “Offene Systeme und deren Schnittstellen fr die Elektronik im Kraftfahrzeug.“) This standard was developed specifically to decouple the application code (algorithm) from the network management tasks and avoid incompatibility problems between the application code and the hardware. It include
41、s a standardized application programming interface, behavior, and protocol. Implementation of OSEK/ VDX should facilitate reusability and portability of software and predictable system behavior. Many automotive microcontrollers are expected to be implemented with an OSEK operating system soon. Safet
42、y Critical/Fault-Tolerant Operation Microcontrollers have been at the heart of automotive safety critical systems for many years. Most of the safety critical automotive systems in which microcontrollers have been used have provided a fail-safe function. Soon, there will be an added requirement for f
43、ault-tolerant electronic control systems. 7There is an important difference between fail-safe systems and fault-tolerant systems. Todays antilock braking systems (ABS) are fail-safe. That is, if an electrical system error is detected, the electronic control unit (ECU) switches to a safe “off“ mode,
44、allowing the foundation hydraulic brakes to operate without interference of the faulty ABS system. A fault-tolerant system must not only recognize that an electrical fault has occurred, but must continue to operate safely with the existing known fault. Antilock braking systems use redundancy to faci
45、litate a fail-safe system. Typically, the central processing unit (CPU) at the heart of the system super- vises the continual testing of all major system components. However, the CPU can validate these components only if the CPU itself is known to be “sane.“ Hence a second, redundant CPU is used to
46、validate the sanity of the first CPU. A redundant CPU can be implemented either as a second stand- alone microcontroller or as an error detection CPU with comparison logic on the same microcontroller. If the two CPUs disagree about the result of an instruction execution, the “fault“ signal will be e
47、nabled, and an interrupt will initiate a sequence of events to switch the control unit into the safe “off“ mode. Dual CPU microcontrollers will increase in popularity in automotive safety critical applications such as steering and airbags, as well as ABS. Electronic Memory Types The standard microco
48、ntroller memory types that have become established in automotive systems are ROM (read only memory), EPROM (electrically programmable ROM), and Flash EEPROM (electrically erasable program- mable ROM) for program storage; RAM (random access memory) for stack and scratch-pad memory; and byte erasable
49、EEPROM for storage of calibra- tion and security data. As Flash EEPROM is becoming more cost effective, it ultimately will replace ROM as the favored memory solution. Many automotive manufacturers now specify that their suppliers must provide Flash EEPROM as standard. Automobile manufacturers often wish to revise software in the field. Unless a remote method of reprogramming the memory array exists, this problem typically requires the sealed ECU to be removed and replaced. This is a time-consuming and expensive process for the automobile manufacturer, not to mention a great inconvenience t
