Electronics in the Car

Motor cars are no longer purely mechanical machines. Electronic equipment accounts for 30% of the value for some luxury cars. If fact a top of the range car has more electronic computing power on-board than that of a 1982 Airbus A310 commercial aircraft. Most modern cars have more computing power on-board than that of the Apollo spacecraft which put the first men on the moon.

In Ireland we do not design or manufacture complete motor cars but we do have more than 3000 people employed in the automotive electronics industry. At the University of Limerick researchers are contributing to the development of computer networking solutions for cars. You might well ask: Why do we need a computer network in a car? Well - consider an expensive car such as the Mercedes S-Class. This car has up to 60 computers on-board. These computers are invisible in the sense that they are contained in small boxes throughout the car and are used for various control purposes. Such computers are referred to as ECUs, or Electronic Control Units. Without some kind of computer network it would be difficult to connect all these control units together where information could be shared in an intelligent fashion. When we want to connect PCs (Personal Computers) together within a building we use a LAN (Local Area Network) and if we want to connect PCs across a wide geographical area we use a WAN (Wide Area Network). Now vehicle ECU devices are being connected together using networks such as Vehicle Area Networks (VAN) or Controller Area Networks (CAN). Figure 1 shows just some of the applications of networks in a modern car.

The CAN (Controller Area Network) network is the most popular car control network standard and is used for applications such as engine control, automatic gearbox control, dashboard instrumentation, climate control such as heating and air-conditioning, and body electronics such as door locking, window control and alarm systems. Car manufacturers are very conscious of costs and are working towards bringing the features of the luxury cars to the average family car at an affordable price. Since the cost of car electronics needs to be kept to a minimum some very low-cost simple networks are now emerging. In figure 1 you will see the LIN (Local Interconnect Network) network is used to connect clusters of electronic devices within very small areas such a single door or a single seat.

When you are playing your favourite computer game on your Dreamcast or Playstation 2 console; you are happy to control the vehicles in your game using your game controller (joystick) which is connected to your game console using a piece of wire. However, would you feel safe in a real aircraft if you thought that the pilot had a joystick in hand with a piece of wire connected to the rudder and the other control surfaces? Well - that is exactly how a modern aeroplane is controlled. This scheme is called ‘fly-by-wire’ (FBW) where electrical signals are sent by wire from the joystick to the actuators which move the control surfaces and control engine power etc. The electrical wire effectively replaces the traditional mechanical and hydraulic linkages. Most modern aircraft, such as the Boeing 777 or the Airbus A320, A330 and, use fly-by-wire schemes. Car manufacturers now want to use this technology to control steering and braking. They refer to this general technology as ‘drive-by-wire’. One application of drive-by-wire is ‘steer-by-wire’ where the steering wheel is connected to the steering actuators using an electrical cable so there is no need for a physical steering column. This gives car manufacturers more scope to design the vehicle shape where more passenger space can be realised up front. Another application is ‘brake-by-wire’ where car network wiring connects the brake computer at each wheel to the brake pedal computer and braking is controlled by sending electrical messages across the brake-by-wire network. Figure 2 shows an artistic view of the drive-by-wire concept. All this is not a far-fetched idea. It is expected that BMW will have a brake-by-wire car on the market in 2002 and Delphi Automotive have a steer-by-wire solution already developed which will be seen soon in commercial vehicles.

Whereas control networks operate behind the scenes, as far as the driver and passengers are concerned, it is the multi-media networks, which will have the biggest impact on customer perceptions; offering new concepts in in-vehicle work and entertainment features such as:

Ø Auto-route planner with real-time updates using the traffic reports from your radio’s RDS or the Web

The MOST (Media Orientated Systems Transport) is one current solution for the vehicle multi-media network. Figure 1 shows the MOST network within the car. This network does not use electrical signals but instead uses light-wave or optical signals carried on fiber optic cables within the car. Soon wireless networks will be available in the car using the new ‘Bluetooth’ standard.

In the future motor car engineers will have to understand many aspects of engineering including mechanical engineering, software engineering, electronic engineering and computer engineering. As an example, a few years ago when the compact Mercedes A-Class car was being developed, the test-car failed an important manoeuvrability test known as the ‘Elk test’ – where the car fell over on an extreme emergency avoidance manoeuvre. The problem was fixed by applying a change in the software on the computer which controlled the electronics for the hydraulic/mechanical active suspension unit.

Mr.Donal Heffernan is a Lectuer in the Department of Electronic and Computer Engineering at UL. His current research interests are in the development of control networking architectures for ultra reliable real-time systems, for automotive and industrial automotion applications.

Gabriel Leen is a PhD student with the PEI research group who is helping to develop the 'next generation' of automotive control networks. Gabriel's Masters degree project was concerned with the use of radar systems so that cars can 'see' other traffic and obstacles in an electronic sense.

Links: