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Development
The development of Motor Vehicle Technology has responded to the consumer need of safe , comfortable and reliable transport
that can meet the demands of economy and efficiency required in modern society through the use of advanced electronic systems
with computerised control.
A top of the range luxury vehicle may have over eleven thousand electrical and electronic components forming a networked
control and operation system.
CONTROLLER AREA NETWORK
The control network consists of sensors to provide input data to control units which process this information to command
actuators which respond to the outputs of the control system.
The system known as CAN ( Controller Area Network) may use a signal from one sensor for several functions, for example
a speed sensor signal may be used for not only the speedometer reading but also linked to traction control, anti lock braking,
engine management , speed related audio volume, rolling door locks and satellite navigation systems .
In the past this may have required individual sensors and wiring for each function but by using a network the number of
wires and sensors can be reduced resulting in cost benefits for the manufacturer which may be passed onto the consumer.
Other benefits mean control units can "talk" to each other , for example when the brake pedal is depressed the
brakes are applied, the brake lights switched on , and a signal sent to the engine management to reduce fuelling.
The benefit of networking means that all data is available to all control units on the network. This multiplexed system
can be used in diagnostics to identify faults.
The future vehicle CAN system may be developed further to communicate with external systems by telematics , in a similar
way to a model aircraft being controlled at distance by a handheld transmitter, or your computer being linked to a wireless
network. A telematics system fitted to a vehicle with diagnostics would theoretically be capable of informing the manufacturer
that the vehicle is about to breakdown before the inevitable occurred. Or if a traffic signal was on stop, it could transmit
a signal to the vehicle to hold the brakes on until a go signal occurred.
A network system may be linked together in Star, Line, or Ring formation.The modules around the network are known as "Nodes"
The "Star" network has a central hub to which all nodes are connected, if this fails the whole network fails.
The "Line" network has spurs branched off a main communication line. If the main line is interrupted a secondary
system is normally in place as backup so it can continue to function.
The "Ring " network links nodes in a ring (similar to the ring main electric supply in a house)
CAN uses a Line Network.
Data is transmitted digitally around the network on a "bus" system.
The nodes are normally linked by a twisted pair cable (ISO 11898) though a single wire standard (SAE J2411) has been developed.
The twin line system is favoured by the majority of manufacturers as it offers greater reliability , lower rate of failure,
and faster data transmission speed. The two data lines are known as CAN-H (CAN High ) and CAN-L (CAN Low).
If a fault exists it can be diagnosed by a further line known as the "K-line " (ISO 9141)
Standardisation allows one manufacturer to link its system to work with that of another manufacturer , for example auxiliary
body equipment fitted to a commercial vehicle enabled with a CANbus system could communicate with the vehicle engine.
Several CAN systems may exist in a modern vehicle.
The structure of the CAN system and its data transmission has been defined by the International Standardisation Organisation
(ISO) and the Society of Automotive Engineers (SAE)
Other Vehicle Network Systems
Other systems of networking data from control units in a vehicle exist including :
LINbus ( Local Interconnect Network) ;this is a secondary system to the CANbus.
MOST (Media Orientated Systems Transport) ;used for multimedia.
The "MOST" network uses optical transmission methods such as Photo diodes and fibre optic cable for high speed
data transmission . This may be used for Audio,TV,and computer multimedia applications.
Byteflight (a BMW system)
D2B Optical (a Daimler Chrysler system)
Bluetooth ; used for wireless transmission of speech signals and data processing.
Power Line Communication ; This system integrates power supply and data lines.
MECHATRONICS
The integration of electronic control to mechanical components is known as Mechatronics.
Mechatronics can be used for such repetative actions as control of the clutch enabling smooth gear changes and increased
comfort.
West Mercia Mechanical Services,
10 Arrow Road,
Telford.TF5 0LF.
United Kingdom.
Telephone: 01952 247007
Mobile: 07703 558610
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