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It doesn't work unless the brain in the engine can talk to the brain in the gearbox... John

24th February 2005
Page 71
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Page 71, 24th February 2005 — It doesn't work unless the brain in the engine can talk to the brain in the gearbox... John
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Which of the following most accurately describes the problem?

Kendall investigates the electronic protocols

that are at the heart of modern HGVs.

It used to be so simple. An engine, a transmission system, axles, a cab, plus the relevant bodywork and equipment.There was nothing sophisticated about a truck and that was more or less how it stayed from the time the first internal combustion engine was harnessed to move freight until the 1980s.

Then several things began to happen at the same time. First, the international drive was on to reduce emissions from cars and CVs. Second, legislation was looming on vehicle safety systems.As a result, vehicle manufacturers began to think about other on-board devices and systems they wanted to introduce. Last,but definitely not least, advances in electronics were revolutionising thinking about computing and control systems.

Suggest to a driver in the early 1980s that by 2005 a truck could be fitted with a vast array of systems controlled by electronics and he would probably have thought you'd lost the plot. Now, even the most traditional operators are at home with automated gearboxes, electronically controlled engines, sat-nay, braking by wire and a whole gamut of safety equipment to safeguard users of ancillary equipment such as tail-lifts, bin lifts and refuse compactors.

And it isn't going to stop there. The Euro-4 emissions regs which take effect in October 2006 will continue the downward pressure on exhaust emissions. Euro-5. expected sometime in 2008, will tighten the screw even further; and by the time we get to Euro-6 around 2012, close control and monitoring of both engine and transmissions will be essential.

Electronic systems are set to develop beyond current safety systems such as ABS brakes. Ply-by-wire' technology will even take over control of steering. Steering movements will be sensed electronically and made electrically or hydraulically. And outside the cab will be road tolling, which will depend on satellite positioning, which adds to the demands on the on-board electronic networks.

None of this would have been possible using the wiring system from an early 1980s truck which had been designed to distribute electrical power around the vehicle to where it was needed, and in general it did the job perfectly well. However, all those new on-board systems demanded a different approach. Monitoring and control systems rely on sophisticated circuitry to distribute power,switch systems on and off, constantly gather data, analyse it and then act on that information.All this hundreds or thousands of times a second.

Increasing demands

In other words, there are a number of computers on board controlling various systems around the vehicle.

Emissions regs and increasing demands for other control systems mean these computers cannot work in isolation; they need to communicate with each other.Take an engine and its automated gearbox: the gearbox needs to know what demands are being made of the engine in order to determine which gear it should select and what gear change pattern it needs to adopt.This mean the electronic control units (ECUs) for the engine and gearbox need to communicate with each other — then there are the ECUs for braking systems, traction control systems,auxiliary braking systems and many others. Not only do the systems need to communicate with each other, they also need to speak the same language if the truck is to avoid grinding to a halt or crawling along in "Limp Home" mode.

Obviously they need a common computer language, and that has far reaching implications. Not only the vehicle manufacturers, but also all the component suppliers must agree on it. Component suppliers could hardly be expected to produce vehicle systems with a different language for each vehicle manufacturer. Similarly, servicing for mixed fleets would become prohibitively expensive.

The arrival of fly-by-wire systems also has safety implications.An essential requirement of any such system is that it is failsafe. Steering or brake failure on a fully laden 44-tonne artic is not acceptable. so the system has lobe designed to eliminate faults completely. Even with goodwill all round,getting agreement from competing manufacturers of vehicles, components and systems is far from easy.A protocol which suits one manufacturer or supplier might not suit the needs of others.This is where bodies such as the Society of Automotive Engineers (SAE) in the US and the Institute of Mechanical Engineers (IMechE) in the UK can play apart. Riccardo Sardelli,UK Country Manager of Allison Transmissions,says:"We look to the SAE or IMechE to make sure a general standard is being created."

The CV industry decided to adopt the SAE standard J1939 for truck electronic networks. This protocol allows reading, measuring and deleting data for components and calibrating controls. So that should be the end of the story shouldn't it? After all a common protocol should enable an easy exchange of data and ensure that components and systems can he used on any vehicle.

man ideal world, that would certainly be the case, but two significant flies in the ointment are commercial confidentiality and the rapid pace of change in electronics and computing.

Vehicle manufacturers will always want to maintain a competitive advantage over their rivals, which means they will never want an allembracing free exchange of data. Sardelli says: "J1939 is supposed to be a common standard, but everyone's perception is different.

Standard system

J1939 uses the Controller Area Network or CAN-bus system for networking onboard systems. This has been the standard system on CVs since the early 1990s. but it's not the only option and it won't be used for fly-by-wire networks because it can't react fast enough for the new safety critical systems.

A new protocol is needed. In the commercial world, that inevitably means competition hut the current favourite is Hexray, which is being developed by a consortium of component and vehicle manufacturers.. Most automotive manufacturers have already signed up to it, but it's not likely to be a commercial reality until around 2010. says an insider at Daf Trucks.

Until then another protocol, Media Orientated Systems Transport (MOST), is in use on a number of trucks. It can handle fly-bywire systems, but there are legal issues to he sorted out before fly-by-wire can be adopted for automotive use, so the fact Flexray won't be available until 2010 is unlikely to be a problem.

In fact Dal's Dueren den Hollander doesn't think Flexray or MOST will replace CAN-bus, for the simple reason that CAN-bus is so widely used. It's more likely, he says, that Hexray will add to CAN-bus systems rather than replacing them. So an agreed standard is failing to simplify on-board data networks, because theory has been overtaken by system developments in the real world.

With regard to service and maintenance, this doesn't make life easy for the independent workshop or mixed fleet. It's still necessary to gather protocols from all manufacturers to carry out servicing.and there isn't much prospect of that changing. While all manufacturers of safety and emissions systems will use the J1939 protocol, standardisation is unlikely to progress much further than that. •


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