IMI Magazine

IMI Magazine

COVER FEATURE - Bugs in the system

Electronics account for around 20% of the value of today’s average light vehicle, with one supplier, Siemens, stating that 90% of innovations in a modern car can be attributed to electronics development.  But here’s the rub: DaimlerChrysler blames electronic faults for 70% of its well-publicised quality problems at Mercedes-Benz.

The three-pointed star is a good guide to the hectic advance of electronics. It began in 1967 with an electronically controlled fuel pump that did not even use software. Compare that with the current Mercedes-Benz S-Class where there are (depending on the options) more than 50 controllers governing different functions, while 600 signals pass along the cables and around 150 electronic messages are multiplexed onto three ‘buses’. To make the car ‘smart’, it was necessary to write 600,000 lines of programme code and if that sounds awesome consider this: within the next 10 years, it’s estimated that there will be around 100 million lines of code on a high-end car.

Engineering consultancy Ricardo warns that, given the current state of automotive technology, the proliferation of microprocessors in a vehicle’s innards is both economically and practically unsustainable. Economically because each microprocessor requires its own separate power supply and EMC/RFi protection, and practically as the process of functional integration of so many nodes becomes unmanageable.

However, on a more positive note, Ricardo goes on to say that rapid changes in silicon design and manufacturing technology – combined with economies of scale for higher performance microprocessors – will bring applications currently limited to the desktop environment into the automotive realm. In other words, expect microprocessors with a performance at least 10 times faster than today’s automotive versions to be featured in cars before the end of the decade.

This in turn will generate dramatic changes in architectures, functionality, safety strategies and development tools and it will also mean carmakers moving from a role as systems integrators to one of software integrators. For the customer, software development offers opportunities to maintain a vehicle’s value over its lifecycle - uprates/upgrades for motor controls, suspension or telematics, for example. From the carmakers’ point of view, though, it presents  “one of the problems downwind”, according to David Oates, managing director of AB Automotive Electronics.

Studies reveal that the volume of software doubles every 18 months (typically accounting for 50-70% of the electronics development cost). The downside to this is that the risk of software errors grows exponentially – and it is this which is manifesting itself in the front line when cars break down for electrical/electronic reasons.

 “Not everything talks with everything else on car,” says Remi Kaiser, general director for the French operation of another major supplier, Delphi. Kaiser, whose responsibilities embrace engineering quality, commented: “The main issue is to ensure that everyone is working as a team and that the correct communications can be established. This means having the same good set of tools. However, one of the issues is that of coding where each change of layer increases the chances of mistakes despite the comprehensive testing that is done.”

Unlike mechanical or electrical/electronic hardware, software does not wear out over time, and it can be argued that it does not fail. However, it’s stored and executed by electronic hardware, so problems can be triggered by failure of this hardware or if the software itself is incorrect.

According to a recent report by Delphi, causes of  hardware break-downs include memory failures in either the code space or variable space. For example, memory cell failures can result in software inadvertently jumping to the end of a routine or into the middle of another routine.

“The overall aim is to make electronics systems that are as reliable as mechanical ones that they replace or supplement,” says Dr David Ward, head of research in the electrical group at the Motor Industry Research Association. “The trouble with software, though, is that you cannot test it for durability. Where mechanical and electro-mechanical components can be tested to achieve reliability figures, you cannot attach a number to software reliability because it’s basically a design.”

According to Claas Bracklo, who is responsible for electronics integration at DaimlerChrysler: “Despite simplifications in the assumptions we made, we arrived at the figure of 10 to the power of 180 potential test conditions for a single vehicle model. If you wanted to examine all these as a simulation, you’d have to book several decades of computing time on a Cray supercomputer.”David Ward commented: “There is also the challenge of hardware/software integration and the integration of modules to the vehicle. Carmakers are moving to standardise CAN functions and so, in theory, all modules will run the same software, but the auto industry is not there yet. There’s also the perception that software can easily be changed, leading to late changes being demanded by the client. However, if part of the software in a network has been upgraded, it does mean that it needs to be checked to ensure that it is still compatible with the rest of the network, but this does not always happen.”

Why? The answer probably lies in the acceleration of new products coming onto the market. As David Oates at AB Automotive Electronics put it: “Vehicles are being developed in tighter timescales which means less testing and sample builds.”

Stephen Wolfsried, head of the electrical/electronic systems and chassis unit at DaimlerChrysler’s Mercedes Car Group, believes that carmakers must shoulder full responsibility for the anger and frustration felt by customers when their new car throws tantrums. “In the past we didn’t pay enough attention to interactions among the different (electronic) systems,” he says. “To be able to meet this challenge, we need new tools that measure up to the requirements of a zero-defect culture.

“The notion that bugs in the software are unavoidable is mistaken as far as I am concerned. They aren’t.” As a mechanical engineer he believes any tolerance for defects opens the way to careless and even negligent work on the part of the software designers. “We have to present the car as a package in which everything has been correctly dealt with and the driver has nothing to worry about.”