Bugatti Veyron: Navigating the Nürburgring in a high-tech simulator

Accelerating from 0-200 km/h in 7.3 seconds, the Bugatti Veyron 16.4 is capable of outrunning a jumbo jet on take-off. As the fastest production vehicle in the world, the Veyron represents the limits of what modern automotive design can accomplish. The development of the car also set new standards, particularly in the area of automotive electronics. Even before production began, this 1,001 hp supercar was already lapping the Nürburgring, within a simulation running on a high-powered supercomputer. The company making this possible was ICT service provider T-Systems, contracted by the Veyron’s prestigious manufacturer to test all of the car’s electronic drivetrain components.

For the rebirth of the Bugatti legend, Europe’s largest carmaker assem-bled a number of test vehicles which were subject to in-depth trials and repeatedly improved over the course of several years. To achieve the car's 1,001 hp peak output and 407 km/h top speed, the engineers at Wolfsburg truly had to push the envelope in terms of what is technologi-cally feasible.

Testing the interactions of electronic components

Traditionally, a number of test vehicles are needed during development in order to ensure valid and reliable results. Particularly in the luxury seg-ment, being able to sharply reduce the number of test vehicles required during development is a matter of fundamental importance. Building an entire fleet of Veyron test vehicles would simply not make economic sense. So, how do the design engineers in the luxury segment deal with this problem? What methods can be applied, when the use of automotive electronics has been on the rise for years? For manufacturers, this means having to test more and more electronic components from various suppliers, as well as having to test them in combination with one another: truly a Sisyphean task. Previous test procedures, most of which were controlled manually, have reached their practical limits in terms of time and costs.

For this reason, in 2003 Bugatti decided upon the creation of a simulator for "Hardware in the Loop" testing (abbreviated HIL). A high-tech testing station of this nature includes diagnostic tools, a simulator and a CAN (Controller Area Network) bus, through which the control units can com-municate with one another. With this approach, Bugatti was able to re-place a good percentage of the tests that were previously conducted us-ing real-life prototypes with virtual trials in a laboratory setting.

This approach not only produced savings in terms of materials used and the nerves of the test drivers, it also allowed for electronics testing around the clock and seven days a week. "Suddenly, the design engineers in charge started taking an interest in the simulator – everybody wanted to use it," says Henry Sirotenko, the T-Systems Project Manager in charge of HIL simulator operation. In order to keep pace with design work, the T-Systems experts then configured the simulator so as to assume the role of a test vehicle. Doing this entailed working in two shifts in addition to the introduction of automated testing, starting in October 2004. ICT service provider T-Systems performed testing on all electronic components in the drivetrain of the Bugatti Veyron.

The answer to the increased use of vehicle electronics: Hardware in the Loop

Since the end of the 1990s, the use of electronic components in automobiles has grown by leaps and bounds. Engine control, ABS, airbags, ESP (Electronic Stability Program) and central locking are just a few of the areas in the automobile that are controlled by computers. In the eyes of customers, technical niceties such as power windows and parking assist have been thought of as standard features for some time now, and such expectations continue to rise. The latest generations of vehicles include as many as 60 different electronic units. The engine control units of the Veyron, for instance, feature several thousand functions. This is a far greater amount of software than that used on the Apollo mission.

For the HIL tests under laboratory conditions, the systems are separated from the system as a whole and are viewed either individually or as partial networks. So that the individual components will "feel at home", the rest of the system is simulated. The task is by no means trivial, since all of the device’s inputs and outputs must act on that test stand as if the compo-nents were on board the vehicle. On the engine control unit, for instance, altered ambient conditions are modeled using corresponding temperature and pressure models and all engine-related variables are simulated. Powerful computers working in real time process the calculations for the sensor signals. In this way, in-depth testing of the electronic system is possible before the first vehicle is available for testing.

"After a lot of hard work on the parameters and validation of the models, we were able to generate test results just as if we had used an additional test vehicle," says Henry Sirotenko. For example, the simulator was used to test the cold starting characteristics of the Veyron. "And we didn’t have to freeze to death to do it." For this, the temperature model simply needed to be set to -20 degrees Celsius. The software model then accurately modeled the real-life physical interaction between the real engine and starter motor.

The Veyron laps the Nürburgring – inside a high-performance super-computer

On the drivetrain, the experts tested two engine control units as well as control units for the transmission, the ESP and braking systems, a regulated all-wheel drive differential, the rear spoiler and the leveling control system using the testing system. Parameters such as temperature changes could be changed whenever necessary. During traditional vehicle field testing, such changes were extremely complicated to implement, if they were possible at all. By contrast, with a simulator advance trials can be conducted to reflect all manner of driving situations. For instance, what happens to the brake control unit when the electricity goes out? Can the vehicle still be stopped? Do the valves still operate as designed? Simple courses, such as straight lines or circular stretches of road can be simulated just as well as in a high-speed lap around the Nürburgring. For the race course, the T-Systems experts used a "test driver", which is a software program that is able to virtually pilot the Veyron around the Nür-burgring. "What was interesting about the Nürburgring tests was how we placed the car in critical situations which represented its absolute limits. Our digital test driver went through some of the curves while simultaneously braking, steering and accelerating," says Henry Sirotenko. In these critical driving situations, no faults appeared – in fact the effects witnessed confirmed that the software works really well.

Fighting for the pole position with bits and bytes

"Our job was to find out, together with the design engineers in charge, exactly how far along their components are in terms of development. Here, we made use of the traditional Failure Mode and Effects Analysis," says Henry Sirotenko. Just as the engine or drivetrain is repeatedly disassembled and inspected in detail during development, the same process can be performed with the control unit software. The following example shows how the Veyron’s battle for pole position was also fought with bits and bytes: For the fuel tank and pump control unit of the Veyron, a new system needed to be developed in which electronics also played a crucial role. Here, a backflow-free system was developed by Bugatti. Such a system requires absolute top-grade regulation of fuel pressure. In the fight for the pole position with 1,001 horsepower, you could say that every millibar counted. The pump electronics needed to be regulated in such a way as to allow the pump speed to increase by several thousand rpm in just a few milliseconds at full throttle to provide precisely the right amount of fuel being demanded by the engine. However, what happens if the pressure sensor is faulty, or if there is pressure loss in the fuel system? How can these faults be recognized, what functions must the control software have in order to recognize these faults, and how can this be tested? Traditional engineering, FMEA analyses and HIL simulation all worked "hand in hand" on this issue to develop a solution applicable for the tank and pump control unit.

HIL simulations as a prerequisite for approval by design engineering

The Veyron project also provided food for thought regarding other devel-opment projects of this type within the Volkswagen Group. At Volkswagen, every engine control unit is now tested in a simulated environment. The approach used in the Veyron project called first for simulator testing followed by in-vehicle testing. Although HIL has been in existence for six years now, this process has not yet firmly established itself in the industry. Henry Sirotenko has the last word: "The significance of HIL simulations as a prerequisite for approval by design engineers is bound to increase over the next few years."

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In modern automobiles, networks with up to 60 control units and upwards are not unusual. Almost all of these mini-computers today are configured according to the customer’s specifications. The increasing testing complexity for these complicated on-board networks can no longer be addressed through conventional means. Test sequences must be adapted and network testing inside the vehicle must be planned for, and in addition measurement equipment and analytical software must also be maintained. Without automated systems support, the challenges presented in this area of automotive electronics cannot be mastered. ICT service provider T-Systems provides support to testing engineers in the areas of test planning, automation and the implementation of testing programs and test procedures, as well as the administration of an automated "Hardware in the Loop" (HIL) testing environment. In this way, a number of standard test cases can be conducted in a short period of time. Fewer prototypes are needed and test times are reduced, while testing depth simultaneously increases. For years, T-Systems has been active in the field of automotive electronics: The networking and system integration of control units are among the tools of the trade. Control units cannot be combined at random – they must all be compatible with one another in order to function properly. As an ICT service provider, T-Systems has already made a name for itself with HIL simulations at Audi, Skoda, Phaeton and Bentley. Since 1999, the company has been working together with Volkswagen in the field of automotive electronics.