Ingolstadt, January 14th, 2000

Audi Opens Centre for Electromagnetic Compatibility

Torture chamber for electronics

Rhythmic chatter emerges from the car radio speakers. An everyday phenomenon. This irritating - but otherwise harmless - interference can be heard whenever the mobile telephone connects with its network. The cause of the problem lies in the high-frequency electromagnetic interference fields that the mobile phone emits.

Audi's new EMC Centre in Ingolstadt, Germany focuses on the influence that such radiation has on vehicle systems. EMC stands for electromagnetic compatibility. It refers to the task of keeping electronic systems as immune as possible to outside interference while simultaneously preventing them from emitting any interfering energy of their own.

The EMC experts in Ingolstadt have one major goal: regardless of the type of electronic troublemaker - it must be ensured that such undesired disturbances do not affect the on-board electronics of Audi's vehicles. This is important because not every disturbance remains as harmless as the cell phone impulses on the radio. This can be seen in the experience that drivers of various makes of car have reported after passing by a powerful short-wave radio transmitter next to an Autobahn in Southern Germany: diverse warning lamps on the dashboard suddenly began to compete with one another for attention. What looked at first to be a complete system breakdown proved on closer inspection to be an apparently unfounded fault display.

For this reason, even in the development phase for new components and vehicles, Audi's electronics specialists use the EMC system's testing rigs to examine the interference immunity of wiring harnesses and microprocessors, electric motors and digital instruments.

Not an easy task. The number of electronic components used in automobiles is constantly on the rise, and these parts communicate with one another (via bus systems, for example). And quite often this interaction is the reason for electromagnetic incompatibility. For the developers this means that every component must first be tested individually, and then must be examined with regard to the effects that it has on other parts of the vehicle's electronics.

During the extensive series of tests, which sometimes take months to complete, Audi's engineers subject the components to a well-aimed "constant barrage" of electromagnetic interference on their testing rig. The frequency spectrum for this interference extends all the way up to the gigahertz range in order to make it possible to simulate the common wavelengths from CB radio to radio stations right up to mobile telephone networks. The testing criteria are precisely defined. Beyond the guidelines that establish the requirements for EU approval, Audi also tests to ensure that components meet vehicle-specific limits that are significantly more stringent than the official standard.

Visitors to the largest room in Audi's EMC Centre could gain the impression that they have found their way into a science-fiction torture chamber. The walls for the entire testing rig are - as is the case with an anechoic room - entirely covered with absorption cones made of polyurethane foam. These cones prevent internal reflections. Oversized antennas, which are brought into position from the ceiling by a crane, are aimed at the automotive test candidates in the centre of the room.

A saloon is positioned on the system's roller test stand, which permits simulation of driving speeds up to 250 km/h. In this way it is possible to examine the influence of electromagnetic radiation at high speeds and with the engine running at full power. Acceleration and powerful braking can also be simulated. These durability tests are necessary in order to verify the immunity to disturbance, which is vital for safety systems such as ABS or airbags.

In order to prevent radiation from entering - or leaving - the testing hall, it has been designed as a steel cube with a volume of approximately 4,000 m3. The use of optical fibres (instead of copper wires) ensures that no internal sources of interference arise either. This large room is not needed for every isolated component test; radiation-proof metal boxes that have been appropriately reduced in size make it possible to perform similar tests under laboratory conditions for individual components or assemblies. These testing rigs are also used to test new elements before they are introduced into series production. Here, the suppliers also have to face the same rigorous requirements that apply to all electronic components in Audi vehicles.

Incidentally, the facility's immunity to radiation does not hinder the control of satellite navigation systems (which are requested by an ever increasing number of Audi customers). A special transmitter located inside the hall makes it possible to receive satellite signals, and thus permits realistic test procedures.

In the end, only those components and systems that have proven reliable in the place that they are to be used (i.e. in the vehicle) are given the go-ahead for series production. Audi drivers can therefore be sure that the electrical systems on board their vehicle are not bothered by unwanted troublemakers. Nor do they need fear encounters with radio stations or radio transmitters.

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