Differentiating between a serious and a more minor road traffic accident is crucial for vehicle safety, since the consequences for passengers vary significantly. In the event of a minor crash (for example, 16 km/h) the belt tensioners and airbags do not have to be or should not be activated. However, when the crash is more serious (for example, 64 km/h) the belt tensioners and airbags need to be deployed immediately. Since both serious and minor crashes can initially slow the vehicle at the same rate, conventional acceleration sensors can have difficulty determining the difference in crash severity soon enough.

Siemens VDO Automotive has developed a sensor at its Regensburg, Germany headquarters that monitors noise vibrations in the vehicle’s chassis, thereby contributing to improving the accident recognition and reaction time of a vehicle safety system. The crash impact sound sensor (CISS), which senses the seriousness of an accident acoustically detects sound wave variations generated by the deformation of a vehicle's chassis during an accident. The deformation noises and acceleration signals together can produce a more precise portrait of the accident and allow integrated safety restraint systems to be individually triggered.

The new CISS, developed by the team of Michael Feser of Siemens VDO in Regensburg, Germany, detects the seriousness of an accident acoustically. This intelligent sensor is able to precisely analyse a crash within a few milliseconds and thus allows faster activation of belt tensioners and optimised airbag deployment.

The crash impact sensor, which measures high-frequency, structure-borne vibrations, has a silicon weight with a number of fingers suspended on the inside. Similar counter fingers connected to the sensor housing are located between the fingers on the silicon weight, creating a meshing tooth structure similar to two combs inserted into each other. When excited by frequency vibration the sensor moves relative to the suspended weight changing the distance between the fingers and thereby varying the capacity depending on the specific acceleration and frequency.

The intelligent sensor is able to precisely analyse a crash within a few milliseconds, thereby allowing more rapid activation of belt tensioners and optimised airbag deployment. The CISS can improve detection of 16 km/h and 64 km/h crash situations. The sensor also helps to prevent the accidental activation (misuse) of the safety system, due to, for example, rocks or running into traffic cones.

"In a sense, the sensor allows the vehicle to listen to the accident as it is happening and react quicker than ever--within milliseconds" stated Derrick Zechmair, Siemens VDO Automotive vice president of restraints - safety electronics. "Depending on the assessed seriousness of the accident, the airbag control unit will trigger the seat belt tensioner and necessary airbags, in order to optimise the protection of the occupants."

CISS devices will be fitted as additional sensors on vehicles beginning in 2007, for an European original equipment manufacturer (OEM). Future generations of the sensor will be integrated into the vehicle's airbag control unit.

With a CISS satellite sensor, it is possible to discriminate between offset and side collisions using a single sensor in the middle of the vehicle instead of two acceleration sensors. Moreover, the structure-borne noise sensor detects the degree of plastic deformation in an offset or angular crash, even when integrated into the airbag’s central control unit in the vehicle’s middle tunnel. Such capability could render additional crash sensors superfluous, especially in certain geographical regions.

Siemens VDO has been supplying crash sensors to vehicle manufacturers, since 1993. At present, acceleration sensors are used to interpret the severity of front and rear impacts by assessing vehicle speed. Pressure sensors can be used to react to side impacts by monitoring changes in air pressure in vehicle body cavities. Siemens VDO Automotive continues to work on improving solutions for mitigating crash severity or for helping to avoid accidents.

Siemens VDO Automotive is a tier-one supplier of automotive electronic or electrical systems and components for applications covering gasoline and diesel powertrain technologies, safety and chassis systems, body electronics and interior products, including infotainment systems.

For the first half of 2005 ended March 31, 2005, Siemens AG, Munich, Germany had sales of €36,730,000,000 (about $44.07 billion at the current exchange rate), and net income of €1,782,000,000 (or about $2.14 billion at the current exchange rate). For the first six months of 2005, Siemens VDO Automotive posted sales of €4,633,000,000 (about $5.56 billion at the current exchange rate) and a group profit of €304,000,000 (about $364.8 million at the current exchange rate).

According to Frost & Sullivan’s North American Original Equipment Sensors Market research service (published October 2003) revenues for high-g accelerometers for original equipment use on North American-made light vehicles, are projected to reach $355.7 million (representing 55.5 million units) in 2009. High-g accelerometers, also known as crash sensors, trigger an airbag when a sudden deceleration is detected.

Details:

Enno Pflug, Corporate Communications

Siemens VDO Automotive

Sodener Straße 9, D-65824 Schwalbach/Ts, Germany

Phone: +49-6196-87-2515

E-mail: enno.pflug@siemens.com

Michael Feser, Siemens VDO, in Regensburg, Germany

E-mail: michael.feser@siemens.com

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