2019 / Integrated mobility technologies

Perfectly coordinated and secured

    The active safety systems, for instance cameras and ultrasound sensors, are of the highest standard in today’s vehicles. In the event of an unavoidable accident there is only a fraction of a second to spare.

    When the safety electronics register a crash, the passive systems, such as seat belt tensioners and air bags, must be triggered in a few milliseconds. The systems must be perfectly coordinated to offer the passenger the best possible protection

    Christian Stöcklein Head of the department seatbelts/passenger protection
    Kai Jennoch from the PSW restraint systems /airbags development department and his colleague Valentin Berrueco from calculation/ simulation supported the customer Audi in the development of passive safety systems of the Audi e-tron. On the one hand, their task has been to develop the corresponding components together with other PSW colleagues from seatbelt and air bag development in coordination with the Audi specialist departments.
    On the other hand, their responsibility has been to guarantee the perfect interplay of components in the complete system. In addition they have jointly secured the systems through virtual simulation methods. This was the first time PSW experts designed the passive safety systems of an electric vehicle. But what difference does this make to a vehicle with a combustion engine?
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    Electric vehicle vs. conventional drive

    ‘It is a question of the pulse’, says Kai, who often loses himself in specialist terminology during the discussion, therefore causing his listener to frown. You notice how passionate he is when he enthuses about his subject. He explains patiently: ‘In a vehicle with conventional drive the engine offers a buffer zone. During a crash the front folds up bit by bit, while the engine provides resistance, to decrease the speed. The pulse, in other words the delay, is correspondingly large. Of course electric cars have no comparable engine, so that depending on the design of the front end of the vehicle, the front folds more quickly. Through this the pulse is less.’ Of course as soon as the structure deformed by the crash meets the entire battery case, the delay rapidly increases, because the battery is protected in such a way, that it cannot be deformed.

    The change from slight to long delay presents new challenges to us in the design of passive safety systems

    Kai Jenoch Development restraint systems/airbags

    Perfect harmony

    The experts achieved the optimum design of systems while using particular systems to intelligently trigger seatbelt tensioners and air bags. On the one hand this information is provided by capacitive seat recognition. The information specifies whether the seat is occupied or not. On the other hand, a switch device in the seat can estimate how large and heavy the occupant is.
    Based on this information and in consideration of the deformation behaviour of an electric car, Kai and Valentin coordinate the trigger time of seatbelt tensioners and air bags to each other. The interaction of both systems must be perfectly harmonised. In the first ignition threshold the seatbelt tensioner is first triggered and shortly after that the air bag. Some air bags have additional levels’, according to Kai. In addition the air bags must be correspondingly softer or harder, depending on the dimensions of the passenger, to provide the best possible protection. For instance, the air bag must be softer for a smaller woman than for a large man.
    The different legal framework conditions posed a further legal challenge. Kai and Valentin must ensure that the design conforms to specific guidelines. For instance only limited forces may act on some body regions, which are specified in kilonewtons. These guidelines vary from market to market, which the engineers must consider during the development.
    Der Innenraum des Audi e-tron
    The interieur of the Audi e-tron.
    Der Innenraum des Audi e-tron

    The final examination of the Euro NCAP

    At the start of the year Kai and Valentin took their ‘Final Examination’ together with their colleague from structural development Markus Kemmler with the Audi e-tron. In coordination with Audi they spent three days at the Bundesanstalt für Straßenwesen (Federal Highway Research Institute) in order to monitor the test procedure of the Euro NCAP for the Audi e-tron. The experiences that the PSW team had at Audi e-tron formed the basis for jointly developing passive safety systems with additional electric vehicles. ‘Mobility of the future will be electric. It is important that such projects will further broaden our already comprehensive know-how’, says Kai. “The e-tron has reached the full five star rating. The tests have also shown that the leg protection is really outstanding. In the design we have ensured that the foot space has many cushioned areas, which makes the vehicle very safe”, Kai Jenoch, PSW department development Restraint systems/Airbags.
    Der Audi e-tron fährt gegen ein Hindernis beim Euro NCAP Test
    The Audi e-tron during its "final exam", the Euro NCAP. He got the full five stars!
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