The 1980 Mercedes S-Class (W 126) was the first series production car equipped with an airbag. In the meantime airbags have firmly established themselves across all vehicle segments. Airbags have saved many human lives and reduced the severity of injuries. Mercedes safety specialists are now working on a further improvement to their protective effect by developing airbags with a variable volume.
There are already adaptive airbags at Mercedes-Benz today, for in many model series the airbags are activated in two stages depending on the assessed severity of the impact. Future generations of this restraint system will not only take accident severity into account, but adapt themselves to the individual vehicle occupants: "Size Adaptive Airbags" automatically adjust their volume to the seating position and stature of the front passenger as recognised by the sensors. For whether a small front passenger is hunched up close to the dashboard or a tall front passenger has his seat moved well back is certainly a factor in the protective effect of the airbag. The weight of the front passenger, and therefore the forces acting on the airbag during an accident, are also important.
"Size Adaptive Airbags" enable occupant contact with the airbag to be optimally timed, whatever his weight and seating position. The restraint system can therefore dampen the impact to optimum effect. This Mercedes development varies the volume on the front passenger side between 90 and 150 litres. For purposes of comparison, conventional front passenger airbags have a volume of around 120 litres.
The system uses three retaining bands with which the airbag contours are adjusted to limit the volume. The retaining bands are fitted on electrically driven spools. When the airbag is activated, only as much band length is released as the control unit has calculated on the basis of sensor data for the seating position and weight of the occupant.