Although the first regulation regarding mandatory fitment of airbags was introduced in the USA in the mid-1970s (but never actually adopted), it was only in 1980 that the world’s first airbag system was installed in a production model – the Mercedes-Benz S-Class. Since that time, airbags have undergone technological advancements to increase levels of protection for the front passengers.
Initially, the focus was in frontal collisions and much development was on the two airbags at the front. Then airbags were added to the sides, either at the seats, in the doors or deploying like curtains over the window openings.
The importance of providing protection at the sides cannot be understated. Studies in Germany show that side impact collisions are among the most dangerous type of road traffic accidents, accounting for nearly 700 deaths per year and nearly a third of all occupant fatalities.
Side airbag installed externally
To enhance the existing side airbag systems installed in many cars, ZF has developed a new pre-crash safety system (still in prototype stage) which uses an external side airbag deployed milliseconds before a collision. It provides an additional lateral crumple zone, which can help save lives and reduce occupant injury severity by up to 40%.
To make this possible, ZF has networked the airbags to the vehicle’s sensor systems and developed algorithms that are capable of determining if a crash is imminent and decide whether or not to deploy the airbag.
ZF is currently the only company to provide the full spectrum of integrated vehicle safety technology – from sensor systems, algorithms, and control units to active and passive actuators. “Our deep understanding of the entire ’see. think. act.’ process enables us to conceptualize and realize integrated vehicle safety solutions such as the new pre-crash safety system,” explained Uwe Class, Head of the Safe Mobility Systems department within ZF’s Advanced Engineering team.
Recognition to deployment – in the blink of an eye
The biggest challenge in the development of this system was reliably recognizing an unavoidable collision and deploying the external side airbag before the collision takes place. The system has approximately 150 milliseconds to make the decision to deploy the airbag and fill it – roughly the amount of time it takes a person to blink.
The vehicle’s sensors first have to identify a potential impact quickly and accurately. This is possible with connected cameras, radar and lidar. Algorithms within the system software decide whether or not a collision is unavoidable and the deployment of the airbag is both possible and beneficial. If these decisions are all affirmative, the system ignites the inflators to fill the airbag.
The airbag, which has a capacity of between 280 and 400 litres (5 to 8 times the volume of a driver airbag) depending on the vehicle, then expands upwards from the side sill to form an additional crumple zone in the door area between the A and C pillars.
In a side impact collision, the occupants on the side of the impact are at particular risk of serious injuries in the chest area if the passenger cabin is severely deformed. The ZF pre-crash safety system can reduce the penetration of the intruding vehicle by up to 30%, helping to significantly reduce the occupants’ risk of injury.
