Inside Out: ZF Tests External Side Airbag System

There was a time when the only thing cushioning your head from a direct impact with the steering wheel in the event of a crash was the skin it was wrapped in. Since then, airbags have proliferated, breeding inside millions of cars to a point where they now explode down from the headliner.

Considering automotive safety pretty much only moves in one direction, this was bound to happen. There may come a day when airbags are no longer limited to the interior of cars.

ZF Group, best known for its transmissions, is currently testing a “pre-crash external side airbag system” that it considers to be the world’s first. Having debuted a prototype in 2016, ZF is now conducting live demonstrations where an inflatable barrier bursts forth from the rocker panel to provide additional cushioning for side impacts.

Three years ago, ZF said the system could reduce impact forces by 30 percent. Now, it claims a 40 percent reduction in occupant injury severity, as well. Apparently, designing and refining on-demand crumple zones was the easy bit. ZF says the biggest challenge to the project involved developing a system that could work with existing sensors to accurate predict when an unavoidable collision will occur.

Since most consumers wouldn’t appreciate external airbag deployments every time they pull out into traffic, the system has to have exceptionally good reflexes. ZF says the entire rig has approximately 150 milliseconds — roughly the same time it takes a person to blink — to make the decision to deploy the airbag and then do so.

From ZF:

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 liters (five to eight 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.

The company recently revealed test footage of the system where it absolutely demolished the car it was stacked against. Unfortunately, that vehicle appears to have been made out of air and rubber tubing. But the impact forces endured are undeniable. The test-bed Opel clearly begins to rotate from the hit, with nary a hint of deformation.

“We highlighted that this safety system has the potential to significantly reduce occupant injury severity in cases of side impact collisions,” said Uwe Class, head of the ZF Advanced Engineering team’s Safe Mobility Systems department. “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.”

As for claims as to whether or not this is a world first, we have to bring up Volvo’s pedestrian airbag system. It’s fallen out of favor with the brand of late, but it technically trumps ZF’s rig for being the world’s first external inflator — forcing the supplier to include the “side” caveat and making them technically correct. Regardless, ZF’s system could become the first airbag to be utilized between cars if it’s ever adopted for use in production vehicles.

[Image: ZF Friedrichshafen]