More protection during side impact

External side airbags could be the first of a new generation of pre-crash technologies.

Even intelligent vehicles, equipped to help predict and prevent collisions, can sometimes encounter situations beyond their control. With the public expecting higher levels of safety from automated vehicles, the challenge will be to find new ways to use the car’s environmental sensing and intelligence to help improve outcomes.

As a result, the next wave of safety technologies may be developed a little differently. Pre-crash external side airbags could be among the first of these next-generation safety systems. Instead of integrating dedicated sensing and data processing functions, the airbags interface with advanced environmental sensing and data processing that is hardwired into the vehicle platform itself.

250 liters volume

ZF's pre-crash external side airbag sits in the vehicle’s side sills. With a volume of 250 liters or more, the airbag is two to three times the size of even the largest side curtain airbags and also requires multiple inflators to fill it. ZF’s concept designs are based on conventional airbag fabric and existing inflator technology.

“The lack of deformation space means cars can be more vulnerable to side impact,” says Dr Swen Schaub, senior manager of Engineering Strategy at ZF. “The airbag is designed to deploy in the last moment before a collision. As it deploys, it opens upwards, staying close to the structure to help cover the doors and pillars at the side of the car.”

The airbag can be more than 300mm thick in places. One design study positions the stiffest, thickest parts of the airbag in front of the vehicle’s stiff side impact structures – mainly the pillars. This creates a larger deformable area intended to engage the opposing vehicle earlier, helping to channel more of the crash pulse away from the occupants. The airbag can cover the rest of the area with softer portions of the bag.

“Tests indicate that, in side impacts, the airbag could help reduce vehicle intrusions and intrusion velocities by more than 30 percent,” says Schaub. “Ultimately, this could also help to reduce certain occupant injury levels by 20-30 percent. However, to deploy the airbag before a collision, the system must be able to determine with great confidence that an impact is actually going to occur.”

Rely on an array of sensors

For vehicles to deploy pre-crash external side airbags, they will rely on an array of sensors to detect an imminent collision. Radar, lidar and camera sensors may be able to provide the necessary data.

Vehicles will also need to detect a potential collision before the impact. Around 100 milliseconds is the approximate time ZF anticipates will be needed to deploy the airbag so that it is in position and ready before the other vehicle makes full contact.

“The system requires the ability to predict both impact direction and location,” says Schaub. “And it needs to do this in a timely manner, as even a small vehicle movement in the final 500 milliseconds before the impact could make a significant difference.”

The introduction of more highly automated driving functions mean future sensor strategies could encompass the vehicle’s entire surroundings. When these systems have the confidence to predict side impacts in a wide range of conditions, a pre-crash external side airbag can use this information and help raise side impact protection to the next level.

The airbag will be the first of a new generation of smart actuators that can interface with the vehicle’s environmental sensors. It will also be a powerful way to demonstrate how automated driving can lead to higher levels of safety.

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