Using internal and external acceleration, yaw-rate, and pressure sensors, a state-of-the-art airbag control unit identifies the type of accident as well as its severity, and deploys the airbag and belt tensioner as needed. In just ten milliseconds – ten times faster than a person can blink – the trigger algorithm interprets the sensor data to determine whether the driver has simply hit the brakes, bumped into a parked car, jumped the curb, or if the vehicle has had a severe collision or is at risk of rolling over. If the situation is dangerous, the system ignites the pyrotechnic gas generator. Within 30 milliseconds, the airbag is fully inflated and can protect the driver and passengers.

Today’s vehicles come with as many as nine airbags installed, which can be deployed individually depending on the accident scenario. Following a collision, the system also sends a signal to cut off the fuel supply, or, in electric vehicles, to disconnect the high-voltage battery. In addition, the system forwards information about the accident to other vehicle systems – for example eCall, which automatically calls emergency services after an airbag has been deployed.

Since 1977, Bosch engineers have worked with automakers on the first electronic airbag control unit, putting it through more than 6,000 crash tests in 60 vehicle models. Today, more than 1.8 million crash simulations are necessary to prepare an airbag control unit for large-scale production in a vehicle model. The first airbag system, which went into production in December 1980 and then had its market launch in the Mercedes-Benz S-Class, consisted of three components – a voltage converter, an energy reserve, and a control unit – with a total of 170 parts. These controlled only an airbag and belt tensioner for the driver and optionally for the front passenger. Today’s twelfth-generation airbag control units have just half as many parts and can manage up to 48 restraint devices, including various front and side airbags, knee airbags, and belt tensioners.