Recognizing head-on collision, function

Function

The heart of the supplementary restraint system (SRS) is the airbag control module (A40). Among other items it contains the head-on collision detector. Collisions with a deviation of  30° to the longitudinal axis of the vehicle are recognized. The driver's airbag control module monitors the vehicle motion. In the event of an accident the vehicle decelerates very quickly (negative acceleration). In this case the difference between an accident and intended deceleration with the brakes is decisive. The actuation threshold is set to a relative change in the velocity of  to 20 km/h upon collision with a flat, rigid barrier while the non-actuation

threshold is set to a relative change in speed of  to 15 km/h. Actuation can be accomplished between these two values. In order to correctly evaluate deceleration when the brakes are applied, two acceleration sensors are installed in the airbag control module whose signals are subjected to different signal processing procedures.

When the deceleration is recognized as an accident the airbag and emergency tensioning retractors are activated.