A-Pillar Satellites (SASL/SASR)

A-Pillar Satellite, Left and Right (SASL/SASR)




The satellites of the A-pillar left/right are virtually identical.

The satellites are installed to the left and right under the A-pillar trim panel in the footwell.

The A-pillar satellites have integrated transverse (side impact) and longitudinal (front or rear impact) sensors.

The SASL is responsible for deploying the Advanced Head Protection airbags (AHPS I/II) and the drivers side knee airbag.

The SASR is responsible for deploying the passenger airbag, the AHPS I/II and the passenger knee airbag.

The A-pillar satellites are connected to the SIM via the byteflight. The power supply of the satellites is also from the SIM and it is buffered by the memory backup capacitor.

In sleep mode of the byteflight, the power supply of the SASL/SASR is deactivated by the SIM. The watchdog function is run by the SIM.







A-Pillar Satellite Sensors

One acceleration sensor for the longitudinal acceleration and one for the transversal acceleration are integrated in the A-pillar satellites.

The sensors provide a variable voltage. This voltage is a measurement of the vehicle acceleration. This voltage signal is filtered, amplified, converted and transmitted as a data telegram.

The strategic arrangement of acceleration sensors in the vehicle and the sensor data recognized in satellites, enable recognition of the direction and crash severity.

For the ISIS system, a detected crash severity and direction of the impact are distinguished according to frontal, side, or rear-end collision.

With the involvement of the seat occupation detection, the seatbelt buckle input and using a stored trigger algorithm, accident-relevant triggering of the pyrotechnic actuators (e.g. seatbelt tensioner, airbags) is intended to achieve the greatest possible degree of occupant protection.

Self-Diagnosis of the Trigger Circuits During the Pre-Drive Check

During the pre-drive check, the entire trigger circuits are checked. If no faults occur during the check, the ignition capacitors are charged and the satellites are ready for triggering.
Self-diagnosis includes:

- Check of the coding of the trigger circuit for plausibility.
- Check of the trigger circuit for short circuit to ground or B+.
- Check of the trigger circuit for open-circuit.
- Check of the ignition capacity and ignition voltage.
- Check of the trigger circuit resistance.
- Test of the low-side switch.
- Test of the high-side switch and the alarm path.

The check of the high-side and low-side switches takes place with the ignition capacitor discharged. If any of the faults listed below are detected in a trigger circuit, the ignition capacitor stays discharged.

This prevents accidental deployment of the trigger circuit if another fault occurs during operation.

For all other faults, there is no danger of accidental deployment. The fault is indicated by the AWL and stored in the fault code memory.

Self-Diagnosis in Normal Operation

In normal operation, there is a constant check of the trigger circuits. A fault message is issued, but only when the fault is confirmed over a specified period of time.

If a short circuit to ground or B+ is detected, the corresponding ignition capacitor is discharged,

In normal operation, the self-diagnosis is restricted to checks of the trigger circuit for short circuits and open circuits.