Satellite Side Impact Sensors; Characteristics; Operation; Seat Belt Pretensioners - Fiat TIPO Handbuch

SATELLITE SIDE IMPACT SENSORS

Characteristics

The side protection system consists of the airbags plus control electronics that ensure that the system
operates correctly. Two satellite sensors containing an accelerometer are installed inside the side
pillars to measure accelerations resulting from side impact.

Operation

If the acceleration level detected by the relevant sensor causes a given threshold to be exceeded, the
information is compared with a measurement obtained by a safety sensor in the airbag system
electronic control unit. If the values measured are consistent, the control unit orders the activation of
the side bags (if installed), of one of the two front pretensioners and of the head bags, only on the side
affected by the impact.

SEAT BELT PRETENSIONERS

Features

The pretensioners are pyrotechnic devices that are activated electrically by means of a signal from the
electronic control unit. They are built into the reel of the front seat belts. The same logic that controls
the airbags controls the activation of the seat belt pretensioners.
The pretensioners perform the function of recovering any slack in the seat belt and retaining the
occupant against the backrest from the very start of the impact, thus reducing the overall movement of
the occupant inside the passenger compartment.
The seat belts are also fitted with load limiters which decrease the force transmitted by the belts to the
chest: the force level at which the limiters act is sufficient to considerably reduce the risk of fracturing
shoulder blades and ribs, even in people with more brittle bones (e.g. the elderly).
The car is equipped with double pyrotechnic pretensioners for each front seat occupant:
One conventional pretensioner is fitted in the seat belt reel and the other in the buckle fixed to the
floor.
In the event of frontal impact, the pretensioners are activated simultaneously at both ends of the belt,
allowing a homogeneous distribution of the slack recovery, and consequently less injury to the
occupant. In the event of side impact, the control unit will order the activation of a single pretensioner
and of the side bags (if installed) and window bags on the side affected by the impact: the activation of
a single pretensioner will effectively restrain the lower chest and legs against the seat, letting the
upper part of the body travel towards the deployed bag to optimise protection.
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