SMART Series 451 - Weight sensing system (WSS)

Supplemental restraint system
Body
109
Introduction of the smart fortwo, Model Series 451
Restraint system
The restraint system consists of the following compo-
nents:
• 2-stage full size airbag for driver and passenger
• Head/thoraxbag for driver and passenger in
outsides of backrests
• Seat belt emergency tensioning retractors and
belt force limiters for driver and passenger
• Passenger seat with Weight Sensing System (WSS)
and belt tension sensor
In the event of a frontal impact and depending on the
deceleration values, the driver airbag, the energy-
absorbing steering column and the passenger airbag
improve occupant protection by absorbing energy in
a targeted manner and thus minimizing the risk of
injury.
The pyrotechnical emergency tensioning retractors
ensure that the occupants are properly restrained in
their seats in a frontal impact and that they follow a
defined forward displacement with the energy being
absorbed by the belt force limiter.
The passenger airbag, emergency tensioning
retractor and head/thoraxbag are switched off in
accordance with the predefined weight class that the
seat is assigned to. The airbag OFF indicator lamp is
located in at the front above the interior lamp and
lights up as soon as the shutoff function is activated.
In order to activate the systems in good time in the
event of a crash and thus keep the physical conse-
quences for the occupants low, sensors are installed
to detect the occurrence of a collision at an early
stage.
The following sensors are installed:
• Side trigger sensors in the left and right inner sills
near the B-pillars for detecting a side impact
• Two frontal acceleration sensor on left and right of
front crossmember
• Trigger sensor in the restraint systems control
unit for detecting a frontal crash, a rear-end
impact or a side-on collision
The central controller unit of the supplemental
restraint system is the restraint systems control unit,
which is located in the center of the vehicle on the
crossmember under the instrument panel.
If the restraint systems control unit detects a fault in
the system, this is indicated by the lighting of a
warning lamp in the instrument cluster.
As well as triggering the restraint equipment, the
following interventions are initiated by the restraint
systems control unit in the event of a crash:
• Shutoff of engine and fuel pump
• Unlocking of door locks
• Activation of hazard warning lamp function
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