Supplemental restraint system
110
Body
Introduction of the smart fortwo, Model Series 451
Weight sensing system (WSS)
To determine the situation in the interior compart-
ment, the system detects whether the passenger
seat is occupied. The seat occupied recognition
pressure sensor determines the weight on the
passenger seat by means of a pressure measure-
ment from a seat mat filled with silicone oil.
The force applied to the seat belt is measured via
the belt tension sensor.
These two measured values are used by the Weight
Sensing System (WSS) control unit to classify the
weight on the seat. The values are transferred to
the instrument cluster via CAN-B, which acts as a
gateway to transfer the data to the restraint
systems control unit via CAN.
The following conditions are defined depending on
the occupant classification:
• Passenger seat not occupied:
Passenger airbag unit, passenger
head/thoraxbag and passenger emergency
tensioning retractor unit are disabled; the
airbag OFF indicator lamp is switched ON.
• Passenger seat occupied - light weight
(e.g. hand luggage):
Passenger airbag unit, passenger
head/thoraxbag and passenger emergency
tensioning retractor unit are disabled; the
airbag OFF indicator lamp is switched ON.
• Passenger seat occupied - person detected:
The required restraint equipment is enabled;
the airbag OFF indicator lamp is switched OFF.
P91.60-3635-00
1 Seat cushion frame
2 Seat mat filled with silicone oil
B48/4 Seat occupied recognition pressure sensor
N110 Weight Sensing System (WSS) control unit
SN_Typ 451_us.book Seite 110 Freitag, 30. November 2007 1:56 13
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