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Siemens Occupant Sensing Innovation Aids in Quest for 'Smart' Airbags

22 December 1998

Siemens Occupant Sensing Innovation Aids in Quest for 'Smart' Airbags; To Be Used in BSRS 'Smart' Airbag System

    AUBURN HILLS, Mich., Dec. 22 -- Siemens Automotive Safety
Systems engineers have developed and patented a new seatframe integrated
Weight Classification System (WCS) for detecting an occupant's weight and
proximity to the airbag when seated in a vehicle.
    The Siemens WCS technology will be a key component in a Tailorable
Occupant Protection System (TOPS(TM)), a system being developed by BSRS
Restraint Systems, the global joint venture of Breed and Siemens Automotive.
TOPS will tailor airbag and seatbelt functions based on individual occupant
data and crash severity.
    "The WCS's ability to determine occupant weight and proximity prior to a
collision is a significant advancement in the ongoing development of 'smart
airbag' systems," said Wolfgang Schaefer, Chief Executive Officer of BSRS.
"At BSRS, we are able to integrate the advanced technology of both Breed and
Siemens Automotive and provide a single system solution for our customers."
    Occupant weight and proximity data will be used in a smart airbag system
to suppress or adjust the airbag deployment to meet the needs of individual
occupants.
    "The Siemens seatframe integrated WCS solution is the sensor breakthrough
we have been striving for in our research and development efforts," said
Kenneth Francis, director of Safety and Chassis Electronic Systems, Siemens
Automotive.
    "In each test case, the Siemens WCS approach proved to be the most robust
and reliable sensor for this safety restraint system's application," Francis
said.

    Sensing the Occupant's Weight:
    The Siemens WCS employs four strain gauge-based force sensors located
within or beneath the seat, and positioned at the seat's four corners.
    Strain gauge technology widely has been used for years in applications
ranging from industrial to highway truck scales.  "We wanted to begin with a
proven, reliable technology, such as the strain gage, for measuring force and
uniquely package it with our electronics," explained Francis.
    The four strain gauge force sensors are connected to an Electronic Control
Unit (ECU) that processes the sensor signals.  From the weight measured, and
its distribution in the seat, the "real" weight of the occupant can be
determined.  The WCS differs from other sensors in that it can account for
that portion of the occupant's weight which is transferred to the vehicle
floor through the legs.
    From the real weight, the WCS system classifies the occupant into one of
four weight classes: "empty"; "child class," based on the weight of an average
six-year old child; "small adult" class, based on the fifth percentile female;
and the "large adult" class, based on the 50th percentile male.

    Sensing the Occupant's Position:
    The Siemens WCS works in conjunction with a seat position sensor that
detects where the seat is positioned in its track relative to the airbag.
From the seat position input and the occupant's weight distribution (center of
gravity) in the seat, the occupant's position to the airbag accurately can be
determined and classified into one of three position zones (red, yellow,
green).
    In general, a "red" zone indication will suppress the deployment of the
airbag.  An occupant in the "yellow" zone will likely require a depowered or
staged air bag deployment.  A "green" zone indication will allow for full
deployment of the air bag.  "When an adaptive restraint system factors the
occupant's weight classification into his/her position zone classification it
is better able to define the optimal restraint scenario," said Francis.
    The Safety Systems Group of Siemens Automotive is responsible for the
research, development and manufacture of single-point air bag ECUs, advanced
software, accelerometer-based and pressure-based crash sensors and new
applications of electronic controls and sensors for adaptive occupant
restraint systems (smart airbags).  Siemens Automotive is presently the
world's leading supplier of single-point airbag ECUs, the kind most widely
used in today's vehicles.  In 1998, Siemens Automotive teamed with Breed
Technologies to form BSRS Restraint Systems, a company with subsidiaries in
North America and Europe.  BSRS was formed to design, develop, and market
complete occupant restraint systems using the combined expertise and
complementary product capabilities of Siemens and Breed.