The Traffic Accident Reconstruction Origin -ARnews-

Re: Airbag Sensors

Chris Borelli (sdl@ids.net)
Thu, 21 Aug 1997 08:45:40 -0400 (EDT)

Ed, I am interested in airbag sytems also and just returned from the SAE
airbag design and performence TOPTEC. I wanted to find some specific
information about the airbag systems installed on different vehicles.
What I did learn is that all of the manufacturers are going to a "single point"
system which appears to be a single black box with one accelerometer. This
will eliminate the engine compartment sensors currently in use. However, the
participants discussed the problems of a single point sensor during a "soft
hit", which appears to be a pole or tree impact in the front/center. The
passenger compartment located accelerometer in the single point system must
not sense the required acceleration threshold to deploy the airbag until
the tree or pole intrudes into the engine or other solid structure. This
will reduce the amount of time available to deploy the airbag.

The delta V at which the aibags deployed varied from car to car, but overall
were lower than I thought. There were several vehicles with airbags which
deployed at a delta V of 7 mph.

Also, several cars did some things that I was not aware of. It was mentioned
that a 1994 Camaro records seat belt use and some BMW's have a seat belt use
sensor.

Knowing how the current mechanical sensors operate, I do not know what can
be gained by taking them apart. There does not appear to be any permanent
markings, component displacement, or other physical evidence which would
help in an analysis. If you have something in mind I would be interested in
knowing if there is something I could look for.

With all of the data collecting sensors available in the newer vehicles
(vehicle speed sensors, accelerometers, % wheel slip, date and time),
I wonder if the manufacturers could design the ECM to store the last week,
day, or even few minutes of data. This data could be contiuously overwritten.
Reconstructionists could use this data for our reconstructions (even low
speed collision G force readings!)
Chris Borelli
sdl@ids.net

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