Page 377 - Understanding Automotive Electronics

2735 | CH 10 Page 364 Tuesday, March 10, 1998 1:27 PM

10 DIAGNOSTICS

Figure 10.19
Accelerometer-Based Airbag System

threshold, the driver circuit sends a current of sufficient strength to activate the
squib and inflate the airbag.
Typically, the threshold is set so that airbag deployment occurs for a crash
into a barrier at or above a specific speed. Depending on the system design, this
speed can be anywhere between 8 and 12 mph. This speed range is chosen by
the manufacturer to optimize the protection offered the car occupants while
minimizing false deployment (that is, deployment when there is no crash).
There will continue to be new developments in airbag technology in
order to improve performance. Complicating this task is the fact that the
signature of a crash differs depending on the crash configuration. For example,
there is one class of signature for a crash into a rigid barrier (i.e. a nonmoving
and incompressible object) and another for a crash between a pair of cars
(particularly when vehicle curb weights are different). In spite of technical
difficulties in implementation, the airbag is finding broad application for
occupant protection and seems destined to continue to do so.

364 UNDERSTANDING AUTOMOTIVE ELECTRONICS