Safety
systems forautomobiles are expected to become more sophisticated over
the next several years. A principal driver of this trend is expecting
regulation, which will impact both the attach rate and the sophistication
of airbags and stability control systems.
The electronic content of these systems
will increase, and with it, the demand on the semiconductor memory used
in these systems. This article is a brief look at what to consider when
choosing a memory solution for the newer classes of airbag. Two major
innovations are occurring in the airbag system.
First, in newer airbag systems,‘intelligence’
is being added:
Instead of deploying as in the past with maximum force as if all
accidents and passengers were the same, deployment force is being determined
by specific accident and occupant parameters. These may include the
severity of the crash, the weight of the occupant and the seat position
relative to the airbag. Those who have been hit by a standard airbag
will consider variable force a positive. The smart airbag also knows
that if the passenger seat is empty, the passenger airbag does not need
to deploy. Given the increased number of airbags per vehicle and the
cost of replacing them in even a minor accident, this innovation has
the potential to provide the consumer with substantial cost savings
in repairs and insurance.
A second innovation is that vehicles
are increasingly being fitted with event data recorders (EDR’s)
that collect crash information similar to an airplane‘black box’.
The EDR function is normally included in the airbag electronic control
unit (ECU). This is a natural grouping because the EDR does not have
the survivability requirements of an airplane ‘black box’
and the airbag controller is the primary recipient of a variety of important
sensor inputs. Vehicle makers are also quick to point out that there
is no room for a stand-alone EDR.
The memory requirements of these two
airbag memory applications are demanding but quite different. Both need
a nonvolatile memory because in all likelihood the power will be lost
at some point during a serious accident. Reconstructing the event means
that the data must be stored in a robust, nonvolatile memory that can
be written in the system.
In the case of a ‘smart airbag’
the ECU designer wants to deploy the airbag with the appropriate force
for a given accident. This requires not only information about the G
forces but also about the occupant. A unique requirement for the memory
in a smart airbag is to record the occupant history leading up to the
event. This includes seat position and occupant weight. In order to
keep a reliable record of the occupant profile prior to any event,
....CONTD
