Advanced Crash and Safety Management
The E93 Convertible is equipped with the second generation
advanced crash and safety management system (ACSM2). In
terms of its scope of functions, the ACSM2 is identical to the
ACSM in the E64 Convertible.
The ACSM2 differs from the ACSM in that the supplier is different
and it features additional interfaces for future function expansions.
The first generation ACSM is supplied by Autoliv while the second
generation ACSM is supplied by BOSCH.
The task of Advanced Crash and Safety Management is to evaluate
permanently all the sensor signals in order to identify a crash situa-
tion. As a result of the sensor signals and their evaluation, the
crash safety module identifies the direction of the crash and the
severity of the impact.
The crash safety module incorporates a longitudinal acceleration
sensor and a transverse acceleration sensor. The sensors serve to
detect and verify front-end, side-on and rear-end crashes.
In the E93 Convertible the crash safety module has additional sen-
sors for rollover detection.
Satellites are also integrated in the B-pillars. The satellites each
consist of a longitudinal acceleration sensor and a transverse
acceleration sensor.
Together with the transverse acceleration sensor in the crash safety
module, the transverse acceleration sensors serve to detect
side-on crashes. Door pressure sensors are additionally installed in
the front doors for the purpose of detecting side crashes.
The acceleration sensors measure the positive acceleration (+) and
the negative acceleration (- / deceleration) in the X and Y directions.
The resultant from the X and Y signals is the definitive factor in
determining the direction of the impact.
US vehicles have additional up-front sensors for front-end crash
detection.
Also included is information on the occupants and whether they
have their seat belts fastened or not. From this information, meas-
ures are taken to selectively trigger the necessary restraint systems.
In order to ensure ACSM operational availability at all times, the
system monitors itself and indicates that it is ready for operation
when the airbag warning lamp (AWL) goes out.
If a fault occurs during operation, this is stored in a fault memory,
which can then be read out for diagnostic purposes.
In the event of a crash, this is communicated to the other users in
the bus-system network by way of a bus telegram. The relevant
control units respond to this telegram by executing their own
activities.
These activities include:
• Opening the central-locking system
• Activating the hazard warning flashers
• Switching on the interior lights
• Deactivating the fuel pump
• Switching off the alternator
•
Automatic emergency call.
E93 Complete Vehicle Workbook
41
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