Rollover Protection System
The rollover protection system is of vital importance to the passive
safety of the E93 Convertible. The rollover protection system helps
to maintain a sufficient survival space for the occupants in the
event of the car overturning or rolling over.
There are different factors which can cause a car to overturn or
rollover. The most common causes are:
• The car hits a ramp (e.g. a crash barrier) on one side. The car
rotates about its longitudinal axis as a result of the high angular
velocity.
• The car skids sideways off the road surface and buries itself
with its wheels in the soft soil. The kinetic energy could be
sufficient to upend and overturn the car.
• The car skids sideways off the road into the curb and is
upended.
The crucial factors which determine whether the car overturns are
not just the angle but also the angular velocity at which the car is
set into the roll. All these vehicle movements can also occur after a
front-end, side-on or rear-end crash.
The rollover protection system consists of two extendable rollbars
which are housed in the partition module behind the two rear seats.
Rollover Detection
The E93 Convertible has a special sensor system in the crash
and safety module ACSM2 for the purpose of detecting rollover
situations. In addition of the two sensors (4) for longitudinal (X-axis)
and transverse acceleration (Y-axis), there is a rotation rate sensor
(2) and a Low-g sensor (3) for the Z-axis and for the Y-axis.
The longitudinal and transverse acceleration sensors (4) register
the positive and negative vehicle acceleration in a range from
0-100 g. They serve to detect heavy accelerations and decelera-
tions in a crash.
E93 Complete Vehicle Workbook
45
Index Explanation Index Explanation
1
Crash safety module (ACSM)
6
K-bus interface
2
Rotation rate sensor
7
Actuator, right
3
LOW-g sensors (Z/Y axis)
8
ROC, control unit
4
Longitudinal and transverse
acceleration sensors
9
Actuator, left
5
Microprocessor
10
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