32
Braking intervention phase
If the driver does not respond to the warning jerk, the ABS control
unit J104 will automatically initiate emergency braking. Maximum
braking pressure is applied. If the vehicle automatically comes to a
halt without driver input, further audible signals will sound.
These signals alert the driver to the fact that he must actively take
control of the vehicle (e.g. by applying braking). If the driver fails
to take control of the vehicle, e.g. in a model with automatic
transmission, the system will release the brake and the vehicle will
start to move.
These warnings are given within a certain time frame ahead of the
last braking opportunity for braking or collision avoidance before
the actual collision occurs. The timing of warnings depends on the
driver's degree of activity. Depending on steering, pedal and turn
signal inputs, the system classifies the driver as active or inactive
and, consequently, as attentive or inattentive. If the driver is
classed as attentive, the warning will be issued later than a
warning for a driver classed as inattentive. At the same time, the
ABS control unit J104 prefills the brake system and modifies the
deployment algorithms for hydraulic brake assist. This means that
hydraulic brake assist starts to build up brake pressure even at low
brake pedal actuation speeds.
If driver does not respond to the warnings, however, the ABS
control unit J104 generates an acute warning by jerking the brakes.
The warning jerk is a very brief but easily noticeable braking
impulse which does not serve to slow the vehicle down. It alerts
the driver to the trac situation and indicates to the driver that he
must react immediately in order to prevent an impending collision.
Depending on how attentive the driver is considered to be, the
warning jerk will be produced within a certain time window ahead
of the last opportunity to brake or take evasive action to avoid a
collision.
Warnings against a possible collision
Flowchart
Precharging of the braking system, hydraulic
brake assist reacts more sensitively
Audible and visual driver warnings
(early warning)
Warning jerk
Emergency or full braking Collision
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