Audi A8 2019 Service Training page 86

Function
Driver Assistance Systems Front Camera R242 continuously
monitors the traffic in front of the vehicle. The resulting
signals are sent to Driver Assistance Systems Control
Module J1121 as data. J1121 sends the data to the Airbag
Control Module J234. J234 evaluates the data and can
instruct other systems to initiate actions appropriate to the
situation.
Response to vehicles
The following preconditions must be met in order to activate the system:
› Audi pre sense front is able to respond to vehicles which are traveling in the same direction and which have stopped or are
stationary.
› Audi pre sense front does not respond to crossing or oncoming traffic.
› Audi pre sense front is active at a speed of approximately 6.2 mph (10 km/h) or higher.
› Audi pre sense front can warn against vehicles up to a speed of 155.3 mph (250 km/h).
› Audi pre sense front can initiate braking up to a speed of 155.3 mph (250 km/h).
Advance warning phase
If the vehicle approaches another vehicle which is traveling
in the same direction at speeds of between approximately
18.6 mph and 155.3 mph (30 - 250 km/h). resulting in a
critical driving situation, the instrument cluster gives the
driver audible and visual early warnings when set limits are
exceeded. 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 activity level.
Depending on steering, pedal and turn signal inputs, the
system classifies the driver as active or inactive and, conse-
quently, as attentive or inattentive. If the driver is deemed
to be "attentive", warnings are issued later than for a driver
deemed to be "inattentive". At the same time, ABS/ESC
Control Module J104 initiates prefilling of the brake
system, and hydraulic brake assist is reconfigured. Hydrau-
lic brake assist is more sensitive to the drivers pedal input.
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The system can, under certain conditions, detect the fol-
lowing scenarios:
› Vehicles in front of your vehicle (passenger cars, trucks,
motorcycles).
› Cyclists in the same lane as the vehicle or moving into
the same lane as the vehicle.
› Pedestrians in the same lane as the vehicle or moving
into same lane as the vehicle.
Acute warning phase
If driver does not respond to the warnings, however, J104
generates an acute warning by initiating a brake warning.
At the same time, a visual warning is issued in the instru-
ment cluster display. The brake warning is a very brief but
easily noticeable braking impulse which does not slow the
vehicle down directly. It alerts the driver to the traffic
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, the brake
warning is produced within a certain time window ahead of
the last opportunity to brake or take evasive action in order
to avoid a collision.