15
DeÞnitions:
The
un-laden position
...
... is the compression exerted onto the wheels
when the vehicle is ready for the road (fuel
tank completely Þlled, spare wheel and
vehicle tools present).
The
design position
...
... is deÞned as the un-laden position plus the
additional load of three persons, each
weighing 68 kg.
The static compression
...
... is the starting point (zero) for the dynamic
spring movements, compression travel (plus)
and rebound travel (minus).
... is dependant upon the spring rate and the
load (sprung masses).
... results from the difference between the
static compression when un-laden
s
stat(un-laden)
and the static compression when
fully laden s
stat(fully laden)
.
s
stat
= s
stat(fully laden)
- s
stat(un-laden)
In the case of a ßat characteristic curve (soft
springs), the difference and thereby the static
compression between full and un-laden is
very great.
242_076
In the case of a steep characteristic spring
curve, this state of affairs is reversed and is
coupled with an excessive increase of the
natural frequency of the bodywork.
Fully laden
Un-laden position
Hard springs
Soft springs
s
stat
soft springs
s
stat
hard springs
58
Self-levelling suspension, A6
The control concept
Stationary mode
The stationary mode is recognised at a speed
of <5 km/h.
In stationary mode, vehicle level deviations
due to e.g. passengers entering or leaving the
vehicle, or due to loading or unloading the
luggage compartment, are readjusted within
a short response time, in order to restore the
reference level as far as possible even before
the journey has begun.
The response time is 1 or 5 seconds,
depending on the level deviation. If the
deviation is great (extremely low position) the
response time is 1 second, at lesser level
deviations (normal deviation) it is 5 seconds. Driving mode
The driving mode is recognised at a speed of
>10 km/h.
In driving mode, level changes in the air
springs caused by fuel consumption or
temperature-related volumetric changes
(changing ambient temperatures) are
adjusted.
So that acceleration or braking does not
affect the control system, long response
times are set in the driving mode.
The response times are between 50 seconds
and 15 minutes depending on the control
thresholds.
Driving mode
Stationary mode
Run-on mode/run-up modeSleep mode
Control process
