Table of Contents
Advertisement
U
The Citroën Guide
call for hard mode, the suspension will revert within
50 ms and restart the one-minute timeout period;
U
below 30 km/h opening the doors or tailgate overrides
any other rules and puts the suspension into soft mode
to equalize the pressures in the spheres.
As already mentioned, the steering wheel sensor is used
to derive two inputs values: steering wheel speed and an-
gle. These values are treated separately with the purpose of
calculating the lateral acceleration of the vehicle (vehicle
speed, steering angle) and the potential change in this ac-
celeration (vehicle speed, steering wheel speed). It is seem-
ingly done this way to save memory which would otherwise
be required for a full three-parameter lookup (based on ve-
hicle speed, steering wheel angle, steering wheel speed).
The steering wheel sensor rules actually give a measure of
potential body roll. Body roll is significantly reduced in hard
mode, consequently, the rules were set up to ensure that
the body roll is minimized when there is potential for it, still
the suspension stays soft to absorb bumps when there is no
body roll caused by the vehicle changing direction.
If the acceleration or deceleration (braking) of the ve-
hicle exceeds 0,3 g (approximately 3 m/s²) while the actual
speed is above 30 km/h, the suspension will be switched to
hard mode and a timeout of 1.2 seconds begin.
The table below shows the thresholds of steering
wheel angle and rotating speed. If any of these values
exceed the threshold for the actual vehicle speed, the sus-
pension will switch to hard mode; it will revert to soft when
the corresponding value drops below the threshold for at
least 1 second if the switching was triggered by the steering
wheel angle and 2 seconds if triggered by the rotational
speed:
Steering wheel
Vehicle speed
angle
(km/h)
(deg)
< 30
always soft
31–40
130
41–60
100
61–80
81–100
101–120
121–140
141 >
The body movement amplitude and speed is derived from
the output of the body movement sensor, although the
two values are used in a different way.
The body movement speed is used as the parameter for
the activation of two types of corrections:
U
Flat tire correction: if the body movement speed ex-
ceeds 300 mm/s, the suspension switches to hard
mode, and all thresholds are modified to 60 mm. The
timeout of the correction will be 0.4 s.
U
Excessive body movement correction: if the body
movement exceeds 60 mm more than three times
within three seconds, the suspension will switch to
hard mode, and all thresholds are modified to 60 mm.
The timeout of this correction will be 0.4 s.
The previous corrections stay enforced until one or more of
the following conditions are satisfied:
Steering wheel
Vehicle speed
(km/h)
< 30
31–60
61–100
52
101–120
40
121 >
18
15
8
Suspension: Hydractive I
U
body movement amplitude remains under the modi-
fied threshold until the correction timeout elapses;
U
suspension selector is set to the Sport setting;
U
the vehicle accelerates above 159 km/h;
U
the steering wheel angle exceeds the threshold value
dependent on vehicle speed as specified in the follow-
ing table.
Once any of these conditions are met, the suspension will re-
vert to normal operation, with thresholds restored accord-
ing to the table. Exceeding any of these thresholds will
force the suspension into hard more. The computer checks
every 0.8 seconds whether the conditions forcing the sus-
pension into hard mode are still present, and if so, the sys-
tem stays in hard mode.
Suspension down > 13 pulses, timeout 1 sec
Suspension up > 9 pulses, timeout 1 sec
Suspension change speed between 30 and 50 ms AND
Durchfederung > 3 pulses, timeout 1 sec
Vehicle
Dive
speed
(mm)
(km/h)
< 30
The values delivered by the throttle pedal sensor are
used with reference to the vehicle speed in order to antici-
pate the vehicle dynamics as a result of acceleration or de-
celeration. The rules for this sensor represent a reaction to
probable vehicle squat (on acceleration) or dive (on deceler-
ation). Both are significantly reduced when the suspension
is in hard mode.
The suspension ECU quantizes the pedal position into
five discrete steps: 0, 30, 40, 50 and 60 percent of the com-
plete pedal travel. The computer measures the time elapsed
speed
as the pedal travels from one step to the next in either direc-
(deg/s)
tion. If this time is inside the intervals shown in the table,
always soft
the suspension will switch to hard mode. It will revert to
196
soft if the pedal movement becomes slower for at least the
167
duration of the timeout specified:
139
128
Pedal press
speed (ms)
< 100
101–150
The brake pressure sensor detects the pressure in the
front brake hydraulic circuit. Since this is a fixed threshold
sensor, the suspension setting rule is simple: if the vehicle
speed exceeds 30 km/h and the pressure is above 35 bar in
the brake circuit, the suspension switches to hard mode.
The system stays so to prevent excessive dive when brakes
are applied while any of these two conditions are met (the
timeout value is one second).
Without ignition and electrical feed to the suspension
computer, the electro-valve would immediately return to
hard mode. Loading or unloading the car, people getting in
or out would induce pressure differences in the hydraulic
system. These differences would equalize abruptly when
the system is started again, causing the car to jump or sink
vehemently. In order to avoid this, the computer allows an
additional 30 seconds of timeout starting when any of the
doors is opened or closed (as communicated by the door
Steering
Vehicle
Squat
wh pos
speed
(mm)
(deg)
(km/h)
—
—
—
< 30
Timeout
Pedal release
(s)
speed (ms)
1
< 100
2
101–200
27
Steering
Dive
Squat
wh pos
(mm)
(mm)
(deg)
—
—
—
Timeout
(s)
1
2
Hide quick links:
Advertisement
Table of Contents
