AIRMATIC function - GF32.22-P-0002GN
MODEL 166 as of model year 2016 with CODE 489 (AIRMATIC)
MODEL 292 with CODE 489 (AIRMATIC)
Block diagram
Function requirements, general
- Drive train operational
- Engine running
System in general
The AIRmatic system is the combination of an air suspension with a continuous damper adjustment in which the dampening is adapted on a wheel by wheel basis corresponding to the road surface condition and driving style. After the ignition is switched on the last selected level and the last adjusted damping stage are active.
The system is made up of the following subfunctions:
- Wake-up mode, function
- Air suspension, function
- Locking position, function
- Variable damping, function
- System and warning messages, function
There are 3 AIRMATIC variants in use:
- AIRMATIC (on model 166.8 with CODE 494 (USA version)) The vehicle only has air suspension without an adaptive damping system with adjustable dampers and damping valve units.
- AIRmatic with ADS
The damping valve units enable adjustable damping in 4 stages
- AIRMATIC with ADS+
The damping valve units enable continuous damping adjustment
Wake-up mode, function
After the vehicle is unlocked, the AIRmatic control unit is activated (woken up) by the active chassis CAN 1 in order to check and, if necessary, correct the current vehicle level. Level control is performed in wake-up mode, e.g. when the vehicle is being loaded and unloaded, without the AIRmatic compressor being activated, provided that the fill level of the AIRmatic central reservoir is sufficient.
A critical condition, for example a too low vehicle level at the front axle, in which the full wheel angle can no longer be guaranteed, is detected by the AIRmatic control unit as a fault.
The driver's attention is drawn to the to the condition by the message "Vehicle lifting, wait briefly" in the multifunction display of the instrument cluster. Through the wake-up of the AIRmatic control unit a chronological lead occurs which is used to correct the vehicle level. This reduces the amount of time which passes before level correction is performed, therefore increasing vehicle availability.
Air suspension, function
Under normal operating conditions, the air suspension operates with different pressures depending on the load. Load detection takes place by evaluating the signal from the AIRmatic pressure sensor that is integrated in the AIRmatic valve unit. The AIRmatic pressure sensor records the bellows pressure in the air suspension bellows. The AIRMATIC compressor is used to supply pressure. The AIRmatic compressor is activated by the AIRmatic control unit via the AIRmatic relay.
The air pressure is distributed to the individual suspension struts of the front axle and the rear axle via the AIRmatic valve unit. The AIRMATIC system has 2 central reservoirs connected in series in which compressed air is stored to provide rapid vehicle level adjustment times independent of the compressor operation. The pressure in the AIRMATIC central reservoirs is monitored by the AIRMATIC pressure sensor. As soon as the pressure drops below the threshold value, the AIRMATIC compressor is activated.
Level control is realized by 4 air suspension bellows. If the AIRMATIC compressor or the AIRMATIC central reservoirs supply air to an air suspension bellows through a corresponding valve in the AIRMATIC valve unit, the vehicle level at the wheel concerned increases. Conversely, the vehicle level decreases when air from the air suspension bellows is released through the corresponding valve in the AIRmatic valve unit and at the AIRmatic pressure reduction valve in the AIRmatic compressor.
The driver can adjust the vehicle level by pressing the vehicle level button (except CODE 430 (On & Off-road package)) or the vehicle level rotary switch (with CODE 430 (On & Off-road package)) in the lower control panel control unit.
Operation of the vehicle level button (except CODE 430 (On & Offroad package)) or the vehicle level rotary switch (with CODE 430 (On & Offroad package)) is read in by the SAM control unit via the center console switch LIN. The signal is transmitted via the interior CAN, the electronic ignition lock control unit and chassis CAN 1 to the AIRmatic control unit.
The wheel speeds are determined by the left front axle RPM sensor, right front axle RPM sensor, left rear axle RPM sensor and right rear axle RPM sensor and directly read in by the Electronic Stability Program control unit.
The status of the level control system and the vehicle level are transmitted by the AIRmatic control unit via chassis CAN 1 to the active roll stabilization control unit.
| Vehicle level s (with CODE 430 (On & Offroad package)) | |||
|---|---|---|---|
| Level designation | Level [mm] | v [km/h] | Remarks |
| Fast driving level | -45 | v > 70 v > 40 |
at v < 70 km/h and t = 20 s at v < 40 km/h and t = 0 s |
| Basic or normal level | -30 | v < 120 v < 140 |
at v > 120 km/h and t = 20 s at v > 140 km/h and t = 0 s lower -45 mm |
| Off-road 1 | 0 | v < 100 | at v > 100 km/h lower to -30 mm |
| Off-road 2 | +30 | v < 70 v < 90 |
at v > 70 km/h and t = 20 s at v > 90 km/h and t = 0 s lower to 0 mm |
| Off-road 3 | +60 | v < 20 | at v > 20 km/h lower to +30 mm |
| Vehicle levels (except CODE 430 (On & Offroad package)) | |||
|---|---|---|---|
| Level designation | Level [mm] | v [km/h] | Remarks |
| Fast driving level | -45 | v > 70 v > 40 |
at v < 70 km/h and t = 20 s at v < 40 km/h and t = 0 s raise to -30 mm |
| Basic or normal level | -30 | v < 120 v < 140 |
at v > 120 km/h and t = 20 s at v > 140 km/h and t = 0 s lower -45 mm |
| Off-road 1 | +30 | v < 70 v < 90 |
at v > 70 km/h and t = 20 s at v > 90 km/h and t = 0 s lower to -30 mm |
Locking position, function
To ensure that, when intentionally raising the vehicle (e.g. with a vehicle jack), air is not continuously released from the suspension struts (which would lower the vehicle), it is necessary to detect this reduction in wheel load automatically and then to initiate a locking position. The locking position is a pure software function which prevents the actuation of the level control valves (draining process). If the locking position is detected by the AIRmatic control unit, nothing is displayed in the instrument cluster and no faults are stored.
The locking position is automatically canceled if the AIRmatic control unit receives left front and right front wheel speed signals with v 0 km/h from the Electronic Stability Program control unit via chassis CAN 1. The level control functions are then reactivated.
The output stage actuations of the AIRmatic control unit via the diagnosis take place independent of the locking status and are thus always possible.
Adjustable damping function (except model 166.8 with CODE 494 (USA version))
The electronically regulated, continuous damping system operates fully automatically.
It provides improved driving comfort and driving safety, compared to the conventional steel suspension. Damping is set harder or softer by the electronics of the AIRmatic control unit depending on the driving situation. If the sensor system records a sporty driving style for example, the comfortable basic damping becomes harder automatically. The driver can set this automatic program using the transmission mode control in the transmission mode control panel (except CODE 430 (On & Off-road package)) or using the off-road package transmission mode control in the offroad control panel control unit (with CODE 430 (On & Offroad package)).
When the transmission mode control is operated, it is read in by the SAM control unit over the center console switch LIN. The signal is transmitted to the AIRmatic control unit via interior CAN, electronic ignition lock control unit and chassis CAN 1 with the ME-SFI [ME] control unit interface (with gasoline engine) or the CDI control unit interface (with diesel engine). The LEDs are actuated in the opposite direction.
The electronics works continuously within a broadly spread damping performance map. The damping force is adapted individually and automatically at each wheel to the current requirements, the road condition and the driving conditions.
As a result, the vehicle rolls smoothly even on poor road surfaces, without impairing driving stability.
The AIRmatic control unit uses the left front level sensor, right front level sensor, left rear level sensor and right rear level sensor to determine the current vehicle level and shock absorber speeds. The acceleration sensors are used by the AIRMATIC control unit to calculate the vehicle's body acceleration.
Based on the input signals, the AIRmatic control unit determines the optimum damping stage for each shock absorber and directly actuates the left front axle damping valve unit, right front axle damping valve unit, left rear axle damping valve unit and right rear axle damping valve unit accordingly. These can be adjusted for each wheel, i.e the damping can be adjusted continuously at each individual wheel.
System and warning messages, function
In the multifunction display of the instrument cluster, system messages and warning messages are displayed for the driver with safety-relevant or system-relevant handling notes. In order to output the messages, the AIRmatic control unit transmits corresponding messages to the instrument cluster via chassis CAN 1, the electronic ignition lock control unit and chassis CAN 2. There are various system and warning messages with different fault priorities, depending on the severity of the fault and the urgency of the request for action to be taken. If several faults exist at the same time, several fault messages will be output accordingly.
Texts displayed in instrument cluster:
- "Stop, car too low", in addition a signal tone
- "Vehicle being raised, wait briefly"
- "Fault", no signal tone
The following system message is also displayed in the instrument cluster:
- "Vehicle lifts up", no signal tone
| Electrical function schematic for AIRmatic | PE32.32-P-2052-97NBA | ||
| Overview of system components for AIRMATIC | GF32.22-P-9994GN |