AIRMATIC function - GF32.22-P-0002RF
Model 205 with code 483 (ADVANCED AGILITY package) with code 489 (AIRMATIC)
Block diagram
Function requirements, general
- Engine running
- Drive train operational
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
Wake-up mode, function
The AIRmatic control unit is activated (woken up) by the active chassis FlexRay after the vehicle is unlocked in order to check the current vehicle level and correct it, if necessary. 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 is made aware of the situation by the message "Vehicle being raised, please wait" on 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. The electric AIRMATIC compressor is used to supply pressure. The AIRmatic compressor is activated by the AIRmatic control unit via the AIRmatic relay.
Level control is realized by 4 air suspension bellows. If the AIRmatic compressor delivers air to an air suspension bellows via 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 by the corresponding valve in the AIRmatic valve unit and released at the AIRmatic pressure reduction valve in the AIRmatic compressor. The driver can adjust the vehicle level by pressing the vehicle level button in the left lower control panel (with automatic transmission) or in the right lower control panel (with manual transmission).
The signals from the vehicle level button are read in by the left lower control panel (with automatic transmission) or in the right lower control panel (with manual transmission). The left lower control panel or the right lower control panel sends the signal via the LCP LIN, the Audio/COMAND control panel, the telematics CAN, the head unit, the user interface CAN, the electronic ignition lock control unit and the chassis FlexRay 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.
| Vehicle levels | |||
|---|---|---|---|
| Level designation | Level [mm] | v [km/h] | Remarks |
| Comfort | 0 -15 |
< 125 > 125 |
raise to 0 mm at v < 80 km/h |
| Sport | -15 | - | - |
| Sport Plus | -15 | - | - |
| Raised level (EN) | +20 | - | lower to 0 mm at v > 80 km/h and 3 min lower to 0 mm at v > 100 km/h |
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 wheel speed signals from the left front and right front sensors with v 10 km/h from the Electronic Stability Program control unit over the chassis FlexRay. 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.
Variable damping, function
The electronically regulated, continuous damping system operates fully automatically. In comparison to the conventional suspension, it provides improved driving comfort and driving safety. 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. This automatic program can be set by the driver via the AGILITY SELECT switch (up to model year 2016) or with the DYNAMIC SELECT switch (as of model year 2016) in the left lower control panel (with automatic transmission) or in the right lower control panel (with manual transmission).
The signals from the AGILITY SELECT switch (up to model year 2016) or DYNAMIC SELECT switch (as of model year 2016) are read in by the left lower control panel (with automatic transmission) or right lower control panel (with manual transmission). The left lower control panel (with automatic transmission) or the right lower control panel (with manual transmission) sends the signal via the LCP LIN, the Audio/COMAND control panel, the telematics CAN, the head unit, the user interface CAN, the electronic ignition lock control unit and the chassis FlexRay to the AIRMATIC control unit. 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 AIRMATIC control unit uses the signals from the left front body acceleration sensor, the right front body acceleration sensor and the rear left body acceleration sensor to calculate the body acceleration and the body speed of the vehicle.
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
System and warning messages with safety and system-relevant instructions for the driver are displayed on the instrument cluster. In order to output the messages, the AIRmatic control unit sends appropriate messages to the instrument cluster via the chassis FlexRay, the electronic ignition lock control unit and the user interface CAN. 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, vehicle too low", plus an acoustic signal
- "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-2052-97FBA | ||
| Overview of system components for AIRMATIC | GF32.22-P-9994RF |