GF32.22-P-5108TX AIRmatic With ADS Control Unit, Component Description
GF32.22-P-5108TX AIRmatic with ADS control unit, component description
- except CODE (489) Airmatic (semi-active air suspension)
Component Identification:
The AIRmatic with ADS control unit (N51) is located under the front passenger footplate.
Task
The AIRmatic with ADS control unit serves to control the chassis dampers, the chassis suspension and the vehicle level depending on the vehicle dynamics and driver's requirement
Function
The functions of the AIRmatic with ADS control unit are divided as follows:
^ Signal conditioning
^ Function logic component
^ Safety circuit
Signal conditioning
The following input signals are processed by the function logic component and used for calculations or to provide information:
^ Calculation of body vertical acceleration
- Signal from left front body lateral acceleration sensor (B24/3), right front body lateral acceleration sensor (B24/4), rear right body lateral acceleration sensor (B24/6):
^ Calculation of vehicle speed
- Wheel speed signal
- Speed status signal
^ Calculation of longitudinal and lateral acceleration
- Wheel speed signal
- Steering angle sensor signal (N49)
^ Calculation of compressor control
- Outside temperature, outside air pressure signal
- Reservoir pressure (AIRmatic pressure sensor (B7))
- Vehicle speed signal
- Vehicle level signal
- Duty cycle
^ Calculation for valve actuation
- Signals from left front level sensor right front, rear axle level sensor
^ Calculation for control of main reservoir charge valve AIRmatic (Y36/6)
- Signals from left front level sensor right front, rear axle level sensor
- Pressure signal
^ Calculation of vehicle level
- Signals from left front level sensor right front, rear axle level sensor
^ Information signals (operation)
- Stop lamp switch signal (S9/1)
- Comfort and sport switch signal (N72s25)
- Level adjustment switch signal (N72s18)
- Signal from door contact switch, trunk, remote control
Function logic components
The conditioned input signals are processed in the logic component and converted into output signals.
^ Signal for left front body lateral acceleration sensor (B24/3), right front body lateral acceleration sensor (B24/4), right rear body lateral acceleration sensor (B24/6):
The vertical acceleration of the vehicle is calculated using the signals from the body acceleration sensors.
^ The signal from the wheel sensors enables the ESP control unit (N47-5) to determine and transmits via engine compartment CAN to the AIRmatic with ADS control unit:
- Vehicle speed
- Longitudinal acceleration
- Vehicle status. A distinction is made between a moving and a stationary vehicle. Incorrect wheel speed signals are also detected.
^ Steering angle sensor signal:
The vehicle lateral acceleration is calculated with the steering angle sensor signal and the signals from the wheel speed sensors.
^ Left front, right front level sensor signal
Rear axle level sensor
Both front axle level sensors each supply 2 signals. The sensors detect and transfer the distance between the wheel center and the body at both the left and right-hand side of the vehicle. The rear axle level sensor supplies 2 signals. The sensor detects and transfers the distance between the wheel center and the body (average calculated from left and right wheel).
^ Stop lamp switch signal (S9/1):
When the driver presses the brake pedal, a signal is received by the ADS logic component and the damping at all wheels is set to "hard". The pitch motion of the vehicle when braking can therefore be reduced.
^ Comfort and sport switch signal (N72s25):
The driver can select between a convenience-oriented and 2 sporty maps with the comfort and sport switch In the "comfort" setting the damping is held in the comfortable range for as long as the driving style and road surface condition permit. The "Sport 1" setting makes the damping somewhat "harder". In "Sport 2" setting the damping is adjusted even more quickly towards "hard". At a speed of above 40 km/h in "Sport 2" in addition the suspension is constantly switched to hard (additional air volume OFF). The driver's requirement remains stored until it is changed again by the driver (also with ignition OFF). In settings "Sport 1 and 2" the vehicle is additionally brought to a lowered vehicle level of -10 mm or -15 mm relative to the normal level.
^ Level adjustment switch signal:
By means of the signal from the level adjustment switch, the control unit detects the driver's requirement concerning vehicle level:
- Normal level
- Increased level (+25 mm, (USA) +20 mm)
The driver's requirement remains stored until it is changed again by the driver (also with ignition OFF) or previous speed thresholds are exceeded.
^ ADS II
From the determined vertical body accelerations as well as the longitudinal and lateral accelerations of the vehicle and the vehicle speed, the AIRmatic with ADS control unit (N51) determines the respective optimal damping stage.
4 different damping forces can be set at each wheel by controlling the damping valves located at each wheel.
As the speed increases and with a sporty driving style the damping is automatically set harder.
^ Level adjustment
The AIRmatic control unit with ADS uses the setting of the level adjustment switch selected by the driver and the ground speed of the vehicle to control the appropriate level control valves and to set the correct vehicle level according to the vehicle load.
The AIRmatic is equipped with a pressure sensor so that the level control time remains as short as possible (e.g. after loading). The reservoir pressure is used only when required in order to prevent filling the reservoir too often. This happens, for example if the vehicle level falls below a critical level when loading the vehicle or if the driver has set the vehicle level to "Increased level". Pressure from the reservoir is also used when the vehicle is stationary to minimize noise. During normal control when the vehicle is moving, the suspension struts are supplied directly by the air compressor.
^ Control of spring rate
An additional air volume is assigned to each spring strut which can be switched in or out depending on the driving situation. In the normal case this additional volume is switched in (greater comfort) with a high dynamic requirement the additional air volume is switched off. At a speed of above 40 km/h in "Sport 2" the additional air volume is generally switched off.
^ Lowering when stationary
If the vehicle is parked with active chassis mode "Comfort", all the vehicle doors including trunk lid are closed and the vehicle is locked with the transmitter key, the vehicle automatically lowers into the "Sleep position".
Function requirements
^ Vehicle stationary
^ Engine Off
If a door is still open after the locking process and if it closed during the run-on time (t = 60 s), as of the condition in which all the doors are locked, the vehicle is nevertheless lowered.
^ AIRmatic central reservoir pressure control
The controlled variables are mainly: The pressure in the central reservoir, the outside air pressure and vehicle speed. With lowering when stationary, the vehicle is raised again from the sleep position to the level last adjusted by the driver.
^ Compressor control
The compressor is controlled via a relay. Since the compressor is not designed for continuous operation, the absolute running time and cooling phase are monitored to avoid overloading the compressor.
^ Wake-up function
A parked vehicle is "woken up" before being started, i.e. through signals from the door contact switches, the luggage compartment and infrared remote control, the AIRmatic with ADS control unit detects that possibly a journey is imminent. The current vehicle level is checked immediately and corrected if required. The vehicle level at the front axle is considered to be critical, for instance, if the full wheel angle can no longer be guaranteed. In this case the driver is warned by the multifunction display in the instrument cluster: "Stop car too low!".
With the waking of the AIRmatic with ADS control unit (e.g. by opening a door) a time delay occurs which is used for immediate correction of vehicle level. This reduces the waiting time required to correct the vehicle level and the vehicle is ready for driving more promptly.
The stationary vehicle is raised by the pressure in the AIRmatic central reservoir. The compressor is only used to assist when the AIRmatic central reservoir is empty. It must be ensured that the battery voltage is sufficient to then start the engine
With lowering when stationary the vehicle is only raised from the sleep position again to the level last adjusted by the driver after the engine is started
^ Locking function
If the AIRmatic with ADS control unit detects unloading of all wheels when the vehicle is stationary, then the valves of the suspension struts are closed. The vehicle therefore remains at the current level. This is essential, for example, when changing a wheel or during repair work (lifting platform).
Safety circuit
The AIRmatic with ADS control unit monitors all the important components of the system after they are switched on and during operation. The task of the safety circuit is to detect faulty sensor signals, faults in the AIRmatic with ADS control unit and in the electrical line system. If a fault is detected, the system is switched off and a message is displayed on the multifunction display in the instrument cluster to warn the driver.
The damper valves for ADS are no longer controlled and remain set to the "hard" damping level (driving safety level).
In addition a fault code is stored in the AIRmatic with ADS control unit. The level control is only partially switched off depending on the fault. The system always strives to maintain the selected vehicle level.
The safety circuit also constantly monitors the battery voltage. If the voltage falls below 9 V or exceeds 16.5 V, the system is switched off until the voltage returns to the specified range.