Stop lamp switch signal
Damping valve units
Level control valve unit
N51
Reception of sensor signals, sensor compensation and sensor monitoring
Adaptive damping system ADS II
1. Recognition of vehicle behavior (vertical body acceleration, longitudinal and lateral acceleration, braking and comfort/sport changeover)
2. Calculation of damping forces
Level control and adjustment
1. Recognition of vehicle level and the driver's requirement (switch position)
2. Calculation of nominal pressures
Monitoring of control module, operating condition and actuation signals,
fault recognition, shut-down, type of fault, diagnosis entry
Conversion of damping forces and nominal pressures into valve actuation times
Output stages
Level required by driver
Vehicle level
Vertical body acceleration
Steering angle
Vehicle speed
Comfort/sport changeover
The AIRmatic with ADS control module is broken down into the following functions:
Signal conditioning
Function logic section
Safety circuit
Signal conditioning
The following input signals are processed by the function logic section for calculation or information purposes:
Calculation of vertical body accelerations
– Body acceleration sensors signal
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Calculation of vehicle speed
– Wheel speed signal
– Speed status signal
Calculation of longitudinal and lateral acceleration
– Wheel speed signal
– Steering angle sensor signal
Calculation of vehicle level
– Level sensors signal
Information signals (operation)
– Stop lamp switch signal
– ADS comfort and sport switch signal
– Level adjustment switch signal
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Function logic section
The conditioned input signals are processed in the logic section and converted into output signals.
Body acceleration sensors (B24/3, B24/4, B24/6) signal:
The vertical acceleration of the vehicle is calculated from the signals from the body acceleration sensors.
Wheel speed signal:
The following are determined by the ETS, ASR or ESP control module by means of the wheel speed signal:
– Vehicle speed
– Longitudinal acceleration
Speed status signal:
This signal comes from the ETS, ASR or ESP control module and is used as a plausibility check of the wheel speed signal. A distinction is made between a moving vehicle and a stationary vehicle. A defective wheel speed signal is also recognized.
Steering angle sensor (N49) signal:
The lateral acceleration of the vehicle is calculated via the steering angle sensor signal and the wheel speed signal.
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Level sensors (B22/2, B22/3) signal:
The level sensors of the front and rear axle each supply two signals which determine the distance between the center of the wheel and the body (mean value from the right and left wheel).
Stop lamp switch (S9/1) signal:
When the brake is operated a signal is recognized by the ADS logic section and the damping set to "hard" on all wheels. As a result the pitch motion of the vehicle can be reduced during braking.
Comfort/sport switch (ADS) (S45/1) signal:
The signal from the comfort/sport switch provides information on the selection between a comfort-orientated and sporty map. The driver's requirement remains stored until it is revised again by the driver (even with ignition OFF).
Level adjustment switch (S77/1) signal:
The control module recognizes the driver's requirement for vehicle level by means of the signal from the level adjustment switch:
– Normal level
– Higher level stage 1
– Higher level stage 2
– Lock-out position
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ADS II
The control module determines the optimum damping stage in each case from the vertical body accelerations determined and the longitudinal and lateral acceleration of the vehicle and the vehicle speed.
The 4 different damping force stages can be adjusted at each wheel by actuating the damping valve units which are assigned to the wheels.
Level control and adjustment
The control module adjusts the correct vehicle level depending on the load from the driver's required setting on the level adjustment switch and from the vehicle speed via the respective level valves.
Safety circuit
The AIRmatic with ADS control module monitors all the important components of the system after switching on and during operation. The task of the safety circuit is to recognize defective signals from sensors, faults in the control module and in the electrical wiring system. If a fault if recognized the system is then switched off and this is displayed to the driver by the ADS MIL (A1e27) lighting up. The damping valve units are no longer actuated and are in the hard damping stage (safe driving stage). A fault code is also stored in the control module.
Depending on the fault, the level control is only partially switched off.
The safety circuit also constantly monitors battery voltage. If the voltage of 10.5 V is not achieved or 17.5 V is exceeded, the system is also switched off until the voltage is within the specified range again.