Comfort system: AIRMATIC air suspension with ADS

The AIRMATIC full air suspension system including the Adaptive Damping System ADS offers a soft basic suspension setup with a low natural frequency, where full spring travel is available even when the vehicle is fully laden. This provides the basis for excellent ride comfort on road combined with noticeably superior handling stability. AIRMATIC compensates for variations in vehicle load and driving state, at the same time as acting as a level control system. Away from the tarmac, the air suspension increases the vehicle's off-road prowess by offering additional ride heights. The body can be raised or lowered with the engine running at any time, either automatically or at the driver's request with a simple turn of the rotary control in the centre console. The system is speed sensitive, meaning that it lowers the body at higher speeds to minimise aerodynamic drag while increasing handling stability too. The air suspension system's basic components include:

Air-filled spring struts on the front axle with integral ADS dampers
Air springs with separate ADS dampers on the rear axle
Electric compressor with central pressure reservoir and pressure sensor
Air spring valves
Electronic control unit
Sensors for level control and damping control

The adaptive damping system ADS II is a fully automatic, electronically controlled system, which adapts the damping force at each wheel to suit changing requirements using a skyhook algorithm. In contrast to a passive system with a constant damper setting, the vehicle's motion is controlled uniformly in all driving situations, leading to improved handling stability and a considerable reduction in body movement. The skyhook algorithm regulates the damping forces at each wheel so as to lessen the forces exerted on the body by the movement of the wheels. When there are low levels of body excitation, the Mercedes-Benz M-Class drives with damping level 1 active. Should the body speed exceed a certain threshold, however, the system will switch to the skyhook algorithm and constantly alternate between the second and third damping levels by means of fast-acting solenoid valves in order to counter the body's rolling and pitching movements. Under even more dynamic handling conditions, level 4 is engaged, and when driving in Sport mode, level 4 damping is activated at all times. Damping control at each individual wheel takes place extremely fast - depending on the control command, the valves are capable of setting one of the characteristic curves described here in less than 0.05 seconds:

Level 1 Soft rebound / soft compression for comfortable ride characteristics, gentle body movements and little longitudinal and lateral acceleration
Level 2 Soft rebound / firm compression (skyhook mode)
Level 3 Firm rebound / soft compression (skyhook mode)
Level 4 Firm rebound / firm compression: for minimising wheel load fluctuations when cornering and braking, high longitudinal and lateral acceleration for enhanced handling safety

The current driving state is determined using a steering angle sensor, 4 turning angle sensors und the road speed as derived from the ESPЃsignal and the brake pedal switch. Based on these signals, the control unit calculates the current damping forces required and actuates the appropriate damper characteristic curves. The driver is able to choose between Sport and Comfort modes manually by pressing a switch.

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