Only floating is better

Sep 2, 2020

Even better ride comfort and agility, as well as innovative functions such as raising the vehicle body in a lateral crash, are provided by the new developed E-ACTIVE BODY CONTROL active suspension, which is combined with the standard AIRMATIC air suspension. This regulates the damping and spring forces individually at each wheel, and not only counters body roll, but also pitch and lift. Together with ROAD SURFACE SCAN and the CURVE function, E‑ACTIVE BODY CONTROL allows an extraordinarily high level of comfort and underpins the claim of Mercedes-Benz to produce the world's most intelligent suspension.

Active suspension systems have a long tradition at Mercedes-Benz. More than 40 years ago, research was already being conducted on spring and damper systems that would allow the power at each wheel to be individually controlled. The objective: to improve both ride comfort and vehicle dynamics. In 1999 ABC (Active Body Control) first entered series production in the S-Class Coupé. In subsequent years ABC was continuously developed further, with the ROAD SURFACE SCAN function added in 2013 to produce the first predictive suspension that already responds to surface undulations before they are reached.

E-ACTIVE BODY CONTROL continues this tradition in a unique way. Developed by Mercedes-Benz, it operates on 48 volts and is available in the S-Class as an optional extra. The system is based on the full AIRMATIC air suspension system, and therefore offers all-round level control which keeps the vehicle level constant irrespective of the load. The level can also be raised or lowered as required, to increase ground clearance.

Furthermore, the air suspension with active hydraulic damping generates dynamic forces that overlay the air suspension forces and actively support and dampen the vehicle body, e.g. during linear and lateral acceleration or when driving on uneven roads. The body no longer squats or pitches during braking and acceleration, and on poor road surfaces the system is even able to recuperate energy, roughly halving the energy requirement compared with the preceding system in the S-Class.

The active suspension also allows a very wide spread of handling characteristics that can be set with the driving mode – from the comfort of a luxury saloon to the agility of a sports car. It is also closely networked with the rear-axle steering and the other suspension and control systems, and achieves a new level of stability and safety as a result. With five multi-core processors, more than 20 sensors and use of the stereo camera, E-ACTIVE BODY CONTROL responds predictively to any driving situation and ensures a completely new driving experience. The control units analyse the driving situation 1000 times per second, and adapt the suspension accordingly. ROAD SURFACE SCAN is a unique function: The stereo multi-purpose camera continuously registers the road surface ahead. The suspension struts are then activated so as to substantially reduce the body movements when driving over surface undulations, as the suspension responds even before the uneven stretch is reached.

The curve inclination function likewise improves ride comfort: in CURVE driving mode, the vehicle actively leans into bends by up to 3° in three stages, like a motorcycle. This reduces the lateral forces acting on the occupants. Cornering is therefore made much more pleasant, especially for the front and rear passengers.

The control function of E-ACTIVE BODY CONTROL depends upon:

  • the driving style, e.g. dynamic
  • the road surface, e.g. surface undulations
  • the vehicle load
  • the selected driving mode: sporty (SPORT), comfortable (COMFORT), comfortable with dynamic curve inclination function (CURVE) or comfortable and particularly energy-efficient (ECO).

How it works: How E-ACTIVE Body Control works

E-ACTIVE Body Control adds semi-supporting hydraulics to the air suspension. The air springs bear the base load of the vehicle body and gradually regulate the level. The hydraulics generate dynamic forces that overlay the air spring forces, and actively support and dampen the vehicle body. They achieve up to 6 kN at the front wheels and 5 kN at the rear wheels. The actuating force is up to 20 kN/s, which also allows raising of the vehicle body when an impending side impact is recognised. More about this extension to PRE-SAFE® Impulse Side in the chapter "Protective measures in a side crash".

At each wheel, a damper is installed within the axle with two working chambers that have an adjustable damping valve and a hydraulic pressure reservoir. The damper is connected to an intelligent motor/pump unit in the 48 V network by hydraulic lines. Actuation of the motor/pump unit enables the hydraulic fluid to be displaced to create a difference in pressure within the damper, allowing an active force to be generated.

The motor/pump units at all four wheels are coordinated by a central control unit which also actuates the valves and the compressor for the air springs, and therefore always controls the entire suspension system.

The transition from a belt-driven hydraulic pump to an electric 48-volt pump also takes into account the increasing electrification of the powertrain: the combustion engine is idle increasingly often – or not used at all.