Innovative suspension systems ensure an impressive travel experience in the new S-Class. Rear-axle steering with a steering angle of up to 10° improves manoeuvrability in urban areas. The optional, fully active E-ACTIVE BODY CONTROL suspension on a 48 V basis offers a unique synthesis of comfort and agility, plus additional protection in the event of a lateral collision. The AIRMATIC air suspension with continuously adjustable damping ADS+ is standard equipment. Close networking between all the suspension and control systems ensures maximum stability and safety. Redundant steering and braking systems are ready for conditionally automated driving acc. to SAE Level 3.
The aim of the developers was to exceed the high level of suspension and ride comfort of the preceding series, while achieving a very high level of vehicle dynamics. E-ACTIVE BODY CONTROL (see separate chapter) replaces the previous MAGIC BODY CONTROL.
At the front the new S-Class has the well-proven four-link suspension. With the exception of the wheel bearings, all the wheel location components are of forged aluminium. The multi-link independent rear suspension has been completely redeveloped to accommodate rear-axle steering. To this end, the kinematics and elastokinematics were adapted, and the track rod at the lower steering arm level was moved from the front to the rear. The rear axle carrier is of welded sheet aluminium, and weighs no more than before thanks to computer-assisted structural improvements and despite greater strength. A newly developed metal/plastic hybrid cross-bar is bolted into this open-fronted section, and has significant weight advantages over the cast aluminium cross-bar of the preceding model. The suspension subframe carriers and the elastomer bearings of the rear axle struts were redeveloped in extensive simulations and driving trials, so as to improve them with respect to NVH and handling characteristics.
The standard-fit AIRMATIC air suspension responds particularly sensitively. It combines air suspension bellows with adaptive ADS+ dampers whose characteristics can be fully automatically varied at each individual wheel, in both the compression and rebound stages. While driving, a sophisticated sensor system and algorithms set the dampers according to the quality of the road to ensure that, for example, driving over a bump with just one wheel is not transmitted to the entire axle and the interior. At the front axle the springs and dampers are housed in one suspension strut. This level control is part of AIRMATIC. It keeps the ground clearance constant irrespective of the vehicle load, but also makes changes. By way of example, in COMFORT mode the vehicle body is lowered by 10 mm at high speeds above 120 km/h and another 10 mm at over 160 km/h to reduce aerodynamic drag and increase driving stability. In SPORT driving mode the body is always 10 mm lower, and in SPORT+ 17 mm. At up to 60 km/h, the body can be raised by 30 mm at the touch of a button.
As manoeuvrable as a compact car: both axles can do the steering
The aim of the engineers at Mercedes-Benz was to make the new S-Class as manoeuvrable as a compact car. The impressive driving function has been realised using rear-axle steering that allows large steering angles of up to 10° and is integrated into the dynamic control systems of the steering, brakes and suspension (more about the rear-axle steering in the next chapter). The S-Class has an electro-mechanical direct steering system at the front. The suspension settings of the DYNAMIC SELECT driving modes allow individual adaptation of the assistance characteristics. Whatever the vehicle weight, tyre size and friction, an innovative control concept ensures consistent and comfortable steering feedback. The steering is also the central actuator for implementing the movement trajectory from numerous driving assistance functions and handling safety systems. In models equipped with the optional rear-axle steering, the front axle has a steering variant with an approx. 15% more direct steering ratio which requires considerably less steering movement in conjunction with the rear-axle steering.
DYNAMIC SELECT: The S-Class drives as the driver wants it to
The driver can individually modify the characteristics of the powertrain, ESP®, suspension and steering. The selection is made using a control at the lower end of the central display. The default setting is COMFORT mode. Different characteristics are firmly assigned to each system. The driver has the choice of selecting fixed driving modes or individually combining sub-modes. The selection is acknowledged by acoustic and visual feedback. The desired driving mode is shown as the status and depicted in the central display.
The individual modes:
particularly fuel-efficient driving
comfortable and fuel-efficient driving
very sporty driving
The CURVE mode is also available in combination with E-ACTIVE BODY CONTROL. Plug-in hybrid models have the BATTERY LEVEL and ELECTRIC driving modes.
Electronic assistance: ESP® dynamic cornering assistance and Steering Assist
The steering assistant STEER CONTROL responds with commensurate steering force at the dynamic limits to support the driver in stabilising the vehicle. To do this, the electronics determine the direction in which the driver must steer to defuse a potentially critical situation, and ensure a corresponding steering movement to indicate the steering direction that will enable the vehicle to be stabilised. For example, ESP® dynamic cornering assistance brakes the inner rear wheel if the electronics detect understeer. Both high handling safety and high driving dynamics are the result.
In combination with the DRIVE PILOT: steering for conditionally automated driving
It is expected that from the second half of 2021, the S-Class will be able to drive in conditionally automated mode at up to 60 km/h with the new DRIVE PILOT where traffic density is high or in tailbacks on suitable motorway sections. The technology for this includes fail-safe steering which executes the relevant actuation and steering commands of the intelligent track guidance system with the greatest precision. Embedded in a twin-channel architecture, this steering relies on a multiple back-up energy supply via independent bus-systems with the vehicle components involved. The front and rear axle have twice the number of rpm sensors.
All the major electronic and electro-mechanical components, assemblies and sensors are redundant in nature. In the event of a channel failure, the redundant component continues the function. The electric motor consists of four sub-motors, so that at least 50% of the maximum output is available at any time. This ensures that during conditionally automated driving, the desired trajectory can be followed by the front axle steering in any situation.
An electric brake booster is used for models with additional equipment for conditionally automated driving, or e.g. the optional Remote Parking Assist or the INTELLIGENT PARK PILOT. To reinforce the driver's braking intention, this does not use vacuum pressure but an electric motor with a reduction gear. During conditionally automated driving or parking manoeuvres, the electric brake booster acts as a redundant pressure generator for the braking system and can bring the vehicle to a safe stop even if the hydraulic unit fails.