The letters IFS once represented the pinnacle of suspension development. They stood not just for independent front suspension but also were used by automotive marketers to establish a certain elitism for a product: a step-change ride and handling solution about which customers could boast.
Earle S. MacPherson’s renowned strut was—literally—at the forefront of this advance, using a coil spring and damper to great effect on monocoque cars from 1949; it remains an independently sprung suspension member still favored by many of today’s chassis engineers.
Another step-change in suspension technology was introduced on the Citroen DS of 1955, its oleopneumatic (hydropneumatic) system of spheres linked to all four wheels that took ride and handling qualities to a then unprecedented level, albeit via a complex and expensive integration of components that could bring problems sufficient for some cynics soon cheekily referring to it as “hydroproblematic.”
Now, Mercedes-Benz, using networked electronic systems (sensor fusion), is introducing on its MY2014 S-Class what promises to be a further step-change—a suspension system that can “see” (via a stereo camera) the road surface ahead and make ultrahigh-speed decisions on how to deal with it.
Called, somewhat surprisingly for generally conservative Mercedes, Magic Body Control (MBC), the anticipatory system will be available initially on the V8 gasoline versions of the new car but is expected to be cascaded through the range and then into other model lines; it is a central part of the company’s Intelligent Drive program.
MBC is one element of a veritable plethora of technologies developed to make the S-Class a vehicle that will be further developed toward autonomous driving and to assume—at least in part—the role of the latter-day Maybach, production of which ceased after 10 years in December 2012. In fact the long-wheelbase version of the new S-Class took precedence in design over the regular model, another echo of Maybach thinking.
Dr. Dieter Zetsche, Chairman of the Board of management of Daimler and Head of Mercedes-Benz Cars, said the S-Class was designed and developed in every respect on the basis of “the best or nothing.”
The car is not seen by the company as just a technological spearhead for Mercedes but for automotive development as a whole.
Intelligent Drive encompasses a host of systems. It includes a hybrid powertrain that can achieve a fuel consumption of 4.4 L/100 km fitted to the 240-km/h (149-mph), 2.1-L S300 BlueTEC; a very impressive best Cd figure of 0.23; the use of almost 500 LEDs and not a single bulb to light the road and the interior of the car; two hi-res TFT split-view color displays; hot-stone principle massage for the seats; active perfuming for the interior; advanced multimedia features and extended safety systems including Cross-Traffic Assist; and comfort items such as heated armrests.
Torsional rigidity is 40.5 kN·m (29,9000 lb·ft) per degree, up from 27.5 (20,300) for the previous generation S-Class. The entire outer skin of the car is of aluminum.
Any one of those items might head the list of outstanding technologies and deserve premier focus, but it is the ability of the car to “read the road” that stands out as something extra special. Prof. Dr. Thomas Weber, Member of the Daimler Board for Group Research and Head of Mercedes-Benz Cars Development, said: “Mercedes’ Intelligent Drive is leading the way by networking the sensors to enhance comfort and safety.”
ABC + RSS = MBC
MBC comes with a Road Surface Scan (RSS) camera system and Mercedes’ established Active Body Control (ABC).
The windshield-mounted camera monitors the road to a distance of 15 m (49 ft) in front of the car. Analyzing the resultant images and information about the car’s driving status, a control unit then calculates its optimum strategy. This includes what Mercedes terms “prolonged bumps.”
In essence, this means softening or stiffening damper reaction ahead of the event and increasing or reducing the load to each wheel via an active hydraulic system. The time frame is cited as “fractions of a second,” which it certainly needs to be as the system operates up to speeds of 130 km/h (81 mph). Caveats on its operation are the need for sufficient visibility and that the road structure is suitable for the system to be activated.
The ABC system has been significantly upgraded for application in the new S-Class, with wheel damping continuously adjustable, spring strut response improved, and pump efficiency increased. A digital interface connects the control unit and the sensors with a FlexRay bus linking the unit and vehicle electronics.
ABC uses four spring struts linked to hydraulic cylinders that facilitate force adjustment of each individually, allowing it to “almost completely” compensate for lifting, rolling, and pitching of the body. Information from accelerometers and pressure sensors in the spring struts and the level sensors mounted on the control arms is compared by the control unit. Control signals for the servohydraulic valves at the front and rear axle are computed. This allows precise metering of oil flows.
Oil entering the plunger cylinders modifies the tracing point of the steel springs integrated into the spring struts, generating the necessary force to counteract body movements. Hydraulic pressure is a constant 200 bar (2900 psi).
The S-Class is available with Distronic Plus adaptive cruise control incorporating Steering Assist and Stop&Go Pilot to enable the car to automatically follow the vehicle in front in heavy traffic conditions. Also available is BAS (Brake Assist System) Plus with Cross-Traffic Assist to detect both crossing traffic and pedestrians; Adaptive Highbeam Assist Plus involves the main beam being selected permanently without dazzling on-coming vehicles; Night View Assist Plus is supplemented by a thermal imaging camera; and, as with other Mercedes’ models, Attention Assist can warn of inattentiveness and drowsiness in an extended speed range.
Mercedes has indicated that the S-Class will form the basis for further advanced technologies in its Green Leadership program, including plug-in hybrid systems and autonomous operation where and when legislation allows (possibly within 4 to 5 years). Which is why its anticipatory aspect moves even further ahead than just MBC, with a line-up of “musts” that are not only anticipated but expected.
Aerodynamics is—or should be—close to the top of the “musts” list for the creators of new cars. Mercedes takes the discipline particularly seriously, with the new CLA pushing down the Cd figure for a series production sedan to an unprecedented level of 0.22.
The new S-Class faithfully follows that determination, the regular version achieving a Cd of 0.24, establishing what Mercedes regards as a new benchmark in its premium sector. But already there is more to come with the S 300 BlueTEC Hybrid slated to reach 0.23. These ostensibly tiny improvements are, in fact, very significant indeed and only gained via the most rigorous programs.
Mercedes’ “how-to-do-it” list includes complete sealing of the front end, with sealing the headlamp section and improved sealing of the radiator area. Airflow guidance is utilized to enhance cooling air efficiency. Adjustable louvers are part of the car’s air metering process.
Ride height is part of aerodynamic considerations on all cars, and the S-Class settles down by 20 mm (0.8 in) at speeds above 120 km/h (75 mph).
Aerodynamic underbody (and under engine) solutions include paneling throughout to below the fuel tank and cladding on the rear axle.
Detail work on the car includes attention to drain channels, exterior mirrors, taillights (they have a spoiler lip), and spoilers ahead of the front wheels complementing aerodynamically optimized wheels and tires. All this is in addition to the routine aerodynamic attention areas including front and rear aprons and rear spoiler. Although with a larger aperture than that of the previous S-Class generation, the panoramic sliding glass roof is no noisier thanks to the use of bespoke airflow deflection, covers, and seals.
The aerodynamic advances bring the added bonus of significantly reducing cabin noise levels.
Mercedes regards the S-Class as the quietest model in its segment. NVH is another salient area of expertise for Mercedes, which uses the company’s 3D Body Engineering philosophy for its aluminum hybrid bodyshell.
Front section NVH reduction includes use of extruded aluminum side members, cast aluminum elements at the transition point between the section and passenger cell, at the damper domes and integral carrier, as a vibration-damping structural component. The S-Class' aluminum roof also brings benefits on NVH levels as well as helping to lower the c.g.
Structural foam pieces are used in functionally critical nodal areas, again to contribute to improved NVH in the continuing campaign for lower passenger cabin noise levels.
Mercedes makes use of bracing struts for enhancing rigidity at particular points. There is a metal and plastic rear panel and cockpit crossmember, and foam is used in the A-, B-, and C-pillars to add rigidity.
Increased use of aluminum for the body (about 50%) has helped offset weight increase brought about by safety and other considerations to bring what the company terms as a slight reduction in body mass.
On a lighter note
While lighter weight is a constant Mercedes target, lighting has also been the subject of major development, with a complete switch to LEDs (light-emitting diodes).
Mercedes is fond of claiming “firsts” for its technology, and it does so with this development, saying that the new S-Class is “the first vehicle in the world to do without a single lightbulb as standard.”
But there is more: brake light intensity is reduced at night or when stationary at traffic lights.
The LED story—depending on vehicle equipment level—includes headlights that use 56; tail lights each with up to 35, with another 4 for the foglamp; and about 300 including ambient lighting for the interior.
Stated Weber: “Our engineers have made great advances where energy efficiency is concerned, reducing power consumption to a quarter of that of conventional headlights.”
For example, LED low-beam headlights take 34 W to produce the same light output as conventional types. Halogen needs 120 W and xenon needs 84 W. This means a typical fuel saving of 0.05 L/100 km and 2.1 g/km of CO2 when comparing LED vs. halogen.
High-performance single-chip LED diodes and a newly developed projector module in the headlamp unit allow deflected beams of light to be reflected back.
Getting masking taped
The S-Class also has Adaptive Highbeam Assist Plus. This technology permits the headlights to remain on high beam permanently but “masks out” other road users who may be dazzled. Part of the system incorporates the stereo camera that also monitors the road ahead. When its image-recognition function registers a vehicle ahead (approaching or being approached), it actuates a mechanism to initiate the masking system.
A low-beam setting, however, is the default selection for some specific situations such as when the LED vehicle is cornering and several vehicles are detected outside the effective masking parameters.
The system can detect glare from reflective road signs and will dim the lighting.
Additionally, the car is available with a long-range—160 m (525 ft)—infrared sensor to supplement night-vision technology for detection of pedestrians and animals. Night View Assist Plus switches the speedometer reading to an image of the road ahead. Pedestrians and animals are highlighted in red, and a spotlight flashes repeatedly to warn both the driver and pedestrian. Animals are not flashed because this may accentuate potentially unpredictable behavior.
A further example of LED application comes from the German company Preh. The control system specialist, which has been supplying S-Class models for more than a decade, has developed a solution for the rear climate-control system to bring benefits in weight reduction, illumination, feel, precise processing, and software development.
Compared to the previous version, the weight of the rear control system can be reduced by more than 50% to around 200 g (7 oz). A light guide design facilitates illumination of the control panel with only 10 LEDs, significantly reducing power requirements. As a result of this new development, the massive and consequently heavy heat sinks can be omitted. Using a combination of snap disks and silicone contact mats with 0.5 N (0.1 lb) actuating force, Preh achieved excellent haptics, as well as the perfect alignment of the individual function keys within the row.
Systems for a variety of control situations lie also on the software side.
An interesting detail that indicates the level of subtlety suppliers can bring to a premium OEM is that if only the driver exits the vehicle at rest in low temperatures, rear-seat passengers can retrieve the motor residual heat from the climate control system while the ignition is off.
Underlining the significance of the latest systems that contribute to the company’s vision of accident-free driving, Weber says that using such new technologies, its specialists are working to reduce the number of accidents and the severity of injuries.
Weber is realistic about it: “We can’t promise the impossible, simply because humans are prone to make the occasional error—including at the wheel of a car.” But he added: “That is why we need new systems that support the driver in critical situations. Our new systems hold great potential.”