SUSPENSION OF (DIS)BELIEF
With the launch of an all-new active suspension concept by Mercedes-Benz, in this article AutoMate’s Harrison Boudakin takes a look at the history of this innovation and explores just how capable the technology can be
With its squared off, ruggedly conservative styling, Mercedes’ new GLE is nothing if not easy to pass by at first glance.
Priced to compete with BMW’s X5 and Audi’s Q7, it appears entirely unexceptional, and in that sense perfectly tailored for the loyal buyers who have kept the GLE, and its forebear, the M-Class, very popular for more than 20 years now.
But beneath the “new boss, same as the old boss” exterior, the GLE sports a bevy of electromechanical innovations that not only belie its straight-laced appearance, but also mark it out as something of a standard bearer in the current automotive cohort.
From bonnet to bootlid, this car is a showcase of mainstream SUV engineering taken to a new level. Using a 48-volt electrical system that’s increasingly finding its way into all sorts of Benz products, Mercedes has unlocked an array of technological marvels designed to bend the laws of physics and consume a little bit less of the world’s resources in the process.
Quite apart from the brand-new inline six cylinder engine, with its entirely beltless ancillaries and mild-hybrid electric starter-generator, the most remarkable feature of the new GLE is surely its E-Active Body Control ‘active’ suspension system.
Now, the concept of an ‘active’ suspension set-up is nothing new – various companies have been experimenting with the technology since the early 1980s. But as you’ll see, Mercedes has done more than any other manufacturer to actually bring the tech into use in production vehicles.
The premise for active suspension is a simple one: by moving to control wheel motion, damping and spring rates individually and relative to the chassis, rather than simply being determined entirely by the road surface itself, engineers are able to deliver a level of vehicle stability significantly beyond that of a regular ‘passive’ suspension set-up.
Before it found its way into road cars, active suspension was pioneered by the Lotus F1 team over 35 years ago. Using a 2200-psi hydraulic pump and a set of powerful rams to control all four wheels independently, the systems allowed the car to actively resist roll forces during fast cornering. Yet despite the obvious potential of such a remarkable concept, it wasn’t until rival team Williams got hold of it in the early 90s that its true genius became apparent.
In fact, Williams’ version was developed to such perfection that their all-conquering FW15C car – driven by the late, great Ayrton Senna – was actually outlawed in F1, and had to be stripped of its Active Ride because it was just too good compared to the competition.
There were major deficiencies, however, with these original hydraulic systems. The total weight of the active ride components was close to 150kg, and it required around five horsepower just to run the hydraulic pump. What’s more, when engineers tried to apply the tech to a road car, they discovered the rams simply couldn’t respond quickly enough to small, sharp bumps, meaning any increase in everyday ride comfort was negligible.
So it wasn’t until 1999 that Mercedes-Benz managed to bring its version of hydraulic, computer-controlled active suspension onto the public highway (though Citroen and Infiniti beat the Germans to market with their own versions).
Launched in the ground-breaking CL Coupe, Mercedes’ Active Body Control (ABC) was fiendishly complex, still very heavy and a magnet for heart-stopping repair bills. Yet thanks to a 3000psi hydraulic pump, 13 body movement sensors, four hydraulic servos and a high-powered central computer, it offered Mercedes’ most prestigious customers a level of body control and ride comfort well beyond even the best air suspension set-ups. It was so advanced that even in its first iteration, ABC was able to almost completely eliminate body roll – and that was just the beginning.
By 2010, ABC had gained a cross-wind stabilisation function, which would actively vary the wheel load distribution to compensate for wind effects at higher speeds. Then, in 2013, there was one more giant leap for suspension-kind: Magic Body Control. This used a stereo camera to scan the road ahead for surface imperfections and bumps, and could then adjust the shock damping at each individual wheel. This version of ABC required double the processing power of the first version – but achieved spectacular results in the W222 S-Class.
Even more innovation came one year later with the Active Curve Tilting system. This used ABC to not only eliminate body roll, but to actually tilt the car into corners up to 2.5 degrees – much like the Italian Pendolino trains, which lean into turns to counter the effect of centrifugal force on the occupants.
Which brings us to today – and back to the GLE’s new E-Active Body Control suspension. Thanks to the addition of the 48-volt sub-architecture, E-Active is a hydro-pneumatic system quite unlike anything else offered on the market today.
E-Active ditches anti-roll bars altogether to allow for truly independent control of each wheel. It then deploys electronically-adjustable dampers and air springs to control body motion, allowing spring rate, damper stiffness and ride height to be adjusted independently at each corner of the car in real time.
On-road, this allows for active curve tilting and pre-surface scanning – as per previous iterations of ABC. Unlike those versions, however, the 48-volt electrical system allows the GLE to harvest energy from vertical suspension movement to recharge the battery – a major breakthrough for passenger vehicles.
E-Active doesn’t disappoint off-road either, with the driver able to individually control the height of each wheel in the event that it loses traction. And best of all, if you’re stuck in sand, the aptly-named ‘Freischaukelfunktion’ will rock or bounce the GLE on its air springs, to help the car find grip on the soft surface.
This, then, is just another example of how 48V mild-electrification is helping manufacturers make some serious technological strides, and in the case of active suspension, it’s adding a new dimension of capability and innovation that we can expect to see cascading through the car parc very soon.
Written by AutoMate Training, a world leading provider of online, video-based technical training, with more than 400 modules featuring high quality graphics, the latest vehicles and real presenters. The AutoMate Training library covers everything from system fundamentals to advanced diagnostics and technology, including training on steering and suspension technology. Subscribe today for only $33 per month for professional techs and just $9.90 for trainees.
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