Audi A8 – Shift


The best of two worlds

At the Audi Summit, the Audi AI active suspension illustrated how automotive technologies old and new can work in tandem.

 Copy & Photos: AUDI AG

One thing quickly became clear to anyone who visited the Audi Summit in Barcelona: we’re now at a turning point where the forms of mobility most of us are familiar with and use are undergoing a fundamental transformation. People who are now in their 40s can still remember the days when cars had carburetors and chokes; fast-forward to the present, and they’re now using car sharing services; and in the not all too distant future they might be riding around in autonomous cars. Under the banner of “Audi AI,” the summit showed that mobility is more digital and connected than ever. But to achieve Vorsprung, smart technologies need to be combined with traditional mechanical engineering. The optional Audi AI active suspension shows how closely intertwined the two disciplines are in the new Audi A8 – probably the most innovative production car that Audi has ever made. The result? A sportier ride sensation, greater comfort, and improved safety.

A scale model of the new Audi A8’s front axle was exhibited in Barcelona, allowing visitors to learn all about the component. Each axle has a specially developed and manufactured subframe with an electric motor on each end that does the physical work. Forces are either transferred to the suspension as required, or the spring rate is adjusted accordingly. For the first time ever, the Audi AI active suspension is able to individually control the forces that are transferred to each of the four wheels, enabling active body stabilization in all situations.

This requires an elaborate mechanical system. Via a belt drive, the motor transfers its torque to a strain wave gear set. From there, the torque passes via a hollow torsion tube to a titanium torsion bar, which run through the gearbox and finally sends the torque via a lever to the suspension/axle system. Up to 350 kg can be added or subtracted at each wheel, which in turn calls for a corresponding amount of drive power. Each of the four electric motors produces 2 kW, which in tandem with the installed mechanical system creates a torque level of 1,100 Nm.

The new system not only reduces vertical body movements, known as “heave” or “bounce,” but also pitching and rolling movements during accelerating, braking, or cornering. The brain of the active suspension system is a controller – the electronic suspension platform – where handling data is recorded, evaluated, and translated into concrete commands. It makes use of another system, which will be absolutely indispensable for cutting-edge assistance systems in future Audi models: the 48-volt electrical system. The increased voltage allows the system to supply the actuator motors with the energy they need even when requirements are high.

Despite this, the system’s average power consumption is surprisingly modest, not least because energy does not need to be supplied all the time. In its damper function, the system actually recuperates energy, with the electric motors operating as generators and the 48-volt battery acting as an internal energy storage system. The mechanical and electronic elements achieve impressive results by working together in harmony. Since all four wheels can be controlled individually, vertical and horizontal body movements are significantly reduced. The new Audi AI active suspension is also integrated into Audi drive select, allowing it to be configured to comfort or dynamic modes as desired.

When cornering, the system always provides a certain amount of feedback. This is entirely intentional – for safety reasons, drivers always need to be able to sense how fast they’re going. It’s not the only feature that demonstrates how mechanical and electronic systems can work in tandem to boost safety: in the event of an imminent side impact at more than 25 km/h, the suspension actuators work in combination with pre sense 360˚ and the optional intersection assistant to raise the body on the exposed side by up to 80 mm within half a second. As a result, the collision is directed to even stronger areas of the body. This can reduce the load on passengers, especially in the chest and stomach area, by up to 50%.