Conti's New CAirS Air Suspension Employs Hydraulic Principles

October 16, 2017

Ian Adcock

CAirS was designed with autonomous operation in mind. It is capable of anticipating upcoming road conditions and future developments might link it to forward-facing cameras as in the latest Audi A8 and Mercedes-Benz S-class. (Continental)

Continental has launched a new electronically-controlled three chamber air suspension system it claims is lighter, more compact and energy efficient than rival systems. Its production debut is on the 2018 Bentley Continental GT and the system is designed for electric and autonomous vehicle applications.

Known as CAirS, the system consists of only two primary components—the air supply system and the compressor, explained Uwe Folchert, head of air supply development.

“In the past we needed three components but these have been integrated saving up to 3.3 lb (1.5 kg) depending on the application [plus] packaging and assembly time on the production line,” he noted. “We’ve added functions and improved noise, vibration and harshness (NVH) as well.”

In a neat piece of lateral thinking, engineers from Conti’s air suspension and braking systems groups have taken principles usually employed in hydraulic brakes and modified them to work with air.

CAirS module as fitted to the 2018 Bentley Continental GT. A closed system, it operates at 87-174 psi (6-12 bar). (Continental)

“Previously the suspension would be controlled across each axle, with this system the four corners are managed independently via a valve block, allowing us to manage the whole vehicle,” added Felix Bietenbeck, head of the vehicle dynamics business unit. “By switching between the four air springs body roll during cornering is controlled and vehicle dynamics are enhanced.”

CAirS can cover the full range from very comfortable to a very sporty mode. The system receives input from sensors around the vehicle including acceleration and height. “The trick is to manufacture the most accurate 'activated passive' system using road forces to stabilize the vehicle’s upper body without bringing too much additional energy into the vehicle. CAirS is a step in that direction,” explained Folchert.

Although the system isn’t predictive, it responds to inputs within 100 ms. Beitenbeck said it could be networked into the navigation system to anticipate upcoming road conditions. A further development might be linking it to forward-facing cameras as in the latest Audi A8 and Mercedes-Benz S-class.

CAirS has been engineered partially with an eye on electric vehicles (EVs) and autonomous driving developments. The challenge with EVs says Folchert is their sensitivity to energy consumption and subsequent loss of range. Because CAirS is a closed system running at 87 - 174 psi (6-12 bar) the engineers claim it is 60-70% more efficient than open systems as it is only moving air between the air reservoir and the springs.

Depending on the vehicle size a typical air tank would be 305 - 610 in³ (5-10 L) and, by nature of its integrated design and assembly, the OEM is free to mount the sealed control unit anywhere within the vehicle structure.

“With an air spring you don’t need an active control, you can achieve a level of comfort just with the air spring itself which is more efficient because it is done passively, whereas with a conventional system more energy is required,” claimed Folchert. “Lowering the vehicle reduces air resistance and cuts compressor power consumption by as much as 70%.

In an SUV this, in turn, could reduce per-vehicle CO₂ emissions by up to 5%, he added.