The hydraulic fully active suspension system known as Active Body Control, or ABC, is marketed under the Mercedes-Benz brand. ABC nearly eliminates body roll in a variety of driving circumstances, including cornering, accelerating, and stopping. Since the air suspension of the 1963 600 and the hydropneumatics (fluid and air) suspension of the 1974 6.9, Mercedes-Benz has been experimenting with these features for vehicle suspension.
Only rear-wheel drive cars can use ABC. Models with all-wheel drive can only be had with Airmatic semi-active air suspension. Released in production form on the new Mercedes-Benz CL-Class C215 at the 1999 Geneva Motor Show.
The ABC system uses hydraulic servomechanisms to control the action of the active suspension after detecting body movement from sensors placed throughout the vehicle. A high-pressure radial piston hydraulic pump delivers hydraulic pressure to the servos. 13 sensors in all continuously track body movement and vehicle level and send fresh information to the ABC controller every 10 milliseconds. Three accelerometers monitor the vertical body acceleration, one accelerometer measures the longitudinal body acceleration, and one sensor measures the transverse body acceleration. Four level sensors, one at each wheel, measure the ride level of the vehicle.
A pressure sensor at each hydraulic cylinder tracks the hydraulic force. The four hydraulic servos, which are each mounted in series on a spring strut beside each wheel, are controlled by the ABC controller as it receives and analyses data. The servo-regulated suspension produces opposing pressures to body lean, dive, and squat during different driving actions almost instantly. Between the car's body and each wheel is a suspension strut, which consists of a parallel connection of a steel coil spring and a shock absorber as well as a hydraulically operated adjustment cylinder. These parts alter the suspension length and the cylinder's movement in relation to the suspension strut. This generates a force that affects the vehicle's suspension and damping in the hertz range up to five. Regular hydraulic oil changes and filter replacements are necessary for the ABC system to operate reliably.
The system also includes height-adjustable suspension, which lowers the car by up to 11 mm (0.43 in) between 60 and 160 km/h (37 and 99 mph) for better handling, fuel efficiency, and aerodynamics.
Self-leveling suspension, another feature of the ABC system, elevates or lowers the vehicle in reaction to a changing load (i.e. the loading or unloading of passengers or cargo). Each car with ABC features a "ABC Sport" button that lets the driver change the suspension range to suit their preferred driving habits. With the use of this technology, the driver can modify the suspension to keep the ride more level under more difficult circumstances.
ABC had already been used in prototype form in the Mercedes-Benz C112 from 1991, the Mercedes-Benz Vario Research Car from 1995, and the Mercedes-Benz F200 from 1996.
In 1999, the top-of-the-line Mercedes-Benz CL-Class featured the first finished and production-ready version of ABC (C215).
The second-generation Active Body Control suspension, also known as ABC Plus or ABC II in technical documents, was first installed in the Mercedes-Benz CL-Class (C216) in 2006. Comparing the improved suspension to the ABC suspension of the first generation, body roll was decreased by 45%. Shorter hydraulic lines and a new location for the pulsation damper on the tandem pump were added to ABC Plus's upgraded hydraulic system design.
The PRE-SCAN suspension, an early prototype road scanning suspension based on Active Body Control and lidar sensors, was unveiled in 2007 with the Mercedes-Benz F700 concept car.
The series production version of PRE-SCAN was first made available in 2013 in the Mercedes-Benz S-Class (W222), however stereo cameras were used in place of laser projectors. The Magic Body Control system has a road-sensing technology (Road Surface Scan) installed that pre-load the shocks for the discovered road surface. The technology scans up to 15 feet of the road surface with a stereo camera.
It adjusts the shock damping at each wheel to take into account road imperfections at speeds up to 130 km/h (81 mph), allowing the driver to see up to tens of meters ahead of the car. Magic Ride Control, which is initially only available on 8-cylinder versions and higher, aims to isolate the body of the car by anticipating speed bumps and ruts in the road rather than just responding to them. With the introduction of the new S-Class, the ABC underwent significant changes. The wheel damping is now continuously adjustable, the spring strut responsiveness has been improved, and the pump efficiency has been significantly increased. The control unit and the sensors are connected by a digital interface, and the fast FlexRay bus is used to connect the control unit and the car's electronics. The prior system's processing power has more than doubled.