Active Body Control, or ABC, is the Mercedes-Benz brand name used to describe electronically controlled hydropneumatic suspension.
This suspension combines a high level of ride quality with control of the vehicle body motions, and therefore virtually eliminates body roll in many driving situations including cornering, accelerating, and braking.
Mercedes-Benz has been experimenting with these capabilities for automobile suspension since the air suspension of the 1963 600 and the hydropneumatic (fluid and air) suspension of the 1974 6.9.
ABC was only offered on rear-wheel drive models, as all-wheel drive 4MATIC models were available only with Airmatic semi-active air suspension, with the 2019 Mercedes-Benz GLE 450 4MATIC being the first AWD to have ABC available.
The production version was introduced at the 1999 Geneva Motor Show on the new Mercedes-Benz CL-Class C215.
Description
In the ABC system, a computer detects body movement from sensors located throughout the vehicle, and controls the action of the active suspension with the use of hydraulic servomechanisms. The hydraulic pressure to the servos is supplied by a high pressure radial piston hydraulic pump, operating at 3,000psi. Accumulators regulate the hydraulic pressure, by means of an enclosed nitrogen bubble separated from the hydraulic fluid by a membrane.
A total of 13 sensors continually monitor body movement and vehicle level and supply the ABC controller with new data every ten milliseconds. Four level sensors, one at each wheel measure the ride level of the vehicle, three accelerometers measure the vertical body acceleration, one acceleration sensor measures the longitudinal and one sensor the transverse body acceleration. As the ABC controller receives and processes data, it operates four hydraulic servos, each mounted on an air and pressurized hydraulic fluid strut, beside each wheel.
Almost instantaneously, the servo regulated suspension generates counter forces to body lean, dive and squat during various driving maneuvers. A suspension strut, consisting of a steel coil spring and a shock absorber connected in parallel, as well as a hydraulically controlled adjusting cylinder, are located between the vehicle body and wheel. These components adjust the cylinder in the direction of the suspension strut, and change the suspension length. This creates a force which acts on the suspension and dampening of the vehicle in the frequency range up to five hertz.
The system also incorporates height adjustable suspension, which in this case lowers the vehicle up to between the speeds of for better aerodynamics, fuel consumption, and handling.
The ABC system also allows self-levelling suspension, which raises or lowers the vehicle in response to changing load (i.e. the loading or unloading of passengers or cargo). Each vehicle equipped with ABC has an “ABC Sport” button that allows the driver to adjust the suspension range for different driving style preferences. This feature allows the driver to adjust the suspension to maintain a more level ride in more demanding driving conditions.
The reliable function of the ABC system requires a regular hydraulic oil change and filter replacement.
The Mercedes-Benz C112 of 1991, Mercedes-Benz Vario Research Car of 1995 and the Mercedes-Benz F200 of 1996 already featured prototype versions of ABC.
The first complete and ready-for-production version of ABC was introduced in 1999 on the top-of-the-line Mercedes-Benz CL-Class (C215).
In 2006, the Mercedes-Benz CL-Class (C216) introduced the second generation Active Body Control suspension, referred to as ABC Plus or ABC II in technical documentation. This updated suspension reduced body roll by 45% compared to the first generation ABC suspension. ABC Plus had an updated hydraulic system design, with shorter hydraulic lines, and the pulsation damper was relocated to be mounted directly on the tandem pump.
In 2010 a crosswind stabilization function was introduced. In strong gusts of crosswind, and depending on the direction and intensity of the wind having an effect on the vehicle, this system varies the wheel load distribution in such a way that the effects of winds are largely compensated or reduced to a minimum. For this purpose the ABC control unit uses the yaw rate, lateral acceleration, steering angle and road speed sensors of the Electronic Stability Program ESP®.
Magic Body Control
In 2007, the Mercedes-Benz F700 concept introduced the PRE-SCAN suspension, an early prototype road scanning suspension, using lidar sensors, based on Active Body Control.