Mercedes-Benz Pioneers ABC Fully Active Suspension
Mercedes-Benz - the company that pioneered ABS anti-lock brakes, traction control and ESP stability control - offers the world’s only fully active suspension system in production. Mercedes-Benz offers the critically acclaimed ABC (Active Body Control) active suspension as standard equipment on all SL roadsters, two-wheel-drive CL coupes, and V8 S-Class sedans (optional on the S550).
ABC active suspension virtually eliminates body pitch and roll during cornering, accelerating and braking. While active suspension is even capable of leaning a car into every turn (like a motorcycle or airplane), Mercedes-Benz engineers use its interplay of hydraulic, electronic and mechanical parts to significantly reduce body roll. An ABC Sport mode button on the center console can virtually eliminate roll if the driver prefers even sportier, flatter cornering.
The Best of Both Worlds - Handling and Comfort
ABC active suspension helps to solve the old tradeoff between ride comfort and handling precision. S-Class sedans and CL-Class coupes with ABC provide the same sumptuous ride comfort as with Airmatic air suspension, while simultaneously exhibiting crisper handling that surpasses many high-performance sports cars.
Four Lightning-Quick Hydraulic Pistons Are the Key
Mercedes-Benz’ ABC active suspension features four hydraulic pistons, one on top of each steel coil spring, as part of an integrated strut assembly. Located between the body and the springs, these pistons apply additional forces in response to split-second signals from the ABC computer. As a result, the pistons actually regulate the action of the springs in relation to incipient body movement, absorbing body vibrations with a frequency of up to five hertz. SL roadsters and AMG models come with modified ABC active suspension tailored for the crisper handling of high-performance cars.
One Computer, Four Control Valves, and 13 Sensors
A total of 13 sensors monitor body movement and vehicle level so that the ABC computer is supplied with new data every 10 milliseconds. This sophisticated system senses body movement just as it begins, and makes adjustments accordingly. Two sensors at each end of the car (one on each wheel) measure vehicle level, while nine sensors - mounted strategically on the vehicle body - detect vertical and transverse body movement. Data from these sensors is processed every 120 milli-seconds by the microprocessor to compute signals for operating hydraulic valves that control each of the four hydraulic pistons atop the springs.
High Hydraulic Pressure Gives Fast Response
A special engine-driven hydraulic pump generates 2,840 pounds per square inch of oil pressure, which helps ensure that the four servos operate within a few milliseconds. The system checks and re-checks itself every 10 milliseconds.
An accumulator, or pressure reservoir, at each end of the car keeps pressurized oil ready, so that the energy for split-second damping and springing is always available, and an oil cooler maintains the right operating temperature in the system.
Stabilizer Bars Not Needed
ABC active suspension handles low-frequency body movements of five Hertz or lower, which means that stabilizer bars are no longer necessary. However, higher frequencies are absorbed by conventional gas shock absorbers and steel coil springs. Although Mercedes engineers tested broader frequency ranges, their energy requirements were best balanced by the five Hz system.
Crosswind Stabilization Feature
Cars with active suspension come with a crosswind stabilization feature that’s part of the ABC system software. If the car is affected by a crosswind, in a split-second, the system uses its suspension servo pistons at each wheel strut to change wheel load distribution and stabilize the car. The ABC crosswind stabilization feature depends on networked signals from the ESP yaw and lateral-accelerations sensors.
Twenty Years of Hard Work Pays off
Mercedes engineers built and tested the first active suspension early in 1978, but the digital control technology they needed did not yet exist. They tested the first research vehicle with active suspension in 1987, and two years later, another version was developed for the Mercedes Group C racecar.
Although this low-frequency system made its debut in the 1991 C11 race car, its use was blocked by new Group C regulations. That same year, this active suspension system appeared on the V12-powered C112 concept car. An early version of ABC active suspension made its debut in 1996 at the Hanover Show on a special prototype for the Mercedes-Benz 0404 high-deck bus.
