Active Suspension Ban

From imaginary skyhooks to hydraulic reality: the actuator-driven evolution of vehicle dynamics.

Active suspension represented a pivotal technological leap in automotive history, utilizing onboard control systems to manage vertical wheel movement relative to the chassis. Unlike conventional passive suspensions that rely solely on springs and dampers, active systems employ actuators to independently raise or lower the vehicle at each wheel. This innovation allowed manufacturers to maintain a stable posture, keeping the chassis parallel to the road during cornering, accelerating, and braking. By virtually eliminating body roll and pitch variation, these systems significantly enhanced ride quality, traction, and steering control. The technology also found practical applications in commercial vehicles, such as buses, where it temporarily lowers the floor to facilitate passenger boarding.

Quick Facts

First hydraulic example year: 1954

Lore & Background

The theoretical foundation for active suspension is known as Skyhook theory. This concept envisions a vehicle suspended from an imaginary hook in the sky, maintaining a constant altitude unaffected by weight transfer or road irregularities. While an actual skyhook is impractical, real systems achieve this stability through actuator operations based on acceleration sensor data. The dynamic elements remain simple linear springs and dampers, yet they contact the ground differently than in normal suspensions to mimic the zero vertical acceleration line of the Skyhook model.

In practice, Williams Grand Prix Engineering brought this theory to the pinnacle of motorsport in 1992. Designer-aerodynamicist Frank Dernie devised an active suspension system for their Formula 1 cars that proved so successful it created a massive performance gap between them and competitors. The Fédération Internationale de l'Automobile (FIA) ultimately decided to ban the technology to level the playing field, ending Williams' dominance and marking a turning point where electronic control was deemed too advantageous for fair competition.

Reader's Guide

Active suspension systems are divided into two primary classes: true active suspensions and adaptive (or semi-active) suspensions. Adaptive systems only vary shock absorber firmness to match changing road or dynamic conditions, whereas true active suspensions use actuators to raise and lower the chassis independently at each wheel. Hydraulic actuation was the first method introduced, pioneered by Paul Magès at Citroën in 1954 with hydropneumatic suspension.

This system used a high-pressure radial piston pump and encased nitrogen to offer six times the compressibility of steel springs, though it struggled with roll stiffness control. Later developments included electronic actuation of hydraulic suspensions, such as Mercedes-Benz's Active Body Control introduced in 1999, which made up to 3,000 adjustments per second. Modern iterations include electromagnetic recuperative systems using linear motors for fast response and power regeneration, and the Audi active electromechanical suspension from 2017.

This system uses front camera data to predictively adjust travel before hitting bumps, directing motors to push or pull the suspension for flatter cornering dynamics.

Did You Know?

The first example of hydraulically actuated suspension appeared in 1954, developed by Paul Magès at Citroën.
In a theoretical Skyhook scenario where the damping coefficient reaches an infinite value, the vehicle would be completely fixed to the imaginary line and not shake.
Nissan's Full-Active Suspension system was capable of recovering motion energy to continuously balance the car.
Williams Grand Prix Engineering's active suspension was so dominant that the FIA banned it specifically to decrease the gap between their team and competitors.