This technology allows car manufacturers to achieve a higher degree of both ride quality and car handling by keeping the tires perpendicular to the road in corners, allowing for much higher levels of grip and control.
Active suspensions can be generally divided into two main classes: pure active suspensions, and semi-active suspensions.
As the computer receives and processes data, it operates the hydraulic servos, mounted beside each wheel. Almost instantly, the servo regulated suspension generates counter forces to body lean, dive, and squat during various driving maneuvers.
In practice, the system has always incorporated the desirable self-leveling suspension and height adjustable suspension features, with the latter now tied to vehicle speed for improved aerodynamic performance, as the vehicle lowers itself at high speed.
Colin Chapman - the inventor and automotive engineer who founded Lotus Cars and the Lotus Formula One racing team - developed the original concept of computer management of hydraulic suspension in the 1980s, as a means to improve cornering in racing cars. Lotus developed a version of its 1985 Excel model with electro-hydraulic active suspension, but this was never offered to the public.
Computer Active Technology Suspension (CATS) co-ordinates the best possible balance between ride and handling by analysing road conditions and making up to 3,000 adjustments every second to the suspension settings via electronically controlled dampers.
Semi-active systems can only change the viscous damping coefficient of the shock absorber, and do not add energy to the suspension system. Though limited in their intervention (for example, the control force can never have different direction than that of the current speed of the suspension), semi-active suspensions are less expensive to design and consume far less energy. In recent times, research in semi-active suspensions has continued to advance with respect to their capabilities, narrowing the gap between semi-active and fully active suspension systems.
In this system, the damper fluid contains metallic particles. Through the onboard computer, the dampers' compliance characteristics are controlled by an electro-magnet. Essentially, increasing the current flow into the damper raises the compression/rebound rates, while a decrease softens the effect of the dampers.
Lotus active suspension pushes the racing envelope. (Lotus Engineering) (includes related article on the market for active suspension)
Dec 23, 1993; Replacing a simple spring-and-damper mechanism with a DSP-controlled actuator may at first sight seem an example of...
Active suspension test drive: riding on electrons. (driving the Infiniti Q45)(includes article on electric active suspensions)
Sep 01, 1990; ACTIVE SUSPENSION TEST DRIVE: RIDING ON ELECTRONS The Nissan proving grounds at Tochigi, Japan, have a particularly challenging...