Active suspension

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Active suspension is an automotive technology that controls the vertical movement of the wheels via an onboard system rather than the movement being determined entirely by the surface on which the car is driving. The system therefore virtually eliminates body roll and pitch variation in many driving situations including cornering, accelerating, and braking.

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.

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[edit] Methods

An onboard computer detects body movement from sensors located throughout the vehicle, and, using data calculated by opportune control techniques, controls the action of the suspension.

[edit] Solenoid actuated

Solenoids inside the dampers alter the flow of the hydraulic medium and therefore change the dampening characteristics of the suspension setup. The solenoids are wired to the controlling computer.

[edit] Hydraulic actuated

Hydraulically actuated suspensions are controlled with the use of hydraulic servomechanisms. The hydraulic pressure to the servos is supplied by a high pressure radial piston hydraulic pump. Sensors continually monitor body movement and vehicle ride level, constantly supplying the computer with new data.

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.

The drawbacks of this design (at least today) are high cost, and the added complication/mass of the apparatus needed for its operation. Thus it is only available on premium luxury cars. In addition, "semi-active" systems continue to advance with respect to their capabilities, narrowing the gap between them and fully active suspension systems.

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.

[edit] Electromagnetic recuperative

This type of active suspension uses linear electromagnetic motors attached to each wheel independently allowing for extremely fast response and allowing for regeneration of power used through utilizing the motors as generators. This comes close to surmounting the issues with hydraulic systems with their slow response times and high power consumption. It has only recently come to light as a proof of concept model from the Bose company, the founder of which has been working on exotic suspensions for many years while he worked as an MIT professor. His brainchild was only a strict set of ideas about the way an ideal suspension should behave until, after many years, he developed a unique algorithm for plotting suspension movements. Although many active suspensions have been proposed, the general consensus is that this approach has the most real world potential.[citation needed]

[edit] Magneto rheological damper

Main article: Magneto rheological damper

Another fairly recently developed method incorporates Magneto rheological dampers. Initially developed by Delphi Corporation, these dampers are finding increased usage in domestic and foreign brands, mostly in prestige vehicles.

In this system, the damper fluid contains metallic particles, and, 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. Thus, instead of modifying the vertical movement of the wheels, it modifies the damping characteristics of the shock absorber, controlling the behavior of the car. This type of system is generally referred to as "semi-active".

[edit] Production vehicles with active suspension

[edit] References