Audi’s Mechanical Active Suspension – Dynamic Ride Control

The Audi RS 6 is the first model to be equipped with the innovative suspension concept Dynamic Ride Control (DRC). It denotes a special damping system which counteracts movements of the vehicle along its longitudinal axis and transverse axis. Both shock absorbers on the same side of the vehicle are connected with the diagonally opposed dampers on the other side, each by means of one central valve.

When a corner is taken, a flow of oil and thus a supplementary damping force is generated via the central valve between the diagonally opposed shock absorbers. When the suspension is compressed on one side, the damper characteristic is modified in such a way that rolling or pitching movements are almost entirely eliminated. As a result, this alert, mechanically active damping system ensures that the RS 6 maintains extremely good tracking stability when cornering and responds precisely to adjustments of the steering wheel, without the use of electronics.

 

I think I'm missing something. If it works how you are describing than the corner of the car with the most load is pumping its fluid to the opposite corner of the vehicle. If that were true it would act like a hydraulic pump and increase the the amount of roll allowed. I might take the time to check it out on my own but if you can offer a better explanation I would appreciate it.

On this same "best suspension" topic I think that GM really has a great thing with their Magnetic Selective Ride Control, if your unfamilar it uses a fluid within the shock that changes viscosity when an electric current is introduced. It has earned great praise everytime someone has spoke of it. It was actually joked about that you could toggle between settings as you circulate the track to match the desired amount of damping necessary.

 

This technology was DIRECTLY copied from the Corvette.

Read about the Corvette (I think it's the Z06 only) suspension and you'll see what I mean.. total ripoff

And even after all that suspension work btw... it still lost out to the M5 in the recent comparo tests by more than a handful of mags

 

The Corvette's suspension uses electro magnetic responses to wheel travel. I would think this would be considered superior to a somewhat sloppy hyrdaulic pump system.

Kudos to Audi though for looking into bettering an already terrific car. I don't think Audi's solution will make it into more mainstream applications, mostly due to weight and complexity. The system used for the Vette is also being used on the new Cadillac XLR roadster (which is to be built on the same platform in the Bowling Green plant). I could see GM looking to improve handling of it's large SUV's (Escalade in particular) and trucks with this type of system.

 

Herc, its only available on the 50th anniversary edition now but will find its way onto the C6 and the XLR when they debut.

 

GM's Magnetic Ride Control is a complete, stand-alone vehicle suspension control system that uses innovative magneto-rheological fluid-based actuators, four wheel-to-body displacement sensors, and an onboard computer to provide real-time, continuous control of vehicle suspension damping.

The system responds in one millisecond to provide superior ride, handling and control on even the roughest road surfaces. The active suspension offers an expanded range of soft-to-firm damping capabilities and helps maintain the maximum amount of tire patch in contact with the road. On bumpy or slick surfaces, the system integrates with traction control to assure maximum stability. It also works with ABS to keep the vehicle balanced and poised. It is the only system without electro-mechanical values and no small moving parts.

Magnetic Ride Control offers greater roll control and handling during transient maneuvers, and helps reduce noise and vibration. This new technology helps reduce the traditional tradeoff between ride and handling, and responds 5 times faster than previous real-time damping systems. In addition, greater reliability is possible with its simpler design.

Magnetic Ride Control is superior to the traditional suspensions and the real-time-damping systems found in other high performance vehicles that use an electromechanical valve to control hydraulic pressure for shock damping. Engineers at GM R&D labs, and later with experts at Delphi Automotive Systems, explored ways to reduce or even eliminate the inherent restrictions of valve-based damping systems. MRC is more advanced than the Lotus active suspension.

Suspension engineers developing vehicles with Magnetic Ride Control can spend their time adjusting the algorithms that control the damping responses on a computer, and are enabled to fine-tune ride and handling characteristics to unprecedented levels of specificity. As a result, drivers will notice better ride quality, less body roll and improvements in overall handling.

 

The dampers are filled not with standard oil but with magneto-rheological (MR) fluid. This is a synthetic oil with millions of tiny iron ***** suspended in it. These iron ***** have a proprietary coating to make them less abrasive and help them float evenly within the shock fluid.

More important, they react to a magnetic field generated by an electric coil on the shock piston, thereby changing the fluid's viscosity. Increasing the power (up to 5 amps) thickens the fluid as it goes though a small electro-magnetic ring. These shocks don't contain conventional valves.

When the core is energized, and magnetic flux is present, the iron particles become magnetically attracted to the walls and to each other, knitting the fluid into a composite matrix. Flow is limited because the magnetic bonds must be sheared. Now, the motion of the tire can be resisted by a very strong damper force, which is proportional to the electric current in the core.

"It can go from no damping to solid almost instantly," says Tadge Juechter, assistant chief engineer for Corvette. "The only question is do you have the computational power to keep up?"

A dual-processor computer adjusts the current about 1000 times per second based on wheel travel and speed, vehicle speed, steering-wheel angle, lateral acceleration, brake application, and also temperature. At 60 mph, that's an adjustment with every inch of the Corvette's forward travel. The goal of these adjustments is to keep the Corvette on a smooth, even keel while maximizing the contact of the tires with the pavement.

 

This technology, developed by GM Research and Delphi, is called Magnetic Selective Ride Control, or F55. A version of it is already found in the '02 Cadillac Seville STS, and MSRC will be fitted to the upcoming XLR roadster. A rotary switch on the console allows the driver to select Tour and Sport modes. Corvette engineers told us that the Sport setting is strictly for ultra-smooth racetracks. On Germany's bumpy, challenging Nurburgring circuit--an increasingly popular suspension-development venue--they report that the F55-equipped Corvette is actually quicker in the Tour mode.

We drove base-suspension, F51-sport suspension, and F55 MagneRide-equipped Corvettes back to back on a brutal durability loop at GM's Michigan Proving Ground. On corduroy-like-surfaced bends that had the standard cars going wide of the cornering line and activating their stability- control systems, the magnetic-ride Vette happily carved clean arcs. It glided across 100-mph bumps that had the regular underpinnings rebounding awkwardly at the top and bottom of suspension travel.

The F55 suspension will be standard on 50th Anniversary models and optional on all other Corvettes (except the Z06). It's estimated to cost around US$1500.

 

... did you C+P that off of SPEED's webpage?? i coulda sworn i heard the exact same thing on a Motorweek/Motor Trend/Autoweek show sometime last summer, on SPEED channel.

anyhoo, that's all well and good, but these fancy-dancy systems are heavier (and obviously more expensive) than your lower tech spring+shock system. where i think the greatest gains are made is in the design of the controlling members, although these neato bump-smoothers are pretty cool.

... look to F1 though. had they still the rules which allowed Active Suspension systems, i doubt Ferrari would opt for it, given the incredible stregth, reliabilty, flexibility, adaptability, and super light mass of their control-blade systems. well, alright, i s'pose that they'd try for something like GM's F55 system, but certainly nothing more than that... the way in which the wheels track and respond to motion has probably a greater effect on the characteristics of a car than it's absorption system.

 

Current Formula 1 cars use torsion bar suspension, which is not practical for a road car's long wheel travel. A better area to look is FIA rally cars.

Ten years ago, F1 active suspension was based on high pressure (3000 psi) hydraulics. It was complex and absorbs engine power.

GM's MRC combines the advantages of active suspension with low cost, low weight and simplicity.

 

no, current F1 designs aren't exclusively torsion bars, which are used in leiu of springs and dampers: Jordan, um, a few others used this system in the front end of their car, whilst Jaguar and a few other teams opted for "Penske" type spring+shock combos in the front. coil springs and shocks are still used almost universally in the multilink systems at the rear of the cars (yes, even Ferrari). the control-blade system i was talking about is similar to the torsion bar system, except that the load bearing member provides the spring (there are sets of components designed to work optimally at a certain ride height, and provide some designed-in spring and damping effect through their flexion/compression).

yeah, those old active suspension systems were cool, but as you say, wouldn't fly anymore.

rally cars are neat, but overcomplicated, and oversophistcated for road cars, i believe.
but yeah, this variable damping system GM has is really really brilliant... too bad they can't build an engine, transmission, or chassis as innovative and great as this anymore :p

 

Praxis Air Suspension

“Bridgestone Corporation introduces the PRAXIS line of aftermarket suspension systems to the sport-compact market. This “first ever” aftermarket application of dual-rate air-spring technology provides the ability to adjust spring-rate, ride-height, and damping. With the simple “push of a button”, PRAXIS provides you the ability to choose between three fully engineered and tuned operating modes. Vehicle performance is transformed without resorting to the time-consuming and costly necessity of physically swapping-out parts.”

“PRAXIS, the advanced suspension system from Bridgestone has been engineered to provide a vehicle that is ideally suited to a wide variety of driving environments. Suspension components utilized in the PRAXIS system have been tuned to work harmoniously and to extract the most from the tire and from the vehicle itself.”

http://www.praxissystems.com

 

*tries, and fails, to suppress a snicker*

 

ok, went to the page, and it's not quite as bad as i first thought... every time i see/hear/speak the words "sport compact" i almost spontaneously chuckle or at least think to myself "supreme-cheezmo-snakeoil"...

anyhoo, bridgestone has actually enacted a pretty decent (small, but decent) program to optimize the system for different models (trucks, sedans, coupes) and suspension types in a few different conditions... of course, (even though it's obvious they're trying to convince you of it) they aren't spending millions making the system perfect for EVERY SINGLE CAR out there, and the system would certainly have downfalls (and incapabilities) right along with whatever advantages it could offer, it IS NOT as bad as i origionally thought...

neato find Super.
...just wish that the site had some real technical information, instead of pics of colourful computer simulation tests...

[edit] remember though folks, that it's only a dampening system: trick components like this can't make a leaf-sprung solid axle rear end compete on any level with a 6-link independant system...

 

If legal, active suspension would be the only suspension used in F1. The weight and power absorption penalties would be overcome easily by the two main advantages:

1. With active suspension there is no need to make a compromise setup. The suspension can be programmed to work well on low speed corners by maximizing mechanical grip (soft) and work well on high speed corners (aero grip) at the same time.

2. The main purpose for F1 active suspension was to optimize the aero characteristics of the car. At high speed these cars are basically aircraft flying upside down. Any bump or end load changes the pitch angle of the car. This changing pitch angle radically affects the aero grip. Active suspension eliminates the pitch changes.

I would say that the Caddy CTS is quite a good chassis. The LS6 engine is also quite a nice piece; small, light and low cost yet 405 hp. The C6 Corvette will be even lighter, have a smaller exterior and a larger interior. The C5 already compares well to it's competitors.

 

...well, i could see that there would be certain (very big) advantages at certain very varied circuits to this system, and i suppose the mass of the system wouldn't be a big problem for modern cars which are built well under the 600kg minimum and ballasted, but i'm just not so convinced that such complexity would be so well utilized... certainly the top teams would be able to extract more performance from it without too much worry or tradeoff (with regards to the bulkiness of the system: the variable dampers probably'd not be too much larger than the coilover/torsion bar systems they have now), but cost cost cost... hmmm... well, okay, there are big benefits over "statically" mechanical systems (how would you qualify the "normal" kind of suspention?? inactive?? ...doesn't seem right)... well, i guess in F1 they'd make it work. point taken.

you'd know better than me, but it's certainly not the best, and not the most sporting (Americanly biggish), either. it's just not for me.

that's true, certainly, about the LS-1... but there's the Ecotec: okay, but not great, and their 3.6 pushrod V6... ick-o-rama... and the NorthStar?? ugh, no thanks... i'll take the Ford.
but why should the biggest car company in the world with SOME of the best technology be finishing second, or even third, in the first place (with regard to OVERALL product quality and refinement)?? yeah, the Corvette is good, but it COULD BE so much better... people point to the C-5R, but looking at the competition offered (not another single MANUFACTURER effort to compete against) it's not a huge accomplishment IMO (as with the 2000-2002 Audi podium sweeps at Le Mans... good, but who's there to run against??)... my point is that they're performing under potential and aren't pursuing technologies which i think they ought to (ie: even some simple valve timing control). DOD is nice, but that's only to hold onto their SUV's and trucks, the only things they seem to make these days, instead of getting back to making passenger cars (that everyone should be driving instead, but that's not really the car maker's fault) that'll beat the imports on more than just price.

...sorry about the GM rant, i don't want the thread to go too far OT...

 

wait 'til grimace sees this. you are going to be so in trouble