New-generation chassis technology from BWI Group

  • 09-Apr-2010 05:41 EDT
BWI 4-10 ASBS Actuator OLD-NEW.jpg

Old and new: BWI Group's compact Active Stabilizer Bar System sees the use of new architecture (bottom) that reduces system weight by about 30%.

The generation game is a familiar part of automotive engineering development. Now, suspension and braking specialist BWI Group has announced the third generation of its MagneRide, with a two-wire dual-coil (TWDC) actuation system, a new ECU (electronic control unit), and new control algorithms together with other changes to improve the dynamic range and speed of system response.

Generation 3 MagneRide has also been developed for use with SUV chassis together with a new version of its Active Stabilizer Bar System (ASBS), described as incorporating a “unique architecture.”

Late last year, BWI (Beijing West Industries) Group acquired Delphi’s Chassis Systems business, encompassing its product portfolio global technical centers, manufacturing facilities, and customer support centers. R&D for MagneRide Generation 3 was carried out in the U.S. and particularly in Europe, where it is seen by the company as being apposite for European market expectations and road conditions.

Generation 2 MagneRide is already fitted to European models, including Audi’s TT, R8, and A3, and Ferrari’s 599 GTB Fiorano, California, and 458 Italia.

A further application of the technology is an active powertrain mount. Designed to obviate compromise between control of the powertrain mass and isolation of powertrain-related NVH, it is available on the Porsche 911 GT3 and Turbo and standard on the RS.

MagneRide technology was acquired by BWI in November 2009 as an important element of Delphi Chassis Systems’ products, with Generation 3 as a significant advance on the previous two.

“We are now very close to completely eliminating the need to compromise between ride quality and dynamic ability,” said Olivier Raynauld, BWI’s Manager, Forward Engineering Controlled Suspensions, based at the company’s Paris facility. He added that the enhanced Generation 3 MagneRide did not bring any increases in packaging or weight.

Basis of the MagneRide system involves the use of fixed orifice dampers with a magneto-rheological damper fluid. Electric coils around the orifice when energized cause magnetically soft particles in the fluid to attract each other and increase the resistance to flow, responding to inputs from sensors that monitor body and wheel motions plus driver inputs.

The use of two smaller coils to replace the original single coil in each damper is combined with the application of a new, bespoke ECU and optimized control algorithms. The system provides what Raynauld terms a quicker “current off” performance for a faster transient response; it also allows a broader spectrum of dynamic range from soft to hard, improving comfort and handling. The authority of the anti-roll bar and springs can be reduced, again improving ride and handling.

For application to SUVs, it was necessary to increase the system’s resistance to side loads, with uprated seals and bearings.

The latest, compact ASBS sees the use of new architecture that reduces system weight by about 30%. Again, it is SUVs that can benefit. Regular stabilizer bars may restrict wheel travel and compromise off-road behavior with accentuated passenger “head toss.”

The BWI ASBS helps reduce the effect. The system incorporates an anti-roll bar split in the middle with a computer-controlled actuator placed at the intersection of the two sections, which applies a variable level of torque as required. In the cruise on straight roads, the system is quiescent to provide optimal comfort, but when a corner is entered roll-stiffness automatically increases as torque is applied. The new generation—to be fitted to a production vehicle in 2012—uses a twin-channel architecture (suitable for both linear and rotary actuators), linking the control of front and rear roll stiffness designed to provide real-time control of understeer or oversteer tendencies.

BWI states that it has eliminated a known tendency of pressurized actuators to suffer a discontinuity—or dead band—around the center position. Said Raynauld: “Existing systems control the flow of fluid between two sides of an actuator. We control the pressure difference between the two sides, thus avoiding a discontinuity at the central position.”

The system has been designed to deal with all vehicle roll and velocity inputs, leaving the springs and dampers to counter only vertical inputs.

Experience in a high center-of-gravity Land Rover Range Rover Sport development vehicle with Generation 3 MagneRide and ASBS demonstrated to this AEI Editor the potential effectiveness of the system in reducing roll and enhancing general handling “sharpness” without degrading ride quality.

Philippe Germain, System Engineering Manager at BWI’s Paris facility, explained: “The current Range Rover Sport has a single-channel valve block so torque distribution between front and rear is fixed. On the Generation 3 with two-channel, we can change distribution between front and rear. At low speed, there can be more balance on the rear for added agility. In a lane-change maneuver, we can put more torque on the front to stabilize the car. This is similar to ESP but does not use the brakes. We also have a comfort feature on the car and can measure roll oscillation and apply torque to counter it. It also changes the steering feel. SUVs offer a very good application for the systems.”

Shougang Corp. has 51% of the equity in BWI Group. Fangshan District, an area of Beijing, has 25% via its Beijing Fangshan State-Owned Assets Management Co. Ltd., and Bao'an Investment Development Co. Ltd., with 24%.

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