TRW's New Active Roll Control Improves Vehicle Safety

Tuesday August 07 by Press Release Submission
Livonia, MI - Many news reports highlight motor vehicle rollover accidents with a focus on vehicles with high centers of gravity, such as Sport Utility Vehicles (SUVs) and minivans. Anticipating elevated safety concerns, TRW Chassis Systems has developed its Active Roll Control (ARC) system to help reduce the risk of rollover accidents.

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With its innovative ARC technology, TRW is poised to assist vehicle manufacturers meet anticipated U.S. federal requirements under the Transportation Recall Enhancement, Accountability, and Documentation (TREAD) Act, which was signed by President Clinton on Nov. 1, 2000. The TREAD Act imposes various requirements for automobile, tire and automobile parts manufacturers, including a requirement for the National Highway Traffic Safety Administration (NHTSA) to develop a dynamic rollover test.

"TRW's ARC system is an effective safety feature, improving roll stability of high center of gravity vehicles," said Phil Cunningham, product director, chassis control, TRW Chassis Systems. "TRW has been a safety system solution provider for many years, researching and producing answers to address safety concerns. TRW's ARC system can help vehicle manufacturers address the legislative requirements of the TREAD Act, including the new dynamic rollover testing standard."

The TRW ARC system is one that allows the vehicle dynamics engineer to achieve both good ride and handling. Due to the increasing need for such a system, TRW is currently in negotiations for development contracts with several vehicle manufacturers in Europe and North America.

For many years, vehicle dynamics engineers have struggled to achieve a compromise between vehicle ride and handling and the results of this are clear in the vehicles we see on the roads today. At one end of the spectrum are large sedan and luxury cars with excellent ride qualities, but only adequate handling behavior. At the other end of the spectrum are sports cars with very good handling but a very firm ride quality. In between the two there are any number of variations dictated by the world's vehicle manufacturers and target customer needs. TRW's ARC system offers many of the advantages of a fully active suspension system at a fraction of the cost. Its unique design allows both improved ride for single wheel bump inputs and eliminated body roll angle, depending on the severity of the lateral forces.

TRW's ARC system utilizes the same advanced technology that TRW employs in the design and manufacture of its anti-lock braking and steering systems. This unique advantage gives TRW the ability to offer its ARC system at an extremely competitive cost, with the same functionality of its other advanced systems. This advantage enables the benefits of ARC to be realized on a greater number of vehicles.

How does it work?
Vehicles lean when cornering due to the weight transfer imposed by lateral acceleration acting on the suspension. Factors contributing to the roll angle of the vehicle include vehicle height and suspension stiffness. TRW's ARC system uses hydraulic and electronic technology to reduce or eliminate the vehicle roll angle in cornering, which improves handling. This improvement to vehicle handling can help reduce rollover risk. The ARC system combines typical steering and braking technologies such as pumps and pressure control valves with additional sensors, including a lateral accelerometer, steering angle sensor, along with other sensors that already exist on many vehicles today, and an actuator at one end of both the front and rear stabilizer bars.

During handling maneuvers, the accelerometer and sensor sense the roll force created by the cornering of the vehicle. The actuators then apply an offsetting force to the end of the stabilizer bar to reduce roll angle and assist the vehicle in maintaining a stable operating condition. These actuators are effectively inactive during normal vehicle operation to allow for a softer ride.

In straight-ahead driving, the stabilizer bar is free to move with wheel motions up to the stroke of the actuator. Since no pressure is generated in the actuators, the bar is, in effect, disconnected. In this condition, the ride of the vehicle is markedly improved, with little or no "head toss" and better single wheel bump performance. In addition, axle articulation is also improved for off-road use. Benefits With ARC, vehicle dynamics engineers can improve both vehicle ride and handling, rather than trading off one to achieve the other, and provide a greatly improved solution in both areas. Benefits of this will be:

* Improved ride comfort, particularly for high center of gravity vehicles, such as SUVs and minivans

* Elimination of "head toss" during straight ahead driving, reducing driver fatigue and increasing ride comfort

* Improved single wheel bump ride performance

* Improved passenger comfort due to reduced lean in cornering

* Improved vehicle handling by reducing lag between driver steering demand and vehicle response * Improved driver control by improving roll damping, reducing roll overshoot

* Increased grip on independent suspensions by improved tire adhesion to road

In addition, by combining TRW's ARC expertise with other TRW technologies in steering and braking, TRW is able to demonstrate higher levels of performance and cost otherwise unrealized by the individual systems. Ultimately, this combination of advancements forms the basis of TRW's Integrated Vehicle Control Systems of the future. These systems will offer drivers unprecedented levels of improved vehicle control which is the ultimate aim of TRW's active safety systems.

TRW Chassis Systems is a world leader in braking systems, steering and suspension systems, commercial steering, engine components and aftermarket replacement parts for the global automotive industry.


TRW Inc. (NYSE: TRW) provides advanced technology products and services to the automotive, aerospace, telecommunications and information technology markets worldwide. TRW, which is celebrating its 100th year of operations in 2001, had 2000 year-end sales of $17.2 billion. For more information, visit http://www.trw.com .

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