TRW Advances Vehicle Safety With Active Roll Control

    LIVONIA, Mich., Aug. 7 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.
    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.