TRW Chassis Systems has developed the Active Roll Control (ARC) system in a bid to reduce the risk of rollover accidents in motor vehicles.
TRW developed ARC in response to US federal requirements under the Transportation Recall Enhancement, Accountability, and Documentation (TREAD) Act.
The TREAD Act imposes various requirements for automobile, tyre and automobile parts manufacturers, including a requirement for the National Highway Traffic Safety Administration (NHTSA) to develop a dynamic rollover test.
The ARC system is, according to TRW, one that allows the vehicle dynamics engineer to achieve both good ride and handling.
Its design allows both improved ride for single wheel bump inputs and eliminated body roll angle, depending on the severity of the lateral forces.
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.
The ARC system is said to combine steering and braking technologies with additional sensors, including a lateral accelerometer, steering angle sensor, along with other sensors that already exist on many vehicles, and an actuator at one end of both the front and rear stabiliser bars. During handling manoeuvres, 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 stabiliser 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 stabiliser 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 said to be 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.