Next-Generation Stabilitrak With Active Front Steering Makes Debut On 2008 Cadillac STS

Source: GM Media
May 4, 2007

DETROIT - StabiliTrak® 3.0, the third generation of General Motors' electronic stability control system, will make its debut on the 2008 Cadillac STS luxury performance sedan.

This latest generation of StabiliTrak - first introduced a decade ago on the Cadillac Seville - incorporates active front steering (AFS) technology and will be available on V-8 all-wheel-drive-equipped models of the STS.

In addition to controlling brakes and reducing engine power, StabiliTrak 3.0 with AFS incorporates a steering motor assembly combined with computer-driven electronic controls that independently measure wheel slippage at all four wheels during acceleration, braking and adverse road conditions.

As a result, when a vehicle's rear wheels lose traction, the AFS system turns the front wheels into the skid - exactly as a trained driver would - to help prevent a loss of control.

For example, if a driver experiences a skid or slide because of poor road conditions, the active steering will react to information from StabiliTrak's yaw rate sensors to modify the steering angle of the front wheels to stabilize the vehicle. This occurs must faster than the driver can react, and if the active steering wheel angle is not enough, other stability control systems - such as braking and engine control - intervene to help.

The AFS technology incorporated on StabiliTrak 3.0-equipped versions of STS also continuously varies the steering ratio (the degree that wheels turn in response to the steering wheel), based on vehicle speed in a range from 12:1 to 20:1.

In turn, vehicles equipped with StabiliTrak 3.0 require fewer steering wheel turns in low-speed parking maneuvers, and the technology makes high-speed driving more relaxing because it is less sensitive to smaller "twitch" inputs. The variable ratio capability of AFS is different from variable assist power steering, which only varies the amount of steering effort, not the actual steering ratio.

In addition to AFS, StabiliTrak 3.0 incorporates multiple chassis control systems, including those for anti-lock brakes (ABS) and traction control (TCS); Magnetic Ride Control (MR) dampers; and inertial and steering sensors. All work together via a GM-proprietary supervisor control module.

StabiliTrak uses its network of sensors to continuously monitor the vehicle's movement and driver's actions, measuring cornering forces, gas pedal movement, brake pedal pressure and how many degrees the steering wheel has been turned, along with other considerations.

Using the data gathered, StabiliTrak takes measures within milliseconds to keep the vehicle from under- or over-steering, as needed. Such measures can include closing the throttle to reduce vehicle speed, applying brakes independently, or - as a result of AFS - modifying the steering angle of the front wheels.

In addition to StabiliTrak 3.0 with AFS, the 2008 Cadillac STS incorporates a host of technology enhancements, including a new, SAE-certified 302-horsepower (225 kW) 3.6L V-6 VVT engine with direct injection as standard equipment; a new Lane Departure Warning System; and a new radar-based Side Blind Zone Alert System.

The 2008 STS is expected to be available in June. The StabiliTrak 3.0 technology will be available after the start of production.