ELECTRONIC STABILITY PROGRAM

To determine whether the car is responding properly to cornering commands, ESP® uses steering wheel angle, yaw (turning) rate and lateral acceleration sensors (combined into Dynamics Sensor). Using signals from these sensors, in addition to individual wheel speed sensor signals, the system determines appropriate brake and throttle actions. Once initiated, ESP® operates much like All-Speed Traction Control, except that the goal is directional stability. If the vehicle yaw response, or rate of turning, is inconsistent with the steering angle and vehicle speed indications, the ESP® system applies the brakes and, if necessary closes the throttle, to restore control. This occurs whether the vehicle is turning too rapidly (oversteering) or not rapidly enough (understeering).

HYDRAULIC BRAKE ASSIST

Brake Assist is programmed into the ESP® system. During a panic stop, a pressure sensor determines when the driver is doing so by measuring the brake pedal pressure application rate. A high rate of pedal pressure application causes the ESP® system to apply maximum available pressure to the brakes and the vehicle stops as quickly as available traction will allow.

TRACTION CONTROL

For information on the All-Speed Traction Control, (Refer to 5 - BRAKES - OPERATION).

ELECTRONIC ROLL MITIGATION

Typically when a vehicle makes a sudden turn, the outside wheel takes the majority of the cornering loads. In order for the vehicle to make the turn, a significant amount of grip must exist at the tire contact patch. The additional body roll that occurs during this event places additional weight on this outside tire. These conditions, plus the lateral acceleration of the vehicle, combined with the center of gravity position in the vehicle can cause the vehicle to lift the two inside wheels in the turn and the vehicle rolls over the outside tire. Electronic Roll Mitigation (ERM) takes advantage of the principle that a tire in slip cannot handle cornering loads by building and applying enough brake pressure to intentionally drive the outside wheel into slip, not to the point of total lockup but close. As a result, the outside tire cannot support the cornering loads and the vehicle cannot maintain its original path. The new path is straighter, reducing the amount of lateral acceleration and transferring some of the weight back over to the inside tires, thus preventing a rollover.