Understanding Electronic Stability Control
By Jeff Youngs, February 24, 2012
In simple terms, stability control is a computer-managed system that is designed to help the driver maintain control of a vehicle during sudden maneuvers. The technology is considered an "active" safety system because it is designed to help the driver avoid an accident. Sudden braking, throttle or steering inputs when traveling on slick surfaces,or during emergency avoidance maneuvers, can put a vehicle in an unstable state which can potentially result in a spin-out. Without stability control, the vehicle could be nearly impossible to keep on the road. With stability control, however, the driver will feel the loss of control only momentarily.
When sensors and software identify a loss of control, within fractions of a second the system will automatically begin to regulate the brakes and throttle in an attempt to bring the vehicle back under control.Throughout the process, the driver only needs to steer the car toward its intended direction of travel as the system will remain working until the person behind the wheel has complete control once again.However, stability control is not fail safe. If the car is violently heading off course, the driver is traveling at a high rate of speed, or the surface is particularly slick, stability control might not correct the situation. It can, however, work to mitigate whatever damage might occur from a loss of control even if it cannot fully correct the skid.
Technically speaking, stability control is a computer-controlled system that regulates hydraulic and mechanical components on the vehicle using sensors shared with the anti-lock braking system (ABS) and traction control system (TCS). With a typical stability control system, the ABSand TCS sensors monitor the speed of each wheel. Additional sensors monitor the vehicle speed, steering wheel angles, and yaw (how the car turns on its vertical axis). During normal driving, all of the sensors report vehicle data to a high-speed microcomputer. By comparing the steering wheel angle to the vehicle readings, the microcomputer is able to determine if the driver has the vehicle under control, or has entered an unstable situation (a skid or uncontrolled slide, for example).
If the stability control system determines the vehicle is experiencing a potential loss of direction, it immediately attempts to correct the problem by controlling the throttle and braking in an attempt to bring the vehicle under control (it does not control the steering wheel). In operation, the stability control system is far more capable than any driver. Not only does it respond faster, but it is able to control each wheel independently-a feat that is impossible from behind the steering wheel.
As an active safety feature, stability control helps the driver avoid an accident. In an emergency, even the most experienced drivers may find themselves in a situation where they are driving outside the normal limits of their vehicle and a loss of control is imminent. Black ice on the highway, a deer bolting across a dark road, an evasive maneuver to avoid another driver: these are all scenarios where a loss of control would be likely. A stability control system can recognize the potential of the situation, even before the driver can take evasive action, and take corrective action to possibly prevent a serious accident.
Stability control shares its technology with anti-lock brakes and traction control so it is often bundled in an option package including all three. While it is not yet required by law on passenger vehicles,stability control is an integral part of any comprehensive active safety package and is a worthwhile option that can prevent accidents and save lives.
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