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Electronic Stability Control

Electronic Stability Control

By Jeff Youngs, February 24, 2012
In the early days of the automotive industry, stability meant keeping the vehicle upright and the passengers comfortable. Engineers spent decades working out ride and handling compromises to develop suspensions that effectively control thousands of pounds of automotive steel, rubber, and glass when in motion.

As vehicle suspensions and roads have become much more refined, the term "automotive stability" has evolved to mean something very different. Today, stability refers to keeping drivers in control and ensuring that the vehicle remains on the road through all types of maneuvers, planned or otherwise. Engineers developed Electronic Stability Control (ESC), a technology designed to help keep the vehicle stable and on the road, regardless of conditions or steering inputs from the driver.

Computers keep your vehicle on the correct path

Technically, ESC is a computerized system that regulates hydraulic and mechanical components on the vehicle to assist driver control. The system works full time, requires no driver interaction, and is completely transparent to the driver-until it is needed.

Sudden steering wheel inputs on ice or snow, on dirt or gravel roads, or even during emergency avoidance maneuvers, can immediately put your vehicle in an unstable state-a condition where it is nearly uncontrollable. In these circumstances, without an ESC system or expert driver training, your vehicle would be nearly impossible to keep on the road.

With ESC, the driver will feel the loss of control only momentarily. Within fractions of a second, the system will automatically regulate the brakes and/or throttle to bring the vehicle under control. Though the vehicle may have slowed, the system will remain working until the driver has regained control. Some systems can even engage the anti-lock brakes or steer the front wheels, without driver input, to maintain vehicle control.

Technology built on ABS and traction control

Following the modern development of automotive anti-lock brakes (ABS) in the 1980s, and traction control in the 1990s, the development of stability control was the next logical progression. All three share the same technology, and all operate in conjunction with one another in an automotive environment.

In a typical electronic stability control system, the anti-lock brake system monitors wheel spin at each wheel. The traction control system controls any wheel spin. As both of these sensors monitor the vehicle's longitudinal (front-to-back) movements, a third sensor monitors lateral (side-to-side) movements, determining if the vehicle has strayed from its intended course, as indicated by the position of the steering wheel. For more precision, and redundancy, additional sensors monitor vehicle speed, steering wheel angles, and yaw (how the vehicle turns on its vertical axis).

During normal driving, all of the sensors report vehicle data to a high-speed microcomputer onboard the vehicle. By comparing steering wheel angle (which indicates where the driver wants to go) to the data readings (that indicate where the vehicle is actually going), the computer is able to determine if the vehicle is under control, or if it has entered an unstable condition such as a skid or uncontrolled slide, for example.

If ESC determines the vehicle is experiencing a potential loss of direction, it immediately, and selectively, controls throttle and/or braking in an attempt to bring the vehicle under control. The electronic stability control system can react faster, and is far more capable, than any driver, as it can control braking at each wheel independently of one another.

Do you need Electronic Stability Control?

Electronic stability control is an active safety feature; it helps you 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. An ESC system will recognize this impending situation, even before the driver can take evasive action, and take corrective action before vehicle control is lost.

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. These are also scenarios where ESC could prevent a serious accident.

Electronic stability control is often bundled with anti-lock brakes and traction control as part of a vehicle stability option package. As all three share the same technology, ESC is an important addition to a comprehensive active safety package.
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