OVERSTEER VIDEO

Electronic Stability Control(ESC)

INTRODUCTION ABOUT ESC

The Electronic Stability Control (ESC) is an active safety system for vehicles, and was launched into the market in 1995. ESC is designed to help drivers maintain control of their vehicles in critical situations. All active safety systems are based on the pioneering ABS technology, which was launched in 1978. In critical driving conditions, the wheels of a vehicle may lock during braking, reducing the adhesion between tires and the road surface. This may mean that the vehicle becomes uncontrollable, since the vehicle no longer reacts to the steering input of the driver. In a vehicle equipped with ABS, wheel-speed sensors detect the speed of rotation of the wheels and relay this information to the ABS control unit.

The Electronic Stability Control ESC integrates the functionalities of the ABS and TCS, but has the added feature of a “yaw torque control” – a functionality that prevents skidding. It is designed to help drivers maintain control of their vehicles in sudden maneuvers such as rapid steering and countersteering, sudden lane changes, and obstacle-avoidance maneuvers.

                                       Fig. 1.  Installation of the  ESC components

THE MAIN POINT WHY WE USE THIS SYSTEM

             When a vehicle cornering or steering, there is possibility to oversteer and understeer that will cause accidents. In other cases, the vehicles prone to yaw and the driver will commit loss of control. The invention of Electronic Stability Control will help minimize this loss of control.

                                   Figure 2. oversteer cause the rear tyre lose traction

                                  Fig. 3. Oversteer effect on the vehicle with no ESC

                                  Fig. 4. Accident that may be cause by understeer

             2.1     BASIC CONCEPT OF ELECTRONIC STABILITY CONTROL

Electronic stability control (ESC) is a computerized technology that improves the safety of a vehicle's stability by detecting and minimizing skids. When ESC detects loss of steering control, it automatically applies the brakes to help "steer" the vehicle where the driver intends to go. Braking is automatically applied to individual wheel, such as the outer front wheel to counter over steer or the inner rear wheel to counter under steer. Some ESC systems also reduce engine power until control is regained. ESC does not improve a vehicle's cornering performance, it rather helps minimize the loss of control.

 2.11    THE PRINCIPLE OPERATION OF ESC

During normal driving, ESC works in the background and continuously monitors steering and vehicle direction. It compares the driver's intended direction (determined through the measured steering wheel angle) to the vehicle's actual direction (determined through measured lateral acceleration, vehicle rotation (yaw), and individual road wheel speeds).

ESC intervenes only when it detects loss of steering control, i.e. when the vehicle is not going where the driver is steering. his may happen, for example, when skidding during emergency evasive swerves, understeer or oversteer during poorly judged turns on slippery roads, or hydroplaning. ESC estimates the direction of the skid, and then applies the brakes to individual wheels asymmetrically in order to create torque about the vehicle's vertical axis, opposing the skid and bringing the vehicle back in line with the driver's commanded direction. Additionally, the system may reduce engine power or operate the transmission to slow the vehicle down.

In fact, this led to some concern that ESC could allow drivers to become overconfident in their vehicle's handling and/or their own driving skills. For this reason, ESC systems typically inform the driver when they intervene, so that the driver knows that the vehicle's handling limits have been approached. Most activate a dashboard indicator light and/or alert tone; some intentionally allow the vehicle's corrected course to deviate very slightly from the driver-commanded direction, even if it is possible to more precisely match it

ESC does not increase traction, so it does not enable faster cornering (although it can facilitate better-controlled cornering). More generally, ESC works within inherent limits of the vehicle's handling and available traction between the tires and road. A reckless maneuver can still exceed these limits, resulting in loss of control. For example, in a severe hydroplaning scenario, the wheel(s) that ESC would use to correct a skid may not even initially be in contact with the road, reducing its effectiveness.