ABS
ABS, also known as Anti-lock Braking System, is a system that prevents the wheels from locking while braking. Even if the driver heavily brakes, he can still maintain steering control of his car. The ingenious system prevents skids and keeps the wheel’s forward roll. It also allows the driver to maintain the lateral control of his car. Studies show that by using an ABS, the braking distance is shorter. However, drivers that have ABS on their cars must not feel over-secured because this system has his limitations.
Since it first appeared, in 1978, the Anti-lock braking system has been greatly improved. The last versions include the handling of other functions aside the main ABS function. These can be traction control, brake assist, and electronic stability control. The ABS version 8 weights only 1.5 kilograms (the first version weighted 6.3 kg).
How does it work? Well, the typical ABS is made out of a central electronic unit, four speed sensors, and two or more hydraulic valves mounted on the brake circuit. The electronic unit of the ABS monitors the rotation speed of every wheel. If it senses that one or more wheels are rotating much slower than the others (the wheel tends to lock) it actions on the valves to decrease the pressure on the braking circuit. This means that it effectively reduces the braking force on the affected wheel. The wheel will then start turn faster and when it turns too fast, the braking force is reapplied. This process is repeated continuously up to 20 times per second. This makes the brake pedal pulse feel.
On surfaces like bitumen or concrete, almost all ABS enabled vehicles tend to have a shorter braking distance. Even an experienced driver can find it very difficult to keep a car without ABS under control, using any techniques. However, in deep snow or gravel, the ABS increases the braking distances. If on these surfaces the wheel locks, it can dig into the snow and slow the car more. The ABS prevents the wheels from locking thus the wheel will not dig into the surface. Particularly on the snow, locked wheels gather a wedge of snow that helps slow the vehicle faster. On very slippery surfaces like ice, all the four wheels can block at the same time, defeating the ABS system which relies on detecting when independent wheels lock.
Because of the pulsing feel in the brake pedal, most drivers that are facing a dangerous situation for the first time tend to reduce the pedal pressure. Many of these drivers never experienced the feel of the ABS and they can panic. By reducing the pedal pressure, the braking distance will be longer. Because of this many manufacturers implemented a system called brake assist. This new system determines if the driver attempts a panic stop and it increases the braking force.
The ABS is widely used in conjunction with the traction control. If the car is accelerating fast some wheels tend to loose traction with the ground. This is where the ABS intervenes, and makes the wheels regain the optimum traction. Although the traction control system is mostly integrated in the ABS, many manufacturers sell it as a separate device.
Because the ABS system can save lives the proper functioning is of great importance. Most of these systems have some own monitoring features. If any failures are detected, the driver is noticed. To provide some redundancy, central control unit generally is made out of two microcontrollers. These are active at the same time and interact with each other. By checking each other’s proper working, the risks of a unnoticed failure in the ABS are greatly reduced. These microcontrollers are also power-efficient in order to avoid heating of the controller which would reduce durability. Even by using the best materials and the last type of software, the ABS intervention time is subject to mechanical limitations.
Overall, if you want to have an ABS system installed on your car, it is best to know how it helps you in tight situations and also what disadvantages it has. You must know exactly all the limitations of the ABS system before using it.