ABS – Anti-lock Braking System
ABS stands for Anti-lock Braking System. The ABS is a safety system which prevents the wheels on a motor vehicle from locking while braking. The theory behind anti-lock brakes is simple – A skidding wheel has less traction than a non-skidding wheel. When a wheel is skidding, the tyre contact patch is sliding relative to the road, and when this happens the braking distance would be greater. By keeping the wheels from skidding while you slow down, anti-lock brakes benefit you in two ways: You’ll stop faster, and you’ll be able to steer while you stop. The benefit with the ABS is that it allows the tire to continue to interact tractively with the road surface, as directed by the driver’s steering inputs. In modern-day vehicles, ABS is coupled with another safety-system called EBD(electronic brakeforce distribution). This solution not only prevents wheel-lockup but also also electronically controls the front-to-rear brake bias.
Working
There are four main components to an ABS system – Speed sensors, Pump,
Valves, Controller. The controller monitors the speed sensors at all times. It is looking for decelerations in the wheels that are out of the ordinary. Right before a wheel locks up, it will experience a rapid deceleration.The ABS controller knows that such a rapid deceleration is impossible, so it reduces the pressure to that brake until it sees an acceleration, then it increases the pressure until it sees the deceleration again. It can do this very quickly, before the tire can actually significantly change speed. The result is that the tire slows down at the same rate as the car, with the brakes keeping the tires very near the point at which they will start to lock up. This gives the system maximum braking power. Skilled drivers practise a method of braking called ‘threshold braking’, which has the same priciple as that of the ABS. The driver applies just enough braking force to keep the wheels at the threshold of locking-up. More brakes would mean a skidding wheel, and at this point he would release the brakes slightly
and then apply them again. However, where a skilled driver can perform this engage-disengage funtion of his brakes about once each second, the ABS with it’s speed sensor and controller can do this about 20 times a second. In fact, on slippery surfaces, even professional drivers can’t stop as quickly without ABS as an average driver can with ABS. During panic braking a car which has ABS brakes, the driver can feel a pulsing in the brake pedal. This is normal, as it is just the ABS kicking-in to release the wheel that has locked-up. The driver need not pump his brake, and simply needs to apply the brake pedal firmly and hold it while the ABS does all the work.
Disadvantage
In low-traction surfaces such as gravel, sand and deep snow, ABS tends to increase braking distances. On such surfaces, locked wheels tend to dig-in and would stop the vehicle more quickly. ABS would prevent this digging-in of the wheels and thus, increases braking distances. Some manufacturers provide an off-road button, which would turn ABS off. This seems a good solution around this problem.
ABS was widely believed to be a breakthrough as far as safety features of an automobile was concerned. However, it has been found that ABS enabled vehicles do get involved in road accidents. There are talks that ABS tends to create a false sense of security in some drivers, who may drive more aggressively. Also, ignorance about the system may lead to some drivers pumping the brake pedal when they feel the ABS pulsating, eventually leading to increased braking distances. These could be some of the reasons for an ABS-enabled vehicle to be proving to continue being susceptible to mishaps. However, there is no denying the fact that ABS does reduce braking distances, and that the system is a piece of engineering excellence.
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