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How does anti-lock braking system (ABS) work?

ABS System

Before giving advice on how to brake with ABS, need to understand, what it is the actual anti-lock system and what its purpose.

ABS and classical mechanics

When driving the vehicle wheels in constant contact with the road as part of its area, which is called the contact patch. Thus, the wheels (and thus the entire vehicle) during its movement constantly affects the force of static friction. Since it is no sliding friction, it prevents slippage of the wheel. Therefore it is logical to stop the car and use that static friction force, not the force of friction.

What happens when we press the brake pedal? The drive wheels are no longer blocked and the car to spin, they begin to act the force of sliding friction, which, though less than the above-mentioned friction forces, but it is enough on the road with a good, dry finish. But if the rain has passed, and the night was freezing, or under the wheels of your car is not asphalt but dirty primer? That sharp pressing a pedal you can easily send your car into a skid. It is to prevent this situation and there is a system of ABS.

The current system is a complex ABS Electrical «organism» consisting of three main elements:

A necessary condition for operation of the system ABS — brake pedal is depressed and at least one wheel locked. Once the speed sensor (one or more) signals that the wheel stops spinning, and it began to operate the power sliding friction, it eliminates the braking force, allowing the wheel to rotate, but at a slower rate, as the first deorbit burn a little time to pay off speed.

ABS is installed on the most produced cars

Once the wheel ceases to act on the braking force, it starts to rotate at a speed which again reads the sensor to a wheel hub, transmitting data to the control unit. That, in turn, to analyze it by a complex algorithm and found not sufficiently low, the brake pulse passes next to the wheel but chooses force so that inhibition produced on the edge of the lock, there is no full stop wheel. Powerful processor antilock time to read data from all the wheels of the car, and analyzing them, send a short brake impulses, trying to slow down the speed of the wheels without their full and sustained lock. In fact ABS — a system of pulse inhibition. Roughly the same brake experienced Formula 1 drivers or NASCAR, repeatedly pressing the brake pedal, so as not to deprive the car handling. However, even the most experienced riders have time to press the pedal is not more than 3-4 times per second, while the ABS makes it 10-15 times.

Applying ABS during hard braking

The standard anti-lock situation does not affect the braking distance — it is the same as for cars without ABS. Plus it is that the vehicle does not lose control and goes into a skid. Provided that the skid is caused by braking and not properly selected high-speed mode and a sharp turn of the steering wheel. But what if you want to apply the emergency brake? How ABS brakes with the risk of an emergency? On auto courses you probably warned by embedding the brake pedal to the floor, as this is what leads to skid. For vehicles with ABS about this rule is better to forget. As soon as you feel the need for heavy braking, immediately squeeze the stop brake and clutch pedals. Yes, don`t forget about the clutch, because it is necessary to completely eliminate from the engine braking.

Don`t try to use the brake pulsation — ABS will do it for you and better than you. Your task — as sharply as possible to press the pedal to the floor two or let them go to a full stop. At the same time, all you have to braking will be heard terrible gnashing — the result of the work of ABS — take it for granted. If you need to stay sharp, even on the icy pavement, then this should be done as sharply as possible, to the anti-lock system worked immediately and you will not lose control of the car. During braking, try to taxi himself, holding the vehicle on a slippery road and avoiding collisions. After all, this is the main advantage of ABS — it leaves you the ability to control the car.

When the ABS is useless?

It is important to not only know how to brake with ABS, but also be able to identify a situation where you can`t rely on the system, and therefore can only rely on their own strength and ability.

On rough roads ABS rather it becomes a hindrance, as it begins to operate with a certain delay. When releasing the brake pad occurs at the moment when the wheel is on the «approaching», respectively, when it lands, it travels for some time before it again starts to operate next brake pulse ABS. Roughly the same thing happens on the roads with mixed coating, for example on a partially icy or snow-covered road, where alternating sections of dry and wet asphalt, snow and ice. ABS just do not have time to react promptly to changing conditions, so it’s best to keep your distance and speed limits. On loose surfaces (sand, gravel) car with anti-lock brakes worse than without it. The point here is that the main role in the inhibition plays a shovel locked wheel shaft in front of him. In this case the ABS doesn`t occur and significantly lengthens the braking distance. Also, anti-lock doesn`t work, and at low speeds, typically below 7-10 km, so it pays to be careful on slippery slopes. In general, car owners experienced as they say, it’s best to avoid the triggering of ABS — so the most reliable!

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Дата: 07.07.15     Просмотры: 1303