ABS braking system. Anti-lock braking system ABS

29.06.2020

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What is emergency braking?

Dedicated to Tinsmith's Day :)

Once in late autumn, when the thermometer was jumping in the plus during the day and minus at night, Masha was returning from work late in the evening. There was a stretch of road a few hundred meters from her house...

Winter surprises or how does the day of the tinker come about? (Real story)

Once in late autumn, when the thermometer was jumping in the plus during the day and minus at night, Masha was returning from work late in the evening. A few hundred meters from her house, there was a stretch of road with a slight incline followed by a 90-degree turn.

According to the law of meanness, it was in this place that the roadway was not sprinkled with reagent that evening, and the shiny wet asphalt under the wheels turned out to be frozen. In addition, the icy surface of the slope before the turn was polished by previously passing cars, which made it slip even more.

But Masha found out about this later, when on this very hill, out of habit, she began to slow down by smoothly pressing the brake. The car slowed down a little, but despite the studded tires, it did not think to stop. Masha pressed the middle pedal even more. Does not help. And here, as for evil, there is also a twist. And what an obsession! The car treacherously drove straight, despite the steering wheel twisted to the side ...

It was the first car for an extreme situation on the ice. She hasn't been out in the winter yet.
My friend still drove to her house that evening, but with a tattered front bumper, a crushed fender and a broken headlight. And the pillar standing alone at the end of the turn was carelessly marked with a silver abrasion.

“I knew how to slow down properly!” she repeated over and over...

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How to slow down in a critical situation?

Sometimes the situation on the road changes so suddenly that the driver has no choice but to "hit the brakes". In this case, it happens that due to incorrect actions of the brake pedal, the car still reaches the obstacle. And everyone hears "BA-A-AMS" :(

Emergency braking is, as you probably guessed, nothing more than a sharp, emergency braking applied to slow down the car as much as possible.

Reference

When you press the brake pedal, both the front and rear wheels of the car are braked. If at the same time at least one wheel is blocked, then an increase in the braking distance and a skid of the car are almost inevitable. When the front wheels are locked, everything else, the car stops turning (does not respond to turning the steering wheel).

Braking on the verge of locking the wheels gives maximum deceleration efficiency, minimum braking distance and avoids all of the above disadvantages, i.e. is the perfect brake.

ABS(Eng. Anti-lock breaking system - anti-lock braking system) - a complex electronic-mechanical system that prevents blocking (skid) of the vehicle's wheels during braking. If the yellow ABS icon lights up on the dashboard of your car when you turn the ignition key, then you have this system installed. If it is working properly, this icon will go out after a few seconds. The presence of ABS can also be recognized by a very light and sensitive brake pedal.

Often on a car without ABS the primary reflex of any unprepared person in a critical situation to put pressure on the brake pedal leads to terrifying consequences.

It is from this innate reflex of the driver, which claimed many human lives, that we will begin our acquaintance with the basic rules of braking.

So please take this article seriously. And if necessary (and most likely necessary), then check that you have exactly the right skills to work with the brake pedal. for their development are given at the end of the article.

The rules for operating the brake pedal during emergency braking are quite different depending on the presence or absence of an electronic ABS assistant in your car. You can not load yourself with unnecessary information and then carefully read only the sections of this article that are suitable for you.

(highlighted in dark blue font).

How to brake urgently on a car with ABS? Advantages of ABS

The vast majority of foreign cars sold are equipped with an ABS system. And if you have just such a car, then you are lucky :)

On a car with ABS during emergency (sharp) braking, the “break the pedal” rule applies. Brake pedal, of course :) If your car also has a clutch pedal, then break two at the same time * until it comes to a complete stop (!).

To reduce the braking distance, the pressing force must be maximum from the very beginning of emergency braking. You will feel the operation of the ABS by twitching the brake pedal and a rather unpleasant chirping sound, similar to a crunch. You should not be afraid - this is the normal operation of the above system, we continue that we have the strength to press the pedal to a complete stop.
________
* - For the correct operation of the ABS system during emergency braking, it is recommended to press exactly the two listed pedals at the same time, excluding the engine from the braking process.

If you need to stop quickly, then even on an icy surface, the same rule applies: press the brake all the way and do not let go (!) Until it comes to a complete stop. In this case, the vehicle electronics will calculate and apply the programmed braking mode for the driver.

In no case should you get rid of the natural reflex to press the brake all the way “to the floor” on a car with ABS!

Advantages of ABS during emergency braking:

in most cases, the length of the braking distance decreases;

the car with such braking reacts to the turns of the steering wheel, while maintaining controllability;

in a turn with such braking, the car does not go into a skid * or demolition;

the driver is not required to have special braking skills (in the vast majority of cases).

_________
* - If the skid is not due to braking, then the ABS will be powerless. (For example, often the cause of skidding in a turn is an incorrectly selected speed and subsequent excessive turning of the steering wheel, etc.). Cornering is a very inappropriate place to brake, regardless of your vehicle's equipment.

Attention!
Familiar to many professional drivers, the reflex of intermittent application of the brake in an emergency can easily increase the braking distance on a car with ABS!

In a second, ABS is capable of performing a series of 12 brake impulses, and even an extra-class race car driver is no more than 8. Therefore, when braking in a straight line on even, uniform surfaces (asphalt, wet asphalt, even ice, etc.), it is usually possible to defeat the electronics in the length of the brake path is not realistic. But on mixed surfaces, especially those covered with snow, not everything is so simple.

How does ABS work? Basic working principle

Two conditions are required for ABS to operate: a depressed brake pedal and at least one wheel that has momentarily stopped*.
If both conditions are met, then the electronics immediately intervene in braking and, oddly enough, slightly release the brake pads on the locked wheel.

The task of ABS is to provide braking on the verge of blocking the wheels, thereby maintaining the controllability of the car.

_________
* - a complex algorithm for the operation of the electronics of the anti-lock braking system also probably provides for its operation without stopping the wheels, but on dry pavement, as a result of its operation, you can almost always detect strokes of a short-term skidding (blocking) of the wheels.

Disadvantages (cons) ABS

Having ABS on board is great, but just in case, know and remember about the disadvantages of such a system, because. some of them are significant.

1. On rough roads (potholes, paving stones, rocky surfaces), the ABS performance is reduced. This leads to an increase (!) braking distance.

This is due to the fact that on uneven sections the “jumped” wheel is blocked much earlier than when braking on a flat road. It is at this moment, when the wheel is approaching and has minimal grip, that the ABS gives the command to release the brake pads. But further, when the wheel lands, its grip increases, and the braking force is already suboptimal - reduced by electronics.

On uneven road sections, there are few options to counteract this disadvantage: we reduce the speed to a similar section or - after (on a flat surface). A safe distance is a matter of course.

Is it possible to use impulse braking if the ABS does not work satisfactorily?
But here the opinions of experts differ: some argue that intermittent pressing of the brake pedal on such cars will not bring a positive result, others admit it, but argue that the old-generation ABS will only respond to the full release of the brake pedal. The gain in stopping distance in this case remains rather doubtful. How to check? Probably only practically on a specific car. I haven't tested mine yet :) So the question remains open.

2. Mixed coatings with different grip properties also lead to reduced ABS performance. Sometimes to a significant (!). A vivid example of a heterogeneous coating: asphalt - ice - asphalt - snow - puddle.

On more slippery surfaces, the wheels lock up earlier, which leads to excessive release of the brake pads in the subsequent section. In other words, the ABS in this case cannot quickly respond and select the optimal braking force for a particular small section of the road. Undoubtedly, this leads to an increase in the braking distance.

The measures of struggle are the same - increased distance, and, ideally, reduced speed to a similar section.

3. When braking on loose, loose surfaces, ABS interferes and usually significantly increases the braking distance!
It can be a sandy or gravel road, or even a snow-covered road(!).

On such surfaces, when skid braking, a compacted “roller” is raked in front of the wheel, for example, from the same snow that will stop the wheel faster, the so-called plow effect occurs. Those. on loose surfaces, skidding is more effective.

4. ABS stops working before stopping. Watch out for slippery slopes!

The fourth minus of ABS is that it turns off at speeds below 5-7 km / h and for some driving conditions (for example, when you roll down a slippery slope), this fact must be taken into account.

That is, for example, in winter, on an icy exit to an underground parking lot, you applied braking to the floor. A car with pulsating ABS continues to slowly and steadily roll down the hill and does not want to stop until the end. This can happen on slippery slopes*.

How to be? And here I don't even know how to come up with a way out. Handbrake? Maybe. Intermittent braking? Maybe ... On a car with automatic transmission in such situations, I think that it is preferable to slow down in "Neutral" ("N" mode). Thank God that such conditions do not occur often.

5. One of the biggest disadvantages of ABS is, perhaps, the illusion that car owners have of the infallibility of this system. Now, obviously, you have realized that this is far from the case!

Usually, anti-lock braking systems are “smarter” on expensive cars, and there will be more electronic assistants there. On budget cars, their performance
in recent years, although it has increased significantly, nevertheless, on certain surfaces, especially snowy ones, their performance is not ideal.

The main advantage of ABS is that during emergency braking, the car reacts to steering turns and in most braking situations “to the floor” it nevertheless reduces the braking distance, thereby providing more chances to avoid an accident.

Winter surprises or how does the day of the tinker come about? (Continuation)

Let's return to the case with Masha described at the beginning. You probably guessed that our heroine's car was without ABS. And, what is most interesting, Masha theoretically knew perfectly well how to brake correctly on slippery surfaces. She solved exam tickets with ease, with virtually no errors, and had heard about intermittent braking more than once.

But in the summer, while learning to drive, no one instilled in her this vital skill for winter, and not only for winter, driving.

What can I say ... Even drivers with experience over the summer wean from the winter driving style and often lose the necessary braking skills on slippery surfaces!

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How to brake urgently on a car without ABS?

If your car does not have ABS, then you yourself will have to be a similar system and control the moment the wheels lock when braking.

How to reduce the braking distance?

Each of us heard the squeal of the tires of a decelerating car. And of course, everyone saw the black marks on the pavement left after such a stop.
Such wheel-lock braking is ineffective and often even dangerous, especially when used on slippery surfaces or at high speeds.

Wheel lock brakingdangerous because:

increases the stopping distance (sometimes significantly);

almost always leads to skidding of the car (its rotation);

when the front wheels are locked, the car does not respond to steering turns (not steerable);

on a turn, such braking leads to the demolition of the car (the car is also not controlled).

Wheel lock can occur not only on slippery surfaces. Even on dry pavement at a relatively low speed, a sharp application of the brake will lead to skid braking, with a full range of all the negative consequences.

When braking in this way, the wheel tire during friction with the road surface heats up to such an extent that it begins to melt and even burn. Of course, you will not see flames - not those speeds - but smoke is easy.

It is clear that melting rubber, like cheese in the oven, is not particularly effective. When skid braking on ice or packed snow at the point of contact with the wheel, a layer of water is bound to form, which almost always leads to an uncontrolled skid and requires a greater distance to stop than when braking ... on the verge of locking the wheels.

The most effective braking is braking on the verge of wheel lock!

What does braking on the verge of blocking mean?

This means that you are pressing on the brake with such a force that it still allows the wheels to spin, but on the verge of stopping them, i.e. if you press the pedal a little harder, the wheels will lock (stop).

When braking on the verge of blocking, the surface of the tire in contact with the road is different at each moment of time, which prevents the temperature at the point of contact from rising to a critical level.

In practice, it is unrealistic to catch the “edge of blocking” by pressing on the brake with a certain constant force. Why? Yes, because at the slightest decrease in speed, this “line” comes with a different effort. Therefore, experienced drivers, even ABS itself, apply

And in order to be able to slow down in this way, i.e. effectively, you must definitely learn to feel the moment of blocking the wheels, regardless of the road surface.

Signs of wheel lock when braking:

wheel vibration occurs or vehicle deceleration worsens*;

there was a sound of tires scratching on the surface of the road or their screech;

there was a skid of the car, he stopped responding to the steering wheel (turn);

__________
* - Usually on slippery surfaces at the moment of blocking, the deterioration of deceleration is especially clearly felt. The car first reacts to braking, and then at some point the brakes seem to disappear - the wheels break into a slip. This is the very moment of blocking!

How to brake properly in a car without ABS?
The main methods of braking in critical situations

Depending on the traffic conditions and the need, drivers use different methods of braking, but, as a rule, they all come down to various variations, or a combination of the following three main methods.

Hard braking (aka emergency)

It is usually used in emergency situations when it is necessary to quickly stop the car. This type of braking is suitable for even surfaces with more or less good grip: asphalt, wet asphalt, etc.

We hit the brake hard. The better the grip, the later the wheels will go into skid.

Effective deceleration with such braking occurs only until the wheel locks occur.

If you feel the wheels lock (tire screeching, vibration or suddenly reduced deceleration), you should immediately reduce the pressure on the brake pedal * and start impulse braking - intermittent pressing the pedal.

By doing this, you will avoid prolonged skidding of the wheels and, thereby, eliminate its negative consequences (skid, uncontrollability, increase in stopping distance).
__________
* - In a critical situation, releasing the brake pedal is not as easy as it seems, especially if there is very little space to stop. Even experienced drivers, frightened, sometimes press the brakes with all their might. Only practical training and, as they say, cold calculation will protect against such erroneous actions.

Impulse braking is performed in at least two ways.

Step braking

Be ready to apply it at the initial moment of using the wheels on any surface, and especially on slippery surfaces: rolled snow, ice, etc. This braking method is very effective, but requires skill.

Push your foot on the brake pedal. It is necessary to press the pedal until the skid occurs, and then you should immediately release it a little. As soon as you feel the disappearance of the blockage, press again.

Press .. Let go a little ... Press ... Let go a little ...

Using the steering wheel, if necessary, we correct the trajectory of the car, while trying to avoid turning the steering wheel at the moment the wheels lock.

The very first pedal press should be as short as possible to avoid prolonged use. So to say to them you produce "reconnaissance coverage" and enough effort to skid.

It turns out that we, as it were, catch the “edge of wheel blocking”, preventing long-term slipping and at the same time constantly applying braking force to the pedal.
At the same time, you yourself choose a comfortable frequency and duration of pressing for yourself, depending on external conditions, but usually, the more slippery the coating, the more often there should be shocks. (As the speed decreases, their frequency can be reduced, and the duration increased).

Intermittent braking

It is used on broken or uneven road surfaces (potholes, etc.), as well as in places where sections of coatings with different slipperiness alternate. For example: asphalt - ice - asphalt - rolled snow, etc.

Push your foot on the brake pedal, fully releasing it each time. In this case, you should press the pedal until the skid of the wheels occurs.

Press... Fully release... Press... Fully release...

At the moment of releasing the wheels, if necessary, by turning the steering wheel, we correct the trajectory of the car (taxi).

It differs from the previous method in that here each pressing of the pedal ends with a complete cessation of braking.

It is desirable to release the pedal exactly on the potholes of the road (when the front wheels come into contact with an obstacle) or on a more slippery surface, where it is not desirable to brake.
The moment of pressing the pedal in this case falls on surfaces that are more preferable for braking (flat sections of the road or places with better grip). On them, if necessary, you can apply

This deceleration method is less effective than the previous one, but easier to perform. Therefore, use it either on the above areas, or on any surface with sufficient margin in the distance.

What to do if the car skids?

If during braking the car skids, it is necessary to stop the started braking and immediately correct the trajectory of movement by turning the steering wheel, turning the wheels in the direction of skidding. Ideally, when leveling the car, it is better not to brake at all. Those. one thing: either we turn the steering wheel, or we brake.

When to depress the clutch pedal?

On a car without ABS during emergency braking, you can forget about the clutch pedal! Yes, the car will stall at this stop. But the deceleration efficiency will be greater, because. in addition to pedal braking, engine braking is added. Ideally depress the clutch immediately before stopping, and when

It is necessary to be able, and not just to know! Knowledge in the head, skills in the body

Do not think that after getting acquainted with various methods of braking, you automatically learned how to properly brake on a real car. Skill (automatism) is developed only in the process of numerous trainings (repetition of the same actions).

Therefore, to get real positive results, you need to take the time, choose a safe place and develop the right skills. And from time to time to replenish (remember) them, especially before the winter season. An icy area would be ideal for such exercises, because. it is on it that you can very well feel the moment of blocking the wheels and develop the right skills to stop the car. But if one is not available, then even dry asphalt is suitable for a start.

All of these exercises are best performed at a relatively low speed. The main thing here is to develop the so-called muscle memory.

Exercising in a car with ABS

Having accelerated and sharply pressing the brake, try to feel the moment of ABS operation, work out the “break the pedal” principle. Those. depress the brake pedal as hard as you can until it comes to a complete stop.

If you initially did not have the habit of intermittently pressing the brake pedal, then you can not be zealous with training - in an extreme situation with a fright, you will press the brakes as it should.

If you have a habit of intermittently pressing the brake pedal, for example, you moved from a simpler car, then you will have to try hard. It will be necessary to unlearn the initial skill and learn how to press the brakes with a constant effort without releasing the pedal.

Exercising in a car without ABS

Having accelerated and sharply pressing the brake, try to get rid of the reflex to press the pedal with all your strength, and at the first sign of wheel lock, practice intermittent shock pedal pressing. You can consolidate such a skill with any more or less sharp braking, not even a real road.

On the court, also practice different methods and compare the difference in deceleration when using different methods.

If there is ice under the wheels, then at low speed try to practice braking while turning the steering wheel (avoiding an obstacle). Compare the difference in car handling when skid braking.

Whether your car is equipped with electronic assistants or not, in any case, you should not forget that the length of the braking distance, first of all, depends on the speed of movement and the condition of the road surface. Moreover, a wet coating increases the braking distance by about 1.5 times, rolled snow or ice by 3-5 times (!).

In any case, a safe distance, speed and timely danger forecast should be above all!

Reconnaissance in combat. Some tricks of experienced drivers.

At times, usually in winter, it becomes necessary to make sure on the go how well the wheels cling to the road.

The surest and most reliable way is to press the brake pedal while driving in a straight line at a relatively low speed and feel the moment the wheels start to lock (ABS actuation). I think it is unnecessary to remind you of the need to look in the rear-view mirror beforehand and make sure that such braking is safe.

Usually at the first frost, this is the fastest way to determine if the road is wet under the wheels or a thin layer of water has turned into ice. And this is possible already at a temperature +3ºС overboard. Bridges and flyovers are the first to freeze, they are above the ground and are better ventilated, so they cool faster.

With such simple training (preferably starting on the site), you can develop a sense of grip on wheels with various surfaces and, along the way, train your eye in determining the necessary distances to stop from different speeds. So to speak, gain experience. But do not forget about security measures.

Try not to brake sharply on the road marking lines, because. you can slip and beware of freshly laid asphalt. A thin bituminous film on its surface will "lubricate" any braking.

Suddenly activated ABS or, worse, squealing of the wheels when braking - this is a signal that you made a mistake in assessing the grip of the wheels with the road. For an experienced driver, there are practically no such surprises, as well as sharp braking in other matters.

I wish you less unexpected situations on the road!

Anti-Lock Braking System (ABS) is a system that prevents the wheels from completely locking up during emergency braking. This solution is one of the first electronic active safety systems that have become universally installed on cars.

Today, such a system is an integral part of almost any modern car, even in the budget segment. Also, in developed countries, the mandatory presence of ABS in a car is enshrined at the legislative level.

At the same time, many drivers know that the car has this system, but they do not fully understand what ABS is and how this solution works. In this article, we will look at how ABS works, what it is, as well as what functions such a system performs and why it is important to monitor the health of the ABS in a car.

Read in this article

ABS system: purpose and features

Before considering ABS, what it is and how the system works, it is necessary to understand the main purpose and functions. Let's begin with . Also, when you sharply press the brake pedal, you can feel the characteristic vibration of the pedal. All this indicates the presence and operability of the specified system on the machine.

So, ABS or anti-lock braking system does not allow the wheels to lock under active braking. Such a system avoids a complete loss of control in the event of blocking of the steered wheels. More specifically, ABS is a system that allows you to control the pressure in the brake lines.

Let's start with the fact that a car without ABS with the brake pedal depressed and with the wheels fully locked simply slides without reacting to the steering wheel. To be able to steer the machine, release the brake pedal and partially unlock the wheels, allowing them to spin.

Race car drivers and professional drivers are well aware of this feature, practicing on a car without ABS the so-called impulse (step) braking technique. The whole technique comes down to the fact that the driver quickly presses and then slightly releases the brake pedal, thereby blocking the wheels for braking, however, not allowing full blocking so that there is no loss of control.

Of course, an ordinary driver, and not an experienced professional, during emergency braking experiences an instant fright and strongly presses the brake. At the same time, a car without ABS becomes simply uncontrollable, turning the steering wheel during braking does not allow changing the trajectory of the vehicle.

In such a situation, control over the car is lost, it is not possible to go around the obstacle, in any way change the trajectory of the car when braking, etc. Naturally, all these factors have long been the cause of numerous accidents with serious consequences.

The ABS system was called to solve the problem. In a nutshell, when the driver applies the brakes hard, the system actually mimics the work of a professional racing driver who applies and releases the brakes very quickly. At the same time, electronics cope with the task much faster and more efficiently than a person.

The vibrations that are felt during the operation of the ABS on the brake pedal in the form of a “ratchet” are those same pressing impulses. More specifically, once the system determines that a wheel is locking up, it reduces the pressure in the brake line at that wheel to allow it to spin.

Until the driver releases the brake pedal, the process of locking and unlocking the wheel occurs continuously several times per second until the driver stops pressing the pedal hard. The ABC system is configured in such a way that the ABS anti-lock system works only with active braking, that is, with light braking, its operation is often not felt.

It should also be added that on a car with ABS, a car with emergency braking has an increased stopping distance compared to models without such a system in exactly the same conditions. In other words, it is a mistake to think that the anti-lock system is necessary to reduce the braking distance. Its main task is to maintain controllability during braking, as well as to ensure uniform and, if possible, rectilinear braking.

If we talk about the braking distance, everything will depend on the coverage. For example, if you brake hard on dry pavement, ABS reduces the braking distance, preventing the wheels from slipping. If you brake on loose surfaces, on snow or ice, the wheels locked without ABS are buried and the braking distance is shorter.

However, even taking into account the increase in stopping distance, it is the ABS that retains the ability to maneuver and control the car, which is often much more important.

ABS device and diagram

So, having dealt with the purpose, you can move on to how the ABS system works, what it is in a constructive way. So, the ABC system (as inexperienced motorists sometimes mistakenly prescribe the abbreviation on the forums) includes the following main elements:

ABS block;
a set of ABS sensors;
pressure relief valves;
wiring;
pump;

To understand how ABC works and what it is, it is enough to think of the entire system as a tool that controls brake fluid pressure at each wheel. Otherwise, the ABS system detects which wheel is locked up, then the valve opens and the brake fluid pressure drops.

After the valve closes and the pressure rises. If a pump is integrated into the ABS system, this solution allows you to quickly create the desired pressure. As a result, a bunch of ABS unit + sensors on the wheels effectively cope with the task.

We also note that ABS systems differ in the number of sensors and valves in the hydraulic lines. Today, four-channel, as well as three-channel, two-channel and even single-channel systems can be distinguished. Depending on the number of channels, it is possible to more or less flexibly control the pressure in the brake system.

For example, if there are three channels, then the ABS works with the two front wheels separately, while at the same time only one channel goes to the rear axle. Two channels involve work with the front and rear axles. Of course, modern systems are four-channel, that is, for each wheel separately. Other solutions are not used, as they are very outdated.

By the way, we also add that ABS sensors are also used in some control systems. It turns out that the ABS system has not only evolved, but also the individual capabilities of its constituent components have been expanded.

If in developed countries cars without ABS are practically never found, then in the CIS there are many such cars traveling on the roads (domestic car industry, old foreign cars, some new super-budget models, etc.). Also, on many cars, this system simply does not work, and the owners are in no hurry to fix the problem.

In any case, understanding what ABS is for, what it is and how it works, allows us to give several recommendations to drivers who do not have such a system. Of course, if ABS is a guarantee that the wheels will not lock up, then the absence of such a system means that the driver must acquire certain emergency braking skills.

In other words, the operation of the ABS can be replaced by intermittent braking by pressing the pedal with frequent jolts. Of course, in an emergency, it is difficult to apply such a technique, since the driver instinctively presses the brake with all his might, without removing his foot.

If the situation is predictable, then this technique is similar to the operation of a single-channel ABS. Intermittent braking will allow you to brake with sufficient efficiency and at the same time maintain controllability during braking.

Summing up

Based on the above information, it becomes clear that in order to increase comfort and safety, equipping a car with an anti-lock system is mandatory. Having considered ABS, what it is and how it works, we can also argue that this is a simple and at the same time important, as well as a very useful solution.

Even despite the statements of skeptics that ABS increases the braking distance, such an assistant is simply indispensable for extreme braking, especially when it comes to ordinary drivers.

As a result, we note that understanding the principles of ABS operation, what it is, as well as what kind of braking should be expected on a car with such a system, allows us to take into account a slightly increased braking distance on certain surfaces in advance.

In turn, this further encourages drivers to keep their distance, as well as avoid other difficult situations that may arise if some features of the anti-lock brake system are not taken into account separately.

Creation

The idea to create a system that prevents the wheels from locking was born before the Second World War. ABS was originally planned to be used in aviation. But the technologies and materials used at that time did not allow it to be implemented in mass production, and even more so on a mass-produced car. In 1964, Mercedes engineers, together with specialists from Teldix and Robert Bosch, got down to business. To begin with, we collected all the patents and reports over the past couple of decades, which mentioned the distribution of braking forces between the wheels.

The main elements of any ABS: control unit and hydraulic unit actuator (1), wheel speed sensors (2). The hydraulic unit regulates the pressure in the circuits of the brake system using a hydraulic accumulator, an electro-hydraulic reverse pump and control electro-hydraulic valves. The diagram shows a four-channel ABS, which is able to regulate the pressure separately in each of the four brake lines.
yellow - information cables;
red - brake circuit of the front right and left rear wheels;
blue - brake circuit of the front left and rear right wheels

All modern systems have four sensors that monitor the speed of rotation of the wheels, and four pairs of valves - two for each circuit or channel of the brake system. Such systems are called 4-channel. They allow you to individually adjust the braking force on each wheel, achieving the most effective deceleration.

Research has brought results, for example, helped to determine the functional diagram of the ABS. Sensors (then only on the front axle) measured the speed of rotation of each wheel. These measurements were recorded and compared by the control unit and, if necessary, gave corrections to the actuator to correct the pressure in any circuit of the brake system. On paper, everything went pretty smoothly. But in real situations, ABS did not work clearly, it reacted with delays to a change in the grip of the wheels with the road, and it was not famous for its reliability.

Back in 1936, Bosch registered a patent for a "mechanism to prevent the wheels of motor vehicles from locking up." But it was only with the introduction of electronics that engineers were able to develop an anti-lock braking system (ABS 1) suitable for use on a car.

One of the first significant steps towards mass production was the replacement in 1967 of mechanical sensors on wheels with non-contact ones using the principle of electromagnetic induction. The advantages are obvious: they do not wear out, are resistant to mechanical stress, there are no false positives. It was with these sensors that in 1970 Mercedes introduced the public to the first electronically controlled ABS for cars, trucks and buses. Sensors sent signals to the block, which controlled the hydraulic module installed between the brake master cylinder and the calipers.

In 1978, Mercedes-Benz was the first automaker in the world to introduce ABS on a production S-Klasse. The option added 2217 marks to the price of the car. A little later, the same ABS 2 was tried on by the BMW 7-series. And today more than two-thirds of all new cars in the world are equipped with anti-lock brakes.

The principle of the first ABS is incorporated in the most modern system. The sensors monitor the speed of rotation of each wheel, the control unit compares the readings and sends commands to the solenoid valves of the hydraulic module that regulates the pressure in the brake system - a pair (inlet and outlet) for each circuit. During emergency braking, the valves operate at a frequency of several tens of times per second (15-20 Hz, depending on the system) - it is their chatter that we hear when the wheels are locked and unlocked. At the same time, the pressure in one or several circuits at once instantly rises and is immediately released, and the pads, respectively, compress and release the disc, providing the same intermittent braking.

The first systems were based on analog technology, which often produced errors, the wiring diagrams themselves were complex and cumbersome. And the level of development of the "numbers" was then incomparably low - the first microprocessors, which appeared in the early 1970s, were not suitable for controlling the anti-lock braking system. Only 5 years later Bosch made a fully digital control unit. The electronic filling has become almost an order of magnitude more compact - the ABS 1 block consisted of about 1000 components, and only 140 were in the "brains" of the second generation system. In addition, the ABS became almost trouble-free and many times faster - the electronics processed the data from the wheel sensors in milliseconds and sent command pulses to the hydraulic module.

In the mid-1990s, anti-lock braking systems began to be installed on motorcycles. They prevented the blocking of the front wheel and the flight of the rider through the steering wheel. The top diagram shows the advantage that ABS provides when braking the average motorcyclist on dry pavement from a speed of 100 km/h.

Many modern motorcycle systems work even if the rider has applied only the rear or front brakes.

The further evolution of anti-lock braking systems went in two directions - the improvement of hydraulics and electronics. For example, consider the development of ABS from Bosch, which is not only the founder of the anti-lock braking system, but also the main supplier for most automakers, including Russian ones.

The most powerful supplier of ABS components is Bosch, which supplies components for most models. Bendix Corporation works for Chrysler and Jeep, Continental Automotiv Systems works for Ford, GM, Chrysler. Infiniti and Lexus use Nippondenso parts, and their countrymen Mazda and Honda use Sumitomo. Aisin Advics, Delphi, Hitachi, ITT Automotive, Mando Corporation, Nissin Kogyo, Teves, TRW and WABCO are also involved in the development and production of ABS components.

So, soon after the appearance of a compact digital filling, the control unit moved to the hydromodule. This not only made life easier for car assemblers and builders, but also reduced the cost of the system. The next generation of ABS 5, which has become not only lighter and faster, has received more advanced mechanics, including a block of new solenoid valves. Now the anti-lock braking system has made it possible to implement additional functions, in particular, the EBD (Electronic Brake Distribution) program, the metering braking force for each wheel separately, the TSC (Traction control system) program, which fights slippage, and the lateral dynamics control program - ESP (Electronic Stability Program). The implementation of these functions required engine management - so, for example, when the electronics detect a slip or cross slip, it automatically reduces the fuel supply.

Mechanical wheel sensors have been replaced by inductive ones. Their principle of operation is simple: when the car is moving, an electric current is induced in the sensor coil. Its frequency is directly proportional to the wheel speed. Over time, they began to measure not only the speed of rotation, but also the direction. Now on some models, sensors are built into wheel bearings.

Modern systems are built on a modular basis. For example, the ninth generation supports many functions that increase comfort and safety - electronics are able to prevent the car from rolling back when starting uphill, adjust the speed of descent from the mountain (implemented on crossovers and SUVs) and even automatically stop the car in an emergency (you can learn more about such systems). Moreover, the automaker acquires the set that he needs for a particular car. And the ABS developer assembles a unit for him from the appropriate electronic and hydraulic modules. In addition, this arrangement made it possible to produce systems for cars cheaper and more expensive. For example, for premium segment models, Bosch offers units with more complex mechanics. So, instead of a two-piston return pump, a six-piston one is installed in the hydraulic module. It very quickly reduces the pressure in the circuit, which is why there are almost no vibrations on the brake pedal.

A simplified diagram of the operation of the hydraulic unit as part of the ABS. For simplicity, the diagram considers the operation of a system with one wheel. In a four-channel system, there are four such circuits for each wheel.

What about in practice?

Not so long ago, we conducted a test that clearly shows the benefits of the anti-lock system. Detour of an obstacle with braking was carried out on a car with ABS and without it. The tires on the experimental Logans were the same - Barum Brilliantis with a dimension of 185/70 R14. For greater persuasiveness, a slippery coating was simulated - plastic soaked in soapy water. It was necessary to enter the "gateway" at a speed of 40 km / h and immediately begin emergency (a strong blow to the brake pedal - the driver was "scared") braking with simultaneous rebuilding.

Vehicle without anti-lock braking system

with the wheels turned out, without changing the trajectory, he knocked down an obstacle and continued to move on. The culprit is sliding friction in contact patches, locked wheels do not perceive lateral forces as they should, therefore, it is impossible to drive a car at this moment. I used intermittent braking, as taught in special courses, the effect on this type of coating is almost zero. Attempts to find the moment of blocking and apply search steering (search for the angle of rotation of the wheels when the car stops responding to the steering wheel) were also not crowned with particular success.

Logan with ABS

with a much more effective deceleration, it allowed even beginners to easily and without straining to get away from the obstacle the first time. The braking distance with ABS for this coating was on average 1.5 times shorter than that of Logan not equipped with anti-lock braking system. What is the trick? In intermittent braking with short-term blocking - ABS has time to slow down and brake each of the wheels 15 times in a second. While the wheel of a fraction of a second is rolling, you have the opportunity to set the direction (at this moment, rest friction is in the contact patches). At the same time, for each type of coating (set empirically during design and refinement), the most optimal degree of wheel slippage (15-20%) is maintained, at which deceleration is most effective. In addition, ABS doses the braking force on each of the wheels individually, preventing skidding.

Why didn't intermittent braking help on a car without ABS? Lock-unlock the wheels, unlike ABS, I have time for a maximum of three or four times per second - I act a priori more slowly. The degree of slippage is not optimal for me, therefore, braking is less effective. Unlike ABS, I act on all the wheels at once with the pedal, and this can cause demolition or skidding, because under the wheels there may be heterogeneous coatings, or the load on the axles and sides can be changed. The trajectory with this method of braking can be learned to change slightly, but training is needed. The same is true for "tracking" braking. The conclusion is unequivocal - with ABS the car is safer.

However, not everything is as rosy as it might seem at first glance. In some cases, ABS can increase the stopping distance, for example, on ice and some unstable surfaces (loose ground, rolling gravel road or hard ground covered with dust, sand or snow). Worn-out shock absorbers and unscrupulous suspension settings can also add fuel to the fire... If at least one wheel breaks off the roadway for a long time during braking and blocks, the system, thinking that it has hit the ice, releases it, and at the same time reduces pressure in the hydraulic lines of the other wheels. The system in this case understands that the wheels are on heterogeneous surfaces and thus seeks to maintain directional stability. In addition, the very adequacy of the ABS setting on some modern models raises many questions. How to deal with these nuances, we'll talk next time.

For quite a long time, the active safety of the car was not given as much attention as it should be: human genius was mainly aimed at making the car faster and, at the same time, comfortable for the driver and passengers. If some developments in the direction of improving the safety of cars were carried out, then few of the innovations proposed by engineers and designers were used on production cars. The main drawback of active safety systems was their imperfection. When humanity entered the age of electronics, many of the previously proposed tools were finalized and finally installed on cars. One of these systems was the anti-lock braking system - ABS, which is now equipped with every car manufactured for the EU countries. This system will be discussed in today's material.

Half a century of recognition

The first prototypes of mechanisms that helped to avoid blocking the wheels during braking appeared in the 1920s. And these systems were installed on the chassis of aircraft. They also tried to install such systems on cars, but they were extremely inefficient due to the cumbersome design of the brake mechanisms themselves. Even after conventional cable brakes began to replace more advanced hydraulic brakes with a vacuum booster (this happened in the middle of the 20th century), the problem was still not solved. The fact is that it took fractions of seconds to process information about braking, and the necessary devices for processing this information did not yet exist in nature at that time. The situation changed when the mass use of electronics began in the industry, including the automotive industry. It was the use of electronic sensors, with the help of which information about braking was read, and control units, in which the information received from the sensors was processed, that allowed automakers to improve anti-lock braking systems and install them on cars in series.

This happened for the first time in 1978, and the pioneer was the German company Mercedes-Benz, which was one of the first in the world to apply various innovative systems in the production of mass-produced cars.

Mercedes-Benz S-Class 1978. It was on these cars that ABS was first installed.

At first, anti-lock braking systems were installed only as an option on the S-Class model. But after other manufacturers were convinced of the effectiveness of ABS, this system began to appear on cars of other brands.

How ABS works

The purpose of the anti-lock braking system is to unlock the wheels during emergency braking. In a car without ABS, the wheels lock up when braking, which can lead to a skid, in which case the driver actually loses control of the car.

A car with ABS in the same situation behaves differently: the system unlocks the brakes, allowing the wheels to rotate, and the driver not to lose control of the car. For example, when braking on an icy section of the road, the car will not go into the skid, and the driver will be able to take it away from the obstacle, thus avoiding a collision.

What is an anti-lock braking system

ABS is a kind of complex consisting of three components. The first is speed sensors. They are mounted on the wheel hubs and constantly analyze how fast each wheel is spinning. The second is control valves. These valves are mounted in the lines of the brake system, their function is to regulate the pressure when the ABS system is activated. The third is the electronic control unit, where, in fact, information from the speed sensors is received. Here this information is analyzed, processed, and if necessary, the ECU sends a signal to the brake line to the control valves. These valves, opening and closing, regulate the pressure in the brake system and prevent the brakes from blocking the wheels until the maximum calculated braking speed (for each model it is unique and calculated on the conveyor) matches the parameters with the given braking speed. Then ABS ceases to function and braking occurs.

Today, ABS is distinguished by the number of channels: single-channel (when the braking force is limited in the entire braking system), dual-channel (when the braking force is limited only on the right or left wheels) and multi-channel (when the braking force is limited on each individual wheel).

Advantages and disadvantages of ABS

The anti-lock braking system has become an effective means of active safety, which has helped save more than one human life. This is her main merit. The advantages include the possibility of simultaneous braking and maneuvering, effective and safe braking when entering and exiting a turn. This system also has its downsides. For example, when ABS is activated, a slight increase in braking distance occurs, and the system does not function at speeds up to 10 km / h.

Already today, the anti-lock braking system is evolving, turning into a complex set of active safety systems, including, in addition to ABS, systems such as brake force distribution system, emergency braking assistance system, traction control system.