How does an ABS car anti-lock system work? What is ABS, and why it has become mandatory for a modern car The abs system works.

Modern cars are replete with various systems that help the driver to safely drive a vehicle on any road. One of the first such "assistants" was the anti-lock braking system (Anti-lock Brake System). Almost all leading auto companies have recently installed it not as an additional bonus, but as part of the basic package.

The principle of operation of the ABS on a car is to not block the wheels unambiguously at the request of the driver after pressing the brake pedal. Instead, instant control and redistribution of the braking force on the wheels is carried out. Thanks to this algorithm, the car remains steerable, directional stability is ensured, while the vehicle safely reduces speed.

Car company engineers, performing safety-related tasks, have been developing ABS since the late 60s of the last century. One of the first versions of these systems proved to be quite successful. In the next decade, such blocks were already being introduced on production cars.

The leading company in this industry was the German Mercedes. After experiments with mechanical sensors, which were installed only on one axis and transmitted information to the control unit about pressure changes in the brake circuits, German engineers switched to non-contact sensors. This helped to speed up the transfer of information to the logical unit. Also, the number of false positives has decreased, wear has disappeared due to the elimination of rubbing surfaces.

The modern ABS system works on the same principle as the first developed anti-lock braking systems.

It was the second generation of this block, released in the late 70s, that began to be installed as a basic equipment on the prestigious Mercedes-Benz 450 SEL cars of that time.

The operation of the wheels in the car

The main task assigned to the ABS is to maintain maximum control of the car during braking. Since a locked wheel has significantly worse grip on the road surface, its braking forces will be much lower than that of a spinning wheel. The driver does not have control of a spinning wheel at all. The most acceptable option for moving a braking car would be straight-line movement, however, often the car goes into an uncontrolled trajectory.

Installed block ABS contributes to the efficient operation of the wheels at a given time, balancing between locking up (not completely stopping the rotation) and the highest level of grip on the road surface. An icy road and a dry dirt road will give different inputs, but in both cases the system will strive to maintain maximum controllability.

It is believed that a well-adjusted anti-lock braking system is able to drive a car at a higher level than a highly skilled driver in a car without ABS.

The anti-lock system calculates its work based on the wheel slip coefficient. It is found as the quotient of dividing the difference between the speeds of the car and the circumferential speed of the wheels to the linear speed of the car. With different driving modes, the indicator changes.

Intensive acceleration gives a high peripheral speed to the wheel at a low linear speed of the machine, and hard braking contributes to the reverse process. An example of 100% slip is two options: a blocked braking wheel and a slipping process without movement, for example, in mud or a puddle.

How ABS works on a car

In a modern brake system, anti-lock controls electronic valves and a pump. The driver initiates braking by pressing the pedal, and if slippage does not occur, then the anti-lock system is not connected to these actions.

The new machines are equipped with four-channel circuit layouts. Thus, control is carried out for each of the wheels. Each circuit is capable of operating in three modes:

• increase in pressure;
• keeping its value;
• pressure drop.

When the moment of blocking the wheels approaches, the pressure is kept at the same level. At this time, the fluid supply from the brake cylinder is cut off and further pressing the pedal does not lead to blocking. If the calculated slip coefficient takes on values ​​of more than 20%, then pressure is released through the pump. Then the slippage can, on the contrary, decrease by more than 15%, then the valves open to increase pressure when the pedal is pressed.

There is an alternate switching on/off of such modes. The process most often stops after a significant decrease in speed to 5-15 km / h. The feedback from the anti-lock braking system can be heard by the driver from the brake pedal. The speed of changing such cycles is not able to repeat even the greatest professional.

ABS elements

If the car hits one wheel on a dry surface and the other on a slippery one, then the vehicle with ABS will be kept straight by balancing the pressure for each of the circuits. If a car hits such a road without this block, the car will go towards a dry road, and during a sharp blocking of the wheels, the situation will lead to a sharp turn with unpredictable consequences.

Operation of the built-in speed sensor

The information on which further actions are based on the operation of the anti-lock braking system is received by the control module from speed sensors. To fully understand what ABS is in a car, you need to understand how they work. The pulses come from four such sensors, which may differ in design and be active or passive.

Passive option execution implies the presence of a comb in the hub block. Using analog signals, the encoder determines the speed of rotation. However, this design at low speeds can produce an error.

Active option The sensor works with a magnetic ring. By reading its labels, a binary signal is transmitted. There is no error due to rotation speeds in this case. All that remains is an accurate impulse diagram.

A set of non-standard ABS for a truck

You need to know that all-wheel drive vehicles are equipped with an additional G-sensor that corrects the speed and acceleration of the vehicle for the ABS module.

This sensor is mounted with an accelerometer.

Driving with and without ABS

Young drivers are often intrigued by the way an anti-lock car brakes. After all, the return to the pedal at its first sensation pushes the foot off the brake. Doing this is not worth it. Intermittent braking is typical for cars without ABS, as the driver wants to avoid complete wheel lockup and loss of control. On modern machines, you can safely drown the pedal, and the automation will do its job.

Regular shutdown of this system in vehicles is not provided. For various reasons, car owners sometimes want to do this. To do this, it is enough to remove the fuse from the block, but you need to remember that in modern transport, the redistribution of inter-axle braking forces is also assigned to the ABS. Accordingly, pressing the pedal leads to a complete blocking of the rear wheels and undesirable consequences.

You also need to understand that you can not shift everything to the machine. The driver must control the situation himself, and the car with its various elements will remain only a quality tool.

In an extreme situation, when we press the brake pedal with all our might, one or several wheels may be blocked, which leads to a significant deterioration in handling and an increase in braking distance. To prevent such blocking, cars are equipped with an ABS system, which we will discuss in this article.

For the first time, such anti-lock braking systems began to be used on cars back in the seventies of the last century. Many car manufacturers and subsequently car owners were able to evaluate the effectiveness of the active safety system, which made it possible to reduce the braking distance, increasing the safety of car operation at any time of the year.

If we talk about the benefits of using such anti-lock systems, then first of all we note the improvement in the safety of using a car. Thanks to this system, it is not only possible to reduce the braking distance, but also prevent the car from skidding, which is caused by wheel blocking.

In particular, such a system will be useful when operating a car in the winter season, when on a slippery road, with any inaccurate braking, the wheels can be blocked, and the car begins to slide forward. However, such a system ABS , having determined the blockage that has occurred, will reduce the intensity of braking, which will allow you to regain control of the car.

We also note the uniform wear of the wheels, which in turn reduces the cost to the car owner for the purchase of new tires. During the blocking of the wheels during braking, the projector can quickly wear out, and literally 3-5 such extreme braking will be enough to completely wear out the tires.

If we talk about the shortcomings of such systems, then it is necessary first of all to note the frequent failures of ABS sensors, which forces the car owner to change broken parts, which can lead to some increase in the cost of operating cars.

Anti-lock braking systems have become today the main element of the active safety of every modern car. Using data from sensors ABS course stabilization systems work, as well as a number of other active and passive safety systems, without which the operation of the car would be impossible. Automakers today are constantly improving their ABS systems, which are becoming more reliable, smarter and more functional.

The anti-lock braking system includes numerous sensors, hydraulic distributors with solenoid valves, a suction pump and a control unit that controls the operation of the brake system, preventing blocking of the entire axle or individual wheels.

In recent years, despite some simplification of such anti-lock systems, their effectiveness has increased, which is explained by the improvement of automation. If in the past most of the work was done by hydraulic systems, today the blocks and actuators are fully controlled by automation, which improves the quality of the work of such an anti-lock system.

The control unit constantly sends signals to the sensors, receiving the necessary information and makes the right decision to reduce the pressure in the brake system. Communication between sensors and control units is carried out via a special high-speed bus, while each wheel can have several individual sensors that provide the central computer with all the necessary data to adjust the operation of various vehicle systems.

The principle of operation of such an anti-lock braking system has not actually changed over the past few decades. When braking, a signal is sent from the control unit to the brake cylinders, after which the working fluid passes through the inlet channels. This brake fluid pressure is transmitted through solenoid valves to each wheel, which effectively slows the vehicle down. In the event that the control unit determines the danger of blocking the wheel, then the electromagnetic sensor receives a corresponding signal, it closes, which in turn prevents braking and blocking the wheels of the car.

Any even the easiest and simplest braking in a car equipped with an ABS system takes place under the control of automation. Depending on the intensity with which you press the brake pedal and the position of the wheels, the system decides whether to open or close the solenoid valves. Such systems using ABS sensors and solenoid valves are simple in design, so they are reliable and durable. Problems can only be caused by sensors, which are often damaged by anti-icing agents and require appropriate replacement.

At the moment when the ABS system works and dissolves the wheels, the car owner feels the pulsation of the brake pedal at that moment. This pulsation occurs when the solenoid valves open and close quickly to properly decelerate and prevent wheel lockup.

Anti-Lock Braking System Tips

Modern anti-lock braking systems are durable and reliable components that do not require any special maintenance. It is only necessary from time to time to check the performance of the sensors in the wheels and, if necessary, replace them.

Do not overheat the control units or fill them with water.

In the event that you need to weld metal in a car or you need to connect to the car's on-board electrical system, the ABS wiring must be disconnected.

Monitor the condition of the contacts on the generator, which will prevent short circuits and failure of sensors.

Avoid connecting your vehicle's battery to another vehicle.

Do not separate the electrical connectors of the sensors when the ignition is on and the engine is running.

In the event that malfunctions of the ABS system are noted, the corresponding control lamp will light up on the dashboard. The car in this case will brake effectively, but with excessive force on the brake pedals, the wheels will be blocked, which can lead to skidding. Therefore, if any malfunctions of the ABS are noted, it is necessary to take this into account and brake smoothly and carefully, and if possible, contact the appropriate service stations as soon as possible for repair work.

Every year, automakers equip their vehicles with more and more advanced active safety systems and driving assistance. One such system that assists with braking is ABS. It is designed to prevent the wheels from being blocked during emergency braking. Thus, this system helps to maintain driver control over the car, which is easy to lose if the wheels are completely locked.

Almost every car is now equipped with an ABS system. Despite some complaints about its work from drivers, the anti-lock braking system can significantly reduce the braking distance during emergency braking. To do this, after the driver presses the brake pedal, it starts to monitor the rotation of the wheels in automatic mode and, if one or all of them are stationary, reduces the braking force, unlocking the wheel.

The principle of operation of the ABS - simple complexities

Any anti-lock braking system, when activated, practically imitates the actions of an experienced driver who “automatically” uses the intermittent braking technique in emergency situations. But unlike a living person, who cannot completely exclude the emotional component, ABS works clearly and impartially, performing its direct duties impeccably. But only on a road with a hard and even surface - on bumps, the ABS efficiency drops sharply, which should be taken into account by any motorist.

The device of the system is quite simple, and the ABS unit acts as the “commander-in-chief”, constantly receiving signals about the speed of rotation of each wheel while the car is moving. Accordingly, there is a special sensor on the hub of all wheels that transmits these signals. At the moment when the driver depresses the brake pedal, the wheels are often completely locked, which leads to loss of vehicle control. When the wheels are stationary, the car's ABS system comes into action.

In the absence of wheel rotation, the ABS unit instantly reacts - it sends the appropriate command to the modulator, and the pressure in the braking system drops. To do this, it has a special valve with an electric drive that communicates with a hydraulic accumulator, where excess fluid flows. The braking force is reduced, the wheels continue to rotate without losing traction. As soon as the wheel speed increases, the system will resume active braking. Thus, you can answer the question of how ABS works on a car. It should be mentioned that intermittent braking is considered the most effective.

Interesting! ABS is activated on average 20 times per second - this provides the greatest braking efficiency. A person is physically incapable of pressing the brake pedal so many times in a row.

Does ABS always help the driver

The advantages of the anti-lock braking system are undeniable, since, regardless of its design, it performs very important tasks:

• improves the safety of the driver, passengers and other road users;
• increases the life of tires;
• significantly reduces the braking distance of a car on a hard surface;
• allows the driver to maneuver the car when braking, for example, to make a turn, which is impossible if the car is not equipped with anti-lock braking system ABS.

Of course, it does not do without negative reviews. Some car owners are frightened by the characteristic crackling that is heard during the operation of the ABS, many have heard about the inefficiency of this system on bad roads or the inability to quickly brake on an icy descent / ascent. It should be noted right away that the anti-lock braking system was created solely to help the driver, if necessary, stop urgently, without losing the ability to control and drive the car.

Not everyone, even a very experienced driver, knows that blocking the wheels during braking is especially dangerous not on a solid continuous surface, when there is little chance of keeping the car on a given trajectory. The slightest bumps, heterogeneity of the coating, and even a different tread pattern with locked wheels inevitably lead to a complete loss of controllability. A car with ABS is almost completely insured against uncontrolled skidding in such a situation, which can quite realistically help to avoid a disaster.

When does ABS interfere?

Like many other innovative systems, ABS is effective under certain conditions. So, the system has proven itself on a hard, even slippery surface (wet asphalt or ice). But as soon as the car leaves it, hitting an uneven road covered with pits or potholes, the effectiveness of the ABS drops sharply. In simple terms, the "smart" system is not able to adequately estimate the speed of rotation of each wheel.

Another situation where ABS can only interfere is a steep descent on a heavily snowy road, or when there is only liquid mud instead of a hard surface. If it is necessary to completely stop the car, the anti-lock braking system simply will not allow this, and the vehicle will gradually roll down due to the force of gravity even with the brake pedal fully depressed. The same problems can be noted when lifting - it will not be easy to stop.

Of course, automakers take this flaw into account, and recently most, for example, SUVs, have a system that constantly monitors the degree of vehicle inclination, and when critical values ​​\u200b\u200bare reached, the ABS becomes inactive. If the vehicle does not have such a system, the driver needs to be as collected as possible when overcoming steep descents or ascents.

Advice! If you need to stop in conditions where the active ABS prevents this, you can sharply pull the handbrake, blocking the rear wheels of the car - the blocking system will temporarily turn off on its own, allowing you to stop the car.

Possible problems when operating a car with ABS

The ABS device of a car is quite simple and reliable, and in the absence of any external mechanical influences, there are practically no problems with it. The electronic component of the system is well protected by fuses and relays, and if problems arise, they are often associated with wheel sensors, which have to work in very difficult conditions - constant dirt, exposure to extremely aggressive environments, and even large play in the bearings of the hub itself can cause incorrect operation of the entire system.

The condition of the car's battery also affects the performance of the anti-lock braking system. So, if the voltage at its terminals drops to 10.5 V and below, the system can turn off on its own and remain inactive. The central electronic unit can also turn off the ABS in the event of power surges in the on-board electrical network. To prevent spontaneous shutdown of the system, you must follow the simplest recommendations:

• with the ignition on and the engine running, do not disconnect the electrical connectors;
• you should not often start a car by lighting from another car, or provide your own for this purpose;
• All contact connections on the battery and alternator must be clean and secure.

Quite often there is a situation when the ABS warning lamp on the dashboard lights up periodically, but goes out after a while. This phenomenon can often be explained precisely by wiring problems - it is urgent to check all the wires and clean the contacts. You can do this yourself, but if the problem is not solved, you will need to contact a specialized service.

Attention! When replacing brake fluid on a car with ABS, it is necessary to “discharge” the ABS hydraulic accumulator, for which, with the ignition off, it is necessary to fully depress the brake pedal 20-30 times.

What affects the number of ABS channels

Currently on the road you can find cars equipped with one, two or multi-channel anti-lock systems. The difference between them is quite large, and the more channels, the more efficient the system is. So, a single-channel ABS creates the same working conditions for all the wheels of the car at the same time - regardless of how many of them turned out to be blocked during braking. The multi-channel ABS system is more efficient because it analyzes the speed of rotation of each wheel, and reduces the braking force of each individually.

It should be understood that, no matter what anti-lock braking system is installed, it is intended only to help the driver, and in no way negates the need for adequate driving behavior. If the driver is not able to adequately assess the traffic situation, is prone to speeding, and does not take into account the condition of the surface and weather conditions when driving, the most advanced safety and assistance systems will be ineffective.

ABS - is it possible to turn it off without consequences

Since for many drivers the effectiveness of the anti-lock system is quite controversial, they are trying to find a way to turn it off. If we discard the fact that unauthorized disabling of standard ABS on a new car is almost guaranteed to deprive the car owner of the factory warranty, the lack of electronic braking assistance can lead to serious consequences.

If, nevertheless, the driver considers it appropriate to disable the anti-lock braking system, this must be done correctly, and not simply by pulling the appropriate fuse from the unit. On almost every car, it is possible to install a home-made relay, with which the ABS can be turned off from the passenger compartment - of course, temporarily, for example, before a steep descent or ascent, after overcoming which the system can be activated again. You can decide whether or not to disable the ABS after watching a video that describes the intricacies of this system:

Most cars on the road today are equipped with some type of anti-lock brake system. Let's see what this system consists of and how it works.

First, let's look at the basic principle of the ABS system.

Since different manufacturers have different versions of ABS, their specifications and parts may have different names.

ABS is a system that works on all four wheels and prevents them from locking up by automatically changing the brake pressure on each wheel during emergency braking.

By preventing the wheels from locking up, the system firstly allows the driver to continue steering the car, and secondly, it can reduce the braking distance.

During normal braking, the ABS and non-ABS systems feel the same to the driver.

During emergency braking, when the ABS is working, a pulsation can be felt on the brake pedal, which is accompanied by vibration of the brake pedal and a characteristic sound.

Vehicle ABS device

Vehicles with ABS are equipped with a pedal drive with a dual braking system.

The main hydraulic braking system consists of:

• hydraulic control valve and electronic control unit.
• master brake cylinder
• brake lines and hoses
• brake cylinders on each wheel.

The anti-lock braking system consists of the following components:

• hydraulic control unit
• ABS electronic unit
• front and rear anti-lock braking system sensors.

How car ABS works

The anti-lock braking system works as follows:

When you press the brake pedal, it presses on the fluid in and as a result, the fluid is squeezed out from there under pressure.

From the brake master cylinder, fluid flows into the ABS hydraulic control unit.

There are 4 outlets in the hydraulic control unit, each of which is connected by a tube to the brake cylinder on the wheel.

At each of these outputs of the ABS hydraulic unit there is a valve that is open in the initial state.

Pressurized fluid is forced out of the hydraulic control unit and travels through tubes and hoses to the brake cylinders at each wheel.

Pressure is created in the brake cylinder on the wheel, and the fluid pushes the piston, which is connected to.

As a result of this, the brake pads press on the brake disc or drum. Because of this, a friction force arises between the brake pads and the brake disc, and it slows down its rotation.

Accordingly, the wheel slows down its rotation.

In brake systems equipped with ABS, a toothed disc and a sensor are mounted on the hub of each wheel.

As the wheel rotates, the disc teeth pass near a sensor that detects this.

Data from the sensor is transmitted to the electronic control unit.

With very sharp braking, the wheel may lock up and the wheel deceleration speed sensor will notice this.

As a result, the ABS electronic control unit, seeing that a wheel is blocked, sends a signal to the hydraulic control unit and shuts off the valve that supplies brake fluid to this wheel.

As the brake fluid pressure on this wheel is reduced, it stops braking and starts spinning again.

As soon as the wheel begins to rotate, the valve on the hydraulic block opens and the brake fluid pressure is again transferred to the braking system of that wheel.

The wheel starts to slow down again.

These actions are repeated very quickly and are manifested for the driver in the very characteristic sound and vibration of the brake pedal when pressed.

Thanks to this, when braking, the wheels do not block and the car does not go, as it is called skidding.

After all, when driving skidding, the car becomes uncontrollable and does not respond to steering. ABS, on the other hand, avoids this and keeps the driver able to control the car.

For example, this will help you avoid an obstacle without releasing the brake pedal. There is a misconception that cars equipped with ABS stop at a shorter distance than cars without ABS. In reality, this is often not true.

A car with ABS in most cases will go a long way to a complete stop, but because the driver can still drive the car, he will be able to avoid an obstacle, and not just helplessly press the brake pedal and hope that the car will stop in time.

Also, the ABS system has a positive effect on the condition of the tire tread. Indeed, in the absence of ABS and when the wheel is blocked in braking, the tire will rub against the asphalt with only one point.

As a result of such braking, the tire can be severely worn in one place. This does not happen with ABS.

This is a description of the simplified principle of the ABS system.

In practice, the design of the brake system and ABS is much more complicated. For example, the brake system of a modern car has at least two independent circuits.

This means that the front and rear wheels are controlled by separate tubes from the brake master cylinder.

ABS from different manufacturers can vary significantly.

In addition, this system can be very complex and require a lot of experience and special tools for maintenance and repair. Therefore, an inexperienced driver should not attempt to repair the ABS on his own, but rather contact a specialist.