How the ABS system works. How ABS works in the car. Intelligence battle. Some tricks of experienced drivers

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The ABS anti-lock brake system is systems equipped with feedback control devices that prevent the wheels from being blocked during braking and retain controllability and coursework car stability. Generally speaking, they also reduce the braking path compared to braking with complete locking wheels. This is especially noticeable on the wet road. Reducing the braking path can reach 10% or several times more than this value, depending on the degree of humidity and the friction coefficient (the clutch of the wheels with the road). With certain, very specific conditions, the braking path may be longer, but the car will still maintain stability and controllability.

Content

Requirements for anti-lock brake system ABS are described in the ECE-R13 rules. These rules define ABS as a component of the working brake system ( fig. "Brake System Scheme with ABS"), which automatically controls the wheel slip in the direction of rotation of the wheels on one or more wheels when braking.

application 13 ECE-R13 Determines three categories. The current generation of ABS meets the highest level of requirements ( category 1.).

Principles of ABS action

Pressure modulation

2/2-chassing solenoid valve (intake valve) with two hydraulic connections and two positions of inclusion is set between the main brake cylinder and the brake cylinder of the traditional brake system wheel ( fig. "ABS design"). When the valve is open (normal setting for standard braking), brake pressure can be created in the wheel brake cylinder. The exhaust valve, also 2/2-chassing electromagnetic, at this moment closes.

If the wheel speed sensor detects a sharp slowing down (risk of its lock), the system will prevent any further increase in the brake pressure on this wheel. The intake and exhaust valves are closed, and the braking pressure remains constant.

If the speed of slowing down the wheel continues to grow, the exhaust valve should be opened. As a result, the pressure in the brake cylinder of the wheel drops and the wheel is slowed down less intensively. The brake fluid, fixed in the intermediate reservoir, is pumped back into the main brake cylinder with a return pump.

Relative Slide Wheel

Relative Wheel Slide occurs when speed v R. With which the center of the car wheel moves in the longitudinal direction (vehicle speed) differs from the linear speed of the rotational movement of the wheel at the point of contact with the surface of the road v U. . Relative Slide Wheel λ It is calculated as follows:

λ \u003d (v U -v R) / V R 100%.

According to this formula, in the case of blocking the wheel, the relative slide will be λ = -1.

At initial braking, the pressure in the drive increases; The magnitude of the relative spray wheel λ Increases and at the maximum point on the clutch curve with expensive / sliding ( fig. "Curve the dependence of the clutch with an expensive from sliding wheels") The boundary of stable and unstable rolling ranges is achieved. From now on, any further increase in pressure in the drive or braking torch does not cause any further increase in the magnitude of the brake force F B. (fig. "Forces on a slowed wheel"). In a steady range, the sliding of the wheels largely is a SMU, it has an increasing tendency to slip in the unstable range.

There is a more or less sharp drop in the friction coefficient μ HF. , depending on the shape of the clutch curve in the unstable range. Without ABS, the resulting overcome causes a very fast blocking of the wheel when braking.

Basic feedback management processes

ABS management processes

The angular velocity of the wheel determines the rotation speed of the wheel ( fig. "Controlling ABS Contour"). If signs of blocking appear in the motion of one of the wheels, the slowdown of the wheel rotation and its slip is increasing. If they exceed critical values, the ABS control unit sends signals to the solenoid camshaft valve (hydraulic block) to stop or reduce the pressure in the brake mechanism before stopping the danger of blocking. Then the pressure must be restored to prevent the wheel's failure. During automatic braking control, it is necessary to constantly determine the steady and unstable combustion of the wheels and hold it in the slip range at the maximum brake force by alternating the phases of increasing, hold and reduce pressure.

In relation to the front wheels, this control sequence is performed individually, i.e. Separately on each wheel. For considerations of sustainability for rear wheels, another management strategy is required. In order to maintain side acceleration and, accordingly, transverse forces, on the rear wheels, when maintaining full power on turns, it is necessary to increase the coefficients of the side friction of the tires. Therefore, the levels of the hind wheels must be minimal, especially at the wheel on the external rotation radius. This is achieved due to the special characteristics of the braking control of the rear wheels "SELECT-LOW" or SL. It means that the control sequence is determined by the rear wheel, which is the first indicate signs of fast blocking. In the 3-channel brake system configuration with separate braking of the front and rear wheels (see " "), This is achieved by parallel compound of hydraulic contours. However, in diagonally separated brake circuits, this is achieved by controlling the rear wheelbase valves with the logic of parallel exposure.

Impact on a closed control loop

When developing the ABS system take into account the following:

• clutch options between the bus and expensive;
• irregularities of the road surface, causing fluctuations of wheels and axes;
• ovality, brake hysteresis, decrease in brake efficiency;
• changes in pressure in the main brake cylinder when exposed to the driver on the brake pedal;
• changes to the radius of the wheel, for example, when installing a spare wheel.

Quality management criteria

Effective anti-lock systems must meet the following management quality criteria:

• preservation of coursework by providing sufficient lateral forces on the rear wheels;
• maintaining manageability by providing sufficient lateral forces on the rear wheels;
• reduction of the brake path compared to braking with wheel lock by optimizing tire clutch with expensive;
• fast adjustment of the brake forces for various clutch coefficients, for example, when the car moves through puddles, through small areas of ice or rolled snow;
• ensuring a small amplitude of the braking torque to avoid vibrations in the suspension;
• achieving a high level of comfort by using silent actuators and feedback through the brake pedal.

Typical cycle control

Pictured by fig. "ABS regulating cycle for large friction coefficients" The control cycle shows automatic brakes control in the case of a high friction coefficient. Changing the wheel speed (slowing down when braking) is calculated using an electronic control unit. After this value falls below a certain threshold (" -Ah "), the valve of the hydraulic modulator switches to the pressure deduction mode. If the wheel speed further decreases below the valve of permissible slide λ 1, the valve switches to the pressure reset, which lasts until the deceleration of the wheel reaches the "-A" value. During the subsequent phase of pressure retention, acceleration increases to the threshold value "+ but", Then the brake pressure is maintained at a constant level.

After exceeding the high threshold " + BUT"It occurs increasing pressure, the wheel is not overly accelerated, as it enters the range of sustainable rolling. After decreasing acceleration to the threshold ( + a) pressure begins to slowly increase until the wheel acceleration becomes again less than the threshold (-A). At this time, the next control cycle begins.

During the first cycle of control, the short phase of pressure retention was originally needed to filter interference. In the case of a large moment of inertia of the wheel, a small clutch coefficient of slow increase in the pressure cylinder of the brake mechanism (careful initial braking, for example, on ice) the wheel can be blocked without a slowdown, to which the system can respond. In this case, the operation of the ABS system takes into account the wheel slip.

Under certain conditions and condition of the road surface on passenger cars with a four-wheel drive and differential locks often encounter problems when using ABS; This forces it to resort to special measures to determine the speed of movement during the control process, lower thresholds for slowing down the wheels and reduce the engine torque.

Managing the work of the brake with a delay in increasing the moment of rotation of the car around the vertical axis

When braking on a road with unequal friction coefficients (for example, different values \u200b\u200bof μ left wheels on dry asphalt, right wheels - on ice), highly different brake forces on the front wheels will result in the moment of rotation of the car around the vertical axis (Fig. "The appearance of the moment of rotation Car around the vertical axis caused by a large difference of friction coefficients ").

On passenger cars of a small class, the ABS system should be complemented by a delay device to increase the moment of rotation of the car around the vertical axis to maintain controllability on time of emergency braking on an inhomogeneous road surface. Delay in increasing the moment of rotation around the vertical axis limits the pressure growth in the front wheel cylinder with a higher clutch coefficient with the road surface.

The concept of a delay in increasing the moment of rotation around the vertical axis is demonstrated in fig. "Curves of brake pressure / reversal angle with a delay in the appearance of rotation torque around the vertical axis (YMBD)": curve 1 is a pressure in the main brake cylinder R Mc. Without a delay in increasing the moment of rotation around the vertical axis (so-called YMBD), the brake pressure on the wheel moving along asphalt, quickly reaches the values \u200b\u200bof p HIGT (curve 2), the brake pressure on the wheel moving on the ice grows only before l.o W. (curve 5.); Each wheel slows down with the maximum transmitted brake force (individual control).

System YMBD 1 (curve 3) is suitable for cars for which controllability characteristics are less critical, A YMBD 2 - for vehicles, more prone to loss of course stability due to the occurrence of rotation of the vertical axis (curve 4).

In all cases when the YMBD system is usedFirst, the wheel with a smaller slip is not realized. This means that the delay in increasing the moment of rotation around the vertical axis should always be very carefully adapted to this car to limit the increase in the braking path.

Currently, several ABS versions are proposed depending on the configuration of the brake contours, the drive configuration and transmission, functional requirements and budget. The most popular distribution of the brake forces is a diagonal separation (X-shaped brake circuit configuration), less popular - separation of the front and rear wheels (H-shaped brake contours configuration). Hi and NN configurations (for example, Daimler Maybach) are specialized and rarely used in conjunction with ABS. Variants of ABS systems differ in the number of control channels and sensors of the angular velocities of the wheels.

4-channel ABS system with 4 sensors

4-channel ABS systems with 4 sensors ( fig. "ABS System Options"It allows you to individually adjust the braking pressure on each wheel in four hydraulic channels, with the separation of brake circuits between the front and rear wheels (for the LL-shaped configuration of the brake contours) or the diagonal distribution (for the X-shaped brake circuit configuration). Each wheel has its own sensor measuring angular speed.

For a segment of super-compact vehicles with an engine working capacity up to 660 cc. Midget.) The Japanese market has developed a highly simplified ABS option. He put an end to damping cameras and return pumps. A small number of components compared to traditional systems provides significant savings, but has a number of functional flaws. Production of systems of this type is gradually stopped.

3-channel ABS system with 3 sensors

Instead of the usual location with a separate angular velocity sensor on each wheel in this embodiment, the rear wheels have one sensor installed in the differential. By virtue of the characteristics of the differential, it allows you to measure the difference in the angular velocities of the wheels with certain limitations. SL control characteristics for rear wheels, i.e. Parallel connection of the brakes of two rear wheels, allow you to do with one hydraulic channel for (parallel) the pressure control of the rear wheels.

Hydraulic 3-channel systems require II-shaped brake circuits configuration (separation of the front and rear wheels).

Systems with 3 sensors can only be used in vehicles with rear-wheel drive, mainly in trucks. The number of cars equipped with such systems falls.

2-channel ABS system with 1 or 2 sensors

The 2-channel ABS systems began to produce due to a small amount of components required and, accordingly, the cost of saving costs. Their popularity was limited, since their functionality was insufficient. These systems are now practically not used in cars.

Some of the USA light trucks with inter-axis separation of brake contours are still equipped with Rwal systems (Rear Wheel Anti-Lock, anti-lock system for rear wheels) - special simplified versions of the 2-channel ABS system consisting of a sensor on the rear axle differential and single control channel (without a return pump) preventing the rear wheel lock. With a sufficiently large brake pressure, the front wheels can still be blocked, which leads to risk of loss of controllability under certain conditions.

Such a system does not meet the functional requirements for ABS Category 1 systems.

Using ABS on motorcycles

In recent years, it was possible to significantly reduce the size and mass of ABS systems. As a result, serially produced ABS systems have become an attractive option for motorcycles. Consequently, this class of vehicles will be able to take advantage of ABS as a security system.

The automotive system for use in motorcycles is modified. Instead of the usual eight 2/2-chassis valves in the hydraulic unit in vehicles (with a X-shaped configuration of brake contours), motorcycles typically use four valves. The control algorithm is also fundamentally different from the ABS used in the automotive system.

Other system options appeared as a result of demand for combined brake systems (CBS), i.e. Systems in which both front and rear brakes can be controlled or a pedal or a manual lever, possibly in combination with individual means of activating the front brakes. For this type, a 3-channel hydraulic unit is required. However, the design of the CBS variant is highly dependent on the motorcycle model.

Examples of ABS systems

Hydraulic ABS block

Development of solenoid valves with two hydraulics switching positions (2/2-chassis valves used in systems ABS, starting from the 5th generation ABS, allowed to completely change ABS compared with the ABS-2S / ABS-2E versionwhere 3/3-chassis valves were used. It radically rationalized the design and manufacture. However, the Basic Hydraulic Concept ABS has not changed since the beginning of mass production in 1978. This means that hermetic brake contours and the principle of returning fluid remained the same.

The main components of the hydraulic unit, also called the hydraulic modulator, the following ( fig. "Hydraulic diagram of the ABS anti-lock brake system"):

• one returned pump on the brake circuit;
• rechargeable camera;
• damping functions previously performed by the battery chamber and flow limiter are now performed both hydraulically and control systems, i.e. software;
• 2/2-way electromagnetic valves with two hydraulic positions and two hydraulic connections.

For each wheel there is one pair of solenoid valves (except for the case with 3-channel configurations with the inter-axis separation of brake contours), one of which opens in a de-energized state to increase the pressure (inlet valve, IV), and the other is closed in a de-energized state to reduce pressure ( exhaust valve, OV). The check valve is installed in parallel with the inlet valve for a faster decrease in the pressure in the wheeled brakes during the termination of their operation.

Electromagnetic valves

The distribution of the functions of increasing and reducing the pressure between the individual solenoid valves with only one active setting (under voltage) made it possible to make the design of the valves compact - to reduce the size and mass, as well as reduce magnetic forces compared with previously 3/3-running electromagnetic valves. This allows you to optimize electrical control with small losses of electrical power in electromagnetic valve coils and in the control unit. In addition, the valve block ( fig. "The design of the hydraulic block ABS 8") You can make a smaller size. This is poured into rather significant mass savings and dimensions.

2/2-running solenoid valves are of different designs and with different characteristics, and by virtue of their compact sizes and excellent speakers, they provide sufficiently rapid electrical switching for cyclic operation with a pulse modulation. In other words, they have the characteristics of proportional valves.

System ABS 8 has a valve control with a "current signal" modulation, significantly improving functions (for example, adaptation to changes in the friction coefficient) and simplified control (less acceleration fluctuations due to pressure steps and analog pressure regulation). This mechatronic optimization has a positive effect not only on the function, but also for ease of use, i.e. On the noise and feedback on the pedals.

ABS 8 allows you to specifically adapt to individual requirements for vehicles by changing components (using different power engines, varying the size of the battery camera, etc.). The power of the return pump can vary in the range of 90 - 200 W. You can also change the size of the battery chamber.

Electronic control unit (ECU) ABS

The results achieved in the development of the ABS system are mainly a consequence of huge progress in the field of electronics. The times when ABS ECU consisted of more than 1000 parts (ABS of the 1st generation - from 1970 parts, analog design) is already far behind. The integration of functions in the LSI contours, the use of high-performance microcomputers and hybrid technology ECU provide high mounting density and, therefore, further miniaturization. At the same time, this leads to a significant increase in the efficiency and functionality of the system. The use of microprocessors made it possible to achieve significant optimization of management algorithms, including adaptation to the requirements of car manufacturers and pattern features.

The control unit is performed in the form of a replaceable computer and mounted directly to the hydraulic unit. The advantage of this placement is to minimize external wiring. The harness becomes less wires. As a result, the need for space is reduced and installation is simplified. The layout circuit requires only one plug connection between the ECU and the hydraulic unit and to connect the return pump motor.

ECU, schematically depicted on Fig. ", It is a 4-channel version with 4 sensors. Two microcontroller handle the control program. In the ABS ECU, they have a frequency of about 20 MHz and the amount of memory is about 128 KB. For ABS versions with special functions, there is enough memory about 256 KB.

In very complex systems, such as a dynamic stabilization system (ESP), the amount of memory can reach 1 MB. Depending on which processing speed is necessary, microprocessors with a higher clock frequency can be used.

Software consists of the following modules:

• operating system;
• Software for self-diagnosis;
• Software for different functions;
• On automakers and software for various applications.

Data exchange with other ECUs and diagnostics are carried out via CAN or FLEXRAY tire.

Anti-lock brake ABS system for commercial vehicles

Anti-lock brake system prevents wheel blocking with too strong braking. Therefore, the car maintains coursework stability and manageability, even with emergency braking on a slippery road. The anti-lock brake system prevents the risk of folding the road train.

Unlike passenger cars, trucks have pneumatic brake systems. However, the functional description of the ABS management process for passenger cars is in principle applicable to freight.

ABS management methods for commercial vehicles

Individual control (IR)

The process at which the optimal pressure is established individually for each wheel, which allows to get the smallest brake path. Under conditions with μ-separation (different clutch with expensive leading wheels - for example, on one asphalt track, and on the other - ice), when braking there is a big moment of rotation of the car around the vertical axis, which complicates the handling of cars with a short wheelbase. This is associated with the emergence of a large torque in the steering control due to the elevated shoulder of running in trucks. Individual control is commonly used in trucks on the back bridge.

Management "SELECT-LOW" (SL)

This process reduces the moment of rotation of the car around the vertical axis and the moment in the steering control to zero. This is achieved by creating the same brake pressure on both axis wheels. For this purpose, one pressure control valve in both wheels of one axis is used. In the case of pure SL control, the pressure level is determined by the wheel, which moves on the coating with the smallest clutch coefficient. Under the conditions of μ, the braking path is increasing, but the controllability and course stability of the car are improved. If the adhesion with expensive (friction coefficients) is the same on both kolas, then the braking path, controllability and course stability are almost identical to individual control systems (IR).

Individual control, modified (IRM)

In this process, the pressure modulation valve is established on each axle wheel of the axis. The moments of the department are reduced only as much as necessary, and the difference in the brake pressure is limited between the left and right side to the permissible level. As a result, a wheel having a higher friction coefficient is slowed down slightly smaller. Such a compromise solution leads to a slightly larger braking path than in time of individual control, but more securely controlled by car.

ABS equipment for commercial vehicles

Modern ABS ECU for trucks, tractors, buses can be used on two and three-axis vehicles ( fig. "Examples of ABS systems for trucks"). On time to memorize the values \u200b\u200bat the first commissionation, the control unit is configured to the appropriate car depending on the connected components. This includes a definition of the number of axes, ABS management methods and additional functions that may be necessary, such as the TCS traction force control system. A similar situation takes place with ABS ECU for trailers and semi-trailers. The same computer can be used in trails and semi-trailers with one, two and three axes and adapt to the level of the existing equipment.

If one axis is lifting, it is automatically excluded from the ABS control process when it is lifted.

When two axis are close to each other, often only one of them is equipped with the sensors of the angular velocity of the wheels. The braking pressure of two adjacent wheels is adjusted together with a single pressure control valve. In multi-axis cars with long distances between axes, for example, articulated buses, three-axis control is preferred.

Individual modified control (IRM) is most often used on controlled axes; SL control is also sometimes used, but very rare. In the rear axes of the tractor, individual control is usually selected.

Control block

The control unit allows you to control various modifications, not described in detail here. For example, both semi-trailer axes have wheel speed sensors, but each side is equipped with only a single pressure modulation valve and the wheel of one side are under control of the SL type.

All ABS systems can be equipped with single-channel pressure regulatory valves. ABS trailers can be equipped with pressure valves with control valves.

For cargo vehicles of a small load capacity with a pneumohydraulic drive, the ABS brakes is connected to the pneumatic mains by means of single-channel pressure modulators and determines the pressure in the hydraulic brake line.

When the car is operated on the roads with a low clutch coefficient, the operation of the auxiliary brake system during braking can lead to excessive slippage of the leading wheels. It may worsen the course stability of the car. Therefore, ABS controls the slip and adjusts it to a certain allowable level when the retarder brake is turned on and off.

Commercial ABS Components

Corner Speed \u200b\u200bSensors

The rotation of the wheels is controlled by the sensors of the angular velocity of the wheels (inductive or hall sensors). In combination with a pulsed ring rotating with the speed of the wheel, they generate an appropriate electrical signal. Electrical signals are processed in the ECU.

Electronic control unit (ECU)

The computer processes the signals of the angular velocity of the wheels. Then the signals are compared. Always compare the leading and slave wheels, wheels in the inner and external rotation radius, as well as dynamically loaded and dynamically unloaded wheels. On their basis, it is calculated to sing individual wheels and the corresponding pressure control valves are activated.

Other functions, such as automatic disconnection of the retarder brake, can be performed during the control. The ABS ECU is supplied with a safety circuit that is continuously controlling the entire system. When a failure is detected, partial or complete system shutdown occurs. Fault codes are stored in trouble and can be read using a diagnostic tester and removed from the problem after troubleshooting.

Some ECUs contain not only the ABS function, but also other functions, for example, a traction force control system (TCS) or a torque control of the engine (MSR).

Pressure control valves are located between the working brake valve and the brake mechanisms operating cylinders and control the brake pressure of one or more wheels ( fig. "Pressure regulation valve"). Pressure control valves consist of a combination of electromagnetic and pneumatic valves. They usually contain one exhaust valve and one pressure retention valve (single-channel pressure control valve), but a combination of one outlet valve and two pressure retention valves can also be used (two-channel pressure control valve). Electronics controls solenoid valves in the appropriate combination in order to achieve the required modes of maintaining or reduce pressure. When the valves are turned off, the pressure rapid mode is created.

When ordinary braking is carried out (without ABS intervention, i.e., if there is no tendency to block the wheel), the air passes through pressure modulators freely in both directions. This ensures trouble-free operation of the working brake system.

Today, new cars are equipped with the most different systems, with which even newcomers can easily cope with control. One of the very first systems, the anti-lock brake system is considered. The ABS system is installed even in the basic configuration of the car. This is an electromechanical block, which is in such complex road situations as slippery, wet path or ice, manages the braking of the vehicle. In essence, this is the right hand of the driver, the more newcomer.

Proper braking without ABS

Each driver should be aware that it is not enough to use the brake pedal in time. Since if at high speed to pull the brake to the brake, then the wheels of the car are blocked, as a result of which there will be no clutch wheels with a road surface. Road coating can be different, therefore, the slip speed will be different. As a result, the vehicle ceases to be manageable and can easily go into skid. If the owner of the car is inexperienced, then the control of the direction of the car may not be possible to be issued.

The most important thing in such braking is to prevent the wheels to be firmly blocked, as a result of which the vehicle goes into a skid. To avoid such cases, it is recommended to use discovery of intermittent braking. To carry out such proper braking, it is necessary to press the brake pedal periodically with a small interval, then you cannot keep the brake pedal pressed until a complete stop. With such a simple braking technique, you can control the car despite the quality of the road surface.

However, it is necessary to take into account the simple human factor - the driver in an unforeseen situation is able to be confused and all the deceleration rules can simply fly away from his head. To control the vehicle in such emergency situations, the anti-lock braking system was developed.

What is the secret of the work of ABS

It is important to know what principle the ABS works, because it has a close connection with the control system, which means that, respectively, with the security level of the route and passenger. So, the main idea of \u200b\u200bthe system of the system is that when the driver rises a brake pedal, an instantaneous control occurs, and the braking force is redistributed on the wheels. Through this, the car is manageable in any conditions, and the effect of reduced speed is achieved. However, it is impossible to rely only on various additional systems because the driver should be mastered its own car - the length of the braking path and behavior in emergency situations. It is recommended to test the abilities of the car on specialized autodromes, in order to prevent delicate situations on the road in the future.

There are still some features of the ABS work. For example, when the chauffeur decided to stop the movement of the car equipped with the ABS system, then when the brake pedal is pressed, there is a light vibration on the pedals, and the accompanying sound can be heard. Vibration and sound is a sign that the system has earned. In the meantime, the sensors read the speed indicators, and the control unit ensures pressure control inside the brake cylinders. Thus, it does not allow the locking of the wheels, and slows down with fast jerks. Due to this, the speed of the car is falling, and at the same time it does not go into a skid, which allows you to control the vehicle until the stop. Even with a slippery road, with the ABS system, the driver only needs to keep the direction of the car under control. Such ideal and manageable braking is possible only thanks to the ABS system.

The following stepships should be emphasized:

1. Dropping pressure in the brake cylinder.
2. Support for continuous pressure in the cylinder.
3. An increase in pressure to the corresponding level in the very brake cylinder.

It is important to know that the hydraulicock in the vehicle is mounted in the brake system in a row right after the main brake cylinder. As for the electromagnetic valve, this is a kind of crane that admits and blocks the inflow of the liquid substance to the brake cylinders themselves.

Control, as well as the working processes of the braking system of the car are carried out in consent with the information that entered the ABS control unit from the speed sensors.

When the braking process, ABS decrypts information from the wheel speed sensors, thanks to which the vehicle speed evenly falls. In case of stopping any wheel, the signal is instantly sent from speed sensors to the control unit. Accepting such a signal, the control module removes the lock due to the activation of the exhaust valve, which blocks the inlet of the liquid substance into the wheel brake cylinder. At this point, the pump returns the liquid into the hydroaccumulator. When the wheel turnover is increased to a permissible speed, the control unit will give the command to cover the graduation and open the inlet valve. After that, the pump is launched, which will pump pressure in the brake cylinder, with the result that the wheel will continue to slow down. These processes are performed instantly, and last until the final stop of the vehicle.

The discussed essence of the ABS works is the most new four-channel system, in which all vehicle wheels are controlled.

Other famous types

1. The single-channel consists of a sensor located on the back bridge whose task is to distribute the brake force synchronously into four wheels. This kind of system has only one pair of valves, due to which the pressure completely varies completely throughout the contour.
2. Two-channel - it takes steam control of wheels, which are located on one side.
3. Three-channel consists of three speed sensors: one is mounted on the back bridge, and the rest are mounted on the front wheels separately. In the mentioned form of the system there are three pairs of valves (intake and graduation). The action of this type of ABS consists in an individual control of the front wheels and in the pair of the rear.

By comparing different types of ABS, it can be concluded that their difference is manifested only in a different number of valves themselves and speed control sensors. However, the essence of the system in the vehicle, as well as the order of the flowing processes is identical to all types of systems.

History of system implementation

Engineers leading automotive companies were diligently engaged in developing ABS in the first half of the 70s. Even the very first systems were quite successful, and already at that decade, such systems began to install in mass production cars.

Initially, mechanical sensors were mounted on the cars only on the same axis, which sent data to the control module on pressure change in brake circuits. Developers with Germany made another step forward in this area and began to use sensors without contacts, and this, in turn, catalyzed the transfer of information to the logical block. In addition, the number of false positives has decreased, and due to the fact that rubbing surfaces eliminated, wear disappeared. In the same principle that was used in the first anti-lock systems, a modern system works.

Component anti-lock system

The hypothetical structure of the ABS is absolutely simple, and consists of the following devices:

• hydrelclock
• speed \u200b\u200bsensors
• electronic control unit

The latter plays the role of "intelligence" of the system (computer), so it is not difficult to imagine what he guides the role. As for the speed control sensors and hydroblock, a deeper analysis is necessary.

How does the speed sensor work

Sensors that control speed work on the principle of electromagnetic induction. In the gearbox of the leading bridge, the coil with a magnetic core is rigidly recorded. Also in the hub, a toothed crown is fixed, which rotates in parallel with the wheel. Then this rotation changes the parameters of the magnetic field, which in response causes the current appearance. The power of electric flow will be directly proportional to grow relative to the speed of rotation of the wheels. Stripping from this force, in turn, a signal is created, and is transmitted to the electronic control unit. The pulses are transmitted from four speed sensors that are two types: active and passive, and also differ in design.

The active type of sensor functions with a magnetic sleeve. The binary signal transmission is carried out by reading its tag. Due to the speed of rotation, there are no errors, and as a result - accurate impulse data.

In the passive type, a certain comb in the hub block is used. Thanks to such signals, the sensor is able to determine the speed of rotation. It is important to take into account one disadvantage of this design - with a small speed it may be inaccuracy.

Hydrelclock

The hydraulic block includes:

• tank for storing brake fluid - hydroaccumulator;
• intake and exhaust electromagnetic valves, due to which the pressure is regulated injected in the vehicle brake cylinders. Each type of ABS is distinguished by the number of pairs of valves;
• thanks to the universal pump, the necessary pressure is carried out in the system, as a result of which the brake fluid is supplied from the hydroaccumulator, and when it is necessary, selects it back.

Some shortcomings of ABS

One of the greatest drawbacks of the anti-lock braking system is that its effectiveness depends on the quality and condition of the road surface. With a not good road surface, the deceleration path is much longer. This is due to the fact that from time to time the wheel loses contact or adhesion with asphalt and stops rotation. ABS defines such a kind of wheel stop, like locking, and thereby stops slowing down. At the time of the hitch with asphalt, the programmed command is not consistent with the necessary in this case, and the system itself needs to be reinsured again, which requires time and increases the braking path. You can only minimize this effect only by reducing the vehicle speed.

In the case of inhomogeneous road coating, for example, snow - asphalt or ice - asphalt, getting on a wet or sliding area of \u200b\u200bthe road, ABS evaluates the coating and adjusts the braking process under this way. At the same time, when the wheels hit on the asphalt, the abs is again rebuilt, which is why the length of the Tupi braking increases again.

On the ground roads, the usual braking system works much better and more reliable than anti-lock braking system. After all, with ordinary braking, the blocked wheel is pushing the ground, creating a small slide that does not allow the transport tool further to move. Thanks to this, the car stops very quickly.

Another definition of the anti-lock braking system is that at low speed, the system is completely disconnected. In the case when the road under the slope and at the same time slippery, you need to remember that it may be necessary to brake a reliable handbrake. Therefore, it must always be in working condition.

The regular disconnection of the anti-lock braking system in cars is not provided. Sometimes drivers want to disable this system. To do this, pull out the plug from the block. It is also necessary to take into account that in new cars from ABS depends on the redistribution of inter-axis brake forces. Therefore, by braking, rear wheels are completely blocked.

It is important to note that the ABS system is an excellent addition to the car braking system, thanks to which you can control the car in the most difficult and unusual situations. Despite this, we should not forget that it is impossible to fully rely on the machine. From the driver side, you also need to apply great efforts to keep the situation under control.

Video

Modern cars are equipped with active security systems, helping to avoid loss of car management at various road situations. Some models use more than ten such systems. The first was anti-lock (ABS, ABS), which is now distributed, and it is used even on budget versions. The abs is also the basis for a number of other systems.

What is needed by ABS car

ABS is needed to prevent full blocking of wheels when braking, which eliminates the likelihood of care and reduces the length of the braking path. The theory of the anti-locking system is such - when braking between the locked wheel and the road cannon, there is friction of sliding, the strength of which is lower than rolling friction (when the wheel rotates). In addition, when sliding, the transverse forces prevail on the longitudinal and the wheel is easier to "leave" to the side than to maintain a given trajectory - a difficult-drilled drift occurs. But if the wheel is turning when braking, then the car does not break into the car, and retain the trajectory of the movement, and the braking system will work with maximum efficiency.

What is the anti-lock brake system

ABS includes two components - an electronic and executive module. The first controls the speed of rotation of the wheels on the machine and on the basis of this fits the signals to the module, and the one prevents the wheel locking.

Electronic component

The electronic component includes a control unit and tracking devices installed on the ABS wheel hubs.

Sensors are the main element of the entire system, since the operation of the ABS depends on their readings. Earlier, passive sensors were used on the car. In the modern models apply active sensors. Both variants consist of two elements - the tracking device, installed on a fixed part, and the specifying the hub located on the rotating part.

Principle of operation of ABS sensors

In passive sensors, the tracking component creates a magnetic field. The specifying element passing through this field leads to its changes. As a result, a pulse voltage is induced in the next component, which serves as a signal for the electronic unit.

In the active sensors, the principle of operation is different. In them, the changing magnetic field creates the specifying components (multiplar rings). On the following elements from third-party source. The acting field leads to changes in voltage parameters (resistance changes in magnetic sensors, voltage itself changes in the hall elements). These changes come to the block, which according to them calculates the speed of rotation of the wheels.

Video: ABS - pluses and cons of the anti-lock system

Electronic unit - control element. It, according to the sensors, the signals coming from the sensors determines the rotation speed of each wheel on the basis of the information obtained fresses the signals to the actuator module for making adjustments to the operation of the brake system.

Executive module

Influence the brake mechanisms by which the wheels are slowed down by changing the pressure in the brake system drive. Therefore, the executive module is embedded in the drive of the brakes and the highways coming from the main brake cylinder are suitable, and pipelines extended to brake mechanisms.

The executive module includes:

• intake and exhaust valves;
• hydroaccumulator;
• pump reverse feed with an electric motor;
• damper chamber.

For each brake mechanism, one sets one set of valves (intake and graduation). On one damper chamber and the hydroaccumulator is used on the contour. As for the pump, it is one to the executive module. Elements are interconnected by pipelines.

The module makes the ring line of the drive highway, which allows, if necessary, part of the working fluid on the generated ring to rush from the output of the module to the input.

Principle of operation

The work of the executive module is cyclic and includes three phases:

1. Pressure increases. When braking the brake cylinder creates fluid pressure, and it moves freely to the mechanisms. The direct movement of the fluid gives an open intake valve, the graduation is closed. As a result, the pressure on the mechanisms increases and the wheel is intensively slowed down.
2. Hold. If the sensor readings revealed a faster slowdown of one of the wheels, then it gives a signal to the closing of the inlet valve of this wheel (the outlet is also closed). As a result, on the mechanism, the increase in pressure stops, the wheel stops slowing down, since the friction force on the mechanism stops at one level.
3. Reset. In the case when the block "noticed" that the wheel on which the hold phase applies, it still slows down faster than the rest, it gives a signal to open the exhaust valve (intake remains closed) and the pressure in the highway is reset due to the flow of a part of the fluid in the module created by the module Ring - the brake mechanism is discharging.

The fluid when opening the exhaust valve arrives at first into the hydroaccumulator (acts as a container for collecting excess). If the fluid is reset a lot and the volume of the battery is not enough, the pump is turned on, which pumpers more superfluous in the module input.

Since there is a fluid ripple when the pump is created, it is first fed to the damper chamber after the pump to eliminate this negative effect, where the pulsation is smoothed and only then in the highway.

The speed of operation ABS is very high. When the machine slows down, the system works up to several hundred times, changing phases to achieve a deceleration of the car. The ABS works on the car constantly and it is impossible to disable it.

The conditions under which ABS is inefficient

ABS prevents care and maintains car handling. But under certain conditions, the effectiveness of its work is highly falling or it has a negative impact.

ABS does not provide efficient braking if the car moves along the road with a bad coating. The fact is that when moving the wheels on the wells and uhabam, the wheel is broken from the surface. Due to the fact that there is no resistance, even the mesmer effect of the pads on the disk or drum will lead to blocking the wheel. And it "notes" the system and dismisses the wheel, although you need pressing the pads only to increase so that the car stops.

The negative effect of ABS has when driving along a loose surface (snow, sand) in such conditions, a blocked wheel in front of itself "heats up" the boulder, which acts as a wedge, additionally slowing down the car. Due to the operation of the system, the wheel when braking is turning, because of which the wedge does not appear and the braking path is extended.

Video: ABS: pros and cons

ABS is an anti-lock brake system. From the title immediately becomes clear its purpose. But how does she work?

What is needed by ABS

Every driver knows that during the braking sooner or later, the moment may occur when the wheels cease to rotate and the car begins to go through. Such a situation is dangerous in that the car becomes unmanaged. Wheels that do not rotate even if they turn them with the steering wheel, they will not be able to change the trajectory of the car movement.

The wheel lock occurs when the braking force exceeds the tire clutch coefficient with the road. This moment occurs every time at different times and on ice will come much earlier than on dry asphalt. Therefore, braking during ice (and even emergency!) Turns into a very difficult task.

To facilitate the driving of a car in difficult weather conditions, an anti-lock brake system was developed.

How ABS works

The principle of operation of the anti-lock system is very simple - it is capable of detecting the blocking of one or several wheels and, when it happens, "turns off" the brakes. It is equivalent to how if you were letting the brake pedal. When the wheel starts to rotate again, ABS registers the start of rotation and again "includes" braking ...

The main "chip" of all these actions is that ABS turns off and includes brakes up to 30 times per second! During the system, the brake pedal is trembling under the foot, and on some cars heard the rigging of operating valves. At the same time, the wheels continue to rotate, the car does not lose control, and the braking occurs with maximum efficiency.

ABS device

The anti-lock brake system has a very modest number of large modules. These include wheel rotation sensors, valve block and control unit. Everything.

Rotation sensors are used to determine the rotation of the wheel. If there is no rotation, but the car moves, it means that the wheel is blocked. The signal from the sensor comes to the control unit, and it turns on the corresponding valve. The valve overlaps the corresponding brake line, turning off the brakes. Accordingly, when the wheel starts to rotate, the signal goes along the same chain, but the command from the control unit turns off the valve. The supply of brake fluid renews and braking continues.

Anti-lock systems are divided into three types:

1) Single-channel. The simplest ABS capable of controlling locking and braking only on all wheels immediately. Ineffective in cases where the wheels of different sides are driving along different coatings (classical situation: under the left wheels asphalt, and under the right - ice).

2) Two-channel. Work with two brake circuits separately. If the contours are distributed over sides, the rotation of the wheels will be adjusted more efficiently than with single-channel ABS

3) Multichannel. Affect each wheel individually. Such ABS are most effective because they are able to control any wheel exactly how it is necessary at the moment. Braking will be excellent, even if all the wheels will be completely different coatings.

The ABS control unit has a built-in self-diagnostic system. Sensor survey and determination of the system performance necessarily occurs after the ignition is turned on. At this time, a special pointer is obliged on the instrument panel. After a few seconds, it is also obliged to go out. If the pointer continues to glow, it means that there is a malfunction in ABS. Exploited a car with a non-working anti-lock system is extremely undesirable - you need to diagnose and repair.