ABS system: what is it and how does it work?

What is ABS, what does it consist of, how does the anti-lock braking system work and what to do if the light comes on – we answer the most pressing questions about one of the main car security systems

Photo: Shutterstock

• What is ABS
• Why ABS is needed
• How ABS works
• How ABS works
• ABS not working
• ABS types
• ABS Operation Tips

What is ABS?

ABS means anti-lock braking system, and in Russian transcription ABS means anti-lock braking system. ABS (ABS) is a system that prevents the vehicle's wheels from locking when braking. The principle of its work is the following. If, during intensive braking of the car, one or more of its wheels are blocked and begin to slide on the road surface, the ABS automatically relieves the pressure of the brake fluid in the corresponding line and the wheel starts to slip again. In this case, if the driver constantly presses the brake pedal, this process of locking and unlocking the spinning wheel continues continuously until the end of braking and, as a rule, occurs several times per second. This behavior of the ABS brake system allows the car to remain steerable even during sudden and emergency braking.

Why is ABS needed?

As we mentioned earlier, the main task of ABS is to maintain control over the car while driving. However, it also has other important properties:

• Maintain control of the vehicle during sudden and emergency braking.
• Ensuring smooth rectilinear braking on surfaces with a non-uniform coating and different coefficients of friction.
• Reduced braking distance on flat, hard surfaces with a smooth surface and a sufficiently high coefficient of adhesion.

The main task of ABS is to keep the car under control during sudden and emergency braking. (Photo: liputan6.com)

How ABS works

The design of the ABS system is integrated into the regular braking system of all modern cars and includes the following components:

• Speed ​​sensors

The speed sensors work on the principle of magnetic induction and are rigidly fixed to each wheel hub, and on some ABSs, to the rear axle gearbox. These are magnetic coils. Each cube has a serrated rim. When the wheels rotate, a current is created in the coil, the magnitude of which depends on the speed of rotation of the wheels. The data received by the sensors is transmitted to the ABS electronic control unit.

• ECU (electronic control unit)

The ECU analyzes the data from the sensors and calculates the moment of blocking the wheels, monitors the fluid pressure in the brake system and, if necessary, issues control commands to the modulator with valves to close the necessary brake circuit.

• valve modulator

The valve modulator is built into the main brake line. Having received a signal from the ECU, the first modulator valve blocks the access of the brake fluid with short pulses, thereby regulating the pressure of the brake mechanisms.

• Hydraulic accumulator

The hydraulic accumulator allows you to adjust the pressure in the system. If the pressure approaches the maximum allowable, the second solenoid valve drains the brake fluid into the accumulator. With a lack of fluid, it flows from the battery back into the brake line.

• ABS pump

The pump, usually of the cam type, is not always installed in anti-lock systems and works only when the ABS is activated, allowing you to quickly restore pressure in the entire brake system of the car.

How ABS works

The principle of operation of the anti-lock braking system is quite simple. So how does it work?

As soon as the driver presses the brake pedal with great effort and presses it, as they say, into the floor, he will immediately feel the characteristic “wheezing” sound and pulsation in the pedals. This means that the anti-lock braking system has worked. After that, the braking process is not controlled by the driver, but by the ABS control unit. At this point, the sensors read the wheel speed and brake line pressure. The computer calculates the braking speed required for a given situation and sends a command to the modulator to close one or another braking circuit. If the deceleration rate matches the calculated speed, fluid access to the brake circuit is resumed. In addition, in modern ABS systems, this operation can be performed for each circuit up to 18-20 times per second,

The ABS system prevents the wheels from locking during sudden and emergency braking and allows the car to stay on track. (Photo: Global Look Press)

ABS not working

Malfunctions of the anti-lock braking system in all modern cars are immediately displayed to the driver by a special indicator on the dashboard. If the ABS light comes on, it may indicate the following problems:

• wire break
• ABS sensors are dirty and disabled or out of order
• Damaged ring gear on wheel hub
• ECU stopped working

So in any case, a lighted up indicator is a reason to contact the service. Especially if it caught fire while the car was moving. In this case, it is necessary to be extremely careful and attentive, especially during sudden braking or sudden stops.

However, before going to a car service, you can try to fix the problem yourself, or at least understand its cause. If violations in the ABS operation are detected, it is necessary to conduct a visual inspection of all elements of the system. First you need to check the ECU for the presence of water inside the device or damage to the case. The ECU is located next to the brake force distributor. For your own safety, it is important to disconnect the battery in order to de-energize the machine.

You can also check the health of the fuses yourself. Various electronic components related to the anti-lock system are located on a common panel under the hood and are marked with the necessary markings.

If you have a jack or a pit in your own garage, the wires connected to the wheel sensors can also be inspected in the area of ​​u200bu200bthe wheel hub. Such a check can also reveal loose cables or chafing and damage.

Visual inspection can reveal loose, worn, or damaged cables. (Photo: Shutterstock)

Types of ABS

There are several types of anti-lock brake systems:

• Four channels is a system where there are 4 sensors that control each wheel individually. Such a scheme is by far the most effective.
• Three-channel is a system with three sensors, one of which works for the rear axle, and the other two for a pair of front steered wheels.
• A dual channel system is a system controlled by separate sensors on the front and rear axles.
• Single-channel is a system in which only one sensor is installed on the rear axle, and it works when two rear wheels are blocked. Such an ABS system is the most economical to operate, but also the least efficient.

Early anti-lock braking systems were single-channel, working only on the rear axle of the car. In addition, the mechanisms worked simultaneously and equally affected both wheels of the rear axle. Modern anti-lock systems support four channels, one for each wheel, each of which can operate independently.

Also, over time, the functionality of the anti-lock braking system was expanded, and with the help of different configurations of the electronic control unit, it was also possible to integrate the EBD brake force distribution system. This system works before the turn and during emergency braking controls the distribution of braking forces in the mechanisms even before the wheels lock. In addition, later steering wheel position, throttle and lateral acceleration sensors were added to work on ABS and EBD, which made it possible to “sew” the traction control system and the ESP stabilization system into the ABS unit. The latter, depending on the car manufacturer, has different commercial names, and can also be called ASR, DSC, VDC, etc.

ABS Operation Tips

For the most accurate and efficient operation of the ABS system, you should:

• Check tire pressure. It should correspond to the value recommended by the manufacturer. After all, the accuracy of measuring the speed of rotation of the wheels directly depends on the radius of the wheel, and, in turn, depends on the pressure in the tires.
• In winter, try not to clean the wheel arches and brake mechanisms from ice and aggressive reagents. An active external environment can lead to oxidation of the ABS sensors and their failure.
• Carefully follow the readings on the dashboard and if an ABS error occurs, contact a specialist immediately.