What does ebd mean in a car. EBD in a car: what it is and how it works. What is ABS, and what disadvantages does it have

The mechanical brake force distribution system used on previous models has been replaced by an electronic control unit (ECU) for the anti-skid system, which precisely controls the braking force depending on the driving conditions of the vehicle.

Distribution of braking force between front and rear wheels

Depressing the brake pedal while driving in a straight line reduces the load on the rear wheels and increases the load on the front wheels. The ABS electronic control unit recognizes this condition from the signals from the speed sensors and sends a command to the brake cylinder control unit, regulating the braking force transmitted to the rear wheels.

The amount of this effort depends, for example, on the vehicle's load and also on the deceleration speed. This ensures the optimum distribution of the braking forces transmitted to the rear wheels, depending on the driving conditions.

Distribution of braking force between the right and left wheels (when braking in a corner)

When braking in a corner, the load on the inner wheels decreases, while on the outer wheels it increases. The electronic control unit of the anti-skid system recognizes this condition from the signals of the speed sensors and sends a command to the control unit for the working cylinders of the brakes, ensuring an optimal distribution of braking force between the inner and outer wheels.

Brake slave cylinder control unit

The brake slave cylinder control unit consists of a hydraulic valve and a skid control ECU.

The brake slave cylinder control unit manufactured by BOSCH is used, as on Avensis cars.

System operation

The ABS electronic control unit calculates the speed and deceleration rate of each wheel, and also monitors wheel locking based on signals from 4 speed sensors. Depending on whether the wheels are slipping, the electronic control unit of the anti-skid system regulates the brake fluid pressure in the slave cylinder of each wheel, including the check and pressure reducing valves in one of three modes: pressure decrease, hold and increase.

Diagnostics

If the skid control ECU detects a malfunction of the ABS with electronic brake force distribution (EBD), the ABS warning lamp and the brake warning lamp will illuminate to indicate a system malfunction (see table below).

Electronic trouble codes (DTCs) are stored at the same time. DTCs can be read by the number of flashes of the ABS emergency lamp: to do this, connect the SST diagnostic tool (09843-18040) or microprocessor tester II to the Tc and CG pins of the DLC3 diagnostic socket.

The diagnostic system provides an active mode for diagnosing sensor signals. The function is activated by connecting the SST diagnostic tool (09843-18040) or microprocessor tester II to the Ts and CG pins of the DLC3 diagnostic socket.

If malfunctions are detected during the sensor check, the skid control ECM will store the corresponding electronic DTCs. DTCs written into the memory during the sensor test can be read by the number of flashes of the ABS warning lamp when the Tc and CG contacts of the DLC3 diagnostic connector are closed or using a microprocessor tester II.

Emergency operation

If a fault occurs in the ABS system, the skid control ECU will block the activation of the anti-lock braking system.

If a malfunction occurs in the electronic brake force distribution (EBD), the skid control ECU will override the skid control system. In this case, the braking system will operate as in the absence of an ABS with electronic brake force distribution (EBD).

Ever since electronics came to the automotive industry, cars began to be equipped with more and more auxiliary systems that were controlled by electronic intelligence. This, in particular, concerned the active safety of the car: the designers improved the braking system, equipping it with an anti-lock braking system, which helped to avoid wheel locking in emergency situations. The evolutionary development of active safety systems associated with braking was the emergence of another mechanism - the brake force distribution system.

What is EBD

EBD (Electronic Brake Distribution), which in Russian means "brake force distribution system", began to appear on cars in the late 1980s - early 1990s. It was then that the engineers of the leading automobile companies noticed that anti-lock braking system could not provide one hundred percent effect of unlocking the wheels. This became especially noticeable when, when braking, the front wheels received a larger load than the rear ones. At the same time, the system successfully unlocked the front wheels, but the rear ones remained locked, which caused the car to turn around. After conducting research, experts have found that the braking force that develops in a similar situation is distributed between all wheels in the same way. But at the same time the wheels are in different conditions - their grip on the road surface is different, therefore, they behave differently: for example, the front wheels are unlocked and "allow" the driver to drive the car, while the rear wheels are locked, which makes the car drift. ... To solve this problem, a brake force distribution system was developed.

EBD consists of three main components: wheel speed sensors (the same sensors are used from which ABS receives information), an electronic control unit (again, common with ABS), and valves in the brake line - return and reduction valves. When the car emergency brakes and ABS is activated, the brake force distribution system is automatically activated. Its control unit receives information from sensors about the speed at which the wheels are spinning. Based on this data, the system infers which wheels have the best grip and which ones have the worst. Then the process of distributing the braking forces takes place: the control unit gives a command to the valves, which, by regulating the pressure in the brake system, distribute the braking force - the front wheels receive less of it, the rear more. Thus, the effort on all wheels is equalized.

At the same time, the ABS system, having received a signal that the braking force is evenly distributed, unlocks the wheels, and this allows the driver to gain control over handling and avoid a collision with an obstacle.

The main difference between EBD and ABS is that this system works constantly, controlling the distribution of braking forces regardless of road conditions and driver activity, and not only in extreme conditions, like the same ABS. Nevertheless, today, cars equipped with an anti-lock braking system often have a brake force distribution system - these mechanisms are so united and complementary to each other.

Pros and cons of EBD

This system has no operational deficiencies. But EBD has many advantages. After all, by distributing the braking force between the wheels, the system helps the driver to maintain the trajectory of driving, reduces the risk of drifting or skidding. It is equally effective in straight-line braking as well as in tight cornering. In the latter case, the system distributes the braking force not between the front and rear wheels, but between the wheels running along the outer and inner turning radius.

Most budget cars are very sensitive to the action of the brake pedal. Basically, pressing the pedal activates the brakes and the wheels slow down. You can't imagine any simpler thing - the harder you press on the "brake", the stronger it works. However, such a system has significant drawbacks.

Electronic brake force distribution (EBD) was introduced in conjunction with ABS. The task of the system is, as the name implies, to correctly distribute the intensity of braking to each wheel. It so happens that the car gets on an uneven road surface. Let's say you had to pull over to the side, and the right wheels ended up on a dirt road, while the left ones remained on the asphalt. Accordingly, the frictional force during wheel traction on the ground and asphalt is not the same. To avoid skidding, EBD will increase the braking on the left wheels and weaken the right ones, thereby maintaining control over the vehicle.

History

The United States was the first to fight wheel lockups. In the late 1960s, Bendix developed ABS, thus setting the stage for the development of EBD and other brake additions. The pioneer was the Chrystler car in 1971.

First of all, executive class cars were supplied with such systems. Today, ABS and EBD technologies are no longer innovative and are installed, at least as an option, on most cars of the middle class and above.

Principle of operation

The task of ABS is to prevent the wheels from locking. Whereas EBD controls the distribution of the braking force.

The EBD system operates with data that is read by the ABS unit. Each wheel is equipped with sensors that transmit the wheel speed using electrical impulses. Also, the system reads the readings, thereby determining the vehicle load. Ultimately, the automation has data on the speed of the vehicle, its load and the degree of adhesion of the wheels to the road surface. The main advantage is that the data is read from each wheel separately, which makes it possible to correctly distribute the intensity of the action of the brake mechanism, therefore, to avoid loss of control.

The easiest way to understand how EBD works is to imagine a tug-of-war competition. As long as the teams pull with equal force, the rope remains stationary, but as soon as one surrenders, the rope abruptly breaks out towards the stronger team. The principle is similar here. To prevent the car from being thrown into a skid, the electronics distributes the forces evenly, “helping” the weakened wheel and, if necessary, loosening the other wheels.

Exploitation

Of course, the system cannot foresee everything. It so happens that the wheel for a short moment can lose traction and the electronics will incorrectly distribute the braking force. In addition, the ABS itself is not always 100% efficient. Especially in winter, skid braking can give better results. The tread on winter tires is much deeper than the summer version, and when driving on a snowy trail, locked wheels will “shovel” the snow, thereby shortening the braking distance.

EBD is an abbreviation for the first letters of the phrase Eltectronic Brake Distribution, which stands for electronic brake force distribution. Although, for sure, even after this decryption, many of you still have questions about EBD or how many people write EBD, what it is and how it works. Therefore, we will consider this system in more detail.

The electronic brake force distribution system EBD works only in conjunction with the anti-lock braking system, or, as it is also called, ABS. EBD, optimizing the operation of the latter, regulates the braking force between the front and rear axle of the vehicle's wheels, as well as between the right and left sides.

It focuses on weather conditions, or rather on the road surface in them, as well as on the technical condition and workload of the vehicle, and determines which wheel needs to make more braking force, and for which - the load should be weakened. This way EBD shortens the braking distance of the car and makes cornering more stable, and therefore safer, because the possibility of skidding is minimized.

How EBD works.

The sensors of this system are installed on each wheel of the car. At the moment of emergency braking, they read the information on which wheels have more braking force and it is possible to block them, and which ones, on the contrary, are little involved, and transmit it to the control unit for the electronic brake force distribution system.

That, in turn, begins to regulate the action of the working cylinders of the brakes, distributing the necessary forces to the wheels, while maintaining the driver's control over the steering. The system works in the same way when cornering. This makes braking more efficient, cornering safer and driving more predictable.

The abbreviation EBD stands for "Electronic Brake Distribution", which means "electronic brake force distribution system". EBD works in conjunction with and is a software add-on. It allows you to more efficiently distribute the braking force on the wheels, depending on the load of the car, and provides higher controllability and stability when braking.

Principle of operation and design of EBD

During emergency braking, the vehicle's center of gravity shifts to the front, reducing the load on the rear axle. If at this moment the braking forces on all wheels are the same (which happens in cars that do not use brake force control systems), the rear wheels may be completely blocked. This results in loss of lateral forces as well as skidding and loss of control. Also, the adjustment of the braking forces is necessary when loading the car with passengers or luggage.
In the case when braking is performed in a corner (with the center of gravity transferred to the wheels running along the outer radius) or arbitrary wheels hit surfaces with different grip (for example, on ice), the action of one ABS system may not be enough.
This problem can be solved by the brake force distribution system, which interacts with each wheel separately. In practice, this includes the following tasks:

• Determination of the degree of slippage on the road surface for each wheel.
• The change in the pressure of the working fluid and the distribution of braking forces depending on the adhesion of the wheels to the road.
• Maintaining directional stability when exposed to lateral forces.
• Reducing the likelihood of the car skidding during braking and turning.

The main elements of the system

Structurally, the brake force distribution system is implemented on the basis of the ABS system and consists of three elements:

• Sensors. They record data on the current speed of each wheel. In this EBD uses ABS sensors.
• Electronic control unit (control unit common to both systems). Receives and processes speed information, analyzes braking conditions and actuates the appropriate brake valves.
• Hydraulic block of the ABS system. Adjusts the pressure in the system by varying the braking forces on all wheels in accordance with the signals supplied by the control unit.

Brake force distribution process

In practice, the operation of the electronic brake force distribution EBD is a cycle similar to the operation of the ABS system and consists of the following stages:

• Analysis and comparison of braking forces. Carried out by the ABS control unit for the rear and front wheels. If the set value is exceeded, the algorithm of actions pre-installed in the memory of the ECU control unit is activated.
• Closing the valves to maintain the set pressure in the wheel circuit. The system detects the moment when the wheel starts blocking and fixes the pressure at the current level.
• Opening the exhaust valves and decreasing the pressure. If the risk of wheel blocking persists, the control unit opens the valve and reduces the pressure in the circuits of the working brake cylinders.
• Increased pressure. When the wheel speed does not exceed the blocking threshold, the program opens the intake valves and thus increases the pressure in the circuit created by the driver when the brake pedal is pressed.
• At the moment the front wheels begin to lock, the brake force distribution system is turned off and ABS is activated.

Thus, the system continuously monitors and distributes the braking forces to each wheel in the most efficient way. Moreover, if luggage or passengers in the rear seats are transported in the car, the distribution of forces will be more even than with a strong displacement of the center of gravity to the front of the car.

Advantages and disadvantages

The main advantage is that the electronic brake force distributor makes it possible to most effectively realize the braking potential of the vehicle, depending on external factors (loading, cornering, etc.). In this case, the system works automatically, and it is enough to press the brake pedal to start it. Also, the EBD system allows you to brake during long bends without the risk of skidding.
The main disadvantage is that, in the case of using studded winter tires, when braking using the EBD brake force distribution system, compared to conventional braking, the braking distance increases. This disadvantage is also typical for classic anti-lock braking systems.
In fact, the electronic brake force distribution EBD is an excellent complement to ABS, making it more advanced. It enters into operation before the start of the anti-lock braking system, preparing the car for more comfortable and effective braking.