Description and principle of operation of the EBD system

The abbreviation EBD stands for “Electronic Brake Distribution”, which means “electronic brake force distribution system”. EBD works in conjunction with four-channel ABS 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 point 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 locked. This leads to a loss of directional stability under the influence of lateral forces, as well as to drifts and loss of control. Also, the adjustment of the braking forces is necessary when loading the car with passengers or luggage.

In the case where braking is performed in a corner (with the center of gravity shifted to the wheels running along the outer radius) or arbitrary wheels fall on 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.
• Changes in the pressure of the working fluid in the brakes 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 a 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 switched on.
• 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 the car carries luggage or passengers in the rear seats, the distribution of forces will be more even than with a strong shift 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 comes into operation before the start of the anti-lock braking system, preparing the car for more comfortable and efficient braking.