Electronic brake force distribution
Electronic brake force distribution (engl. Electronic Brake Force Distribution , EBD) is a system for stabilizing vehicles .
principle
When braking hard, the vehicle's weight is shifted to the front wheels. As a result, the rear wheels can lock because the load is relieved and the braking power can no longer be transferred to the road due to the reduced contact with the ground. In this case there is an immediate risk of skidding (see oversteering ).
A weighting of the braking force is achieved in part by making the front brakes stronger, i. H. brake harder than the rear ones with the same pedal pressure. However, since the braking power of the rear wheels is the reverse of the deceleration, another mechanism is necessary.
Older vehicles usually have a mechanical brake force distributor which is attached to the rear axle and which uses a lever to reduce the brake pressure of the rear wheels when the rear is raised via a valve. The electronic brake force distribution replaces this relatively imprecise mechanical solution with an electronic system, especially since the required sensors and actuators are already available when an ABS is present.
Technology and functionality
Normal function
Unlike the anti-lock braking system (ABS), EBD does not prevent the wheels from locking, but only distributes the brake pressure between the front and rear axles, thus stabilizing the vehicle, for example when braking in a curve. EBD supports the anti-lock braking system (ABS), as this only reduces the brake pressure when the corresponding wheel is already locked.
In contrast to ABS, where the brake light switch only represents a "supporting and informative" signal, but not a safety-relevant signal (ABS calculates the valve actuation from the wheel speeds and would also function without a brake light switch signal), an EBD intervention is only activated by a valid brake light switch signal in conjunction with the amount of the calculated slip is initiated on the rear axle.
Error case and error detection
A good method to avoid overbraking the rear axle if the brake light switch fails and to recognize the fault condition at all is therefore to use redundant (double) switches. Other solutions aim at a simple (i.e. non-redundant), more cost-effective switch and extended software that tries to detect the missing switch signal - more or less well - by means of plausibility checks.
history
Introduced electronic brake force distribution , starting in 1994 by Opel and Bosch in the car Opel Omega B . The driving force behind the development of the system was the weight and cost advantage resulting from the elimination of the mechanical brake force distributor. Since the electronic brake force distribution within an ABS or ASR system was only part of software that was expanded by a few hundred bytes, it did not require any new additional hardware.
The product name DME (pressure reducer replacement logic) originally intended by Bosch sounded too complicated and consequently never caught on.