Predictive system maximises braking effect

A Bosch Automotive OE Division product story

Edited by the Engineeringtalk editorial team Mar 17, 2005

Bosch's new driver assistance system, Predictive Brake Assist, helps drivers in the event of an imminent accident by preparing the brake system for emergency braking.

Bosch's new driver assistance system, Predictive Brake Assist, helps drivers in the event of an imminent accident by preparing the brake system for emergency braking.

This represents the first stage of Bosch's Predictive Safety Systems product lineup - systems with preventive effect.

While unnoticed by the driver, Predictive Brake Assist builds up preventive brake pressure by placing the braking pads on the brake disks as a matter of precaution and setting the hydraulic brake assistant into a state of alert.

If the driver actually brakes, he gets the fastest possible brake response with optimal deceleration values and the shortest possible stopping distance.

When there is no braking action, the alert status is simply cancelled.

The Predictive Brake Assist will be installed for the first time worldwide as additional function of the adaptive cruise control (ACC) system in the new Audi A6.

The Predictive Safety System model is part of Bosch's Combined Active and Passive Safety (CAPS) concept.

CAPS presents a comprehensive cross linkage of sensors and electronic control units of existing vehicle safety systems, such as the electronic stability program (ESP), ACC as well as airbag controls, to provide an enhanced safety offering to vehicle occupants.

A look at the accident statistics reveals the great potential of the new Bosch safety systems: about one third of all car accidents are due to collisions with other vehicles or obstacles on the road.

Even in critical traffic situations, only some 30% of drivers will initiate a full braking action, most drivers are much too hesitant.

In this case, the Predictive Brake Assist function helps to prevent accidents or lessens the severity of impact to a large degree.

When the system identifies a dangerous situation, it boosts the hydraulic brake assistant to prepare for a full emergency braking manoeuvre.

If required, a full braking effect is reached some 30ms sooner, given the braking system has been prepared for emergency braking.

Current estimates indicate that around 2.5% of crashes with oncoming traffic could be avoided with this system, as well as 3.5% of accidents in intersections and 5% of rear-end collisions.

The Predictive Brake Assist is an upgrading of ACC from a purely convenience feature to a safety system.

In its basic function, ACC recognises vehicles driving in front, measures their speed and keeps the desired safety distance.

The heart of the ACC system is a sensor control unit which houses a radar sensor and control unit in a compact entity.

The radar sensor detects the vehicle in front up to a distance of 200m, while the electronic control unit measures the speed and the distances.

The ACC then adjusts the speed of the vehicle to match the flow of traffic through controls of engine and brake system.

Once the road is clear again, the ACC accelerates the vehicle to the speed preselected by the driver.

In 2006, Bosch plans to launch a Predictive Safety System which gives an early warning to the driver in critical traffic situations - such as by giving a noticeable brake pulse - which will in many cases help to prevent accidents.

In a further stage of upgrading, the system will additionally trigger a fully automatic emergency braking with maximum vehicle deceleration if a collision is unavoidable, thus helping to reduce the severity of the accident and its consequences.