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Mercedes-Benz TecDay Special Feature:  PRE-SAFE And PRE-SAFE Brake
Posted November 12, 2008 At 4:20 PM CST by C. Danielson

Mercedes-Benz S-Class testing the PRE-SAFE Brake driver assistance system

Mercedes-Benz is the world's only car brand to offer an anticipatory occupant protection system that activates protective measures for the car's occupants if there is an imminent risk of an accident. This multi-award-winning technology, called PRE-SAFE®, is fitted as standard in numerous Mercedes model series and has now been further enhanced by Mercedes-Benz.

The intelligent PRE-SAFE® system takes its lead from nature in that it activates protective measures for the car occupants as a precaution, just as living things react instinctively and search for cover when they are in danger. The aim is to prepare the occupants and the car for an imminent collision so that the seat belts and the airbags can deploy with maximum effect in the event of an impact. What's more, the PRE-SAFE® protective measures are reversible: if the accident is averted, the advance tensioning of the seat belts is halted automatically and the occupants are able to reset the positions of the seats and the sunroof. The anticipatory occupant protection system is then ready for action again straightaway.

Early accident detection is possible because PRE-SAFE® is an intelligent synergy of active and passive safety. It is linked to Brake Assist and the Electronic Stability Program (ESP®), whose sensors detect potentially critical driving situations and send the relevant information to the electronic control units within a matter of milliseconds. PRE-SAFE® also uses these sensor data for anticipatory occupant protection.

PRE-SAFE® celebrated its world premiere in the S-Class in 2002 and has been fitted as standard in the E-Class since 2006.

Like the S-Class, the new E-Class can activate further preventive measures ahead of an imminent accident:

  • Whereas PRE-SAFE® previously responded to emergency or panic braking – in other words when the driver hit the brake pedal reflexively – the system in the new E-Class can also be activated if Brake Assist PLUS has used the radar system to predict an impending collision and a certain level of deceleration is exceeded when braking. The occupants are prepared for the potential collision by preventive tensioning of the front seat belts and repositioning of the front-passenger seat (if the seat memory function is specified), enabling the seat belts and airbags to offer the best possible protection.

  • A newly developed multicontour seat ensures that the driver and front passenger are seated even more securely, thereby limiting dangerous whiplash movements by the upper body. If the PRE-SAFE® control unit detects a critical driving situation, it instantly activates the air chambers in the seat cushions and backrests. These then envelope the seat occupants and give them support. Tests at the Mercedes-Benz Technology Center have shown that this PRE-SAFE® function and preventive belt tensioning increases the distance between the shoulder and the inner door lining by up to 40 millimetres at a lateral acceleration of 0.6 g. This enables the sidebag to fulfil its protective function more effectively.


PRE-SAFE® when braking in an emergency
PRE-SAFE® when there is a risk of skidding
Driver and front-passenger seat belts are tensioned
Bolsters in the seat cushions and backrests of the multicontour front seats* are inflated
Front-passenger seat* is moved backwards or forwards into the optimum position whilst the cushion angle and backrest inclination are also optimised
Side windows at the front and rear are closed
 
Sunroof* is closed
* depending on equipment


When installed in combination with DISTRONIC PLUS and Brake Assist PLUS, PRE-SAFE® will also use the information provided by the short-range radar sensors in the front bumper to tension the front seat belts at the very last moment before an unavoidable collision, thus reducing the forces exerted on the driver and front passenger during the crash. This PRE-SAFE® function is literally the "ultima ratio" of anticipatory occupant protection, since the accident occurs around 200 milliseconds later.

Belt tensioning reduces the forces exerted on the occupants by up to 40 percent

Analyses performed during crash tests show just how important and effective anticipatory occupant protection can be. In the case of belt tensioning, for example, the precautionary measures mean that the driver and front passenger are held in their seats in the best possible position and so do not move forwards as much in the event of an impact, thus reducing the load exerted on the head and neck area. These tests showed that the head was subjected to around 30 per cent less stress, while the Mercedes engineers recorded a reduction of around 40 per cent in the neck area.


PRE-SAFE® Brake: Automatic emergency braking can greatly reduce the severity of a head-to-tail crash

Mercedes-Benz has continued to further develop the PRE-SAFE® Brake, which was first unveiled in 2006. From spring 2009, a version of the system that activates the maximum braking power automatically if there is an acute risk of an unavoidable accident will be available for the new E-Class and the S-Class. The PRE-SAFE® Brake therefore acts as an electronic crumple zone and can greatly reduce the severity of an impact.

Accident research shows that drivers do not always react as quickly as necessary at critical moments – for example because they are distracted and therefore do not recognise the immediate threat of a head-to-tail crash, or because they fail to heed the warning signals given by an assistance system. The PRE-SAFE® Brake intervenes in situations such as these by braking the car automatically.

What's more, it does this in two stages: around 1.6 seconds before the calculated impact point – after three audible warning signals – the system initiates partial braking autonomously and decelerates the car with around 40 percent of the

maximum braking power (approx four m/s²). Designed to supplement the visual and audible warnings, autonomous partial braking gives the driver a further, perceptible signal to act. If the driver then brakes immediately, the maximum braking force is made available or, if the driver swerves, the accident can be avoided at the last moment, depending on the driving situation. Mercedes-Benz first unveiled PRE-SAFE® autonomous partial braking in the CL-Class and the S‑Class in 2006.

Mercedes will be offering a further enhanced version of this safety system from spring 2009. If the driver fails to react, even after automatic partial braking, the PRE-SAFE® Brake activates the maximum braking power around 0.6 seconds before the now unavoidable collision. This emergency braking can greatly reduce the severity of the impact.

The system therefore acts like an "electronic crumple zone", offering the car occupants even greater protection.

Like Brake Assist PLUS, the PRE-SAFE® Brake uses state-of-the-art radar technology to monitor the situation in front of the car and detect an imminent accident. Two short-range radar sensors with a range of 30 metres and a beam width of 80 degrees are located behind the front bumper covering. The additional long-range radar in the radiator grille has a range of 200 metres.

The PRE-SAFE® Brake greatly reduces the severity of accidents

Mercedes-Benz has tested the operation and effectiveness of the PRE-SAFE® Brake, both on the road and in the road simulator. Around 400 drivers took part in the road tests in Germany and the US, clocking up a total of around one million kilometres in test cars.

Mercedes engineers conducted a series of tests, lasting several weeks and involving 70 drivers, in the road simulator at the Daimler research facility in Berlin. Each of the drivers drove for half an hour and was distracted by an accident on the other side of the road, whilst at the same time the traffic in front of the car braked suddenly. The results of the test, which reflects an everyday situation on the road, highlight the safety-enhancing effect of the sophisticated assistance systems: a total of 70 percent of these test drives remained accident-free thanks to the fast reactions of the drivers and the assistance provided by BAS PLUS and the PRE - SAFE ® Brake. In a third of the simulator tests, those taking part were unable to avoid a crash. In these cases, automatic braking greatly reduced the accident severity.

Realistic tests carried out by the Mercedes engineers have revealed that autonomous PRE-SAFE® emergency braking reduces the impact speed by 16 km/h on average.

The PRE-SAFE® Brake is active at speeds of between 30 and 200 km/h when moving vehicles are detected in front of the car. The system also reacts if the car approaches a stationary queue of traffic, providing its speed is below 70 km/h.

This component is an important part of the PRE-SAFE® anticipatory occupant protection system, which is fitted as standard in many Mercedes models. It uses the otherwise wasted seconds (from an occupant-safety standpoint) between the point at which a potential accident risk is detected and the point at which the protective systems in the interior are activated.

Just like the airbag, seat-belt tensioner, ESP® and other trailblazing Mercedes inventions, the PRE-SAFE® Brake was developed based primarily on real accident situations. When used in combination with Brake Assist PLUS, this technology can make a key contribution towards reducing the high number of head-to-tail crashes or reduce the severity of such collisions. In Germany, over 17 percent of all serious road accidents involve head-to-tail crashes. In the US, meanwhile, one in three road accidents involving deaths or injuries are head-to-tail crashes.



Mercedes-Benz PRE-SAFE

Mercedes-Benz PRE-SAFE

Mercedes-Benz S-Class testing the PRE-SAFE Brake driver assistance system

Mercedes-Benz S-Class testing the PRE-SAFE Brake driver assistance system

Mercedes-Benz S-Class testing the PRE-SAFE Brake driver assistance system

Mercedes-Benz S-Class testing the PRE-SAFE Brake driver assistance system

Mercedes-Benz S-Class testing the PRE-SAFE Brake driver assistance system

Mercedes-Benz S-Class testing the PRE-SAFE Brake driver assistance system

Mercedes-Benz S-Class testing the PRE-SAFE Brake driver assistance system

Mercedes-Benz S-Class testing the PRE-SAFE Brake driver assistance system

Mercedes-Benz S-Class testing the PRE-SAFE Brake driver assistance system

Mercedes-Benz S-Class testing the PRE-SAFE Brake driver assistance system

Mercedes-Benz S-Class testing the PRE-SAFE Brake driver assistance system

Mercedes-Benz S-Class testing the PRE-SAFE Brake driver assistance system

Mercedes-Benz S-Class testing the PRE-SAFE Brake driver assistance system

Mercedes-Benz S-Class testing the PRE-SAFE Brake driver assistance system

Mercedes-Benz S-Class testing the PRE-SAFE Brake driver assistance system

Mercedes-Benz PRE-SAFE Brake

Mercedes-Benz PRE-SAFE Brake

Mercedes-Benz PRE-SAFE Brake

Mercedes-Benz PRE-SAFE Brake

Mercedes-Benz PRE-SAFE Brake



Mercedes-Benz PRE-SAFE Brake

Copyright © 2008, Daimler AG


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