MB S-Class In Depth

Press Release

Safety:
PRE-SAFE inaugurates a new era in automotive safety

• The S-Class pioneers a trend-setting safety concept
• Pre-crash protection measures activated during emergency braking and skidding
• Advance deployment of PRE-SAFE belt tensioners
• Automatic front passenger weight classification

Crumple zones, airbags, belt tensioners, sidebags, belt force limiters, windowbags -- these are just some of the milestones clocked up in five decades of intensive and successful safety development work at Mercedes-Benz. These landmark systems have become a matter of course on state-of-the-art passenger cars of today. These pioneering safety features have saved thousands of people's lives and preserved thousands more from serious injury. Thanks to such systems, Mercedes models have now achieved an outstanding level of safety which it would be difficult to improve on by conventional means, since most of the potential of passive safety technology has now been exploited. Further advances require new concepts. Mercedes-Benz has therefore developed an innovative solution which is now poised to inaugurate a new era in vehicle safety: with PRE-SAFE. The model-year 2003 S-Class points the way -- PRE-SAFE will be standard equipment on the flagship Mercedes saloon range. The new Mercedes-Benz safety concept is based on the principle of advance protection: PRE-SAFE can detect an imminent collision before it occurs, and goes into action immediately to prepare both the vehicle and its occupants:

• The driver's and front passenger's seat belts are tensioned in advance of the potential impact.
• A very unfavourable pre-crash front passenger seat fore/aft setting and/or seat cushion and backrest angle can be corrected.
• The power-adjustable individual seats in the rear can be adjusted to optimise the angle of the seat cushions.
• The sunroof is automatically closed.

In two thirds of accidents, there is enough time before the crash occurs to activate PRE-SAFE protection measures PRE-SAFE is based on the findings of the Mercedes accident researchers which show that more than two thirds of all accidents are preceded by critical dynamic situations -- such as skidding, emergency braking or a sudden evasive maneuvre -- which provide advance warning that a collision is imminent. In the past, no use was made of this valuable "window", which may last several seconds: the familiar protection systems like the seat belt, airbag or belt tensioners are triggered only when the impact actually occurs. PRE-SAFE, on the other hand, reads the danger signals in advance and uses the remaining time prior to the potential accident to activate precautionary safety measures. In other words, PRE-SAFE equips the car with "reflexes", like those of a living organism. Just as sudden danger triggers a reflex action on the part of the organism, which takes precautions to protect itself, so the innovative safety technology of the S-Class immediately triggers special systems designed to reduce the risk of injury to the occupants. Sensors detect accident risk in advance PRE-SAFE gains advance warning of an impending collision due to unprecedented collusion between the active and passive safety systems. PRE-SAFE is linked up to the anti-lock braking system, Brake Assist and the Electronic Stability Program ESP, whose sensors identify critical driving manoeuvres and within milliseconds relay appropriate messages to the control units of these standard-fitted active safety systems. Now, for the first time, Mercedes-Benz is also using the information provided by these sensors as a basis for pre-crash occupant protection, thus opening up a whole new dimension in automotive safety. PRE-SAFE belt tensioners return to their original status if the accident is averted The pre-crash protective measures initiated by PRE-SAFE ensure that by the time an accident takes place, the seating position of the occupants has been optimised and the seat belts and airbags can operate more effectively. In other words, PRE-SAFE is not intended as a substitute for the tried-and-trusted restraint systems such as the front airbags, belt tensioners, sidebags and windowbags but as a complement to them, allowing them to operate with maximum efficiency. If the accident is prevented, the advance tensioning of the seat belts is automatically terminated and the occupants can reset the seats and the sunroof to their original positions. This reversible design means that PRE-SAFE is instantly ready to go into action again if required. Emergency braking triggers pre-crash activation of the belt tensioners If the Brake Assist system on board the S-Class carries out an emergency braking operation, the PRE-SAFE system is triggered too, and takes appropriate precautionary measures:

• The reversible PRE-SAFE belt tensioners prevent the driver's and front passenger's bodies from moving too far forward during braking. The belt tensioner, driven by a powerful electric motor, can reduce the belt slack within just 120 milliseconds. The engineers have carried out measurements which show that the forward movement of a front passenger who was not expecting sudden emergency braking is reduced by up to 150 millimetres.
  • Advantages: the driver and front passenger are optimally secured in their seats when the impact occurs and are moved further away from the instrument panel; the airbags are thus able to provide more effective protection.

• PRE-SAFE preemptively corrects the position of the front passenger seat: if the seat is positioned too far forwards, it is automatically moved further back. At the same time, if the backrest is angled too far back, it is automatically adjusted to an upright position. Then the angle of the seat cushion is also adjusted if necessary. This all takes place using the powerful electric seat motors of the S-Class, which can propel the seat in fore-and-aft direction at a speed of up to 22 millimetres per second and can adjust the backrest angle by 3.5 degrees per second.
  • Advantages: PRE-SAFE adjusts the front passenger seat to a position in which the airbag can deploy more effectively and the shoulder belt can develop a more effective restraining effect. The risk of submarining, with consequent injuries, is also reduced. If a rear-end impact is also imminent, the steeper backrest angle provides better support for the front passenger.

• PRE-SAFE optimises the position of the power-adjustable individual rear seats (optional) in the Mercedes-Benz S-Class dur-ing emergency braking. If one or both seat cushions is in a very flat position, PRE-SAFE will adjust it to a more steeply inclined position.
  • Advantage: The risk of the rear passengers submarining, with consequent injuries, is reduced due to the steeper angle of the seat cushion.

In a skid, PRE-SAFE also closes the sunroof PRE-SAFE uses data supplied by the sensors of the Electronic Stability Program ESP to identify dangerous skidding movements of the vehicle (strong understeer or oversteer). If such a situation is detected, it automatically intervenes:

• The reversible belt tensioners on the front seats reduce belt slack. Tests show that in this way lateral movements of the torso can be reduced by up to 300 millimetres, depending on the situation.
  • Advantages: driver and front passenger are optimally secured in their seats prior to a collision. The risk of the occupants being poorly positioned when an impact occurs is significantly reduced.

• If necessary, as in the case of emergency braking, PRE-SAFE can correct the positions of the front passenger seat and the power-adjustable individual seats in the rear. The system increases the distance between the front passenger and the instrument panel, adjusts the front passenger's backrest to an up-right position and modifies the angle of the rear seat cushions.
  • Advantages: If an accident risk is detected, the passengers' seats are adjusted to a safe position. The belts, belt tensioners and airbags can thus offer optimal protection.

• In critical skidding situations, PRE-SAFE also automatically closes the (optional) sunroof. This precautionary measure is based on the findings of the Mercedes-Benz accident researchers which show that violent skidding is frequently followed by a roll-over.
  • Advantages: Closing the sunroof reduces the risk of occupants atng thrown out of the vehicle in a roll-over, or of external objects intruding into the interior and causing injury.

PRE-SAFE builds on the Mercedes-Benz "real-life safety" concept PRE-SAFE is the logical next step in the "real-life safety" concept which the company has been pursuing for many years. The philosophy is that the development of safety innovations should always be based on careful analysis of the causes and consequences of real world accidents. Likewise, the effectiveness of such innovations should be assessed first and foremost with reference to real accident scenarios. This goes both for active safety systems, i.e. systems which like ABS, Brake Assist and ESP are capable of preventing accidents, and also for passive occupant protection systems. The Mercedes-Benz accident research findings have now been translated into a new system, PRE-SAFE, in which both active and passive safety systems work together. In this way PRE-SAFE develops and extends the Mercedes-Benz integrated real life safety concept: Warning phase
Sensors monitor the vehicle's behaviour. When the vehicle's dynamic limits are reached, a warning symbol lights up. Assistance phase
ABS, Brake Assist and ESP® intervene in critical situations and help to make these controllable for the driver. PRE-SAFE
The sensors detect the enhanced probability of an accident. To prepare for the potential accident, the front seat belt tensioners are activated and the front passenger seat and individual rear seats are adjusted to optimal positions. If there is a risk of skidding, the sunroof is closed as well. Light impact
In the case of an impact up to 15 km/h, the bumpers and crash boxes in the front end module absorb the impact energy. The inertia reels on the seat belts are locked. Sensors monitor the impact severity and trigger the airbags only if they are actually needed. Minor accident
In a more serious impact, robust structural members in various parts of the body absorb energy and distribute the forces over a wide area. The belt tensioners go into action. Depending on impact severity, the front airbag may deploy (first stage). Sidebags and windowbags provide protection during a side impact. The fuel supply to the engine is cut off. Serious acci-dent
If there is a more serious risk to occupants, a second stage is activated in the front passenger airbag. The belt force limiters are activated. Rescue phase
The doors are automatically unlocked after the accident. The TELEAID emergency call system (optional) alerts the emergency rescue services in the case of certain types of accident. The hazard warning lights are switched on. Real and simulated crash tests demonstrate the high efficiency of PRE-SAFE PRE-SAFE is the result of some six years' intensive development work by Mercedes engineers. Hundreds of drivers took part in the testing and refining of PRE-SAFE on test tracks and in the DaimlerChrysler Berlin driving simulator. This acceptance testing programme delivered a clear verdict: pre-crash occupant protection in no way restricts the freedom of the driver or the drivability of the car but rather, since the reversible PRE-SAFE belt tensioners keep the occupants firmly secured in the vehicle in critical situations, gives occupants an enhanced feeling of safety. The PRE-SAFE systems now making their world debut in the S-Class represent the first generation of a ground-breaking new Mercedes safety concept. The engineers are already working on further components of an adaptive pre-crash occupant protection system. They see this as the biggest challenge on the safety front in the coming years. Their long range goal is to develop a vehicle whose safety systems take into account occupant characteristics such as size, weight and age and thus combine "advance deployment" with customised protection. Two-stage front passenger airbag takes into account body weight The model year 2003 S-Class sets trends in another way too: the front passenger seat is equipped with a special measuring membrane which allows body weight to be taken into account when deploying the front passenger airbag. The system automatically assigns the front passenger to one of four weight categories. This means that even in low impact collisions, both stages can be triggered in order to offer optimal protection for heavier front passengers. In the case of lighter passengers on the other hand, the second stage is triggered only in a more serious impact. The new membrane, which is a refinement of the seat occupancy recognition system, also ensures that the front passenger's airbag, belt tensioner and side bag are automatically disabled if the seat is unoccupied. Thus this adaptive system also helps to save on accident repair costs. "Up-front" sensors allow precise assessment of accident severity Two newly developed "up-front" sensors in the front end of the S-Class body provide valuable input for adaptive actuation of the restraint systems. Their exposed position allows them to detect how severe the collision is even sooner and with greater precision than the crash sensor on the transmission tunnel. This allows the airbag control unit to further shorten the time lapse between the impact and the point at which the belt tensioners are triggered. At the same time the passenger airbag can be deployed earlier and its two stages can be activated more accurately. In a minor frontal impact, the system fires only one stage of the gas generator, so that the airbag is inflated with reduced pressure. If, thanks to the up-front sensors, the control unit detects a severe frontal collision, it also activates the second generator stage, within some 5 to 15 milliseconds of the first. The airbag is then inflated to a higher pressure, providing appropriate protection for a more serious accident. Windowbags also protect the occupants in a roll-over The windowbags and belt tensioners are now also triggered in a roll-over: from autumn 2002, Mercedes-Benz will be equipping the S-Class with a special sensor which can detect imminent rollovers and which relays all relevant data immediately to the central control unit supervising the restraint systems. Here a microprocessor determines whether the windowbags could provide additional occupant protection in the impending roll-over. If so, they are deployed within the space of just 25 milliseconds.