Mercedes ESF S400 Hybrid Concept 2009 In Depth with 3 Videos

Press Release

PRE-SAFE Structure: inflatable metal structures

It sounds like science-fiction: concealed metallic structures that wait patiently in a collapsed, space-saving state until they are required to go into action. Daimler researchers working together with the gas generator specialists at Autoliv spent two years actively researching such active metal support systems, and tested a variety of applications. For the very first time, inflatable metal side impact protection can be seen in the ESF 2009.

Imagine an inflatable mattress. When it is not needed, it is rolled up flat and e.g. consigned to a shelf in the attic. When inflated, however, it has a highly resistant structure that can easily carry a man weighing 100 kilograms. Inflatable metallic structures work in the same way: when not in use, the metal section is folded together to save space. Once its protective effect is needed, a gas generator just like those used to inflate airbags builds up an internal pressure of 10 to 20 bar within fractions of a second, the metal section is unfolded and the structure has significantly greater stability.

The advantages are obvious, and mainly involve packaging and weight: more stable structures can be accommodated within the increasingly tight installation spaces of an automobile, or weight can be greatly reduced while maintaining the same stability. Using the example of the side impact protection member in the doors of the S-Class, the researchers have calculated that around 500 grams less weight per door would be feasible.

Daimler safety researchers examined various applications for these innovative, crash-responsive metal structures, among them side impact protection, the side skirts and the seat cross-members. These have the advantage of being several centimetres away from the impact zone. The gas generator therefore only needs to be activated when a crash has definitely taken place.

One of the still unsolved problems of these protective members is that unlike the PRE-SAFE® measures already in series production, their active deformation is not reversible. Moreover, the activation of protective members installed well to the outside of the bodyshell that can be inflated by internal pressure requires their deployment before the crash. The pre-crash sensor system must therefore provide highly reliable signals.

Another hurdle is the currently still uncompetitive cost level of the required gas generators in relation to the cost requirements for weight-saving measures. These crash-responsive metal structures are therefore still a thing of the future - but the same was also once true of standard safety features like the airbag, ABS or ESP®.

PRE-SAFE Pulse: an automatic nudge in the ribs

With the multiple award-winning PRE-SAFE® system, Mercedes-Benz has once again been underlining its role as a pioneer in the safety field since 2002: once the system recognises certain critical driving situations, PRE-SAFE® activates occupant protection measures as a precaution. As a further development, PRE-SAFE Pulse is able to reduce the loads acting on the torsos of the occupants by around one third during a side impact by preventively moving them towards the centre of the vehicle.

Out of harm's way - every millimetre counts during an accident. When an impending lateral collision is recognised, PRE-SAFE Pulse as an active restraint system moves the driver and front passenger towards the centre of the vehicle, using air chambers in the side bolsters of the seat backrests. If the onboard sensors report that a side impact is inevitable, these are inflated within fractions of a second and give the seat occupants a slight nudge in the ribs. This impulse is enough to move them out of the danger zone by up to 50 millimetres. Even before the accident, it also accelerates the seat occupant in the direction he/she will later take during the accident. This reduces the loads acting on the occupant during the impact. The seat does not need to be replaced or repaired when this preventive safety system has been activated, as PRE-SAFE Pulse is reversible.

PRE-SAFE Pulse is being developed on the basis of the dynamic multicontour seat in the new Mercedes E-Class. Depending on the steering angle, lateral acceleration and speed, the inflation pressure and volume of the air chambers in the side bolsters of the seat backrests are already varied to give the driver and front passenger even better lateral support.

PRE-SAFE 360°: full emergency braking before an impact

With the multiple award-winning PRE-SAFE® system, Mercedes-Benz has once again been underlining its role as a pioneer in the safety field since 2002: once the system recognises certain critical driving situations, PRE-SAFE® activates occupant protection measures as a precaution. As a further development, PRE-SAFE 360° monitors not only the areas to the side, but also to the rear of the vehicle.

PRE-SAFE 360° uses short-range or multi-mode sensors to monitor the area behind the vehicle to a range of up to 60 metres. If the accident early-warning system registers that a collision is unavoidable, the brakes are applied around 600 milliseconds before the impact. If the already stationary car is braked during a rear-end collision, this not only prevents secondary accidents where the car is e.g. uncontrollably shunted into a road junction or onto a pedestrian crossing. The severity of possible whiplash injuries to the occupants can also be reduced by application of the brakes, as the vehicle and therefore its occupants have less forward acceleration. The driver always has the final decision with PRE-SAFE 360°, however: if he accelerates because he is able to prevent the rear-end collision by moving forward, for example, the brakes are instantly released.

Contrary to the widely held opinion among drivers, it does not make sense to take one's foot off the brake pedal before an impending rear-end collision. The correct action would be to apply the brakes as hard as possible, however accident research findings show that the driver of a stationary vehicle impacted from the rear is moved backwards by up to 20 centimetres. This inevitably causes his feet to slip from the pedals.

The protective effect of PRE-SAFE 360° supports that of the NECK-PRO crash-responsive head restraints, which are already standard equipment in many Mercedes model series. If the sensor system detects a rear-end collision with a
defined impact severity, it releases pre-tensioned springs inside the head restraints, causing the head restraints to move forward by about 40 millimetres and upwards by 30 millimetres within a matter of milliseconds. This means that the heads of the driver and front passenger are supported at an early stage than with conventional head restraints.

PRE-SAFE Demonstrator: a realistic PRE-SAFE® experience

The preventive occupant protection system PRE-SAFE® activates a number of safety systems if an accident appears to be unavoidable. Fortunately, many drivers never find themselves in a situation where they can experience PRE-SAFE® for themselves. A realistic impression of these safety systems is provided by an innovative PRE-SAFE Demonstrator, which will have its world premiere at the 21st ESV Conference in Stuttgart on 15 June.

For the first time for this purpose, the simulator uses a linear motor to accelerate the vehicle cabin to up to 16 km/h within a distance of four metres. This corresponds to an acceleration of two g, i.e. twice freefall speed. After around 1.2 seconds the cabin impacts the specially designed hydraulic shock absorbers. In the interim the occupants not only experience the effects of the PRE-SAFE® functions at first hand, e.g. belt pretensioning, NECK-PRO and the inflatable side bolsters on the seats, but also the restraining effect of the seat belts during the impact.

The linear drive of the PRE-SAFE Demonstrator, which is similar to that of the Transrapid train system, has a power consumption of 10 kW, is freely programmable and also works in the opposite direction. This enables various acceleration profiles, and also a rear-end collision, to be demonstrated. The cabin can also be rotated by 30 degrees on its sledge to simulate an oblique impact. If the cabin is rotated by 90 degrees, the drive system can be programmed a produce to-and-fro motion that gives the impression of taking corners at high speed.

The moving mass of the Demonstrator is 500 kg. This includes the cabin, which was created from a real S-Class saloon whose front passenger seat, dashboard and door were adopted. To keep the Demonstrator compact in size, the driver's side, engine compartment and the body section to the rear of the B-pillar were removed. Specially designed plastic components close off the cabin at these points. The Demonstrator weighs a total of around 2.5 tonnes, and is designed to be easily loaded onto a vehicle by fork-lift truck. Easy transport is also facilitated by the double electrical interfaces directly on the Demonstrator and at the control console. The unit has hydraulically extendable rollers to allow precise placement at the destination.

The PRE-SAFEDemonstrator was developed and designed on behalf of the Mercedes accident research department by the prototype production function of MB-technology GmbH. The MBtech Group is a globally operating automotive engineering and consulting business within the Daimler group. Project manager Markus Pscheidt recalls: "This commission was a very special challenge, for as far as we were aware, a linear drive system had never been used for automotive purposes. To ensure the safety of the cabin's occupants under all circumstances, we had to design many of the features ourselves in close consultation with the TÜV safety inspectorate."