Interseat Protection: don’t get too close to me

Danger not only comes from outside during an accident. In unfortunate cases even passengers wearing their seat belts can come into contact and injure each other. Interseat Protection in both seat rows helps to prevent this.

Mercedes safety specialists are presenting two proposed solutions in one with Interseat Protection: a protective system for the driver/front passenger and one for the rear-seat passengers. As a common feature of both, the occupants are physically separated from each other if the PRE-SAFE system registers an accident. Within fractions of a second, a lattice-like airbag support structure extends from between the front seats to keep the driver and front passenger apart. A seat-mounted solution like this has the advantage that the protective barrier adapts itself to the position of the front seats.

The seat position does not need to be taken into account in the rear, therefore a protective pad located above the centre armrest is used when an accident is detected. This pad helps to prevent the two passengers in the rear from impacting each other. When the pad is at rest it can be activated as part of PRE-SAFE. Within fractions of a second, the seat divider emerges and the two head supports are deployed.

Mercedes accident research has shown that during a side impact, and also during a rollover, the heads of the passengers move along different paths: around 50 milliseconds after the accident, the head of the person facing the impact changes the direction of its evasive movement towards the centre of the vehicle – impelled by the sidebag and head airbag. A second important finding from these analyses is that a collision between the passengers can only be avoided if the torso is supported. The protective pad of the Interseat Protection system is dimensioned accordingly.

In normal cases the protective pad in the rear is more of an innovative comfort feature: the pad is designed to be extended by the passengers at the touch of a button, when it can be used as a head and shoulder support for a comfortable sleeping position. It would also be conceivable to use the space for stowage or a cooler box, or an entertainment console.

Hybrid Battery Shield: seven-stage safety system

A drive train with hybrid technology lowers fuel consumption and CO2 emissions. At the same time this introduces high-voltage electricity and sophisticated battery systems into passenger car engineering, however. Thanks to their long experience with fuel cell technology, Mercedes development engineers are extremely well prepared for the new challenges this presents. A comprehensive, seven-stage safety concept is the result.

The challenge lay in not only complying with all the worldwide and in-house crash test requirements, but also in ensuring the greatest possible safety for the electrical components. This safety system already applies in production, includes workshop personnel during servicing and maintenance, and also takes the emergency services into account when passengers need to be recovered following an accident. The seven-stage concept in detail:

1. In the first stage all the wiring is colour-coded to eliminate confusion, and all components are marked with safety instructions. This makes the regular technical inspections easier to carry out.
2. The second stage comprises comprehensive contact protection for the entire system by means of generous insulation and newly developed, dedicated connectors.
3. As part of the third stage, the lithium-ion battery has been given a whole package of carefully coordinated safety measures. This innovative battery is accommodated in a high-strength steel housing, and also secured in place. Bedding the battery cells in a special gel effectively dampens any jolts and knocks. There is also a blow-off vent with a rupture disc and a separate cooling circuit. An internal electronic controller continuously monitors the safety requirements and immediately signals any malfunctions.
4. The fourth stage of the safety concept includes separation of the battery terminals, individual safety-wiring for all high-voltage components and continuous monitoring by multiple interlock switches. This means that all high-voltage components are connected by an electric loop. In the event of a malfunction the high-voltage system is automatically switched off.
5. Active discharging of the high-voltage system as soon as the ignition is switched to “Off”, or in the event of a malfunction, is part of the fifth stage.
6. During an accident, the high-voltage system is completely switched off within fractions of a second.
7. As the seventh and last stage, the system is continuously monitored for short circuits.

“Still many more ideas for more safety”

Interview with Prof. Dr. Ing. Rodolfo Schöneburg, Head of Safety Development, Mercedes-Benz Cars. Prof. Dr. Ing. Rodolfo Schöneburg was born on 30 October 1959, studied aerospace engineering and obtained his doctorate at the Technical University of Berlin. He holds an honorary professorship at the College of Technologyand Business Economics (HTW) in Dresden. He has been active as the head of the centre for safety/vehicle functions at Mercedes-Benz since April 1999. It was under his aegis that the preventive occupant protection system PRE-SAFEentered series production in 2002, with which Mercedes-Benz started a new era in vehicle safety. Here are some of Prof. Schöneburg’s comments on the Mercedes ESF 2009 experimental safety vehicle.

Question: Prof. Schöneburg, during the period from 1971 to 1974 Mercedes-Benz presented four Experimental Safety Vehicles (ESFs) to the public. Then there was silence. Why?

Prof. Schöneburg: At the end of the 60s, vehicle safety suddenly became a focus of public attention. In 1969 the Mercedes-Benz Safety Centerwas founded in Sindelfingen. Numerous developments were initiated, ranging from active safety with ABS and ESP to fundamental improvements in vehicle structures and innovative restraint systems such as the airbag. All of these were tested and presented in our ESFs, and from the mid-70s more and more of these innovations reached series production maturity. Accordingly they were subsequently presented with the launch of new series production models.

Question: So why are you presenting another research vehicle now, the Mercedes ESF 2009?

Prof. Schöneburg: Both in-house and externally, the large number of safety features that we already have in our series production cars has created the impression that we do not have much more to offer in this respect. This impression is quite wrong – we have a wealth of ideas on how safety might be improved still further. Some of these can be realised within a relatively short time, for example PRE-SAFE for rear-end collisions. Other concepts like the inflatable metal sections in PRE-SAFE Structure lie well in the future. And with Interactive Vehicle Communication we are only just starting to develop a completely new field. The Mercedes ESF 2009 comprehensively offers up all these perspectives. Moreover, our intention was to send out certain signals for the ESV Conference, which is being held in Stuttgart for the first time since 1971.

Question: What is particularly special about the Mercedes ESF 2009?

Prof. Schöneburg: As with the ESFs of the 1970s, this is a comprehensive embodiment of our safety philosophy. The primary aim is to prevent accidents in the first place. Where this is not possible, the aim is to mitigate their effects. Moreover, we want to approach both of these goals without increasing the vehicle’s weight, restricting its practicality or compromising the autonomy of the driver. He or she bears the final responsibility – and the car should provide support in the process.

Question: What new ideas have been incorporated into the Mercedes ESF 2009 to prevent accidents where possible?

Prof. Schöneburg: These start with the concept of “seeing and being seen”. The LED headlamps of the ESF2009 not only illuminate the road further and more efficiently, but also ensure that other detected road users are not dazzled in the process. The Spotlight function is something quite new: it precisely pinpoints obstacles or objects that have been recognised by the infrared Nightvision camera. Thanks to new reflective strips on the sides, which leave the body design unaffected during daytime, the Mercedes ESF 2009 is also much more easily visible to other road users in the dark. One technology which we think has tremendous potential for the next few years and decades is car-to-car communication. This makes it possible to warn drivers of hazards on their route as the situation requires.

Question: In addition to highly developed restraint systems, Mercedes cars with PRE-SAFE have a preventive safety system that can recognise an impending accident and mitigate its effects with numerous actions right up to automatic emergency braking. Is it still possible to make significant improvements to this already high standard? Prof. Schöneburg: Yes indeed. The basis for PRE-SAFEis a network of onboard sensors and systems, and this is where we still have plenty of ideas for further developments. Take side impacts as an example: with the help of air chambers in the seats, it would be possible to move the passengers away from the danger zone to some extent. We have already spoken about improvements where rear-end collisions are concerned. And the Braking Bag is a completely new approach to scrubbing off energy before an impact occurs.

Question: At first glance this is a crazy idea – using an airbag under the car to force a high-friction coating against the road surface as an auxiliary brake…

Prof. Schöneburg: …certainly unusual, but by no means crazy. Initial trials of the principle have shown this idea to have considerable potential. In the next few years we intend to research and develop this potential further.

We look forward to the results, and thank you for this interview.

This is how the Mercedes ESF 2009 was created: 13 innovations, 1 team

The Mercedes ESF 2009 is the first Experimental Safety Vehicle Mercedes-Benz has built since 1974. Like its historic predecessors, it attractively combines trailblazing innovations in the field of safety and makes the progress achieved visible. Integrating all the ideas and implementing them for a clear appreciation was an extraordinary challenge for the team in the test vehicle workshops.

The go-ahead for the ESF was given in October 2008, and the decision was received with great enthusiasm in the test workshop: “Making safety visible – I was quickly able to assemble a highly qualified team for this interesting project”, says Axel Wittig, the team leader for the entire workshop facility. “The complexity of this assignment was a welcome challenge, as we not only had to integrate the numerous innovations into an S 400 HYBRID, but also make them fully functioning in demonstration mode and provide a look behind the technical scenes by incorporating eight inspection windows in the bonnet, bumpers and doors.”

The core workshop team for the Mercedes ESF 2009, headed by coordinator and facilitator Hans Peter Hiller, consisted of three model-builders and two electricians. The team was supported by Jürgen Arnold, who took care of the electrical engineering, and designer Matthias Rissmann, who e.g. prepared the body apertures for the inspection windows. It was only possible to keep to the ambitious time-plan because countless internal (from the upholstery specialists in Design to production engineering) and external suppliers gave rapid and unbureaucratic assistance. “The great enthusiasm for the core Mercedes expertise of safety could be felt at all times”, project manager Michael Fehring remembers: “The ‘Daimler spirit’ ensured rapid decisions without time-consuming consultation processes.” Sheer fascination for technology also played an important part. The chance to take a look into a radar sensor, which is normally only supplied as a ‘black box’ but was in this case integrated into the front bumper in a cutaway state, attracted many an engineer who was not involved in the project into the workshop bay for the Mercedes ESF 2009. The complexity of this project, which involved the integration of 13 safety innovations into the hybrid version of the S-Class that only existed as a prototype when the work started, is already shown by the fact that a completely new wiring harness had to be designed and produced. At the heart of the demonstration technology is a divided compressed air tank in the boot, with a compressor and external power supply, which provides the airbags and the air chambers for PRE-SAFE Pulse and Interseat Protection with air. The finishing touch for the Mercedes ESF 2009 is a central remote control system for all the functioning demonstrations.

The result of all this work was two experimental vehicles in the special ESF paint finish, which includes black-painted chrome trim and reflective strips on the door seals and tyres: the actual Mercedes ESF 2009 and its externally identical brother, which can be used for driving and photographic purposes.

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.”