TecDay Safety 2009: The ESF 2009 Experimental Safety Vehicle - PART IX


Stuttgart, Germany, Jun 10, 2009

Belt Bag: a clever combination of a seat belt and airbag

The seat belt is regarded as one of the most important inventions of the 20th Century, and has saved countless lives. It has been further improved with belt tensioners and belt force limiters, but that is not the end of its development: an innovative extension to the width of the belt, known as a Belt Bag, is able to reduce the risk of injury even further in an accident.

When a seat belt limits the movement of its wearer's torso as intended during a collision, it subjects the body to considerable forces. The Belt Bag, on whose
development Mercedes-Benz is working intensively with the seat belt specialist Autoliv, practically doubles its width within fractions of a second during an accident. This increase in the width of the belt spreads the pressure over a wider area, thereby reducing the risk of injury. This is particularly beneficial for older passengers, whose ribcage is no longer so flexible.

As the name suggests, the Belt Bag is a combination of a seat belt and airbag. When the crash sensors detect a serious impact, the airbag control unit activates the Belt Bag. A generator at the belt armature inflates the double-layered belt, which has Velcro seams. The volume of the Belt Bag is around four litres. The developers consider the Belt Bag to deliver the greatest benefits in the rear of the car, where conventional airbags cannot be installed. It is therefore conceivable that the Belt Bag could be used here by Mercedes-Benz in the foreseeable future.

Child Protect: safety and comfort for very small passengers

Mercedes engineers have thought about how children might travel even
more safely in a car.

The two major advantages of the Mercedes concept study "Child Protect" over conventional child safety seats are an improved protective effect and greater
comfort for the child. This is accompanied by a high level of quality and attractive
visual integration of the seat into the interior of Mercedes models. This system jointly designed with the restraint system specialist Takata is suitable for children aged between three and 12 years (weight categories II and III). One special feature is its modular construction, as the height and width can be individually adapted to the child’s physical proportions.

"Child Protect" has a tubular frame construction. This design offers better support and greater rigidity than versions of moulded plastic during a side impact. The prominent side bolsters in the shoulder and head area keep the child in place and minimise body movement during an accident. At the same time they prevent the child from coming into contact with vehicle components penetrating into the interior, or with the passenger in the adjacent seat. This seat study, which is approved according to the ECE R44.04 standard, is also equipped with automatic, sensor-controlled airbag deactivation on the front passenger seat.

As an additional benefit, Mercedes engineers are considering the addition of a buggy subframe to the child seat. This would also ensure that children travel in comfort, style and safety outside the car.

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.

Size Adaptive Airbags: tailor-made airbags

The 1980 Mercedes S-Class (W 126) was the first series production car
equipped with an airbag. In the meantime airbags have firmly established themselves across all vehicle segments. Airbags have saved many human lives and reduced the severity of injuries. Mercedes safety specialists are now working on a further improvement to their protective effect by developing airbags with a variable volume.

There are already adaptive airbags at Mercedes-Benz today, for in many model series the airbags are activated in two stages depending on the assessed severity of the impact. Future generations of this restraint system will not only take accident severity into account, but adapt themselves to the individual vehicle occupants: "Size Adaptive Airbags" automatically adjust their volume to the seating position and stature of the front passenger as recognised by the sensors. For whether a small front passenger is hunched up close to the dashboard or a tall front passenger has his seat moved well back is certainly a factor in the protective effect of the airbag. The weight of the front passenger, and therefore the forces acting on the airbag during an accident, are also important.

"Size Adaptive Airbags" enable occupant contact with the airbag to be optimally timed, whatever his weight and seating position. The restraint system can therefore dampen the impact to optimum effect. This Mercedes development varies the volume on the front passenger side between 90 and 150 litres. For purposes of comparison, conventional front passenger airbags have a volume of around 120 litres.

The system uses three retaining bands with which the airbag contours are adjusted to limit the volume. The retaining bands are fitted on electrically driven spools. When the airbag is activated, only as much band length is released as the control unit has calculated on the basis of sensor data for the seating position and weight of the occupant.

Child Cam: keeping an eye on the kids

With the help of a small camera, drivers will in future be able to keep
children travelling in the rear under control without taking their eyes off the road.

"Mum, Vanessa keeps pulling my hair!" "John's seat belt isn't properly fastened." - Parents know that when the kids are on board, there is usually no shortage of action on the rear seats. But if the driver looks back to see what is going on, there is a risk of an accident. Accordingly Mercedes safety experts have developed "Child Cam", a simple camera system that enables the kids to be observed without taking one's eyes off the road.

A small camera is mounted on the roof lining behind the front seats. If required its images can be transferred to the dashboard display – not in video form, but as sequences of stills to avoid distraction. The camera position provides a slight bird's-eye view, which allows children in rear-facing child seats to be
observed more easily.

"Child Cam" also shows rear areas that are not easy for the driver to observe, e.g. the seat directly behind. And in the case of an estate car, SUV or van, it is also possible to monitor the luggage compartment. This is very useful if domestic pets are on board, for example.

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-SAFE®entered 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 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 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 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 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 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 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-SAFE®is 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.

Copyright © 2009, Mercedes-Benz-Blog. All rights reserved.

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