(from Daimler Press Release) Experimental Safety Vehicle
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®.
Braking Bag: a braking parachute for the car
Airbags in cars have previously only been used as a restraint system for the occupants. In the future they might also be a PRE-CRASH- component, activating an auxiliary brake in the vehicle floor and improving both deceleration and compatibility with the other vehicle involved in the accident.
Energy is not only reducible by braking the road wheels: jet fighters and dragsters use braking parachutes, for example. And as early as 1952, Mercedes-Benz was already experimenting with an air-brake at the Le Mans race: when decelerating, the driver was able to move a metal panel on the roof of his racing SL to a vertical position. Even earlier, coachmen used special wheel chocks. These were placed in front of one of both rear wheels on long downhill gradients, and their iron-clad base helped to brake the vehicle during the descent.
This is an old idea that Mercedes safety researchers have revitalised on a similar principle with the Braking Bag, an airbag installed between the front axle carrier and the underbody panelling. If the sensor system concludes that an impact is inevitable, the PRE-SAFE® system not only initiates automatic emergency braking. At the same time the Braking Bag is deployed just before the crash, supporting the car against the road surface by means of a friction coating. The vehicle's vertical acceleration increases the friction and has an additional braking effect before the impact. The Braking Bag uses the PRE-CRASH sensors in Mercedes-Benz cars, which are already able to initiate preventive occupant protection measures in critical driving situations.
There are several advantages to this unusual auxiliary brake:
-- The rate of deceleration is briefly increased to over 20 m/sec/sec. This scrubs additional energy beyond the potentials of a wheel brake, thereby reducing accident severity.
-- Because the car is raised upwards by up to eight centimetres within a short time, the dive effect that occurs with conventional brakes is substantially compensated. This improves geometrical compatibility with the other party in an accident.
-- This vertical movement also improves the effects of the restraint systems: the seats move towards the occupants by around three centimetres, which enables the belt tensioners to take up more slack. The high deceleration rate before the impact has a "pretensioning" effect on the occupants, so to speak.
-- Downward support for the vehicle during the crash reduces the typical diving motion during a collision.
All in all, the braking airbag has the effect of an additional crumple zone. Mercedes engineers have calculated that even at a low 50 km/h, the additional deceleration has the same effect as lengthening the front end by 180 mm. Initial driving tests in a C-Class have already shown the effectiveness of this new auxiliary brake – though it will still be some time before the Braking Bag becomes another component of the PRE-SAFE® system.
Interactive Vehicle Communication: cars report what their sensors have detected
Cars sometimes know more about their surroundings than their drivers. With the help of intelligent communication systems, vehicles themselves are able to contribute to improved road safety and mobility.
A patch of black ice on the next bend? A bank of fog three kilometres down the road? A new traffic tailback where roadworks are being carried out? What used to come as an unpleasant surprise is far less frightening if the approaching driver receives an up-to-date is warning beforehand. This is a task that will in future be carried out by the other vehicles on the roads at the time – automatically, by radio. This is the basic idea behind Interactive Vehicle Communication.
Cars are nowadays able to collect a great deal of information about the current driving situation, as the numerous sensors, cameras and control units for the dynamic and assistance systems can register e.g. poor weather conditions just as well as sudden braking and avoiding manoeuvres, or broken-down vehicles on the road. There are also other sources of information, for example local police reports. This information can be passed on via additional relay stations ("car-to-x") such as radio masts at the roadside, stationary nodal points (e.g. traffic centres and overhead gantries) or via the internet. The onboard computer classifies all the reports according to plausibility and relevance. Tailback reports on the radio which are out-of-date or irrelevant to the individual driver will then be a thing of the past.
Mercedes engineers have been working on "Interactive Vehicle Communication" as a technology of the future for more than seven years. The ESF 2009 safety concept vehicle demonstrates the current status of this research: this Mercedes can automatically recognise an approaching police car, for example, and warn its driver by showing a symbol in the display. It is also possible to send and receive warnings of bad weather or obstacles in the road.
The exchange of data between vehicles is via so-called "ad hoc" networks, connections that are spontaneously formed between the vehicles over short distances. These wireless local area networks (WLANs) are self-organising, and require no external infrastructure. Transmission and reception is at a frequency of 5.9 gigahertz, over a distance of up to 500 metres. In fact the achievable communication range is much greater, as oncoming vehicles pass the messages on.
Cars that communicate with each other can do more than just pass on information: linked to modern proximity control systems such as DISTRONIC Plus from Mercedes-Benz, they can help to harmonise the traffic flow and avoid tailbacks by automatically selecting the most suitable vehicle speed when joining a motorway. And collisions can be avoided if onboard sensors recognise an impending accident and automatically regulate the distance.
This technology is currently demonstrating its practicality in the "Safe Intelligent Mobility – Test area Germany" project (simTD), in which Mercedes-Benz and other German manufacturers and suppliers are taking part. Up to 400 vehicles communicate with each other in these, the world's largest field trials for Interactive Vehicle Communication. simTD is being conducted in the densely populated Frankfurt/Rhine-Main area from autumn 2008 to 2012. Experts expect usable mobile information networks with full coverage to become a possibility when around ten percent of all vehicles have this communications capability.
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.
Partial main beam: full beam ahead at all times
Whether as brake lights and indicators in many Mercedes models, or as daytime driving lights in the new E and S-Class, LED lighting technology is seeing increasing use at Mercedes-Benz. And things will be brightening up at night as well in future: Mercedes lighting specialists are working on an adaptive LED main beam system that automatically excludes oncoming traffic from the cone of light. A special spotlight function also allows potential hazards to receive additional illumination.
Main beam, low beam, main beam… anybody travelling on country roads in western Europe at night is seldom able to drive with the main beams on for very long. The frequency of oncoming traffic dictates that the driver is soon obliged to switch to low beam, either manually or more conveniently using the Main Beam Assist in the new Mercedes E-Class. This is not enough to satisfy the researchers at Mercedes-Benz, however. Because during the phases when the driver switches to low beam - with its shorter range - to avoid dazzling others, it is possible to overlook other road users or potential hazards.
The lighting specialists at Mercedes-Benz are therefore working on an LED-based adaptive main beam system. This enables the driver to leave the main beams switched on constantly. As soon as the system detects oncoming traffic with the help of a camera, it automatically adjusts the light distribution accordingly. The Mercedes ESF 2009 experimental safety vehicle shows precisely how this works. A headlamp is made up of 100 LEDs. These semiconductor elements can be individually activated, so that when there is oncoming traffic, the precise beam area in which other road users are located can be darkened down. The system recognises these using an infrared camera. The purely electronic module is also able to respond much faster than present electro-mechanical shutter/roller assemblies.
The light distribution can also be refined in the opposite direction: a special spotlight function in the LED array of the research vehicle also enables potential hazards to be highlighted. If the infrared camera detects pedestrians in the road ahead, for example, they can be briefly lit up beyond the normal main beam illumination, as if by an aimed spotlight. The driver is thus alerted to the potential danger.
Reflect: not all Mercedes are grey at night
Reflective material on the body and tyres could further improve the lateral visibility of vehicles, and help to avoid accidents at road junctions.
Reflective materials have long been commonplace in children's clothing, and in the case of bicycles it is even mandatory to have reflectors in the wheel spokes. So the engineers at Mercedes-Benz asked themselves why the perceptual safety of cars could not be improved in the same way. Accordingly the ESF 2009 research car features appropriate reflective elements when viewed from the side. These modifications are not visible during the daytime, but the additional benefit shows up when dusk and darkness fall.
Together with the manufacturer Continental, Mercedes specialists have developed a reflective strip on the tyres which visually enlarges the wheels in daylight and creates an easily visible band of light when illuminated at night. As a further safety feature there are reflective seals between the doors and the roof, a joint development with the adhesive foil specialist 3M. The aim is to make the vehicle's silhouette more easily visible in the dark. This enables potential accident situations on junctions or in the form of unlit, parked vehicles to be defused.
Reflective foils consist if a reflective base layer with tiny balls of glass. When a ray of light hits the foil, it is refracted by the glass balls, reflected by the base layer and refracted again on exiting. As a result, most of the light is reflected back in its original direction.
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 System: 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 System" 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 System" 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.
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.
Rear seat camera: 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 "Rear seat camera", 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.
"Rear seat camera" 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.