The night-driving simulator at Mercedes-Benz in Sindelfingen

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Let there be light

Darkness, rain, and snow — when can you get all that by simply asking the weather fairy? Hardly ever. Or only when you really don’t need them. But for the light developers at Mercedes-Benz it’s crucial to test the latest innovations under these kinds of extreme weather conditions in particular. And because you can’t simply order these conditions to happen, the developers use a clever technical solution: a unique night-driving simulator.

It’s almost 7 p.m. on a spring evening. The sun is already low on the horizon. At the Mercedes-Benz Technology Center in Sindelfingen, or MTC for short, the workday is coming to an end. The last colleagues are leaving the testing grounds for a well-deserved evening at home.

But for Andreas Hauser and his colleagues in the headlamp testing unit, this is when their workday begins — normally, at any rate. But today no one’s around in the Lighting Technology department either. No daily briefing. No night drive. “Ever since we got the light simulator, we’ve been trying out many things virtually during normal daytime working hours,” says Hauser the next morning.

Andreas Hauser’s (right) job is all about light and headlamps. Here he’s showing our author the Mercedes-Benz night-driving simulator in Sindelfingen.
Andreas Hauser’s (right) job is all about light and headlamps. Here he’s showing our author the Mercedes-Benz night-driving simulator in Sindelfingen.

For him and his colleagues, the workday is all about light. The lighting system of a vehicle serves several purposes. The main one is to help users see and be seen: During a night drive, the more brightly lit the roadway is, the sooner the driver can recognize potential hazards. Efforts to improve car headlamps also play a key role in making it even safer to drive in the dark. That’s because, unfortunately, it’s still the case that the risk of being involved in a traffic accident increases after sundown. From a statistical viewpoint, every kilometer driven at night is twice as prone to accidents as one that is driven in the daytime. It’s just that the absolute accident numbers do not reflect this –simply due to the fact that the average number of kilometers driven is much higher for daytime than for nighttime driving.

Of course a good light pattern for nighttime driving is a crucial factor not only for safety but also for driving comfort. And finally, the shape of the headlamps is also a trademark of the brand. There are self-appointed experts who can identify every model series of a brand by its headlamps alone. Innovative light sources such as the revolutionary DIGITAL LIGHT® headlamps technology from Mercedes-Benz. It allows completely new functions, e.g. the projection of marking aids or warning symbols onto the road ahead. In each headlamp, DIGITAL LIGHT has a light module with three extremely powerful LEDs with light that is refracted and directed by 1.3 million micro-mirrors. The resolution is therefore more than 2.6 million pixels per vehicle.

The DIGITAL LIGHT® headlamps from Mercedes-Benz generate light with a very high resolution. Besides, a vehicle’s headlamps alone are enough for some automobile experts to recognize the model series.
The DIGITAL LIGHT® headlamps from Mercedes-Benz generate light with a very high resolution. Besides, a vehicle’s headlamps alone are enough for some automobile experts to recognize the model series.

Headlamp development requires testing, testing, testing

Who’s responsible for ensuring that the headlamps installed in a Mercedes-Benz vehicle measure up to the brand’s high safety standards? This is where the light systems testers from Sindelfingen come into play. And because car lighting systems naturally can’t demonstrate their strengths in daylight, most of their testing takes place at night. Today, however, a new technology — the night-driving simulator — is enabling the developers to conduct many of the necessary testing scenarios during the daytime.

“For us, one advantage of the simulator is that it enables us to reduce the number of night drives,” says Hauser. It’s easy to understand why he and his colleagues have welcomed this innovation: During the summer months they have to wait until late evening before it gets dark enough for them to test the lighting systems under real-life conditions. In the winter the sun already sets in the afternoon, but going on test drives when it’s snowy or there’s black ice on the road is no fun either.

But of course the innovative simulator offers not only greater convenience for the testers but many more advantages besides. It enables the light experts to test the headlamps much more intensely in a shorter period of time — without needing to do more driving on the road. The simulator also makes practical testing much easier: “Thanks to the simulator, we are completely independent of weather conditions, and we can simulate a whole range of scenarios at the push of a button,” Hauser says. Besides, in the simulator the light developers can repeat exactly the same driving situation as often as they like. As a result, they need to change only a few parameters in order to see at once how the light pattern has changed. Apropos parameters, a light simulator can of course also simulate headlamps before thgey even exist as physical components that can be touched (and installed). That way, the results of the testing can be incorporated into decision-making early on in the development process.

This is what the night-driving simulator looks like

Andreas Hauser lets me sit down in the seat box located in the middle of the projection screen. The car in question is an E-Class that has been cut in half just behind the B-pillar. It’s equipped with all the technology that is needed to give the driver a sense of driving a real car. All of the technical components that are not relevant for simulating the light pattern have been removed from this former test vehicle. Nonetheless, typical car sounds can be heard as soon as the starting button is pushed. “This helps to create the sense that you’re driving a real car, and that’s why we add the sound,” Hauser explains.

This element of the simulator is known internally as the “seat box.” From the outside, with a little imagination it looks a little like a vehicle cockpit. Once you’re sitting inside it, you rapidly sink into the virtual world.
This element of the simulator is known internally as the “seat box.” From the outside, with a little imagination it looks a little like a vehicle cockpit. Once you’re sitting inside it, you rapidly sink into the virtual world.

And then it’s time to dive all the way into the virtual world. “This is where we turn day into night,” Hauser says, and then he uses his mobile phone to turn off the light in the room, which has been almost completely painted black. And indeed, the room is now so dark that you can’t even see your own hand in front of you. “This is necessary, because it’s the only way the advantages of the very special projection system can take effect,” he says. Next, he uses a tablet to ramp up four high-tech video projectors. It takes about a minute to boot up the entire system. And that’s a good thing, because the human eye needs time to adapt from photopic (daytime) to scotopic (nighttime) vision. When day slowly fades into night in the natural world, our brains automatically initiate this mechanism, and we’re not really aware that it’s happening. “This is important, because it enables our eyes to perceive even tiny differences between degrees of brightness,” Hauser explains. “It’s important for the quality of our headlamps that we give the eye enough time to adapt. That way, when we’re running tests we can also recognize nuances in the luminance and subsequently further optimize the headlamps’ distribution of light.”

The acronym VTD shines out on a huge semicircular projection screen. It stands for Virtual Test Drive — comprehensive driving simulation software that the manufacturer has expanded with a high-resolution lighting application especially for Mercedes-Benz. “This lighting software in connection with the projection system is unique in the automotive industry,” says Hauser with pride. “Our biggest thanks go to our colleague Martin Borowski in the Lighting Advance Development unit for that. He’s been something like the father of the night-driving simulator in Sindelfingen, ever since he presided over its design and implementation.”

Driving around a curve presents the light testers with a complex scenario. But the simulator can handle this discipline, too.
Driving around a curve presents the light testers with a complex scenario. But the simulator can handle this discipline, too.

In front of the seat box, a white screen curves around in a semicircle. Four projectors mounted on the ceiling project images of the road ahead and the light pattern onto it. Because of the curved screen, the driver has a wider field of vision than he or she would if the screen were flat. That makes the driver’s simulated surroundings seem more real. And there are small monitors in the rear-view mirrors that depict the virtual traffic going on behind the car.

As though you’re sitting in a real car

Andreas Hauser says, “You feel as though you’re sitting in a real car. And then when the light goes out and all you see is the projection of the road in front of you, you feel that you’re driving along a road rather than in the test lab in Sindelfingen.”

In other areas, simulators that convincingly depict the real world are already very common. Simulators of this kind have been used for a long time in pilot training programs to simulate the takeoff and landing of airplanes and to bring routine into the pilots’ procedures.

A special, and challenging, requirement in the design of the light testing system is the simulation of absolute darkness. When night drives in the countryside go outside the range of the blazing lights of major cities, almost everything looks deep black. That’s why the simulator requires an extremely high black level; otherwise, the screen would simply be a curtain of shimmering gray. In such a situation, our testers could not meaningfully assess the distribution of light. The solution is to use projectors that have been specially developed for such simulations. Their patented technology, which is unique on the market, makes it possible to simulate the optimal night situation that our light engineers in Sindelfingen need for testing the latest developments.

The longer the simulation lasts, the more it feels like a real drive — as our author experienced for herself on her visit to the test lab.
The longer the simulation lasts, the more it feels like a real drive — as our author experienced for herself on her visit to the test lab.

Hauser says that driving in a simulator can be compared to playing a computer game. It’s true that there are no movements of the car itself; when accelerating or going around a curve, the driver is not pushed back into the seat. However, after being in the simulator for a few minutes, the driver is immersed in a whole new world. “At some point you forget you’re sitting inside a simulator, and it simply feels extremely real,” says Hauser.

The light comes not from the headlamps but from the control unit

Naturally, the right software is required to make sure the hardware components do what they’re supposed to. The software causes the previously programmed driving route to be projected on the screen, integrates the car’s motion and the assistance systems, and realistically replicates the distribution of the light. Unlike the process in a genuine test vehicle, the light in the simulator doesn’t simply come from the headlamps. The software uses a digital control unit to forward the programmed parameters to the projectors. The result is then integrated into the test environment and displayed on the screen. In other words, depending on what the light testers want, the software can merge all the individual components together. In most cases, the light system that is being tested exists in various stages of development. Thus the developers can depict and compare them at the push of a button. That can’t be done inside a car in the real world.

The intricately programmed software also makes it possible to “drive” along any desired route. The developers generally use standardized virtual routes, but it’s also possible to reproduce actual ones.

The simulator is controlled by means of a tablet PC. The tablet can be used, for example, to make pedestrians appear on the road system, where they are recognized by the assistance system. At the push of a button, the simulation can also make several cars or a construction site part of the surroundings. The developers can test the light distribution in all of these situations. The possibilities are practically endless.

For the light testers, curves are especially complex

Certain driving scenarios can be run through over and over again under a variety of weather conditions. That makes it easy for the light testers to systematically check how the light algorithm behaves.

It’s an exciting process, especially in curves, which present the light testers with an especially complex scenario. That’s understandable: After all, there are right-hand curves, left-hand curves, different curve radii, and the supreme discipline, winding roads. Our headlamps are tested in all of these scenarios, and in many cases that can now be done in the simulator. This eliminates strenuous real-life test runs. After all, there are no genuine winding roads in the region around Sindelfingen.

One of the simulator’s great advantages is that it no longer needs need a change of location to run a test of the light pattern under different traffic or weather conditions — it’s enough to just adjust the parameters as required.
One of the simulator’s great advantages is that it no longer needs need a change of location to run a test of the light pattern under different traffic or weather conditions — it’s enough to just adjust the parameters as required.

Besides, for some scenarios the testers need a second vehicle that is driving a certain distance in front of the test car. In order to create such a situation in real-life road traffic, a colleague always has to be driving a second vehicle. In the simulator, that can be done at the push of a button — and without the danger of having the test distorted by a vehicle cutting in between the two cars.

The biggest advantage of the simulator is its speed

The first automobiles already had lighting systems (they were equipped with candles), but automotive lighting systems are still being developed, and there’s no end in sight. As a digital development area, this is a future-oriented process. And, as with the smartphone, it involves fierce competition and a steady stream of innovations. The simulator is giving our colleagues a crucial speed advantage: Because they can use it to assess the headlamp function independently of the actual physical component, they can more rapidly validate the light systems in the development process.

Andreas Hauser is especially proud of the simulator because so far it’s the only one of its kind in the world. “That’s pretty cool!” he says. In the near future, the simulator will probably also be able to precisely reproduce the situation in which the driver is temporarily blinded by the glare of oncoming traffic. “Then we’ll be able to observe how our light system affects other road users, and in the future we can ensure even more effectively that our vehicles won’t cause glare that blinds other road users,” Hauser explains.

The development of the night drive simulator has now been going on for more than three years, and it’s being steadily optimized. The current setup, in which the developers dive all the way into the simulation, was created a year ago, but expansions and improvements are already being planned.

Is there anything the simulator still can’t do?

Currently the simulator can only represent the intensity — but not the color impression — of the light distributions. The developers hope that in the future they can create a data format that can represent both kinds of information. That way, they could also use the simulator to assess how the headlamps represent the color transitions between the individual light modules and what the blue fringing along the field of light looks like. Experts use the term blue fringing to refer to the blue edge of a headlamp’s beam, which can appear when the white light is split into its color spectrum at the headlamp’s lens. This blue fringing can act as a distraction for the driver and other road users.

If Andreas Hauser could be granted one wish concerning the night drive simulator, he would ask for a slider control on the tablet that he could use to adapt all of the important headlamp functions. Then he could adjust all the variables with the slider until he arrived at a result he liked. However, this wish will remain unfulfilled, because the technology and the software that underpin the light simulator can reproduce lots of scenarios and many different model series. That makes the technology and the software fairly complex — probably too complex to represent the multiple parameters with a couple of slider controls.

Will headlamps one day not be tested on the road anymore?

Will the simulator one day be able to replace all real-life testing? Hauser answers both of these questions with a definite no: “Even if the simulation is perfected at some time in the future, we still have to test our light system under real-life conditions. A light system has hardware as well as software components, so the headlamp also has to be tested as a physical component. It must be able to deliver the functions we specified when we programmed the software. The vehicle light system is absolutely essential for the safety of every Mercedes-Benz. That’s why it must always and unconditionally be tested in real-life situations and actual night drives. That’s the only way we can deliver a high-quality product to our customers.”

The night-driving simulator is controlled by means of a tablet computer. Andreas Hauser explains its functions.
The night-driving simulator is controlled by means of a tablet computer. Andreas Hauser explains its functions.

For the light developers in Sindelfingen, the light systems of Mercedes-Benz vehicles are in effect their signed personal contribution to automobiles that could be regarded as complex works of art. What are the characteristics of a good light system? After a bit of thought, Hauser says, “It supports drivers so discreetly that they don’t even notice it. That’s why we try to generate a very undisturbed and homogeneous light pattern. The light should not jerk or flicker. For us it’s important to make sure the maximum possible light reaches the roadway and enables a Mercedes-Benz driver to have an optimal driving experience at night — without blinding other road users with glare. It’s not only a question of range. We also want to give drivers a system that doesn’t overwhelm them but instead supports them without requiring them to make any adjustments. That's the only way we can guarantee a high level of driving comfort.”

The developers want the driver to be able to get into the car, switch on the engine, and then let the vehicle control the rest on its own. That’s what Andreas Hauser is doing this summer evening. Today he doesn’t need to do an official night drive, because he has carried out the scheduled tests on the simulator. He’s got purely private reasons for driving off toward the setting sun. And by contrast to the sunsets he has seen in the course of his workday, this time everything is very real.

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Nina Kotschner

is studying Literary and Cultural Theory at the University of Tübingen and was an intern at Daimler’s Corporate Communications department. During her studies, she has also spent time in the light development unit — or, more precisely, the headlamp development unit — at Mercedes-Benz. As a result, she’s fascinated not only by beautiful cars but also by their headlamps.

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