advanced headlight system: 3d high beam · pdf filethe headlights were connected to the...

Advanced Headlight System: 3DHigh Beam

Robert Büthorn, Hadj Hamma Tadjine, Bert Auerbachand Karsten Schulze

Abstract In this paper, a new concept for an advanced headlight system ispresented. The weather or the road geometry cause a reduced illumination range orglare which is critical for driver safety. An optimal headlamp system should beable to adapt on a multitude of parameters from the ego vehicle and the envi-ronment to ensure a sufficient illumination of the street without glaring other roadusers. A perfect road illumination without providing glare for other traffic par-ticipants and giving the maximum additional information about the environment tothe driver is still a hard task for these systems. The improvement of such systemswill be achieved only with the combination of lane data and a list of detectedobjects provided from the camera system with the PSD format data of the GPS(Global PS) and the navigation system. The most part of the technology which isneeded for the realization of an optimal adaptive system is still available.

Keywords Vehicle lighting � Bending light � Adaptive main beam � Prediction �Camera based � Global positioning system � PSD-data

R. Büthorn (&) � H. H. Tadjine � B. Auerbach � K. SchulzeIAV GmbH, Carnotstraße 1, 10587 Berlin, Germanye-mail: [email protected]

H. H. Tadjinee-mail: [email protected]

B. Auerbache-mail: [email protected]

K. Schulzee-mail: [email protected]

J. Fischer-Wolfarth and G. Meyer (eds.), Advanced Microsystems for AutomotiveApplications 2013, Lecture Notes in Mobility, DOI: 10.1007/978-3-319-00476-1_8,� Springer International Publishing Switzerland 2013

77

1 Introduction

The first vehicles were left parked in darkness because the drivers could barely seewhere they were driving. Light is an important factor of a person’s comfort andwell-being, especially for the elderly. Having appropriate lighting conditions in ahousehold is both crucial and difficult to achieve. The only choice a car driver hadfor a long time was to switch the lights on or off. This is different today:The headlights think with the driver, sometimes even faster than him. They canilluminate corners, automatically switch between high beam and low beam andeven leave out or highlight certain areas.

The first car with adaptive lights was already built in 1918 [1]. Electric lightswere not invented until the 1920s of the last century. The adaptive light enteredseries production in the 1960s [2]. The headlights were connected to the steeringaxle and followed the steering motions through a simple pulley system. Today thisis all managed electronically: Either using additional headlights which switch onsimultaneously with the indicator lights or swiveling headlights [3].

In the last years the development of driver assistant systems which can improvethe visibility range have hardly increased. Reasons for this development are theusage of the new technologies such as the Xenon head-lights, new adequate opticalsensors, High dynamic range cameras and very faster ECUs.

Studies on the well-being of drivers at night show that 48 % of drivers feelstressed when driving in low-light conditions [4] and 34 % of drivers are usinglight assistance systems [5–7].

Accident statistics show that the current task of the automotive industry is toguarantee for the driver more safety, more comfort and more security. One of themost important topics is the improvement of street visibility at night. In 2011 died4,002 peoples due to traffic accidents in Germany. Approximately 38 % of theseaccidents are happened at night. In contrast the driving performance amounts only25 % at night. Furthermore 29 % of all seriously injured and 36 % of all killedpeople are listed at night [8] (see Fig. 1).

Fig. 1 Accident statistic—comparison between day and night

78 R. Büthorn et al.

2 State of the Art Light Functions

2.1 Evolution of Light Functions

It has been a long way from a headlamp that normally illuminates the area in frontof the car to modern light based driver assistance systems. The first system wasintegrated at the beginning of the 20th century, when two differently angledheadlamps were integrated and installed that enabled low beam and high beamsettings. Almost 40 years later, the first type approval for headlamps with asym-metrical light distribution was granted. Although different approaches for cor-nering light and bend lighting have been carried out over the time, it took until thebeginning of this century to establish these dynamic light functions. Moreover, in2006, legislation allowed the use of adaptive front lighting systems that providespecialized light distributions for different driving situations.

Currently, more than 25 % of all new German cars were equipped with adaptivelights, compared to 2009 where only 15 % were equipped [9]. In the currentautomotive market, there are a variety of technical solutions to facilitate these lightdistributions like: dynamic bending light, high beam assist, adaptive main beamand the adaptive high beam. All of these systems could improve the visibility forthe driver. However, all these systems are technically limited and suffer from theproblem of the package and the high costs [10].

2.2 Dynamic Bend Lighting

Dynamic bend lighting is a well visible lighting function with great benefit for theend-customer, because the entire headlamp light distribution is swiveled up to±15�. This dynamic movement of the light distribution represents an active gain insafety due to the increased range of illumination along the road. On winding roads,visibility can therefore be increased by up to 50 %, depending on the curve radius.The calculation of the swivel angle depends on the vehicle speed, steering angleand yaw angle [10, 11].

The proposed system suffers from some limitation. Due to the CAN Vehicledata, the swivel angle could be calculated only in one time and the system couldnot allowed any prediction. In several scenarios the light distribution due to themain beam will not be distributed on the street, where the driver needs it. As seenin the Figs. 2 and 3 at the beginning of a curve the main beam shines straightforward, not into the curve. Also, in the end of a curve, the main beam is bended tothe left or right side but the lane in front of the car is already straight.

Advanced Headlight System: 3D High Beam 79

2.3 High Beam Assist

High-Beam Assistant System manages the operation of dipped and main beamlights whilst driving at night. The system comprises primarily of a camera locatedin the interior rear-view mirror housing. The camera monitors the light from anysource at the front of the vehicle (e.g. rear lights of a vehicle in front, street lights,and headlights of an approaching vehicle) which then triggers the system toautomatically operate the dipped or main beam function of the Xenon headlights.

Fig. 2 Dynamic bendinglight at the beginningof a curve

Fig. 3 Dynamic bendinglight at an alternating curve


This system can be overridden by either manually selecting the ‘On’ position forthe headlights or by using the dipped beam selector on the indicator stalk.

As benefits, an optimum light control and visibility at all times with improvedfocus on the road and a reduction of actions required from the driver will beenabled. Also, the possibility of dazzling approaching drivers by automaticallyselecting dipped or main beam headlights will be reduced. This system has a mainlimitation. In case of automatic deactivation due to oncoming vehicles the area upto the car in front is not illuminated and obstacles especially in this area can bemissed (Fig. 4).

2.4 Adaptive Main Beam

The adaptive main beam assistant is a camera based system which adapts the rangeof the main beam to the distance to the other cars. The headlamps work in con-junction with a camera fitted on the inside of the windscreen that detects oncomingvehicles and vehicles in front. The system automatically adjusts the headlamps toprevent other drivers from being dazzled by gradually transitioning to high-beammode if the road ahead is clear (see Fig. 5).

A front camera recognizes continuously the oncoming traffic. Blobs of the headlights or the rear lights will be automatically detected and classified using an imageprocessing algorithms. The cone of the main beam always ends at the nearestdetected light to the ego-car. With a presence of other cars near to the ego-car, themain beam will be in the normal position or in another height without anyassistance.

Obstacles at the roadside will not be marked und could be overlooked ormissed.

Fig. 4 The high beam assist


2.5 Adaptive High Beam Assist

A camera system mounted on the front windscreen is used to detect an oncomingvehicle in the opposite lane or another vehicle in front and could automaticallyadjusts the headlamp range to the appropriate distance—in contrast to traditionalsystems which only switch between dipped and main beam. This allows the rangeof the dipped beam to be increased from around 65 to approaching 300 m withoutdazzling other drivers (Adaption of the illumination range dependent on theposition of other road users). Consequently, the driver always benefits from theoptimum illumination range, providing earlier and better recognition of the roadahead, pedestrians and danger spots [3].

With the current adaptive System, the high beam is almost active. An optimumlight distribution needed for the driver will be calculated and generated from theSystem in order to reduce the dazzling effect. This is pretty up-to-date, so thecurrent camera system and the headlamps adapted for the system are realexpensive. Furthermore the system is set inactive, if the traffic density is high and alot of turn ups and dips of the headlamps is needed (Fig. 6).

Fig. 5 The adaptive main beam

Fig. 6 The adaptive high beam assist


3 Adaptive Bending Light

During night time driving it is more demanding to keep the vehicle within the laneboundaries. The automotive lighting equipment illuminates the driver’s viewingfield and has to deliver the appropriate information for lane keeping under manydifferent driving situations.

Regarding the driver’s needs for visual information about the road ahead,present headlight technology insufficiently lights up bends in the road ahead. Theadvantage of using an adaptive lighting system, where one observes a country roadlit correctly. Instead of illuminating some fields or trees, the available light isdirected dynamically in the direction where it is actually needed, enhancing thevisual information for the driver. The adaptive bending light is not realized due tovehicle speed, steering-, and yaw angle, like the dynamic bending light.

The new systems are controlled by means of path prediction based on vehicledynamics, lane information from the camera system and route vectors of thenavigation system.

With the output of the path prediction model it is possible to control themovable headlamps appropriately. To assure a best illumination of the street, themid-position of the light distribution is placed on the left lane of the road (seeFigs. 7 and 8).

The prediction consists of an estimation of the lateral accelerations acting onthe vehicle body and a prediction of the future path of the vehicle based on thecurrent vehicle dynamic states in combination with a simple model of the vehicle.Extra filtering has been added to improve the quality of the prediction. If no PSD-and GPS-data are available, the adaptive system will fall back automatically to thenormal lighting function such as the dynamic bending light.

Fig. 7 Comparison betweendynamic and adaptivebending light at beginning ofa curve


4 Adaptive Main Beam at Hilltops and Dips

Classic headlamps are static systems which emit the light always in the samedirection independent from the road geometry. The optimal range can be achievedfor a straight, horizontal street geometry. In case of cambers, dips and curves theilluminated range on the street can decrease while the glare of the oncoming trafficcan increase. According to this an optimal headlamp should be able to adapt on thehorizontal (curves) and vertical (cambers and dips) street geometry to assure abetter illumination, a constant visibility range and a minimized glare.

One possibility to realize this concept is a swiveling light module. Somemodern headlamps, especially from cars of the upper class are already equippedwith this system which is called dynamic bending light. They offer an adaption oncurves. The potential of these systems to increase the road safety is classified asvery high. The risk to cause an accident in curves increases significant at nightespecially in curves with a small radius [4].

The dynamic bending light offers only an adaption on the horizontal roadgeometry. Not yet realized in production cars but also important is an adaption onthe vertical road geometry. Cambers and dips can cause a reduced visibility dis-tance or glare of the oncoming traffic, too. A vertical swiveling light moduleensures a constant illumination range.

For this purpose, the headlight of oncoming traffic and the traffic backlightsahead will be used as reference for the distance estimation between the ego vehicleand other oncoming vehicles. The system will be activated if no other vehicles inthe relevant area where other drivers could be dazzled are detected. Else, the

Fig. 8 Comparison betweendynamic and adaptivebending light at an alternatingcurve


system will be switched to the adaptive mode. That means, the cut-off of the mainbeam is lowered infinitely variable up until the headlights or backlights of theother car. A maximal high is not intended (see Figs. 9 and 10).

5 Proposed Approach

As extension for the existing system, a combination of the adaptive main beamwith the adaptive high beam assist will assure the best possible illumination of theroad is proposed. This improves the headlamp illumination by means of contin-uous adaptation of the headlamps according to the current driving situation andcurrent environment. For this reason the vehicle trajectory must be analyzed three-dimensional. To assure a good functionality of the proposed system and to becomea close view of the real lane, an adequate prediction is required.

First road estimation is achieved based on the camera system. The road verticalcurvature estimation is performed, due to the fact that at far distances the road maybe not plane. Once, this road curvature is estimated, a vertical offset correction is

Fig. 9 Adaptive main beamat a hilltop and a dip withtraffic ahead


only done for those objects located close to the horizon line, at the infinity.A representative features are calculated for each tracked object, and then objectsare classified (main nuisance light source due to the reflections of the own vehi-cle’s light over the road-traffic signs) or vehicles, using a special classification. Toestimate the distance between the ego vehicle and the detected vehicles usingmonocular camera, the Dickmanns Model is used [12].

By using the road vertical curvature estimation camera based, a correction ofthe vertical image coordinate of all the objects located at the infinity where the flatroad assumption is not valid is performed [13, 14]. Vertical and horizontal map-ping models can be carried out. However, this distance is only an approximation,since some sources of error can affect this estimated distance, such as: elevation ofthe vehicle’s light, road unevenness, object’s centroid, etc. In order to minimizethese errors, a vertical coordinate correction is proposed [15].

Generally, the road is assumed as plane. However, this is a dangerousassumption, since at far distances (more than 500 m) the road vertical curvaturemay influence the vertical position at which the objects appear in the image. As asimplifying assumption, the horizontal road curvature is assumed to be so small

Fig. 10 Adaptive main beamat a hilltop and a dip withoncoming traffic


that is not considered in the perspective model [16, 17]. If the road verticalcurvature is significant, some mistakes can arise in the classification process due tothe flat road assumption, so road vertical curvature estimation must be includedinto our camera perspective model. For these reasons additional information fromother systems are needed.

In addition to the vehicle dynamic parameters, route vectors from the naviga-tion system are used. The navigation system permanently keeps track of the pre-cise location of the car, and with its built in digital road map it knows the roadcharacteristics ahead. Finally, the path prediction, the navigation data, vehicleCAN data and an objects list provided from the camera system will be coupled toensure consistent control of the headlamps (see Fig. 11).

6 Conclusion

In this paper, a new concept for an advanced headlight system is presented. Theweather or the road geometry cause a reduced illumination range or glare which iscritical for the driver safety. An optimal headlamp system should be able to adapton a multitude of parameters from the ego vehicle and the environment to ensure asufficient illumination of the street without glaring other road users. A perfect roadillumination without providing glare for other traffic participants and giving themaximum additional information about the environment to the driver still a hardtask for these systems.

The improvement of such systems will be achieved only with the combinationof the lane data and the list of detected objects provided from the camera systemwith the PSD format data of the GPS (Global Positioning System) and the navi-gation system. The most part of the technology which is needed for the realizationof an optimal adaptive system is still available. But these systems are not man-datory by the Economic Commission for Europe (ECE).

Fig. 11 Block diagram


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http://www.frost.com/

https://www.destatis.de

http://www.dat.de/products/

http://www.patentstorm.us/patents/6947577-fulltext.html

http://www.patentstorm.us/patents/6947577-fulltext.html

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