Файл: rt-light-sim-ilft-e.pdf

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Application of real-time lighting simulation

for intelligent front-lighting studies

A. Dubrovin, J. Lelevé, A. Prevost

VALEO Lighting Systems

34, rue Saint André

93012 Bobigny Cedex, - France

Phone : +33 1 49 42 62 62

Fax : +33 1 49 42 62 82

email : alexis.dubrovin@valeo.com

M. Canry, S. Cherfan, P. Lecocq, J.M. Kelada, A. Kemeny

RENAULT

Technocentre Renault - TCR AVA 2 12

1, Avenue du Golf

78 288 Guyancourt Cedex – France

Phone : +33 1 34 95 19 85

Fax : +33 1 34 95 27 30

E-mail : andras.kemeny@renault.com

RESUME

Des études ont été menées dans la cadre de la conduite de nuit  [4,7]. Afin d’améliorer la conduite
nocturne, le Département Eclairage de VALEO et RENAULT étudient et développent de nouveaux
systèmes d’éclairage intelligents. Les éclairages frontaux ont ainsi été étudiés de manière à améliorer
l’illumination de la route, plus particulièrement dans les virages, à travers deux stratégies de contrôle
simulées. La première est basée sur les informations du véhicule telles que la vitesse et l’angle au
volant. Elle permet d’ajuster l’orientation des faisceaux dans les situations de virage. La seconde
approche utilise les données de navigation pour déterminer à l’avance la géométrie de la route. La
direction des faisceaux est corrigée en conséquence et permet ainsi au conducteur de mieux apprécier
les courbures de la route.

Les deux stratégies d’éclairage ont été intégrées dans un des simulateurs de conduite RENAULT
spécialement dédié à la simulation d’éclairage [3]. Le simulateur comporte un environnement de
conduite classique, un générateur d’images pour une restitution réaliste de l’éclairage des faisceaux sur
la route et un générateur de son. Un ensemble de logiciels permettent de générer un trafic routier
réaliste, de créer des scénarios et de visualiser en temps réel des données issues de la simulation.

Des développements logiciels spécifiques ont été réalisés pour intégrer dans le simulateur Renault les
stratégies d’éclairages développées par Valeo. Les deux stratégies ont été comparées en temps réel sur
le simulateur. Ce dernier a permis de réduire les coûts et les délais de développements nécessaires à la
construction de prototypes. De nombreuses heures de mises au point sur véhicule réel et d’essais de
nuit ont été ainsi évitées.

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ABSTRACT

Road safety studies have been carried out in night time visibility conditions [4,7]. To help night time
driving, VALEO Lighting Department and RENAULT are studying and developing new intelligent
lighting systems. Lighting strategies for front lighting systems have been explored to better control the
illumination of the road, especially in curves. Two different adaptive strategies have been realised : the
first one consists in studying specific vehicle parameters like the car speed and the steering wheel
angle to adjust front-lighting performance on curves. The second one, based on navigation data and
the vehicle speed, determines easily the shape of the road in advance. Additional beam correction is
then supplied to help drivers better negotiate the curves of the road.

Both strategies have been integrated in a Renault automobile driving simulator dedicated to real-time
lighting simulation [3]. The driving simulator includes a driver cockpit, an image generator providing
realistic restitution of headlight distribution, a sound generator, realistic traffic and user-friendly man-
machine interfaces to define car and headlight data as well as test scenarii.
Specific software developments were carried out to perform the integration of adaptive front-lighting
strategies in the simulator environment. A system that detects curves in the graphical database was
created to simulate a navigation system. The comparison between strategies is then easily handled by
switching from one to the other in real-time driving conditions.

The driving simulator allows to reduce significantly developments costs for building prototypes. It
also enables to save hours of tuning and testing on physical vehicles at night. Therefore, the driving
simulator appears as a cost- and time-saving tool for the development of new headlamp systems.

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Night-time driving with conventional headlamps is particularly unsafe : only 25% of the driving is
done at night but 55% of the driving fatalities occur during this period [4,7]. In order to reduce these
road traffic hazards, developments are carried out in 

the Valeo Lighting Systems Branch

 at the request

of

 the Renault Lighting Department

 aiming at dynamically directing additional headlamps according

to the behaviour vehicle, environmental and road  conditions. The lighting simulator of 

Renault

Simulation and Virtual Reality Research Group

 was then used to tune and test lighting control

strategies. It enabled to reduce development costs and delays while enhancing the quality of the new
front-lighting strategies.

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Car lighting today

For efficient lighting respecting road traffic safety, the headlamps must provide the best possible
performances and avoid at the same time glares for the oncoming drivers.

Performance improvement has been achieved thanks to the source and the optical unit :
-

Halogen bulbs provide 30% more light than previous generation.

-

Clear lens complex shape allows the use of 80 % of the light that was previously wasted on shields
and bezels.

Halogen Renault Scenic

Since ten years, Xenon lighting has been pushing the performance into a new range : doubled flux and
beam width, 30 % increased range, day-light colour rendering and 40% reduction of electrical
consumption.

According to the European Xenon 1996 regulation, the vehicles must be equipped with headlamp
cleaning devices and automatic levelling that modify the light beam in order to compensate situations
where it could be glaring (heavy weights at the rear of the vehicle…). Latest generation of levelling
are acting in real time and therefore may reduce the glares during accelerations.

The first Renault Xenon headlamp has been installed in the Safrane in early 1997.

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Halogen lighting

Xenon lighting

Xenon Nissan Primera

Bi-function systems allow the same performance for low beam and high beam with only one Xenon
bulb, through a relative mechanical movement of the bulb to and from the optical surface.

Bi-function mechanical system

Further improvements

Many researches are going on in the field of lighting improvement. They usually take advantage of the
future availability of information networks at the vehicle front end.
-

Infra Red lighting may give a clear image of  the dark part of the road,

-

Additional optical surfaces or modified low beams may perform as suggested by the “Adaptive
Front lighting Systems“ future regulation (see below),

-

CCD camera may be used in order to replace levelling sensors,

-

Automatic Cruise Control radar antennas may benefit from the Xenon levelling,

-

…

Future optical block

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Adaptive Front lighting Systems (A.F.S.)

The European working group A.F.S is preparing a regulation change for the years 2003-2005 in order
to allow new improved beam patterns for the low beam lighting.
The main proposed improvements are 

:

“

Motorway Light

”

The lower the vehicle speed, the closer and wider is the light
requirement. A navigation system may help to insure that the
oncoming drivers cannot be glared (highways with central
separation…), otherwise, the range must prudently be increased.

“

Adverse weather light

”

Following road reflectivity and weather condition, the beam pattern
may be improved by :

-

reducing the light that may glare the oncoming drivers after

a reflection on the wet road,

-

increasing the road side lighting.

“

Town light

”

The purpose is mainly to increase the lateral light when the car is
under city lighting conditions, and allow nearly perpendicular
pedestrian and cyclist identification (without glaring) at crossings.
A navigation system is required for an  efficient automatic
anticipation of the crossings.

“

Bending light

”

The light is following the direction changes of the road. This
function is more detailed in paragraph 2.4.