Adaptive
Light Control Systems

Mohamed Khaled, Technical University of Chemnitz,
Deutschland

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Abstract— ALC
(Adaptive Light Control) system has been attracted much attention because it
has a potential to reduce traffic accidents and driver’s stress.This paper
discuss AFS (Adaptive Front Light) system which is an active safety system;
improve the vision to thr driver during the night driving and in curves and
over hills. In tight curves the standard headlights keeps its lighting to
forward, which mean illuminating the side of the road and making the road in
front of the driver in the dark. AFS can overcome this problem by adapting the
headlights angle and intensity according to wheel speed, steering wheel angle,
and yaw and tilt rate of the car. In this article, we will find out at how AFS
can solve this problem, how it is differ from the standard headlights and how
its increase the safety in night driving.

Keywords— AFS, headlamb, light
illumination, light beam

xxxx-xxxx/0x/$xx.00 © 200x IEEE        Published by the IEEE Computer
Society

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1   Introduction

“… The IIHS (Insurance
Institute for Highway Safety in the United States) estimates that adaptive
highlights could have helped in 142.000 craches per year in the United States
in 2008? including 29.000 that
resulted in injury and 2.480 that resulted in death (IIHS 2010)” 1:2

Normally the headlights shine of the vehicle goes in a straight line
forward of the car, it does not matter what the direction or position of the
car, its mean that in curves road the headlights’s shine will focus its
illumination on the side of the road and leave the road ahead of the driver in
the dark and causes other problem like blind vision of cars coming in the
opposite direction.

Adaptive light control react to wheel speed, steering wheel angle, and
yaw and tilt rate of the vehicle and automatically adjust the headlights angle
and intensity to illuminate the road ahead of the driver. When the vehicle turn
to right, the headlights also turns to right, when the vehicle turn to the
left, the headlights turn to left. Similary when the vehicle is going over a
hill, the headlights points its shine up or down, deending on the position of
the vehicle 2:362.

 

 

 

 

             Fig.1
vehicle with and without AFS

 

 

                    

2     HOW DO AFS WORK

2.1 AFS Parts

AFS is consists of three
main parts, Vehicle sensors; AFS control unit and actuator unit which cnonnects to the CAN bus of the Vehicle.3:1

Wheel
speed sensor is a type of the sensors that
used for measuring the speed of rotation of each wheel by counting the number
of laps that the wheels is making.

Yaw
sensor it is a sensor that measure the
curvature of the Vehicle on the road by measure how far the axis of the car is
tilting in the curves. This output information are collected and send into a microcomputer,
which compares this information with the data values of steering angle, wheel
speed and accelerator position if, if the system detect high load of yaw, the
sutiable brake is applied. Lateral speed sensor measures the g-force for the
curve then sends this information to the ECU.

Steering
input sensor is a sensor that measure the
angle of the steering wheels.

Small
motor is the actuator unit that linked
to each headlight to control in their moving.

 

2.2 AFS Working

The data
collected from the sensors are processed by the AFS controller, and then
determines the speed of vehicle, the angle and length of the curve. AFS
controller send this information with his commands through the LIN bus.
Afterthat the intensity and position of the headlights shine are adjusted
depending on the commands comes from the AFS controller. 4:5, 6, 7

 

 

 

 

 

 

 

 

 

 

 

 

 

                       Fig.2 Structre of
AFS                                                     
                                          

 

 


 MAJOR FUNCTION

3.1 Town Passing Beam

“… At speed below 50 km/h? town light provides a wider light distribution at reduced range? helping drivers to more clearly see pedestrians on the edge of
road” 4:3

 

 

 

 

 

 

 

 

 

 

Fig.3 Light red area indicates beam extension to the

side.

3.2 Basic/Country Passing Beam

“… The basic light illuminates the left –
and right-hand edges of the road more brightly and widely than the convential
low beam. It is usually activated at speeds between 50 and 100 km/h” 4:3

 

 

 

 

 

Fig.4 drive’s view of Basic/country passing beam

3.3 Motorway Passing Beam

“… Motorway light improves vision on
highways and expressways. From 100 km/h, this beam illuminates the roadway
significantly further ahead and focuses more on the left hand edge of the road.
The motorway light switches on automatically at speeds greater than 100 km/h” 4:3

 

 

 

 

 

 

 

 

 

 

 

Fig.5 driver’s view of
motorway passing beam

 

3.4 Wet-road passing beam

“… This beam is activated when the rain
sensors detects precipitation or the windshield wipers are on for 2 minutes or
more. The edges of the road are more strongly illuminated for better
orientation to the guiding lines” 4:3

 

 

 

Fig.6 Driver’s view of Wet-road passing beam.

3.5 Static Cornering Light

“… Static cornering light helps during
maeuvers in dark access road. At speeds up of to 40 km/h, one additional
cornering light comes on when the indicator is actuated or the steering wheel
turned through about 90 degrees to the right or to the left” 4:4

3.6 System Leveling

Dynamic
Swiveling and leveling helps during pass the hills. At hills, the light beam
goes up to the Sky. Additional hight sensors located in the chassis can deteminr
the heigh and position of the Vehicle. According to this information the light
beam will change acoording to the vetical position of the Vehicle causing the
better illumination to the driver.5:42

4 Regulation Change

In order to
improve efficiency of AFS and distribution of the light beam, the Europian
Working Group make this regulation changes.

4.1 Motorway Light

Whenever the
Vehicle’s speed is low whenever the light beam have to be more wider and more
nearest.6:5

4.2 Adverse Weather Light

Considering
the weather conditions and light reflection rate for the roads then the
distribytion of the light beam can be improved by:

1-       On the wet road and after
consider the reflection of the road, the light reduction that may cause a blind
view to the oncoming drivers.

2-       Increase the number of
light lambs on the both side of the road.6:5

4.3 Town Light

To
increase the safety to the pedestrians especially in the passages and under the
town lighting conditions, the number of light lambs on the both sides for the
road have to incease considering the glaring for the pedestrians.6:5

4.4 Bending Light

The beam light should keeps track of changes in the
road. 6:5

5 Light Beam Distribution

5.1 Led Headlamb

Better light beam distribution can occurs by
creating a matrix of LED Chips on an image. With the ability to control in
every LED chip in the matrix separately, that is lead to the ability of
creating difeerent patterns of the light.

When a small motor that attached at
every lamb recieved a PWM input (Pulse Width Modulation) from the AFS
controller to move to right or left. 7

We can also use PWM principle in the
LED-Chips matrix drive the ability to generate different shapes of light with
different intensity acoording to the situation and to the road condition.8:4

 

 

 

 

 

 

 

 

 

 

Fig.7 show distribution for low and
high light beam using LED-Chips Matrix.

5.2 Dmd (Digital Micro-mirror Device) Headlamb

The concept of DMD is an array of micro mirrors has
the ability to reflect the light comes from a high intensity light.9:32

 

 

 

 

 

 

 

 

Fig.8 How DMD headlamb work.   Light
distribution

Array of micro mirror consists of thousands of reflect

mirrors placed upper a CMOS device. It is possible
to change the position of the movable mirrors to two different position. There
are two ways to distribute the light, by directing the light through a
projection lens to illuminate a specific area or by directing through an
absorbing surface.

By there ways; black and white
pixels area could be generated which mean more controlling on the light distribution
and ability to display symbols as in Fig. 9:33

5 Adaptive Headlight Blinding

One of problems in the curved roads that the
blinding of the oncoming Vehicle driver, to eliminate this problem and continue
to provide intense illumintation, the AFS should be able automatically to
reshape the patterns of the light beam. 10:8

“… The aim is to prevent it from
illuminating certain areas in the vicinity of a light forward of it; more
specically, to a headlight With an output comprising a multiplicity of
microbeams projecting a composite beam of light in the forward direction,
Whereby the direction of an incoming beam of light impinging on the forWard projecting
headlight Will be sensed by sensors controlling the individual microbeams to
darken those microbeams that Would otherwise illuminate areas near to the
source of the imping ing beam, thus eliminating the blinding of a driver in an
oncoming vehicle, While continuing to provide intense for

Ward illumination” 10:9

6 Fault Management

Like any system in the Vehicle, the fault due error
in one part of this system is available, so the system should have high
reliability. In AFS the error may occur in AFS controller, one of the related
sensors or in the actuator unit (Small motor); thus the lighting of the
headlight will be affective.

So to deal with any unexpected error
like stopping lighting and to prevent this erorr from causing blind vision to
the oncoming vehicle driver, a fault management function is used. 3:4

 

TABLE 1

Fault Management

 
Fault Parts

 
Error Items

 
Disposal Method

 
Horizontal Motor

 
Circuit open or short, overload

In vertical plant, light axis
will go down to the bottom

 
Vertical Motor

 
Circuit open or short, overload

In horizontal plant, light axis
will go to initial position

Steering wheel sensor

 
Sensor circuit open or short,
invalidation value

In both horizontal and vertical
plant, light axis will go to initial position

Velocity sensor

Horizontal sensor

The table
above shows the fault part, the expected error and disposal method; once one
error happen causes fault in one part, the AFS controller detect that and the
appropriate action will taken. 3:4

7 Advantages

 

Nowdays
most of car manufactors going to replace the old headlight (Halogen lamb) with
the most recent lamb (LED), this last one is characterized by most lumen efficiency
than the conventional lamb ( 5 times better ), also offer better color
displaying, better illumination and longer life ( 5000 hours compared with 1500
hours in the conventional lamb). Thses adavantages are common reasons for why
most of cars’s manufactors are going to use them. 11:12

TABLE 2

Comparsion
between Halogen and LED lamb

 

 

 

 

 

 

 

 

8 Challenges

8.1 Limitation

Like most of Advanced Driver Assistant System technologies,
to realize the top benefits from AFS technology, the driver should interact
appropriately with this system. This mean to gurantee the safety for the
driver, he have to consider his behavior like the speed or driving under
tirednesss. For example the driving under stress or under alcohol drinking are
affect on the driver ability to quick react to the unexpected dangerous
situation therefore the possibility to avoid hazard is very difficult. 12:10

 

8.2 Costs

LED lambs has two challenges,
converter design and ballast control. These type of lamps need a very special
ballast design circuit to realize the special transient characteristics and the
best efficiency for DC/DC converter. For these reasons, some cars’s manufactors
make this type of lamp technology as optional in the luxury cars. 13:650,651

 

8.3 The Power

In the beginning os switching on this type of lambs,
it is      require a high voltage for ignition. Afterthat
a large current is require in order to transiting the lamp state from the glow
discharge state to the arc discharge state. As the lamb be in the arc discharge
state, a long period current is required to each electrodes in order to warm up
and keeps on the arc state. 14:650,651

 

8.4 The Temperture

 

Due to the high temperature
surrounding the lambs and high cost for thermal management. It is very
important to improve the efficiency of the ballast. Because the core part in
terms of efficiency in the whole system is the front-part, it is very important
to design very carefully. 15:422,423

 

9 Conclusion

In
this paper, we study the working concept of the adaptive front-lighting system
AFS of vehicles at the curves and explained the overall design for the system,
the system consist of three modules: the vehicle’s sensors module, AFS
controller module and the actuator module. 16:4

We also study how the adaptive headlight is better
than the conventional headlight that can be steering from left to right and
vice versa according to the situation, also better in illumination. 2:3

How DMD headlamb has better
illumination distribution than LED lambs.We see how Europian Working Group
provide different regulations change on the AFS system to realize best
efficiency for the system. With all these advantages, remains AFS system has
limitation and like most safety technology, the driver has to deal appropriately
with the system. Adaptive headlights are most often          offered as an optional in luxuaru
vehicle; however, the effort to attach this type of headlights with most
vehicle and with different models is in increasing.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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