AdaptiveLight Control SystemsMohamed Khaled, Technical University of Chemnitz,DeutschlandEmail: [email protected]
tu-chemnitz.de Abstract— ALC(Adaptive Light Control) system has been attracted much attention because ithas a potential to reduce traffic accidents and driver’s stress.This paperdiscuss AFS (Adaptive Front Light) system which is an active safety system;improve the vision to thr driver during the night driving and in curves andover hills. In tight curves the standard headlights keeps its lighting toforward, which mean illuminating the side of the road and making the road infront of the driver in the dark.
AFS can overcome this problem by adapting theheadlights 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 AFScan solve this problem, how it is differ from the standard headlights and howits increase the safety in night driving.Keywords— AFS, headlamb, lightillumination, light beam xxxx-xxxx/0x/$xx.00 © 200x IEEE Published by the IEEE Computer Society —————————— u ——————————1 Introduction”… The IIHS (InsuranceInstitute for Highway Safety in the United States) estimates that adaptivehighlights could have helped in 142.000 craches per year in the United Statesin 2008? including 29.000 thatresulted in injury and 2.480 that resulted in death (IIHS 2010)” 1:2 Normally the headlights shine of the vehicle goes in a straight lineforward of the car, it does not matter what the direction or position of thecar, its mean that in curves road the headlights’s shine will focus itsillumination on the side of the road and leave the road ahead of the driver inthe dark and causes other problem like blind vision of cars coming in theopposite direction.
Adaptive light control react to wheel speed, steering wheel angle, andyaw and tilt rate of the vehicle and automatically adjust the headlights angleand intensity to illuminate the road ahead of the driver. When the vehicle turnto right, the headlights also turns to right, when the vehicle turn to theleft, the headlights turn to left. Similary when the vehicle is going over ahill, the headlights points its shine up or down, deending on the position ofthe vehicle 2:362.
Fig.1vehicle with and without AFS 2 HOW DO AFS WORK2.1 AFS PartsAFS is consists of threemain parts, Vehicle sensors; AFS control unit and actuator unit which cnonnects to the CAN bus of the Vehicle.3:1Wheelspeed sensor is a type of the sensors thatused for measuring the speed of rotation of each wheel by counting the numberof laps that the wheels is making.
Yawsensor it is a sensor that measure thecurvature of the Vehicle on the road by measure how far the axis of the car istilting in the curves. This output information are collected and send into a microcomputer,which compares this information with the data values of steering angle, wheelspeed and accelerator position if, if the system detect high load of yaw, thesutiable brake is applied. Lateral speed sensor measures the g-force for thecurve then sends this information to the ECU.Steeringinput sensor is a sensor that measure theangle of the steering wheels.Smallmotor is the actuator unit that linkedto each headlight to control in their moving.
2.2 AFS WorkingThe datacollected from the sensors are processed by the AFS controller, and thendetermines the speed of vehicle, the angle and length of the curve. AFScontroller send this information with his commands through the LIN bus.
Afterthat the intensity and position of the headlights shine are adjusteddepending on the commands comes from the AFS controller. 4:5, 6, 7 Fig.2 Structre ofAFS 3 MAJOR FUNCTION3.1 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 ofroad” 4:3 Fig.3 Light red area indicates beam extension to theside.
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 conventiallow beam. It is usually activated at speeds between 50 and 100 km/h” 4:3 Fig.4 drive’s view of Basic/country passing beam3.3 Motorway Passing Beam”… Motorway light improves vision onhighways and expressways. From 100 km/h, this beam illuminates the roadwaysignificantly 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 ofmotorway passing beam 3.4 Wet-road passing beam”… This beam is activated when the rainsensors detects precipitation or the windshield wipers are on for 2 minutes ormore. The edges of the road are more strongly illuminated for betterorientation 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 duringmaeuvers in dark access road. At speeds up of to 40 km/h, one additionalcornering light comes on when the indicator is actuated or the steering wheelturned through about 90 degrees to the right or to the left” 4:43.6 System LevelingDynamicSwiveling and leveling helps during pass the hills. At hills, the light beamgoes up to the Sky.
Additional hight sensors located in the chassis can deteminrthe heigh and position of the Vehicle. According to this information the lightbeam will change acoording to the vetical position of the Vehicle causing thebetter illumination to the driver.5:42 4 Regulation ChangeIn order toimprove efficiency of AFS and distribution of the light beam, the EuropianWorking Group make this regulation changes.4.1 Motorway LightWhenever theVehicle’s speed is low whenever the light beam have to be more wider and morenearest.6:54.2 Adverse Weather LightConsideringthe weather conditions and light reflection rate for the roads then thedistribytion of the light beam can be improved by:1- On the wet road and afterconsider the reflection of the road, the light reduction that may cause a blindview to the oncoming drivers.
2- Increase the number oflight lambs on the both side of the road.6:54.3 Town LightToincrease the safety to the pedestrians especially in the passages and under thetown lighting conditions, the number of light lambs on the both sides for theroad have to incease considering the glaring for the pedestrians.6:54.
4 Bending LightThe beam light should keeps track of changes in theroad. 6:55 Light Beam Distribution5.1 Led HeadlambBetter light beam distribution can occurs bycreating a matrix of LED Chips on an image. With the ability to control inevery LED chip in the matrix separately, that is lead to the ability ofcreating difeerent patterns of the light.
When a small motor that attached atevery lamb recieved a PWM input (Pulse Width Modulation) from the AFScontroller to move to right or left. 7We can also use PWM principle in theLED-Chips matrix drive the ability to generate different shapes of light withdifferent intensity acoording to the situation and to the road condition.8:4 Fig.7 show distribution for low andhigh light beam using LED-Chips Matrix.
5.2 Dmd (Digital Micro-mirror Device) HeadlambThe concept of DMD is an array of micro mirrors hasthe ability to reflect the light comes from a high intensity light.9:32 Fig.8 How DMD headlamb work. LightdistributionArray of micro mirror consists of thousands of reflectmirrors placed upper a CMOS device. It is possibleto change the position of the movable mirrors to two different position.
Thereare two ways to distribute the light, by directing the light through aprojection lens to illuminate a specific area or by directing through anabsorbing surface.By there ways; black and whitepixels area could be generated which mean more controlling on the light distributionand ability to display symbols as in Fig. 9:335 Adaptive Headlight BlindingOne of problems in the curved roads that theblinding of the oncoming Vehicle driver, to eliminate this problem and continueto provide intense illumintation, the AFS should be able automatically toreshape the patterns of the light beam. 10:8″… The aim is to prevent it fromilluminating certain areas in the vicinity of a light forward of it; morespecically, to a headlight With an output comprising a multiplicity ofmicrobeams projecting a composite beam of light in the forward direction,Whereby the direction of an incoming beam of light impinging on the forWard projectingheadlight Will be sensed by sensors controlling the individual microbeams todarken those microbeams that Would otherwise illuminate areas near to thesource of the imping ing beam, thus eliminating the blinding of a driver in anoncoming vehicle, While continuing to provide intense forWard illumination” 10:96 Fault ManagementLike any system in the Vehicle, the fault due errorin one part of this system is available, so the system should have highreliability.
In AFS the error may occur in AFS controller, one of the relatedsensors or in the actuator unit (Small motor); thus the lighting of theheadlight will be affective.So to deal with any unexpected errorlike stopping lighting and to prevent this erorr from causing blind vision tothe oncoming vehicle driver, a fault management function is used. 3:4 TABLE 1Fault 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 tableabove shows the fault part, the expected error and disposal method; once oneerror happen causes fault in one part, the AFS controller detect that and theappropriate action will taken. 3:47 Advantages Nowdaysmost of car manufactors going to replace the old headlight (Halogen lamb) withthe most recent lamb (LED), this last one is characterized by most lumen efficiencythan the conventional lamb ( 5 times better ), also offer better colordisplaying, better illumination and longer life ( 5000 hours compared with 1500hours in the conventional lamb). Thses adavantages are common reasons for whymost of cars’s manufactors are going to use them.
11:12TABLE 2Comparsionbetween Halogen and LED lamb 8 Challenges8.1 LimitationLike most of Advanced Driver Assistant System technologies,to realize the top benefits from AFS technology, the driver should interactappropriately with this system. This mean to gurantee the safety for thedriver, he have to consider his behavior like the speed or driving undertirednesss. For example the driving under stress or under alcohol drinking areaffect on the driver ability to quick react to the unexpected dangeroussituation therefore the possibility to avoid hazard is very difficult.
12:10 8.2 CostsLED lambs has two challenges,converter design and ballast control. These type of lamps need a very specialballast design circuit to realize the special transient characteristics and thebest efficiency for DC/DC converter. For these reasons, some cars’s manufactorsmake this type of lamp technology as optional in the luxury cars. 13:650,651 8.3 The PowerIn the beginning os switching on this type of lambs,it is require a high voltage for ignition. Afterthata large current is require in order to transiting the lamp state from the glowdischarge state to the arc discharge state.
As the lamb be in the arc dischargestate, a long period current is required to each electrodes in order to warm upand keeps on the arc state. 14:650,651 8.4 The Temperture Due to the high temperaturesurrounding the lambs and high cost for thermal management. It is veryimportant to improve the efficiency of the ballast. Because the core part interms of efficiency in the whole system is the front-part, it is very importantto design very carefully. 15:422,423 9 ConclusionInthis paper, we study the working concept of the adaptive front-lighting systemAFS of vehicles at the curves and explained the overall design for the system,the system consist of three modules: the vehicle’s sensors module, AFScontroller module and the actuator module. 16:4We also study how the adaptive headlight is betterthan the conventional headlight that can be steering from left to right andvice versa according to the situation, also better in illumination.
2:3How DMD headlamb has betterillumination distribution than LED lambs.We see how Europian Working Groupprovide different regulations change on the AFS system to realize bestefficiency for the system. With all these advantages, remains AFS system haslimitation and like most safety technology, the driver has to deal appropriatelywith the system. Adaptive headlights are most often offered as an optional in luxuaruvehicle; however, the effort to attach this type of headlights with mostvehicle and with different models is in increasing.