Adaptive Headlight System

Transcription

1 Research Paper Volume 2 Issue 7 March 2015 International Journal of Informative & Futuristic Research ISSN (Online): Adaptive Headlight System Paper ID IJIFR/ V2/ E7/ 043 Page No Subject Area Key Words Mechanical Engineering Headlamp, AFS, Advanced Front lighting System, Curved Road, Automotive, Microcontroller, Servomotor, Sensor Shinde Ganesh R. 1 JadhavTushar D 2 Varade Shubham A. 3 Korde Goraksha K. 4 Belkar S.B 5 Assistant Professor Abstract The highest fatal traffic accident rate occurs on curved roads at night time. In most cases, the late recognition of objects in the traffic zone plays a key role. These facts point to the importance of the role of automobile forward-lighting systems. In order to provide enhanced night time safety measures, this work aims to design and build a prototype of steerable headlights by adapting a conventional static headlamp with every close eye on cost and reliability. Components that are easily available in the market and suitable for developing a steerable headlight system were tested. Different kinds of tests were done on critical parts of the system in order to determine its accuracy, its response time, and the system impact. Finally, the results acquired from these various tests will be discussed. Any findings and changes that should be made are discussed and may be useful for future development. Copyright IJIFR

2 1. Introduction Preventive and active safety of road vehicles is one of the top priorities in car design and development nowadays. Passive and active safety systems have been developed in R&D activities to produce vehicles that will perform at the highest level of safety and ensure comfortable driving under various conditions. Moreover, researchers have been trying to develop preventive and active safety systems that will actively support driving safety using today's advanced mechatronic systems. The reason as to why researchers focus on the subject of producing safer cars is related to the statistics that expose the serious consequences of accidents. In 2004, out of 494,851 accidents, 3,082 people died and 109,681 people were injured with a corresponding financial loss of approximately 0.5 billion dollars in Turkey. In 2002, in 1023 urban accidents 1685 people died and 153 billion dollar worth of damage occurred. In the world, the statistics are similar: in 2002, approximately 6,977 people in Germany, 7,720 people in France, 3,450 in UK and 6,682 in Italy died due to traffic accidents. Lighting in modern vehicles has been steadily improving in the last decades. Modern technology provides new light sources and more powerful optical systems. With current sensors and control equipment, advanced dynamic lighting systems are possible. The Adaptive Headlight System (AHS) is the outcome of engineering efforts in developing the next generation lighting systems not only for drivers but also for all other road users. AHS is introduced in order to prevent a possible accident from happening by increasing the visibility at night. AHS automatically adjusts the light to match the direction of travel. That enables the driver to react more quickly because he/she will see the road ahead more clearly. AHS significantly enhances driving safety in the dark by dynamically adjusting the headlights according to the car s current direction of travel to ensure optimum illumination of the road ahead and to give the driver much better visibility Problem Statement The major problem hindering safer and more comfortable driving is the driver and his/her limited reaction time in the presence of changing road conditions. An aim of development in active safety is to reduce the reaction time of the driver by improving visibility and thus achieve a significant increase in road safety and driving comfort. Alexander and Lunen feld mentioned that driving an automobile primarily a visual task because vision contributes as much as 90% of the information needed to drive. Good visibility contributes to driver confidence and enables more relaxed and safer driving. Moreover, statistics clearly show that the majority of accidents take place at night or in bad weather because of low visual conditions. Under such conditions, or in bad weather, drivers have difficulty in being able to see traffic control devices, lanes, other vehicles, pedestrians, animals, and other potential hazards. Studies show that visual perception, with which we absorb 90 percent of all relevant traffic information, is reduced to as little as four percent during foggy or rainy nights. Furthermore, according to Germany's Federal Statistics Bureau, more than 40 percent of all automobile accidents resulting in death occur at night, despite the fact that there is up to 80 percent less traffic on the road than during the day. Reduced vision increases reaction time which can have fatal consequences. Drivers rely on headlights in the dark and in bad weather for a clear view of the road and to illuminate possible hazards ahead. It is, therefore, of great importance to use available technology to contribute to road safety by improving the visual conditions provided by vehicle headlights. According to Börnchen et al appropriate solutions will be based on the 2291

3 mechatronic design concept and will incorporate components from heterogeneous fields such as lighting technology, mechanics, actuators, sensors, power electronics and system control. 3. Objectives Of Project To investigate the lighting conventional system and mechanism in automobiles. To study the properties of an IR and potentiometric sensor and its working principles. To design and develop an Adaptive Lighting System to be implemented in automobiles. To propose a lighting system that can be commercialized for the types of Transportation 4. Scope Of Project Adaptive headlights are an active safety feature designed to make driving at night or in low-light conditions safer by increasing visibility around curves and over hills. When driving around a bend in the road, standard headlights continue to shine straight ahead, illuminating the side of the road and leaving the road ahead of you in the dark. Adaptive headlights, on the other hand, turn their beams according to your steering input so that the vehicle s actual path is lit up. Similarly, when a vehicle with standard headlights crests a hill, the headlight beams temporarily point upwards towards the sky.. This makes it difficult for driver to see the road ahead and for oncoming motorists to see the driver approaching. In contrast, adaptive headlights use a self-levelling system that points the light beam up or down, according to the position of the vehicle. Adaptive headlights can be implemented in two ways 1) Mechanical system 2) Mechatronic system 4.1 Mechanical system-in this system two headlights are mounted, which are mechanically operated by a four bar kinematic chain mechanism. The linkage is connected to stub axle from where it receives motion of the wheels. This motion is transmitted to headlights through four bar linkage. The headlights are connected to two opposite links of four bar linkage. Components of system: a) Rack and pinion steering mechanism Rack and pinion systems give a much better feel for the driver, and there isn't the slop or slack associated with steering box pitman arm type systems. In a rack and pinion system, the track rod is replaced with the steering rack which is a long, toothed bar with the tie rods attached to each end. On the end of the steering shaft there is a simple pinion gear that meshes with the rack. When you turn the steering wheel, the pinion gear turns, and moves the rack from left to right. Changing the size of the pinion gear alters the steering ratio. It really is that simple. The diagrams here show an example rack and pinion system (left) as well as a close-up cutaway of the steering rack itself (right). Figure 4.1 : Rack and pinion steering system 2292

4 b) Steering ratio Steering ratio gives mechanical advantage to the driver, allowing you to turn the tyres with the weight of the whole car sitting on them, but more importantly, it means you don't have to turn the steering wheel a ridiculous number of times to get the wheels to move. Steering ratio is the ratio of the number of degrees turned at the steering wheel vs. the number of degrees the front wheels are deflected. So for example, if you turn the steering wheel 20 and the front wheels only turn 1 that gives a steering ratio of 20:1. For most modern cars, the steering ratio is between 12:1 and 20:1. This coupled with the maximum angle of deflection of the wheels gives the lock-to-lock turns for the steering wheel. For example, if a car has a steering ratio of 18:1 and the front wheels have a maximum deflection of 25, then at 25, the steering wheel has turned 25 x18, which is 450. That's only to one side, so the entire steering goes from -25 to plus 25 giving a lock-to-lock angle at the steering wheel of 900, or 2.5 turns (900 / 360). c) Turning circles The turning circle of a car is the diameter of the circle described by the outside wheels when turning on full lock. There is no hard and fast formula to calculate the turning circle but you can get but you can get close by using this, Turning circle radius = (track/2) + (wheelbase/sin(average steer angle)). d) Headlights Halogen headlights are used for cost effective purpose. 4.2 Mechatronics system- The purpose here is to disassemble the conventional headlight and modify the projector light for beam rotation. In order to manage system costs and complexity, a simple framework was laid out for the developed AFS. The latter consists of three important components: input sensors, a microcontroller as the brain of the system, and a motor for positioning the headlights. Figure 4.2 : Basic Block Diagram Sensor-A potentiometer is used as sensor. The position of the headlights is dependent on the direction of the vehicle so the input to the headlight system is attached to the vehicle s steering shaft. A simple geared mechanism is attached to a low-power type potentiometer that can then feed directly into the microcontroller. As the steering shaft rotates (taking corners), it will turn the axle of the potentiometer and therefore vary the voltage input. a) DC motors An electric motor is a device using electrical energy to produce mechanical energy, nearly always by the interaction of magnetic fields and current carrying conductors. The reverse process, that of using mechanical energy to produce electrical energy is accomplished by a generator or dynamo. Traction motors used on vehicles often perform both tasks. Electric motors are found in myriad uses such as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and computer disk drives, among many other applications. Electric motors may be operated by direct current from a battery in a portable device or motor vehicle, or from alternating current 2293

5 from a central electrical distribution grid. DC motors(10rpm) for turning of electronically operated headlights. b) Microcontroller:- A Programmable Intelligent Computer (PIC) microchip was used to control the motor. The PIC selected is the PIC16F877A which is an 8 bit microcontroller with 8KB flash program memory and USART. The PIC16F877A was selected because of its availability, low price, reliability, and its use of C language for its programming. The selected PIC also required minimal additional components in order to operate, further controlling system costs. c) Programming of the Microcontroller The potentiometer is used as the input; the pot will vary the voltage in the PIC which is from 0V to 5V. The potentiometer gives an analog input; therefore the PIC needs to convert it into a digital input via ADC. The digital number provided by the ADC relates to the proportion that the input voltage is of the full voltage range of the converter. For instance, applying 2V to the input of an ADC with a full-scale range of 5V will result in a digital output that is 40% of the full range of the digital output (2V / 5V = 0.4). The output digital ranges are usually expressed in terms of bits, such as 8 bits provided by thepic16f877a. The number of bits at the output determines the range of numbers that may be read from the output of the converter. An 8-bit converter will provide outputs from 0 to 28-1 or 255. Hence, when 2V is applied to a converter with a full scale range of 5V, an 8-bit converter would read 40% of 255,or 102. d) Assembly:- i. Firstly, we made a frame of MS bars as show. Then we mounted a Maruti 800 steering mechanism on the frame. ii. Then we mounted two headlights at the top on front side of the frame as These headlights are electronically operated. iii. Further we mounted two headlights below these electronically operated headlights, which were mechanically operated by a four bar kinematic chain mechanism. The linkage is connected to stub axle from where it receives motion of the wheels. This motion is transmitted to headlights through four bar linkage. The headlights are connected to two opposite links of four bar linkage. iv. One IR sensor is mounted for rpm measurement. Two DC motors (10rpm) are mounted for turning the headlight. One potentiometer sensor is mounted on the steering wheel for measuring the angular measurement the angular displacement of the steering wheel. v. Microcontroller and its associated circuitry is mounted at middle of the frame. 5. Testing Results And Discussion To put this whole system into practical use, there are several critical functions that need to be tested and analysed. The first critical function is to determine whether the head lights or motors are moving as desired prior to the rotation of the potentiometer which represents the steering wheel. The second function is the response time of the motor i.e. the time taken for the headlight to move from one position to another. Finally, the headlight will be installed on a car to see how effective it is. The theoretical results have been compared with the experimental results as shown in Figure 5.1. In this experimental test, the input voltage variable is measured by a multi-meter, whereas the frequency of the signal is measured by using an oscilloscope, and the motor position is measured using protractor. 2294

6 Figure 5.1: Comparison of results It is a slight difference during the motion. For example, for an input voltage of 3.6V, the expected motor position is 5.88degrees, whereas the actual position is 5.5 degrees. The voltage scale is also different; the calculation used a voltage scale from0 to 5V whereas measured voltage scale is only from 0 to 4.8V. This difference in voltage scale was not noticed during the tests and may have been due to a voltage drop in the PIC itself. However, the maximum and minimum degree positions are still the same and therefore this slight difference in voltage will not cause any significant effect to the functioning of the steer able head light. Another possible cause of error of that invariant degree is the gear slop in the servo motor. Gear slop means that a gear is able to move without moving another gear because of the small space between the teeth of both gears. Another source of errors could come from the measured data, for example, the motor position is measured by a protractor which is only accurate to 1 degree. By taking all of this error into the consideration, the average percentage error of this test is about 4.6%. 6. Conclusion The design and build of steerable headlights from conventional static headlamps has been achieved. Moving the headlights from left to right or vice versa continuously corresponding to a sensor is achieved. An advantage of the developed headlight system is in its high adaptability as it can be easily configured to fit within space confines of a variety of vehicle designs. Indeed, the latter provides a bending lamp that allows for significant angular displacement of the light beam of a headlamp assembly without excessive light beam distortion and without the need to move the entire headlamp assembly. Furthermore, the system is of inexpensive, simple and dependable assembly. References [1] Alexander, G. J. and Lunenfeld, H. (1990), A users guide to positiveguidance, third ed., Report No. FHWA-SA , U.S. Departmentof Transportation, Federal Highway Administration, Washington, DCpp [2] [3] T. Börnchen, R. Lachmayer, and J. Wallaschek, Methods and toolsfor the design of novel multifunctional automotive lighting, 2295