The Vehicle Lighting Systems Engineering Essay

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It has been many years since the first introduction of lighting systems of the motor vehicle and the progress of development has been very slow. The main milestone in lighting was developed in the early 1920s, this was in the form of the dual filament lamp. The early 1950s saw the introduction of the first asymmetrical lamp which combined a low and high beam combined single enclosure.

The next big development is the bulb that most of us know of today, the single-filament halogen bulb, This type of bulb became available in Europe in the mid to late 1960s. This type of bulb had a much longer life and took less energy than incandescent lighting, it can also provide 50% more light.

A normal bulb is generally made from a large thin glass casing, inside this casing is an inert gas such as argon and/or nitrogen. At the center of the casing is a tungsten filament. The electricity makes the element heat up to somewhere around 2500 deg C, Just like any hot metal the tungsten becomes "white hot" and that heat produces a great deal of light in a process called incandescence. A normal light bulb is not very efficient, and will only last around about 750 to 1,000 hours in normal operating conditions. This type of lamp is not very efficient mainly because in the process of emitting light it also generates a very large amount of heat, which is far more heat than light produced. Since the general purpose of a bulb is to generate light, the heat is a wasted element. It does not last very long because the tungsten in the filament dissipates and deposits on the glass casing. Eventually, a thin spot appears in the filament this thin spot with added heat causes the filament to break, and then the bulb "burns out."

A halogen lamp also uses a tungsten filament, but it is encased inside a much smaller quartz glass casing. Because the casing is so close to the filament element it would melt if it were made from ordinary glass. The gas inside the casing is also different this is a gas in the halogen group of gasses. These type of gases have very special properties: They combine with tungsten vapors, if the temperatures are high enough, the halogen gas combine with tungsten atoms and as they evaporate the will then redeposit back on to the filament. This process allows the filament to last much longer then normal bulbs. In addition, it is now possible to run the filament to a larger temperature, thus meaning you get more light compared to the amount of energy although it still generates a great deal of heat. Because the quartz glass casing is so close to the filament, it is excessively hotter compared to a normal light bulb.­­

Gas Discharge Lighting is Halogen lighting that uses different gases, either xenon gas or neon gas this element is used to produce a very high concentrated light which is very much suited to the automotive lighting industry. In gas discharge systems an arc is created inside a glass enclosure filled with the gas. This arc produces significantly more light than a normal glowing filament, this setup provides much better visibility .

High-pressure gas-discharge systems (xenon) - high pressure XENON lamps are ideal for automotive head lighting systems. It offers nearly more than twice the amount of light of halogen for roughly half the energy and a much better quality of light output. Most designers are given a lot flexibility to develop entirely new headlamps that give a car its own character. Many high-end car manufacturers like Audi, BMW and Porsche have incorporated XENON systems into their top-of-the-range models.

LED Brake Lights & Signal Lighting - Approximately 40% of the European automotive market uses LED high-mount brake lights -- more than 90% of which are manufactured by Hewlett-Packard. LED advantages such as reliability, design flexibility and safety have been embraced by the automotive industry since the 1980s.... now we are seeing many innovative new designs for full combination lamps -- those that combine turn, tail and stop signals.. The LEDs, which emit true red-orange and amber colours, are not dependent on lens colour.

LEDs or light emitting diodes are just tiny light bulbs that fit easily into an electrical circuit But unlike ordinary incandescent bulbs, they don't have a filament that will burn out, and they don't get especially hot They are illuminated solely by the movement of electrons in a semiconductor material, and they last just as long as a standard transistor. LEDs are specially constructed to release a large number of photons outward. Additionally, they are housed in a plastic bulb that concentrates the light in a particular direction. As you can see in the diagram, most of the light from the diode bounces off the sides of the bulb, traveling on through the rounded end.

LEDs have several advantages over conventional incandescent lamps. For one thing, they don't have a filament that will burn out, so they last much longer. Additionally, their small plastic bulb makes them a lot more durable. They also fit more easily into modern electronic circuits.

But the main advantage is efficiency. In conventional incandescent bulbs, the light-production process involves generating a lot of heat (the filament must be warmed). This is completely wasted energy, unless you're using the lamp as a heater, because a huge portion of the available electricity isn't going toward producing visible light. LEDs generate very little heat, relatively speaking. A much higher percentage of the electrical power is going directly to generating light, which cuts down on the electricity demands considerably.

Vehicle Wiper Systems

The main purpose of a vehicle wiper system is to make sure the windscreen is cleaned enough to provide adequate visibility. Correct system design, high quality manufacturing with good quality components are required for both the windscreen wiper and washing systems. The ways of cleaning the windscreen by the blades varies extensively provided that the legally prescribed area of the screen is cleaned as laid out by government guidelines. The vast majority of are operated electrically. In today's world it has become a common practice to fit two wiper blades for the front windscreen and both blades driven from a single motor. The windscreen wiper on the driver's side must operate effectively and efficiently and clean the area set out by current legislation. Most Hatchback cars will use a single wiper for a rear window and some high level vehicles will install wipers for the headlamps, headlamp washers are also a required for HID headlights fitted as standard equipment.

Very large forces are needed for a wiper blade to move across the windscreen surface, and this force is increased even more when a blade has to clear away any volumes of water, snow or dirt. Windscreens of modern vehicles have a double curvature, as in they curve in both directions, this design requires long articulated blades with a correct amount of flexibility to follow the contours of the glass. Most systems will use two wiper speed settings to suit driving conditions and they will also incorporate an intermittent wiper system.

The wiper motor should be a high powered quiet unit operating on a current range of around 2 - 4 A. In past history of the wiper system, shunt-wound motors were used but in the modern day system a permanent magnet motor is used. A typical layout of a wiper system is shown opposite, a worm on the motor shaft drives a worm wheel connected to a type of crank, its aim is to provide the back and forth action required to move the wiper blades. A gearing set provides an adequate speed reduction and in turn this increases torque to a level that is able to drive the wiper blades all conditions.

On most vehicles the windscreen wiper blades are parked off the windscreen to allow for better visibility while they are off. To achieve this the electrical circuit is designed so that the current through the motor is reversed after the motor has stopped. This charges the polarity of the brush in the permanent magnet motor so that the armature rotates in the opposite direction. By arranging the gearbox linkage the wiping stroke can be extended by the reverse motion, and this movement parks the wiper blades away from the glass screen.

For the protection of the motor, a thermal switch is connected in series with the supply lead. A bimetallic strip controls the switch. When the strip is heated by a higher-than-normal current, the contacts are opened disconnecting the circuit.

Vehicle Entertainment Systems

Vehicle entertainment systems have come a long way forward since their introduction back in the late 1900's and on modern day vehicles you can expect more technology then you could ever wish for, From CD players to satellite navigation systems.

Most vehicles in today's world will always come with a basic radio system, the Radio Data System(RDS) is always incorporated in to the radio but is only available on VHF/FM, it has been around for roughly 25 years, this data transmits program service name known as PS using eight character alpha numerical displays, it also transmits Travel information using the travel program(TP) and Travel Announcement (TA) flags, RDS can also be used for Traffic Message Chanel (TMC) once the radio is tuned in to a station using RDS EON (Enhanced other Networks) other channel information will be received including time information to update the time on the radio.

a step up from this would be a CD player incorporated in to the radio system, this advances the audio system to play user specific music or even to play MP3 music stored on CDR media, one problem of a cd player in a vehicle is to overcome the jumping/skipping that is caused when knocking or vibrations happen on a vehicle, So to counter this problem in-car cd players incorporate an anti shock system, this is usually in the form of rubber feet/springs separating the lens to the casing system creating a damping effect to overcome light vibrations, this combined with buffering( where the cd player reads 10 seconds or so in front) avoids any cd jumping and gives a continuous playing system.

Another system incorporated in to modern day vehicles is satellite navigation, its main components comprise of a monitor or screen, a main control unit that contains a built in map which is cross referenced with longitude and latitude numbering and a GPS receiver, the system places a marker on the screen using the location from the GPS receiver, this receiver uses a method call Triangulation to get the actual coordinates, Triangulation of an unknown position via the Global Positioning System is accomplished solely by GPS satellite transmission to the receiver, it is the received signal propagation time delay that determines the distance and the signal delay, or slowness, is proportional to signal distance traveled. Getting GPS information requires at least 3 satellites to receive the correct information for marking out the current GPS location most systems use around 7 - 12 satellites to get the position data

An example of Triangulation

X is a position to be triangulated(GPS Receiver), and S1, S2, & S3 are three satellites.

Since the distances marked on the image R1, R2, & R3 are determined from the respective satellites, the three dimensional coordinates of X are uniquely determined.

Vehicle Security Systems

Car crime is a big business in todays modern times and as criminals become further advance then so does the technology to counter this, the majority of vehicle alarm manufacturers are constantly trying to improve their systems against the modern day theif. There has been rapid improvements made re3cently by incorporating the security system as an integral part of the vehicle electronics. Even the After market systems are still very effective. There are three main types of security alarms used in todays modern vehicles:

Switch operated Doors, Bonnet & boots.

Battery voltage sensing.

Volumetric sensed.

In addition these types are also used to disable the vehicle (i) Ignition and/or starter circuit cut off.

Engine ECU code system lock.

Alarms can be set by a separate switch or IR transmitter. More commonly now, they are set automatically when the doors are locked. Professional car thieves always find ways to maneuver the latest alarm systems. The vehicle manufacturers strive to stay one step ahead. Legislation is being considered for installing tracking devices in an unknown part of a vehicle's chassis. This can be activated during the theft of the car, allowing the police to trace the vehicle.

The good alarm systems now available are either retro-fit systems or factory fitted. Most are made for 12 V negative earth vehicles. They use electronic sirens and generate an audible signal when arming and disarming. All of them are triggered when the car door opens and automatically reset after a period of time, often 1 or 2 minutes. The alarms are triggered instantly when the entry point is breached. Most systems are two pieces, with separate control unit and siren. The control unit is installed in the passenger compartment and the siren under the bonnet in most systems.

Most recent systems use two infra-red remote keys, which incorporate small button type batteries and have an LED to indicate when the signal is being sent. They operate with one vehicle only. Intrusion sensors, which detect car movement or use volumetric sensing, can be adjusted for sensitivity.

When operating with flashing lights most systems draw current about 5 A and without flashing lights (siren only) the current drawn is less than 1 A. The sirens produce a sound level of about 95 dB, when measured 2 m in front of the vehicle. A block diagram of a complex alarm

Some factory fitted alarms are coupled with the central door locking system, known as lazy lock. One press of the remote unit sets the alarm, close windows and sun roof and finally locks the doors.

One of the recent ideas is to use a security code in engine electronic control unit so that it can be unlocked to allow the engine to start only when it receives a coded signal. Ford is using a special ignition key, programmed with the required information. Citroen uses a similar idea in some of their models, but the code has to be entered via a numerical keypad.

Of course with this arrangement also the car can be lifted onto a lorry and driven away, but when this is done a new engine control ECU is required, which is costly.

SRS Systems

The Supplementary Restraint System (SRS) is basically an air-bag system. This system works in conjunction with 3point seat belts these combined reduces the chances of impact to the driver's face and chest with the surrounding vehicle components the collision situation. SRS may sometimes be installed to the passenger's side to protect the passenger. Side-impact air-bags are also fitted to protect the upper body and head during a side impact.

The system comprises of an ECU/Control Module, this is used to monitor the sensors. Impact and Safing sensors are used to sense if the vehicle is in a collision, an air bag module is used to deploy the airbag.

Impact Sensors

Impact sensors are used to trigger the airbag, they operate when there is a collision force that is equal to hitting a wall at around 15 to 20 miles per hour, in order for the airbag to deploy, the safing sensor and at least one impact sensor must be triggered, this is a security measure to stop the system activating under false conditions. A rear safing sensor must be activated first to avoid accidental deployment.

Control Module

The control module monitors the inputs from the safing and impact sensors, when the correct combination of these sensors are active, the module will trigger the airbag(s) to deploy.

Airbag Modules

The airbag system rapidly inflates a nylon airbag immediately after a large impact. The airbag helps to protect the driver (and passengers in most vehicles) from serious injury.

The airbag module contains an igniter, gas generating pellets and the airbag.

When an impact occurs, the igniter fires the pellets which burn rapidly to create a large volume of nitrogen gas The gas inflates the airbag in around 50 milliseconds. The airbag (module) is fitted with vents. These allow it to deflate in a very short time period, to allow for driver or passenger movement.

SIPS (Side Impact Protection System) uses impact sensors in vehicle doors to detect a side impact. These sensors trigger airbags in the side of the seat.

WHIPS (Whiplash Protection System) are specially designed seats that absorb sharp movement, protecting the neck and back.

Inflatable curtains are available that drop down from a vehicle's roof to cover both front and rear side windows, giving better head protection than SIPS.

SRS SYSTEM TIMELINE EXAMPLE

The vehicle collides with a solid object at an angle within about 30° of the centre line and at a speed greater than 20 mph.

At 10ms The front crash sensors and the safing sensor have moved to the closed-circuit position, causing the SRS diagnostic module to transmit a firing pulse to the igniter.

The pyrotechnic seatbelt unit has detonated.

3 ms after the arrival of the igniter firing signal, gas generation has started with a loud bang. The driver is still upright in his seat. The seatbelt has been partially tightened.

The air-bag has partially inflated, breaking the cover crease.

At 15ms The seatbelt is almost fully tightened

At 20ms The vehicle is starting to crumple and the driver has moved very slightly forward towards the steering wheel but is being restrained by the seatbelt which is now fully tightened.

At 30ms The air-bag is fully inflated and the driver's chest and face are about to come into contact with it. The seatbelt is helping to restrain the driver

At 80ms The load of the driver on the air-bag causes the nitrogen gas to escape through the outlet holes at the rear of the bag and so it starts to deflate. Gas pressure beneath the pyrotechnic seatbelt piston is falling and so it starts to move back down the tube, feeding some slack back into the belt.

At 120ms The driver has moved back into his seat and the air-bag is deflating, providing unrestricted visibility and allowing an easy exit from the wrecked vehicle.

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