wheel align cat

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OPTICAL WHEEL

ALIGNER


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Abstract

This catalogue aims at providing a profound description of the design,

construction, working, features, specifications, advantages and applications of

Space Matrixs Optical Wheel Aligner present in the Internal Combustion Engines

Laboratory of the Department of Automobile Engineering, Madras Institute of

Technology.

Wheel alignment sometimes referred to as tracking, is a part of the standard

automobile maintenance that refers to the adjustment of the angles of the wheels so

that they are set to the car maker's specification. The purpose of these adjustments

is to reduce tyre wear, and to ensure that the vehicle travel is straight and true.

Alignment angles can also be altered beyond the maker's specifications to obtain a

specific handling characteristic. Motorsport and off-road applications may call for

angles to be adjusted well beyond "normal" for a variety of reasons.

Optical wheel alignment uses infrared sensors to determine the primary angles of

wheel alignment relative to each other and to the cars body. The wheeled control

unit houses the data processing and management computer, the printer and the

high-resolution monitor. Special supports on the side of the control unit permit

recharging of the measuring head batteries while not in use. It consists of Windows

XP based program and latest accurate CCD technology with 6 CCD sensors and

big wheels trolley for easy movement. On-screen operator prompts test selection

menus and diagnostic messages and the membrane function keys acts as remote

control. The striking advantage is that it permits on-line Correction of Camber,

Caster and Toe with Graphical Display. For easy understanding of the operation

the equipment is preloaded with live Demonstration software thereby making it

more user-friendly. The user can also edit the wheel size so that the corresponding
http://en.wikipedia.org/wiki/Tirehttp://en.wikipedia.org/wiki/Tire


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Toe value can be automatically calculated. Complete database comprising of the

standard primary angles and method of adjustment is available for all Indian and

European cars which make it highly advantageous in addition to the fact that more

data can be stored if required. This innovative design concept and use of state-of-

the art technologies and components makes it the very best choice in terms of

price/performance ratio.


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WHEEL ALIGNMENT

Wheel Alignment should be checked whenever new tires are installed,

suspension components installed, when the vehicle has encountered a major road

hazard or curb and any time unusual tire wear patterns appear.

Wheel Alignment is the measurement of complex suspension angles and the

adjustment of a variety of suspension components. It is a suspension-tuning tool

which greatly influences the vehicle's handling and tire wear.

Wheel alignment consists of adjusting the angles of the wheels so that they are

parallel to each other and perpendicular to the ground, thus maximizing tire life

and ensures straight and true tracking along a straight and level road.The primary static suspension angles that need to be measured and adjusted

are caster, camber, toe and thrust angle. The following are definitions

Conditions and Possible Causes of each angle and its influence on a vehicle and its

tyres.

CAMBER:

Camber is the angle of the wheel, measured in degrees, if the top of the

wheel is tilted out then the camber is positive, if it's tilted in, then the camber is

negative.


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If the camber is out of adjustment, it will cause premature tire wear on one

side of the tire's thread. When the camber is out of adjustment it can cause a

pulling problem to the side with the more positive camber.

This usually happens when the vehicle has been involved in an accident which has

caused structural damage or damage to the strut and / or spindle assembly. Camber

also goes out of adjustment when the springs sag and causes ride height to change,

or when ball joints and or other attached parts are worn or defective. It also varies

depending on speed as aerodynamic forces changes riding height.

After repair and alignment, pulling problem could persist due to the

insufficient and or uneven tire to road contact. If a tire shows camber wear pattern,

moving it to the rear might be effective but replacement might be best. Whenever

camber changes, it directly affects toe. On most front-wheel-drive vehicles, camber

is not adjustable; however there are aftermarket kits that allow sufficient

adjustment to compensate for accident damage or the change in alignment due to

the installation of lowering springs.

CASTER:

Caster is the angle of the steering pivot, measured in degrees.


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Viewed from the side, the caster is the tilt of the steering axis. When the wheel

is in front of the load the caster is positive. Three to five degrees of positive caster

is the typical range of settings, with lower angles are being used on heavier

vehicles to reduce steering effort.

If the caster is out of adjustment, it can cause problems in straight-line tracking. If

the caster is different from side to side, the vehicle will pull to the side with the

less positive caster. If the caster is equal but too negative, the steering will be light

and the vehicle will wander and be difficult to keep in a straight line. If the caster

is equal but too positive, the steering will be heavy and the steering wheel may

kick when you hit a bump. Caster has little or no effect on tire wear.

One of the best ways to visualize caster is to picture the caster on a shopping cart.

The pivot while not at an angle intersects the ground ahead of the wheel contact

patch. When the wheel is behind the pivot at the point where it contacts the ground,

it is in positive caster. Like camber, on many front-wheel-drive vehicles, caster is

not adjustable. If the caster is out of adjustment on these vehicles, it indicates that

something is possibly bent from an accident, and must be repaired or replaced.

TOE:


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The vehicle's toe is the most critical alignment settings relative to tire wear. If

the toe setting is just 1/32-inch off of its appropriate setting, each tire on that axle

will scrub almost 3 1/2 feet sideways every mile, therefore reducing tire life. Like

camber, toe will change depending on vehicle speed, as aerodynamic forces

changes the riding height hence affecting camber and toe due to the geometry of

the steering linkage in relation to the geometry of the suspension.

The toe angle identifies the direction of the tires compared to the centerline of

the vehicle. Rear-wheel drive vehicle "pushes" the front tires, as they roll along the

road; resistance causes some drag resulting in rearward movement of the

suspension arms against their bushings. Most rear-wheel drive vehicles use

positive toe to compensate for suspension movement. Front-wheel drive vehicle

"pulls" the vehicle, resulting in forward movement of the suspension arms against

their bushings. Most front-wheel drive vehicles use negative toe to compensate for

suspension movement.

Toe can also be used to alter a vehicle's handling traits. Increased toe-in will

reduce oversteer, steady the car and enhance high-speed stability. Increased toe-

out will reduce understeer, free up the car, especially during initial turn-in while

entering a corner.

Before adjusting toe outside the vehicle manufacturer's specification to

manipulate handling, be aware that toe setting influences tire wear. Excessive toe

settings often cause drivability problems, especially during heavy rain. This isbecause most highways have tire groves from the daily use by loaded tractor

trailers. These heavy vehicles leave groves that fill with water. When one of the

vehicles front tyres encounters a puddle, it loses some of its grip, the other tire's


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toe setting will push causing excessive toe-in, or pull causing excessive toe-out.

This may cause the vehicle to feel unstable.

STEERING AXIS INCLINATION:

Steering Axis Inclination (SAI) is the measurement in degrees of the steering

pivot line when viewed from the front of the vehicle. On a SHORT-LONG ARM

(SLA) SUSPENSION the line runs through the upper and lower ball joints.

This angle (SAI), when added to the camber forms the included angle and causes

the vehicle to lift slightly when the wheel is turned from a straight position. The

vehicles weight pushes down and causes the steering wheel to return to the centerwhen you let go of it after making a turn. Like caster, it provides directional

stability and also reduces steering effort by reducing the scrub radius.

If the Steering Axis Inclination (SAI) is different from side to side, it will

cause a pull at very slow speeds. SAI is a nonadjustable angle; it is used with

camber and the included angle to diagnose bent spindles, struts and mislocated

cross members.

The most likely cause for Steering Axis Inclination (SAI) being out of

specification is bent parts, which has to be replaced to correct the condition. On

older vehicles and trucks with kingpins instead of ball joints, Steering Axis

Inclination (SAI) is referred to as (KPI) King Pin Inclination.


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INCLUDED ANGLE:

Included angle is the sum of the Camber and Steering Axis Inclination (SAI)

angles Included angle is not directly measurable. It is used primarily to diagnose

bent suspension parts.

If the camber is negative, then the included angle will be less than the Steering

Axis Inclination (SAI), if the camber is positive, it will be greater.

The included angle must be the same from side to side even if the camber is

different. If there is a difference, then something is bent, possibly the steering

knuckle.


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THRUST ANGLE:

Thrust angle is the direction that the rear wheels are pointing in relation to the

centerline of the vehicle.

The vehicle will "dog track" if the thrust angle is not zero and the steering wheel

will not be centered.

The best solution is to first adjust the rear toe to the centerline and then adjust the

front toe. This is done during a all wheel alignment if the rear toe is adjustable. If

the rear is not adjustable, then the front toe must be set to compensate for the thrust

angle, allowing the steering to be centered.

If the thrust angle is not correct on a vehicle with a solid rear axle, it often requires

a frame straightening shop to correctly reposition the rear axle.

A vehicles with independent rear suspension, the toe must be adjusted individually

until it has reached the appropriate setting for its side of the vehicle, incorrect

thrust angle is often caused by an out-of-position suspension or incorrect toe

settings.

So in addition to the handling problems that are the result of incorrect toe settings,

thrust angles can also cause the vehicle to handle differently when turning left vs.

right.


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OPTICAL WHEEL ALIGNMENT:


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The basic components of a computerized wheel alignment system are:

o Optical wheel alignment gauge IR sensor CCD detector Transmitting cables

o Computer( having in built data of wheel alignment specifications)o Printer


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The main component of a computerized wheel alignment system is a IR sensor.

The car whose wheels are to be aligned is first mounted on a platform so that its

wheels can be adjusted easily and the wheel alignment gauges are placed near to

each wheel of the vehicle. wheel alignment gauge consists of IR sensor and CCD

detector. The CCD detector gives output voltage corresponding to the alignment of

the wheel. This is fed to the computer with pre defined data and error is found.

OPTICAL WHEEL ALIGNMENT GAUGE:

The basic component of a wheel alignment gauge is a passive infra red

sensor(PIR). The infra red sensors are placed such that the wheels are positioned in

the field of view of sensor and the detector. A Passive Infrared sensor (PIR

10-measurement device

12-base

14-vertical support

16-blade

20-motor

30-vision sensor


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sensor) is an electronic device that measures infrared (IR) light radiating from

objects in its field of view.

the light from the infra red transmitter gets deflated depending on the angle of

alignment of the wheel.

The deflected IR rays are received by CCD detectors which finds the

intensity of the incident IR rays which is a representation of the angle of the

wheel. A charge-coupled device (CCD) is a device for the movement of electrical

charge, usually from within the device to an area where the charge can be

manipulated, for example conversion into a digital value. This is achieved by

"shifting" the signals between stages within the device one at a time. CCDs move

charge between capacitive bins in the device, with the shift allowing for the

transfer of charge between bins.The CCD is a major technology for digital

imaging. In a CCD image sensor, reverse-biasedpn junctions (essentially

photodiodes) are used to absorb photons and produce charges representing sensed

intensity; the CCD is used to read out these charges. Once the CCD has been

exposed to the rays, a control circuit causes each capacitor to transfer its contents

to its neighbor (operating as a shift register). The last capacitor in the array dumps

its charge into a charge amplifier, which converts the charge into a voltage. By

repeating this process, the controlling circuit converts the entire contents of the

array in the semiconductor to a sequence of voltages. In a digital device, these

voltages are then sampled, digitized, and usually stored in memory; in an analog

device (such as an analog video camera), they are processed into a continuous

analog signal (e.g. by feeding the output of the charge amplifier into a low-pass

filter) which is then processed and fed out to other circuits for transmission,

recording, or other processing.


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CCD DETECTORS:

A charge-coupled device (CCD) is a device for the movement of electrical

charge, usually from within the device to an area where the charge can be

manipulated, for example conversion into a digital value. This is achieved by

"shifting" the signals between stages within the device one at a time. CCDs move

charge between capacitive bins in the device, with the shift allowing for the

transfer of charge between bins.

The CCD is a major technology for digital imaging. In a CCD image

sensor, reverse-biased pn junctions (essentiallyphotodiodes) are used to

absorb photons and produce charges representing sensed pixels; the CCD is used to

read out these charges. Although CCDs are not the only technology to allow for

light detection, CCD image sensors are widely used in professional, medical, and

scientific applications where high-quality image data is required.

BASICS OF OPERATION:

In a CCD for capturing images, there is a photoactive region (an epitaxial layer of

silicon), and a transmission region made out of a shift register (the CCD, properly

speaking).
http://en.wikipedia.org/wiki/Digital_imaginghttp://en.wikipedia.org/wiki/Image_sensorhttp://en.wikipedia.org/wiki/Image_sensorhttp://en.wikipedia.org/wiki/Reverse_biashttp://en.wikipedia.org/wiki/P%E2%80%93n_junctionhttp://en.wikipedia.org/wiki/P%E2%80%93n_junctionhttp://en.wikipedia.org/wiki/P%E2%80%93n_junctionhttp://en.wikipedia.org/wiki/Photodiodehttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Pixelhttp://en.wikipedia.org/wiki/Epitaxyhttp://en.wikipedia.org/wiki/Epitaxyhttp://en.wikipedia.org/wiki/Pixelhttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Photodiodehttp://en.wikipedia.org/wiki/P%E2%80%93n_junctionhttp://en.wikipedia.org/wiki/Reverse_biashttp://en.wikipedia.org/wiki/Image_sensorhttp://en.wikipedia.org/wiki/Image_sensorhttp://en.wikipedia.org/wiki/Digital_imaging


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An image is projected through a lens onto the capacitor array (the photoactive

region), causing each capacitor to accumulate an electric charge proportional to

the light intensity at that location. A one-dimensional array, used in line-scan

cameras, captures a single slice of the image, while a two-dimensional array, used

in video and still cameras, captures a two-dimensional picture corresponding to the

scene projected onto the focal plane of the sensor. Once the array has been exposed

to the image, a control circuit causes each capacitor to transfer its contents to its

neighbor (operating as a shift register). The last capacitor in the array dumps its

charge into a charge amplifier, which converts the charge into a voltage. By

repeating this process, the controlling circuit converts the entire contents of the

array in the semiconductor to a sequence of voltages. In a digital device, these

voltages are then sampled, digitized, and usually stored in memory; in an analog

device (such as an analog video camera), they are processed into a continuous

analog signal (e.g. by feeding the output of the charge amplifier into a low-pass

filter) which is then processed and fed out to other circuits for transmission,

recording, or other processing.

The photoactive region of the CCD is, generally, an epitaxial layer ofsilicon. It

has a doping of p+ (Boron) and is grown upon a substrate material, often p++. In

buried channel devices, the type of design utilized in most modern CCDs, certain

areas of the surface of the silicon areion implanted with phosphorus, giving them

an n-doped designation. This region defines the channel in which the
http://en.wikipedia.org/wiki/Lens_(optics)http://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Charge_amplifierhttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Epitaxialhttp://en.wikipedia.org/wiki/Siliconhttp://en.wikipedia.org/wiki/Boronhttp://en.wikipedia.org/wiki/Substrate_(materials_science)http://en.wikipedia.org/wiki/Ion_implantationhttp://en.wikipedia.org/wiki/Phosphorushttp://en.wikipedia.org/wiki/Phosphorushttp://en.wikipedia.org/wiki/Ion_implantationhttp://en.wikipedia.org/wiki/Substrate_(materials_science)http://en.wikipedia.org/wiki/Boronhttp://en.wikipedia.org/wiki/Siliconhttp://en.wikipedia.org/wiki/Epitaxialhttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Charge_amplifierhttp://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Lens_(optics)


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photogenerated charge packets will travel. The gate oxide, i.e.

the capacitor dielectric, is grown on top of the epitaxial layer and substrate.

Later on in the process polysilicon gates are deposited by chemical vapor

deposition, patterned with photolithography, and etched in such a way that the

separately phased gates lie perpendicular to the channels. The channels are further

defined by utilization of the LOCOS process to produce the channel stop region.

Channel stops are thermally grown oxides that serve to isolate the charge packets

in one column from those in another. These channel stops are produced before the

polysilicon gates are, as the LOCOS process utilizes a high temperature step that

would destroy the gate material. The channels stops are parallel to, and exclusive

of, the channel, or "charge carrying", regions.

Channel stops often have a p+ doped region underlying them, providing a further

barrier to the electrons in the charge packets (this discussion of the physics of CCD

devices assumes anelectron transfer device, though hole transfer is possible).

The clocking of the gates, alternately high and low, will forward and reverse bias

to the diode that is provided by the buried channel (n-doped) and the epitaxial layer

(p-doped). This will cause the CCD to deplete, near the p-n junction and will

collect and move the charge packets beneath the gatesand within the channels

of the device.

CCD manufacturing and operation can be optimized for different uses. The above

process describes a frame transfer CCD. While CCDs may be manufactured on a

heavily doped p++ wafer it is also possible to manufacture a device inside p-wells

that have been placed on an n-wafer. This second method, reportedly, reduces

smear, dark current, and infrared and red response. This method of manufacture is

used in the construction of interline transfer devices.
http://en.wikipedia.org/wiki/Capacitorhttp://en.wikipedia.org/wiki/Dielectrichttp://en.wikipedia.org/wiki/Polysiliconhttp://en.wikipedia.org/wiki/Chemical_vapor_depositionhttp://en.wikipedia.org/wiki/Chemical_vapor_depositionhttp://en.wikipedia.org/wiki/Photolithographyhttp://en.wikipedia.org/wiki/LOCOShttp://en.wikipedia.org/wiki/Channel_stophttp://en.wikipedia.org/wiki/Oxidehttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/P-n_junctionhttp://en.wikipedia.org/wiki/Dark_current_(physics)http://en.wikipedia.org/wiki/Infraredhttp://en.wikipedia.org/wiki/Infraredhttp://en.wikipedia.org/wiki/Dark_current_(physics)http://en.wikipedia.org/wiki/P-n_junctionhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Oxidehttp://en.wikipedia.org/wiki/Channel_stophttp://en.wikipedia.org/wiki/LOCOShttp://en.wikipedia.org/wiki/Photolithographyhttp://en.wikipedia.org/wiki/Chemical_vapor_depositionhttp://en.wikipedia.org/wiki/Chemical_vapor_depositionhttp://en.wikipedia.org/wiki/Polysiliconhttp://en.wikipedia.org/wiki/Dielectrichttp://en.wikipedia.org/wiki/Capacitor


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Another version of CCD is called a peristaltic CCD. In a peristaltic charge-coupled

device, the charge packet transfer operation is analogous to the peristaltic

contraction and dilation of the digestive system. The peristaltic CCD has an

additional implant that keeps the charge away from the silicon/silicon

dioxide interface and generates a large lateral electric field from one gate to the

next. This provides an additional driving force to aid in transfer of the charge

packets.

COMPUTER:

The computer here is already fed with datas of wheel alignment specifications of

all the makers. The data from the wheel alignment gauge is fed to this computer

through wires. This data is compared with the in built data and the error is

measured. this error is adjusted by adjustingthe wheels manually.

PRINTER:

The computer is connected with a printer which is used to print the datas

such as the makers specifications and the values to which the wheels are currently

aligned. This will help when the wheels are damaged due to some accident and the

alignment can be compared with initial alignment. The car owner will also get to
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know how well his cars wheels have been aligned according to the companys

specifications.

FEATURES:

Windows XP based Program Latest accurate CCD technology with 6 CCD sensors On-screen operator prompts, test selection menus and diagnostic messages Membrane function keys acts as remote control Service Station name, address, Vehicle Number and Mileage can be printed

with Test results On-line Correction of Camber, Caster and Toe with Graphical Display Big wheels trolley for easy movement inside the workshop. Simple Calibration procedure with 3D pictorial printout of calibration

readings.

Self Calibration- Casters Compensation and Steering angle Self Calibration For easy understanding of the Operation the Equipment is preloaded with

live Demonstration software which makes the equipment more users

friendly.

In Two wheel drive Model it has option for doing front axle alone orcombined with rear axle.

User has the option to edit the wheel size so that the corresponding Toevalue will be automatically calculated.

Complete database for more than 20,000 Automobiles all around the Worldwith the method of adjustment and the user can be store more data if

required.


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standard primary angles and method of adjustment is available for all Indian and

European cars which make it highly advantageous in addition to the fact that more

data can be stored if required. This innovative design concept and use of state-of-

the art technologies and components makes it the very best choice in terms of

price/performance ratio.

wheel align cat

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