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CHAPTER 5

DESIGN OF HEADLAMPS FOR

PASSENGER CAR APPLICATION

5.1 COMPONENTS OF HEADLAMP

Automotive headlamp components are highly controlled products

that must conform to performance standards. The primary components of

headlamps are lens, reflector and bulb. Bulb produces light for illumination.

Bulb is positioned in the focal point of a parabolic reflector by means of

standard holders fixed on the casing of headlamp assembly. The concentric

beams produced by the bulb impact the reflector that directs light to

illuminate roads. In the earlier design of headlamps outer glass lens was used

as diffuser for achieving illumination distribution. Figure 5.1 shows the

important components of headlamp, namely, casing, reflector, bezel and lens.

Figure 5.1 Components of headlamp

Casing

Lens Bezel

Reflector

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The following sections briefly describe the components of headlamps.

5.1.1 Lens

In modern headlamps, the required illumination distribution on road

is the function of reflector alone, where the clear glass lens protects the

interiors of headlamp against external influences. It constitutes the exterior

surface of headlamp having an important role in styling of passenger car. It is

a transparent or translucent surface that encloses the light source and allows

conformance with photometric and calorimetric requirements. Lens is used to

filter unwanted colours from the white coloured light emitted from reflector.

For fog lamp or signal lamp application, dyed lens can be used.

Conventional lenses are manufactured from high purity glass free

of blow holes and streaks. Modern cars use clear lens mostly made out of

plastic due to its light weight and cost advantages. Previously, lenses were

fluted for dispersion optics, and were made out of glass. Material for lens has

resistance to heat, good optical properties, durability and ease for

manufacture. In most of the headlamp applications polycarbonate is used as

lens material. Standard polycarbonate can withstand a temperature up to

129oC while high heat polycarbonate can withstand up to 171oC. Normally,

lens is manufactured by injection moulding process followed by coating to

protect the surface from aging and scratches. The standard material for lens is

given in SAE J576 standards. Lens is normally adhesively bonded to

headlamp assembly.

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5.1.2 Reflectors

The purpose of reflector is to collect as much light as possible from

the light source for getting maximum beam range. The shape of reflectors

generally originated form a paraboloidal surface. Modern reflector technology

consists of variety of configurations such as stepped reflectors or free-form

reflectors based on optical imaging technology such as Poly-Ellipsoid system.

Parabolic reflector produces parallel beam of reflected light if the light source

is located at the focus.

Efficiency of a reflector is related to its reflection factor. New

reflector coated with aluminium by vapour deposition process has a reflection

factor of 90%. The reflector surface should be maintained clean and free of

corrosion and scaling. The shape of parabolic reflector is governed by the

focal depth of reflector which is determined by the constant of parabola, ‘K’.

Reflectors with shorter focal depth exploits major portion of light emitted and

achieve high efficiency levels. But Low value of focal depth reduces the

aperture of reflector. The value of focal length of conventional reflector is

within the range of 15 – 40mm (Moore, D.W 1998).

Reflector is exposed to high temperature and radiation. Reflector

material should not distort at high temperatures. Reflector is manufactured by

deep draw moulding followed by galvanization or powder coating. The

reflector is then painted to produce a smooth surface after which aluminium

reflective layer is made by vapour deposition techniques. Plastic reflectors are

manufactured by injection moulding or compression moulding process

followed by reflective layer coating. Standard materials for manufacture of

reflectors can be found in SAE J576.

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5.1.3 Headlight bulb

Bulb is the light source of headlamp. Headlamp manufacturers use

standard light sources according to the illumination requirements of markets.

Since this research work deals with design and data management of

headlamps and the bulbs being standard components details of bulbs are not

included in this work. The major technological breakthrough in bulb

technology is incandescent lamps, Halogen lamps, high intensity discharge

tubes and latest light emitting diode (LED) technologies. The evolution of

lighting technology has been discussed in section 1.2 .

5.1.4 Bezel

Bezel is not a primary component of headlamp. However, it has an

important role in the functioning of reflector. In some designs, bezel is coated

with reflective layer and acts as a secondary reflector. Reflector is anchored to

the casing of headlamp by using adjustable screws and has to be free to move

(vertical adjustment) for aiming purpose. Bezel acts as a ‘spacer’ in between

reflector and lens with aesthetics. It is generally fastened to the ribs of lens

allowing disassembly for maintenance and inspection.

5.1.5 Casing

Casing provides housing for mounting all the components of

headlamps. Lens is hermetically sealed to casing by adhesives. Casing

includes a reference plane for mounting bulbs and reflector maintaining their

relative positional accuracies. Reflector is screwed to casing bracket by

adjustable screws, while bulb holder is fixed on the bracket ensuring bulb to

be positioned correctly.

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5.2 KNOWLEDGE BASED DESIGN OF HEADLAMPS

Knowledge based engineering (KBE) has generated impressive

saving in time and cost involved in automotive design. KBE systems aim to

capture product and process information in such a way that engineering

design processes are modelled and these models automate all or part of the

design processes. The emphasis is on providing, information for complete

product representations, captured in a product model (Chapman and pinfold,

1999).Classical CAD packages like Pro-engineer, CATIA, Unigraphics, Solid

works, Ideas, etc. immensely support KBE by built-in knowledge tools for

product design. In this thesis, a design methodology is proposed for capturing

design intents in different abstraction levels of knowledge such as value,

parameter, feature, objects, rules, formula, design table, and macro. Figure 5.2

shows the architecture of KBE in design.

Figure 5.2 Knowledge application in design

Product model allows to instantiate design output by the input

parameters. This type of encapsulation of functions makes design process

easy. The product model is made available to design clients; changes in

design could be implemented by communicating the parameters alone,

Product Model User Interface

Design output

Part Libraries

Surface/solid model drawing Surface evaluation NC code

Meta data

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whereas the design model need not be communicated. The use of parameters

between product structure and product models have already been discussed in

literature review.

5.3 PRODUCT MODELLING FOR HEADLAMPS

Product modelling deals with the meeting of different types of

requirements with the support of existing tools for achieving pre-defined

strategy of product development. Figure 5.3 shows the product modelling

process applicable to headlamp design.

Figure 5.3 A generalized view of product modelling system

for headlamps

The OEMs of passenger cars are the customers in the headlamp

supplier’s perspectives. The requirements of end users and distributors as

shown in Figure 1.2 are included in the OEMs requirements. In addition to

this the users can view the model during the product development process.

The passenger car manufacturers experience mass customized market

conditions where the frequent changes in design are inevitable. However, in

this thesis the OEM requirements are expected to vary according to the

PRODUCT MODEL

Customer Requirements

Technical Requirements

CAD/CAE/CAM

Regulatory Requirements

SUPPORT DESIGN STRATEGY

Market driven design

Design for Manufacture

Design for ‘X”

Market Analysis

Design Analysis

Functional Design

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general trends that prevail in the passenger car market. Since last few decades,

the shapes of headlamps are totally integrated with the car front fender

surface. In addition, performance requirements such as the type of drive, right

hand or left hand, material preferences, reflector shape, etc are included.

Customer requirements are actually a small subset of total

requirements. The requirements related to manufacturing process,

requirements originated from other disciplines, etc. are included in this type

of requirements. Regulatory requirements are very important and are

sensitive requirements in the case of headlamps. Standards of road

illumination distribution are to be followed strictly. Common standards are

Federal Vehicle Safety Standards (FMVSS) and Society of Automotive

Engineers (SAE) followed in United States; and Economic Commission for

Europe (ECE) in Europe and Asia.

5.4 AESTHETIC ASPECTS IN DESIGN OF HEADLAMP

Modern trend in headlamp, as discussed in previous section, is that

the headlamp exteriors are visually pleasant to observers. Automotives and

aircrafts are generally developed using free-form surfaces, for which solid

modelling software provide special functionalities for modelling and analysis.

Free-form surfaces are curvature continuous surfaces free of edges and sharp

corners. Conventional CAD systems support development of free form

surfaces from sketches. Figure 5.4 shows the constraint views, top, side and

front of surface modelling.

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Figure 5.4 Views of car body for constructing free form surfaces

The traditional practice was to record digitized surface data from a

life-size clay model of the new car. This would then be translated into a CAD

model and sent to a headlamp supplier who would perform a feasibility test

on it. The design of the vehicle would then be altered to accommodate the

headlamp (Kochan, 1999). The increased styling preferences of automotive

market, forces the headlamp manufacturers to develop headlamp for a specific

requirement following a make to order strategy.

5.5 FUNCTIONAL ASPECTS IN DESIGN OF HEADLAMPS

The designer’s freedom is heavily constrained by the customer’s

requirements. The functions in the view of product are mapped into forms

during the conceptual stage of design. Therefore, conceptual design begins

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with function modelling. The functional relationship among the components

of headlamp are shown in Figure 5.5.

Figure 5.5 Functional relationships among headlamp components

For simplification, the object ‘user’ stands for any actor depending on the

function performed. The required functions are decomposed and mapped onto

the product structure. Following sections discuss a methodology for design of

headlamp components using the KBE supported CAD tools from the

perspectives of manufacturers of headlamp.

5.6 GENERATION OF EXTERIOR SURFACE FOR

HEADLAMP

The totally integrated shape for the headlamp is obtained by

developing a curvature continuous surface with the front fenders of the

passenger car. The front fender surfaces leave a closed profile, which separate

the headlamp with the car surface. Now the method of construction of surface

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is based on the surface curves on the front fender surface which propagate

across the closed profiles with curvature continuity conditions. Figure 5.6

shows a front fender surface from the set of information provided by OEM.

Figure 5.6 Front fender surface of car – an input for design of headlamp

Let the surface of the car from which the lens for headlamp is to be

derived (primary surface)

constructed (derived surface) as S (u,v). The latter has to be curvature

continuous with the former. Both the surfaces are separated by boundary

curve. The generalized representation of a set of cross linkage curve G,

normal to boundary curve, with the vector field V is shown in Figure 5.7.

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Figure 5.7 Curvature continuous propagation of surface across

boundary curve

The normal curvature nk of the linkage curve C at a point P on the

curve is defined as the projection of the vector cN.k to the normal at the point

P, where k is the curvature of any curve on the surface through the point P

and cN is the normal to curve at the point. There exist a maximum and

minimum curvature values (principal curvatures) at the point, noted as 1k and

2k . According to Meusnier theorem, all curves lying on the surface have the

same normal curvatures at a point P, if these curves have the same tangential

direction. Therefore normal curvatures can be considered as a measure

attached to a vector V in the tangent plane of the surface at the point P.

In the research reported in this thesis, visual continuity is achieved

by satisfying the conditions for smooth propagation of cross linkage curve

subjected to the set of conditions as in (Ye, 1996). That is, for curvature

continuity, it has been found that vector V along the linkage curve C that has

the same normal curvature corresponding to each surface (R and S) there

exists a set of curvature continuous cross linkage curves G on R and S along

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the linkage curve C. This also guarantees the curvature continuities of R and S

along C if R and S are tangent continuous along C. The cross linkage curves

are created as intersection curves between normal planes on the boundary

curve and car body surfaces. The intersection curves are discontinuous and

are in two segments owing to the absence of lens portion, which could be

blended with curvature continuity.

A quintic Hermite interpolation or PDE with specific boundary

conditions may be used for the surface construction. However in this work,

solid modelling software has been customized so that the required surface is

generated from the input that is a CAD file of car body profile. Figure 5.8

shows the surface generated for the front fender surfaces shown in Figure 5.6.

Figure 5.8 View of exterior surface developed for headlamp

The automatically generated surface is used in the design of lens / cover of the

headlamp.

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5.7 ANALYSIS OF SURFACE

Analysis of the surface for quality control of car body surfaces is an

important issue in the development of a passenger car. Since the surface

construction is governed by various intrinsic properties, the proposed tools for

surface analysis rely on the intrinsic properties such as principal curvatures.

Focal planes have been used for surface analysis (Hagan 1992b; Choi and

Lee, 1996). In addition, the focal planes could be easily modelled making use

of knowledge capabilities inbuilt in commercial software. In this work

CATIA V5 R16 was used.

5.7.1 Global Interrogation

The surface construction is followed by analyzing the quality of the

surface by the process called surface interrogation. Reflection line, highlight

line, and isophotes are the widely used techniques for surface interrogation.

Reflection lines have been used in ‘cubing’ of passenger cars for examining

the surface qualities. In a CAD environment, these tests could be effectively

simulated in the design stage itself. The result of a reflection line depends on

the location of light source. In the case of highlight lines, the result is

independent of the light source location and provides unique result.

For the surface generated, the curvature continuity with the car

body is shown in Figure 5.9, which is the result of highlight line analysis for

the input profile with the generated surface for lens. The zebra lines on the

car body are continuously propagated to the lens. The lens surface is

individually analyzed for surface qualities using reflection lines and highlight

lines. Figure 5.10 shows the global surface analysis by high light line method

showing the point of discontinuities.

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Figure 5.9 Curvature continuity of lens surface with the car fenders

Figure 5.10 Surface analysis by highlight line method

Associated surfaces

Lens

Undesirable region

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5.7.2 Local evaluation of surface by focal surface method

The undesirable points on the surface during global analysis are

chosen for local analysis. The local evaluation includes the test of convexity

of a surface, location of inflection points and flat points and visualization of

technical smoothness of surfaces. Surface analysis of lens is evaluated by the

focal point method which is described here.

Normal curvature ( nk ) of the curves at any point is calculated by the formula

nk = k. c (5.1)

where ‘k’ is curvature of the su

between the surface normal at the point and the normal vector to the curve at

the point. The value of ‘k’ using the CAD

software and nk can be found by Formula 5.2. The principal curvature values

are obtained by the equation

nk (V, S) = 1k Cos22k Sin2 (5.2)

the test point and principal direction, E1

The focal points of a normal congruence are the centres of

curvature of the two principal directions. The normal curvatures, 1k and 2k

are projected to the surface normal. The process is repeated for all the points.

The principal curvatures can be determined using equations 5.1 and 5.2. The

principal curvatures can also be determined by intersection plane method

discussed below which can be implemented easily in CAD softwares.

Let ‘A’ be a tangent vector with modulus unity, then

A= u.dx du+ v.dx dv (5.3)

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u v are increments in surface parameters u and v. The

surface is intersecting with a set of orthogonal planes defined by N, the

normal at the point and unit tangent vector A. The intersection curve ‘y’ is

related to the plane as

dy ds = A (5.4)

and

e2 =N (5.5)

where ds is the incremental distance along the curve y, N is the

normal direction and e2 is principal normal vector of the space curve y.

The principal curvature values found by the above method are used

in the generalized focal surface formula:

F(u,v)=S(u,v)+a. f ( 1k , 2k ).N(u,v) (5.6)

where ‘a’ is scale factor and f is a scalar function of 1k and 2k . The

scale factor could be a user defined value for scaling the focal surface. For

creating focal points from the test surface, the following formula is used.

F(x, y,z)=S(x,y,z)+a.f ( 1k , 2k ).N(x, y, z) (5.7)

The surface at any point can be convex, non convex or flat. If the

surface at the point is convex, Gaussian curvature, ( 1k . 2k ) is positive.

Substituting the value of f in equation 5.7 as f = 1k . 2k and interpreting the

focal length term (a. f( 1k , 2k ). N(x,y,z) it can be seen that focal line does not

cross the test surface. If the surface is non-convex, it can be interpreted that

focal line crosses the test surface. At flat point the focal point and test point

coincide. The Gaussian curvature could be zero if either 1k or 2k is zero. So

for flat point test equation 5.8 is used as scalar function

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22

21 kkf (5.8)

The distance between the test point and its focal point is called as

focal length. It is the measure of surface quality. Table 5.1 shows the values

of selected points from the good region as per global evaluation. The values

of focal length are higher than the focal length values of regions of singularity

as per global evaluation shown in Table 5.2

The focal surface generated using the above equation encapsulates

many useful properties of the surface of lens including surface continuities.

The scalar function is always positive or zero and the focal surface never

cross the test surface. Moreover, the order of the focal surface is reduced by 2.

If the surface of lens has an order continuity three, focal surface has an order

continuity of one. The technical smoothness of a surface is evaluated by the

scalar function

21

22

21

kkkkf (5.9)

The degree of smoothness is associated with the difference of

surface area of the focal plane and the lens surface. (Hagan et al; 1992) has

presented C2 discontinuity theorem on test surface which states that if S (u,v)

is a surface with principal curvatures 1k and 2k ; its generalized focal surface

is given by

z)y,N(x,.kkkka.z)y,S(x, z)y,F(x,

21

22

21 (5.10)

If S (u,v) is technically smooth and ds)k(k 22

21

s

minimum,

then A(S)-A(F) is minimum ,

where A(F) and A(S) are the surface area of F(x,y,z) and S(u,v). The

mathematical formulae discussed above for evaluation of surface quality can

be implemented in CAD packages.

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70

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The surface properties are closely associated with certain

intrinsic properties as principal curvatures. Generally, 3D modelling software

do not provide principal curvature values for any selected points on the

surface. Softwares give the values only in fly mode without snapping the

points on the surface. So an interactive method is proposed for determining

the maximum and minimum curvatures of selected points on the surface. This

is achieved by customizing the CAD software using knowledge entities such

as parameters, rules, relation and macros. Figure 5.11 shows the method of

determination of principal curvature, implemented in CATIA V5.

Figure 5.11 Determination of principal curvature near singularities

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From this, the focal points corresponding to any point on the surface is

obtained. The local evaluation of the surface involves the following steps:

i. Import the surface developed for lens using ‘publish’ tool available in

CATIA V5 R16 so that changes in the surface is automatically

updated.

ii. Create a set of isoparametric curves on the surface in such a way that

they are intersecting at the point of interest (i.e. the point where local

evaluation is to be carried out). The curves are then linked to the

parameters of curves declared in the module. The principal

curvatures, Gaussian curvature and mean curvatures are calculated

and focal points are located. The user can interactively manipulate

the ‘resolution controller’ the angle parameter defined for further

refinement of extreme curvature values. The process is repeated for

neighbouring points.

iii. Export the values of curvatures and coordinate values of focal points

for each test point and record.

iv. Create generalised focal surface from the recorded values.

The steps used for determining principal curvatures are given

below.

Intersect the two isoparametric curves and identify the test point.

Create a unit normal (N) to the surface and a tangent plane at the test point as

shown in Figure 5.11. A tangent line to any one of the curves is sketched on

the tangent plane from which another line with user defined angular offset

(called here as resolution controller) is created. Using a circular pattern, the

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angular offset line created is multiplied for a user defined number (say 20) for

an angle of 180 degree. The circular pattern as a whole could be rotated using

the resolution controller defined by the user. Planes were created based on

each line with surface normal (N) already created at the test point. Thus, all

the planes are normal to the surface at the reference point. Intersect all the

planes created with the surface of lens to get a family of normal section

curves y as per equation (5.4). The normal section curves are passing through

the test point, whose tangents (A) at the test points are known. The curvature

value at the point is calculated using the formula available in the CAD

software and extreme points are plotted. This method could be used to any

point on the surface where critical evaluation is required after the global

analysis of surface.

The undesirable area noted in highlight analysis shown as encircled

in Figure 5.10 were located close to the boundary curve. Property of surface is

characterized by the quality of boundary curve and the type of propagation

such as point continuity, tangent continuity and curvature continuity.

Figure 5.12 shows the control plot by highlight analysis on surfaces

developed by the three types of propagation. It is inferred that the

discontinuity is originated from the boundary. It should be noted that as the

surfaces are created by lines or curves as inputs, the quality of curves would

affect the surface quality of lens largely.

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a) Curvature continuity b) Tangent continuity c) Point continuity

Figure 5.12 Surface interrogation by contour plots

Figure 5.13 shows the focal surface constructed for the surface of

lens including the point of discontinuity. The focal surface tends to meet the

test surface at the points of discontinuity. The focal length is a measure of

continuity.

Figure 5.13 Generalised focal surface based on Gaussian curvature with

scale factor = 2000

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5.8 DESIGN OF LENS / COVER FOR HEADLAMP

Previous section presented the conceptual part of design of lens or

cover of headlamp, where the shape of headlamp was obtained and the surface

interrogation was carried out. This section covers the refinement of design to

complete a detailed design of lens for the given input conditions where

attempts are made to capture the design intents so that it could be re-used.

Features of the lens are decomposed into surface feature, rib feature and

material feature. Surface feature is a free-form feature which controls the

exterior shape. Rib feature governs mating with the casing and ensures

alignment with front fenders of car. It also ensures the watertight and airtight

conditions, and is critical in assembly as detailed in Figure 5.5.

The function of curvature continuity of free-form surface within the

boundary curve was implemented in ‘knowledge template’ within CATIA V5.

The template can be reused for the development of lens for any car body

shapes. The template is shown in Figure 5.14 which encapsulates the design

knowledge and support re-use. In case of collaborative design the template

can be stored in a common database. The designer instantiates the class for a

specific condition. Conceptual design of rib feature is also implemented

within the CAD package. The boundary curve is offset for a user defined

radius from which surface for rib can be interactively developed by extrusion

features. The reference axis is user controlled.

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Figure 5.14 Product template supporting conceptual design of lens

Figure 5.15 shows a lens designed with all the features.

Figure 5.15 Design of lens

Free form surface generated from four input surfaces with visual continuity Boundary curve

Input surfaces for design of lens

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5.9 DESIGN OF REFLECTOR

Reflector is the ‘heart’ of headlamp. The conceptual design of

reflector includes development of paraboloidal surface. A paraboloidal

surface is constructed for the basic dimensional parameters such as width,

height and K value (Width_reflector , Height reflector and K value).

Figure 5.16 shows the method of obtaining the dimensions of reflector from

the boundary curve.

Figure 5.16 Method of reflector dimensioning

The width (Width_reflector) is associated with the diameter of

offset circle as

Width_reflector = offset circle_dia (5.11)

The height of the reflector is related to the width as

Height_reflector = Width_reflector × Aspect ratio (5.12)

Projected boundary curve

Inscribed circle and offset circle

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where aspect ratio is a user defined parameter. The above equations

associate the feature class for reflector with the car body profiles which was

discussed in the proceeding paragraphs:

The design of reflector surface is governed by the parabolic equation

(4.1) in which the shape of the reflector depends on the value of ‘K’, the

constant of parabola and is a predefined parameter decided by the designer.

A shape feature model class is constructed for reflector coordinate

points using the equation (4.1) and is implemented in Microsoft Excel. The

reflector feature model is automatically instantiated by filtering ‘y’ and ‘z’

coordinate values with respect to the parameter values of Width_reflector

and Height_reflector parameters as per relation given by

(Width_reflector)/2 < y < (Width_reflector)/2 (5.13)

and (Height_reflector)/2 < z < (Height_reflector)/2 (5.14)

The feature model is implemented in Microsoft Excel spreadsheet

from which coordinate values are exported into CAD software. The reflector

surface is obtained from the cloud points.

The reflector design is largely restricted by the regulatory

requirements which ensure adequate visibility of road. A tailored reflector

from a base parabolic reflector has been reported by Prasannakumar (2006) in

which the authors have segmented the reflector surface and the segments are

rotated for illuminating the corresponding portion in measuring screen. As per

the standard, ECE regulation, image screen is kept at a distance of 25 meters

from the reflector. In this work, the segmentation is done at the reflector

coordinate points (cloud points) level by filtering the points from the cloud

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point data implemented in Microsoft Excel. Figure 5.17 shows the tailored

reflector surface modelled in CATIA V5 satisfying the requirements of ECE

standards. The segments are joined by blend surface which are continuous to

segments.

Figure 5.17 Detail design of reflector – segmented for illumination

distribution as per ECE regulation

Each segment is created individually and is rotated so that the

segment illuminates the specified area in the image screen. Image screen for

testing illumination is also identically segmented so that each reflector

segment has its targeting segment in image screen. This tailored reflector is

again ray traced for evaluating the standard illumination distribution. The

illumination E at the test point for the oblique incidence is calculated by the

equation

2

3

HCos.CE (5.15)

where C is lumens of the headlamp bulb, H is the normal distance to test

tailored

reflector is blended so that a continuous surface is obtained. Evaluation of the

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reflector surface is carried out by tracing the incident and reflected rays and

the illumination intensity was calculated using the equation 5.15. Figure 5.18

shows the interactive tracing of reflected beam.

Figure 5.18 Evaluation reflector surface using optical principles

5.10 DESIGN OF OTHER COMPONENTS

In a headlamp there are more than 25 components including

standard parts. In this thesis, bezel and casing are considered apart from the

components discussed in previous two sections.

Bezel also has an important role in styling. In Modern headlamps

bezel also polished and coated with metallic film as reflector. In some designs

bezel separates the compartment for headlamp and associated signal lamps.

The conceptual design of bezel starts from the boundary profiles as the case

of reflector and lens. In addition, the details of free edges of reflector are

required. This thesis covers the conceptual model of bezel from which skin

model is obtained. The reflector edge and offset boundary curves are

implemented in the template as shown in Figure 5.19.

Reflected ray

Incident ray

Normal

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Figure 5.19 Template model for construction of skin model for bezel

Casing provides housing of the component assembly in

positions. The location of the headlamp unit with the car body is achieved by

casing. Design of casing is based on a plane, which may include the OEM

requirements, as a reference for mounting bulb. The design of casing also

largely depends on the conceptual models of lens, reflector and bezel.

Boundary curve, reflector’s anchor points and focus point are other

information required by the designer.

5.11 SUMMARY

This chapter explained the design of critical components of

headlamps namely, lens and reflector in detail. The design procedure of lens

allows incorporating the high level aesthetic aspects in design while the

design procedure of reflector enables to carry out design according to the

standards of illumination of roads. The design of bezel was also presented.

The design methods support parameter based multiple view product

modelling which will be discussed in the chapter 6. Assembly analysis and

part identification for finished assembly will also be discussed in chapter 6.

Edge reflector

Offset boundary