CHAPTER 1 INTRODUCTION TO ERGONOMICS AND

ANTHROPOMETRY

1.1 ERGONOMICS:

Ergonomics is an approach which puts human needs at the focus of designing

technological systems. The name “Ergonomics” comes from the Greek word “ergon”

which means work and “nomos” which means law. The core sciences from which

ergonomics is drawn are:

Psychology: It is concerned with human information processing and decision-making

capabilities.

Anatomy: The contribution of basic anatomy lies in improving physical 'fit' between

people and the things they use.

Engineering: it is related with designing of technical products and services by taking

human characteristics into account.

Ergonomics comes into everything which involves people. Work systems, sports and leisure,

health and safety should all embody ergonomics principles if well designed. The aim behind

having a product with ergonomic design or an ergonomic workplace is to ensure that the

human working over there is safe and comfortable to be in the same position for a longer

period of time.

For ergonomics, human is a part of a system and must be fully integrated into it at the

design stage. Human requirements are, therefore, system requirements, and can be stated in

general terms as:

Equipment that is usable and safe.

Environment that is comfortable and appropriate with the task.

Tasks those are within people’s limitations.

The implementation of ergonomics in the system design should make the system work better

by eliminating aspects of systems which are undesirable, such as,

Fatigue

Accidents, injuries, and errors.

User difficulties.

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1.1.1 DOMAINS OF ERGONOMICS:

Domains of specialization of ergonomics can be classified as follows:

1. Physical ergonomics is concerned with human anatomical, anthropometric,

physiological and biomechanical characteristics.

2. Cognitive ergonomics is concerned with mental processes, such as perception,

memory, reasoning, and motor response, as they affect interactions among humans

and other elements of a system.

3. Organizational ergonomics is concerned with the optimization of sociotechnical

systems, including their organizational structures, policies, and processes.

1.1.2 APPLICATIONS OF ERGONOMICS:

Ergonomics is successfully applied in fields of:

i. Aerospace

ii. Product design

iii. Transportation

iv. Nuclear and virtual environments.

v. Designing of workplaces.

1.2 ERGONOMICS IN AUTOMOBILES GOT TO INCLUDE POINTS

from design of automobile interiors

It is essential that the ergonomic input to the vehicle takes place throughout the design

process. For this very purpose, most of the automobile manufacturing companies employee

ergonomists. Ergonomists, usually, follow an inside out approach for the design. By

following this approach, the ergonomist would get clear idea about the size, number and age

of the future occupants along with their comfortable posture. This would then help the

ergonomist to design the display and control interfaces with the knowledge of hand and eye

ranges. The exterior of the vehicle would then be designed.

As far as an automobile design is concerned, an ergonomist has to work on

following aspects:

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Design of driver’s seat

Design of control systems

Design of hand lever and steering.

Ergonomists have had to find methods of communicating ergonomic information to

those who need to use it. There are a wide range of standards, guidelines and

recommendations available in many areas of ergonomics that are pertinent to automotive

design. The Society of Automotive Engineers (SAE) in the US has been particularly active in

the generation of such Standards. The most relevant to the ergonomist are:

SAE J826 H-point (ISO 6549)

SAE J1100 Seating reference point

SAE J1100 H-point travel path

SAE J1517 Driver selected seat position

SAE J941 Eyellipse (ISO 4513/BS AU 176)

SAE J1052 Driver and Passenger head position contours

SAE J287 Hand controls reach envelopes (ISO 4040/BS AU 199).

Other tools which may be used involve use of various soft wares like CAD,

MANIKINS, and 2D package drawings. These MANIKINS are basically used to examine

occupant accommodation. The 2D package drawings often provide the first visualizations of

the proposed vehicle occupants. They are produced after the product planning stage, when the

market specification has taken place and the basic parameters of the vehicle are known.

1.2 ANTHROPOMETRY

The word Anthropometry has been derived from the Greek words “anthropos” meaning man

and “metron” meaning measurement of human body. Anthropometric data are used in

ergonomics to specify the physical dimension of workspaces. It can be divided into two

types:

Static anthropometry

Dynamic anthropometry

Static anthropometry is concerned with the measurement of human subjects in rigid,

standardized positions (e.g. static arm length being equivalent to its anatomical length). Static

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anthropometric data are used in designing equipment for the workplace where body

movement is not a major variable, e.g. seat breadth, depth and height.

Dynamic anthropometry is concerned with the measurement of human subjects at work

or in motion (e.g. functional arm reach is a factor of the length of the upper arm, lower arm

and hand, as well as the range of movement at the shoulder, elbow, wrist and fingers).

Dynamic anthropometric data can be used to establish control locations using reach

envelopes for the hands and feet and locations of head restraints, seat belts.

For any design involving the use of anthropometric data, 4 set of constraints have to

consider. They are as follows:

Clearance: Clearance means provision of sufficient space around the work-place.

Reach: Reach constraint refers to the ability to operate controls from a comfortable

position.

Posture: Posture means the way in which the driver

Strength : Strength is concerned with the application of force in operation of controls.

1.2.1 APPLICATIONS OF ANTHROPOMETRY:

Anthropometric studies are used in the design of modern aircraft, preparation for cosmetic

surgery, etc. When paired with ergonomics, it is used to craft office workstations, aircraft

cockpits, and home furniture. Anthropometry is also used in safety design, specifically for

infants and children.

1.3 ANTHROPOMETRY IN AUTOMOBILE DESIGN

In case of automobile design, anthropometric factors are used for occupant accommodation.

Various anthropometric factors have to be considered, which may include,

i. Sitting height

ii. Sitting eye height

iii. Sitting shoulder height

iv. Thigh clearance, etc.

In order to establish statistical concepts that determine human variability, a large amount of

data relating to various dimensions of different humans is carried out. With the help of this

data a normal distribution curve is obtained.

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A normal distribution is fully defined by its mean and standard deviation—if these are known

any percentile may be calculated without further reference to the original measurements of

individual people.

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CHAPTER 2 DESIGN OF DRIVERS SEAT

Seat is an important part of car. Drivers spend great deal of time on the seat. The purpose of a

seat is to provide stable bodily support in a posture that is:

(i) Comfortable over a period of time;

(ii) Physiologically satisfactory;

(iii) Appropriate for driving.

Comfort will depend upon the interaction of seat characteristics, user characteristics.

Seat characteristics include seat dimensions and seat angles while user characteristics include

body dimensions, body aches and pains.

2.1 Anthropometric factors related to user characteristics:

User characteristics 1

1) Seating height: Vertical distance from the sitting surface to crown of

the head. It is used to determine overhead clearance.

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1. Seating height2. Seating eye height3. Sitting shoulder height4. Sitting elbow height5. Thigh clearance height6. Popliteal height

2) Seating eye height: Vertical distance from the sitting surface to the

inner canthus (corner) of the eye.

3) Sitting shoulder height: Vertical distance from the seat surface to

the acromion (i.e. the bony point of the shoulder).

4) Sitting elbow height: Vertical distance from the seat surface to the

underside of the elbow.

5) Thigh clearance height: Vertical distance from the seat surface to the top of the

uncompressed soft tissue of the thigh at its thickest point, generally where it meets the

abdomen.

6) Popliteal height: Height of underside of the knee above the bottom surface.

User characteristics 2

7) Forward reach: horizontal distance between back of the seat and fingertip.

8) Knee height: vertical distance between floor and top of knee.

9) Buttock popliteal height: horizontal distance between seat and underside of knee.

10) Buttock-knee length: horizontal distance between seat to front of knee.

2.2 Anthropometric factors related to seat design:

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7. Forward reach

8. Knee height

9. Buttock popliteal height

10. Buttock knee length.

1. Seat height (H): As the height of the seat increases beyond the popliteal height of the user,

pressure is felt on the underside of the thighs. Also, if the height decreases, the driver will

face greater problems in sitting down and standing up and also will require greater leg room.

It is therefore necessary to have proper seat height. Optimal seat height may be that chosen

close to the popliteal seat height.

2. Seat Depth (D): The seat width should not be increased beyond the buttock popliteal

height. If this happens the driver will not able to rest his back effectively without giving

adequate pressure on the knees which is undesirable.

3. Backrest: The higher the backrest, more effective it is to provide rest to back while in the

driving posture. Another factor such as mobility of shoulder should also be taken into

account. Backrest may be differentiated into 3 types any one of which may be applicable:

Low level backrest

Medium level backrest

High level backrest.

For design of automotive seats high level backrest is preferred, since it provides support right

from the lumbar to head. It is usually of the shape of the spine.

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D- Seat depth

H-Seat height

A-Seat surface to bottom of backrest

B- Seat surface to midpoint of

lumbar curve

C- Vertical height of backrest.

Seat dimensions 1

SEAT DIMENSIONS 2

4. Seat angle or tilt (ß):

A proper seat angle should be chosen as it helps the user to maintain good contact with the

backrest. Excessive angle reduces the comfort ability of the driver. For most cases it is

approximately 5-10 .

5. Seat width: Distance between the hands rests of a seat. It should be some 25 mm less on

either side than the maximum breadth of the hips

6. Backrest angle rake angle (α): As the backrest angle increases, a greater

proportion of the weight of the trunk is supported. Increasing the angle

between trunk and thighs improves lordosis. (A medical term used to describe an

inward curvature of a portion of the vertebral column).

Seat dimensions 3

7. Forward leg room:

In sitting position the provision of adequate forward leg room is essential

if the user is to adopt a satisfactory posture.

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ß: Seat angle or tilt

α: Backrest angle

rake angle

As shown in the figure above “D” is the forward legroom, which is the total horizontal

distance between buttocks and the toes, buttock-popliteal length B and foot length F sitting

on a seat of height H.

7. Seat surface: The purpose of shaping or padding the seat surface is to provide an

appropriate distribution of pressure beneath the buttocks. The seat surface should be

more or less plane rather than shaped, although a rounded front edge is

highly desirable. Covering materials should be rough to aid stability.

2.3 Seat Material:

Conventional seating systems include a steel frame, with springs attached to provide

support and flexibility to foam cushions. The main structure of seat backs is traditionally

made of metal. This is often a tubular steel frame, with various brackets and reinforcements

attached by welding or mechanical fasteners. The central section of the frame is normally

closed using steel sheet, which may have contours to provide added stiffness.

Some of the properties which an designer should keep in mind while selecting a

material for driver’s seat are as follows:

1) Transmissivity: It amounts for the vibrations transmitted from the seating platform to

the driver.

2) Durability: The consistency of foam characteristics during prolonged use.

3) Weight: Higher weight of seat higher will be weight of the car.

4) Ease of economy: The cost of material should be affordable as increase in this factor

will cause an increase in price of the vehicle.

5) Easy to recycle: It should be environment friendly.

Traditionally steel has been the material of choice to meet stiffness and loading

requirements for automotive seating applications. The use of plastics in these structural

applications has been limited due to its low stiffness and strength when compared to steel.

As far as foam material is considered, flexible polyurethane foam (FPF) is used, which has

good reliability and flexibility. Polyurethane foam can be formulated to dampen the

vibration that causes discomfort for the operator of a vehicle effectively.

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Chapter 3 Design of steering and controls

3.1 Introduction-Design of steering

The most common way to transmit movement by mechanical control is rotation.

According to shape, different types of rotary controls can be differentiated- steerings, rotary

switches, and knobs.

Design, selection and arrangement of hand wheels must be considered according to the

criteria of human factors and ergonomics. The dimension and position of hand wheel affect

the strain to which user is subjected. Design dimensions of hand wheel must be compatible

with anatomical, anthropometrical and physiological marginal human conditions.

3.1.1 Anthropometric Design Parameters

The movements of flexion and extension must be considered while designing a steering.

These movements occur at the wrist joint complex—that is at the ‘true’ wrist joint and at the

various articulations which are present between the eight small bones of the wrist .

The grip used for hand wheels is power grip- in which the fingers and thumb are used to

clamp the object against the palm. The thumb wraps around the back of the fingers to provide

extra stability and gripping force.

Thus for defining the dimensions of hand wheel various anthropometric measurements of

hand has to be considered.

IMPORTANCE OF THESE FACTORS WID VALUS AND FOOT

IMAGES JUST LIKE HAND

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Anthropometry Of Hand 1

Anthropometry Of Hand 2

Anthropometry Of Hand 3

The design dimensions of the hand wheel — such as shape, material, and surface — are

important factors influencing the operating effectiveness, with the characteristics

performance, stress and strain of the user and safety criteria.

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1. Hand length

2. Palm length.

12. Hand breadth

13. Hand breadth (across thumb)

3. Thumb length

4. Index finger length

5. Middle finger length

6. Ring finger length

7. Little finger length

9. Thumb thickness

10. Index finger breadth

8. Thumb breadth

11. Index finger thickness

14. Hand breadth

15. Hand thickness

Shape – it should be such that minimum strain on the hands is guaranteed.

Surface- Surface quality should neither be so smooth as to be slippery nor be so rough as to

be abrasive.

Material-. Skin´s degree of moisture and the material´s properties such as surface roughness

must be considered as unsuitable materials lead very quickly to destruction of the upper skin

layer.

Handwheels should facilitate two-hand control and permit rapid movements as well as

accurate movements when needed. If rotations > 60° are required on a handwheel, the hands

must be repositioned. The thickness diameter of the handwheel should not

be less than 1.9 cm or more than 3.2 cm.

3.2 CONTROLS MANUAL CONTROL DEVICES AND

FROM BODYSPACEThere are many interactive modes that can be used to link a human response to a desired

machine action. For ordinary human–machine systems, for large, slow controls

requiring high levels of force the arms and legs are used with force and position feedback

occurring through the hands and feet as occurs in the use of levers and foot pedals. These are

known as manual controls.

Manual controls can be classified according to any number of functional categories

depending on the technical aspects of the machine being controlled. From an operational

viewpoint, controls are classified by the nature of their machine function

and by physical structure and appearance.

Controls for an automobile can be classified as follows:

1) Large linear controls

Foot pedals

Levers.

2.) Small Linear Controls

Push–Pull Knobs And Handles

Push Buttons

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3.) SWITCHES

Toggle

Rotary

Rocker

1. Foot pedals: For accelerator pedals, the resistive force should not exceed 44 N. The

recommended angle between a foot pedal and the floor varies with seat height.

Recommended foot pedal stroke length varies with the type of vehicle. Larger displacements

(10–18 cm) are desirable for brake pedals for safe braking especially under slippery road

conditions. Foot pedals should be approximately the same width as the sole of the shoe. Pedal

separation should be at least 5 cm edge to edge. Pedal shape is not a significant factor except

in providing initial visual orientation.

2. Levers: They are used for shifting gears. The knob at the end of a lever is labelled to facilitate

identification with a particular function. A knob in the shape of an end rounded cylinder or

ball is preferable when a firm or prolonged grip is required. Recommended ends diameters

are 3.2 cm for full grip.

2.) Small linear controls-push buttons:

Minimum force required to operate them is 0.25kg and maximum is 2 kg. For a sloping

vertical plane, buttons are preferred to be at 90 to the panel.these buttons may have built in

illumination. The minimum distance throught which they should be separated from other

buttons is 15mm and maximum is 22mm. The radius through which the swith gets pushed in

is 50 mm.

3.) switches:

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Spring is loaded between central positions, which provides the resistance to build up then fall

down.

3.3 Direction of Control Movements:

To prevent control reversal errors, it is important for controls to operate in directions that are

compatible with associated display or vehicle movement. Factors to be taken into account

include:

1. Location and orientation of the control relative to the operator.

2. Position of the display in relation to the control and the

3. Orientation of the operator relative to vehicle.

4. Type of action being caused by activating the control.

Action desired Control movement

Turn on Up or press inwards.

Turn off Down or pull outwards

Turn or move

right

Right,clockwise

Turn or move left Left,anticlockwise

3.4 HUMAN FACTORS IN CONTROL:

3.4.1. Anthropometric Factors

Anthropometric factors to be considered in designing manual control systems include those

related to clothed body dimensions for the desired population percentile in combination with

reach capabilities, working positions for operators.

3.4.2. Biomechanical Factors

Biomechanical factors include strength in terms of specific force exertion capability, type of

control motions required to operate controls, speed and precision of control motion required,

reach capability for given control operation and effects of body acceleration upon

performance. Good anthropometric design facilitates good biomechanical design.

3.4.3. Psychological Factors

Psychological factors designing manual controls include those related to control location,

arrangement, spacing, feedback generated, and logic as affected by interaction with the

operation of other controls.

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CHAPTER 4 DESIGN OF DISPLAY PANELS

4.1 INTRODUCTION

The ways in which displays can be used to support human–machine systems have

multiplied. The basic aim behind the display design is that the information provided to the

user should be appropriate for both user and machine system. Providing appropriate

information support, in a way that is meaningful and easily interpreted, will improve the

overall performance of the human–machine system. Displays may provide simple warnings

or quantitative information. Most of the displays are based on the rise and fall of the needle.

4.2 CAR DASHBOARD DISPLAY

A dashboard is a control panel placed in front of the driver of an automobile. A

dashboard display atleast has a speedometer and a fuel gauge. In addition to these, the display

will feature some combination of a tachometer, charging system gauge, oil pressure gauge

and engine temperature gauge.

4.2.1 Speedometer: The speedometer, one of the most frequently used tools, is used to

judge how fast the car is going in kp/h (kilometres per hour).

4.2.2 Fuel gauge: it gives an idea about the fuel quantity in the vehicle. It indicates full,

empty & half filled tank.

4.2.3 Temperature Guage: this measures the temperature of engine coolant in degrees. It

is important to monitor the temperature guage to ensure the engine is not overheating.

4.2.4 Charging System Guage: The charging system provides the electrical current to the

vehicle. There are two types of gauges used to monitor charging systems: a voltmeter which

measures system voltage and an ammeter which measures amperage going out of, or coming

into the battery.

4.2.5 Tachometer: It measures the rpm of engine.

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4.3 DESIGNING OF DISPLAYS

To design an display panel, various factors have to be considered which are in relation

with:

1. Design of symbols or icons for display

2. The use of words and numbers.

3. The organization of display.

4.3.1 design of symbol or icons in display:

Symbols and icons are commonly used in displays to indicate system functions and to

provide information from the system. Various characteristics that have to be considered while

designing a symbol are as follows:

4.3.1.1 Size: The precise size of symbols in a display is usually determined by three

features: typical viewing distances, display quality, and viewing conditions. Display quality

may vary in accordance with resolution, contrast, focus, and glare. Viewing conditions

depend upon environmental factors such as noise, smoke or dust; they also include

physiological and psychological factors such as fatigue, eye strain, and workload.

4.3.1.2 Shape: If effective contrasts in shape are used they can reduce the time it takes for

users to identify appropriate information. Symbol shape can also be used to help organize

displays.

4.3.2 The use of words and numbers.:

Symbols often rely on visual associations and the context in which they appear for

their meaning whereas words are rarely ambiguous. Words can also convey more complex

meanings and ideas in a way that would be virtually impossible with symbols.

Similarly, use of numbers is often the most effective way of conveying quantitative

information. Various factors which are to be considered for designing words and numbers ar

as follows:

4.3.2.1 Size, simplicity, and shape:

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As with symbols, the size of letters is largely determined by viewing distance, display

quality, and viewing conditions. Font size is almost always determined via agreed

international standards. Letters are usually kept as simple as possible in order to enhance

legibility. Also, proper space between words and letters is to be ensured.

4.3.3 The organization of display:

Good display organization is the most important determinant of whether or not users

can direct their attention to the relevant information. It also plays an important part in

determining how easy that information is to understand and respond to.

4.3.3.1 Configurality:

Configurality refers to the way in which elements within displays are arranged in

order to convey information effectively. Careful attention is paid to the nature of the

relationship between elements in displays in order to allow easy interpretation.

4.3.3.2 Design simplicity:

In addition to the use of simple symbols and text, the simplicity of the display as a

whole needs to be considered, for which following factors should be taken into account:

(a) Overall density: This refers to the percentage of the total number of possible

characters or symbols which could occur in the display space.

(b) Local density: This is the amount of space which is filled around a target area or

symbol.

(c) Layout: this builds on consideration of grouping and considers the irregularity, or

layout complexity, of functional groupings in a display.

4.3.3.3 Creating contrasts between groupings:

Creating contrasts between different parts of the display layout can help users to direct their

attention quickly to appropriate parts of the display. Discrimination between symbol and text

clusters, or families, can also be achieved by the use of elementary features in the displays.

These features include:

(a) Colour

(b) Size

(c) Shape

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(d) Orientation

(e) Increasing the size of critical symbol features.

4.4 Creating:

Once the designer is done with all the considerations required to design the

dashboard, the next step is the actual process of designing. The process of creating and

evaluating the design is as follows:

There a number of steps which designers typically follow when designing displays.

The earliest phase of design usually consists of formulating a clear statement of requirements

for the display. This will include details about what should appear in the display. Prototype

display designs will be created. The precise nature of the display, however, will be

determined by a number of other considerations. These include the tradition and philosophy

of the company for whom the display is being created, precedents created by displays of a

similar nature, customer expectations, recommendations from international standards along

with government requirements, and the likely costs for development.

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CHAPTER 5 USE OF SOFTWARES IN ERGONOMIC DESIGN

5.1 Introduction

Day to day technology is changing for better customer satisfaction in the Automobile

sector. Due to the evolution of CAD tools, the accuracy of designs has increased. Various

CAD packages like CATIA, RAMSIS, and SAMMIE CAD system are used for the

ergonomic analysis of the automobile. The basic aim behind using this software is ensuring

comfort and safety to the passengers.

5.2 SAMMIE CAD:

The SAMMIE system is a computer based Human Modelling tool. It was developed by

SAMMIE CAD Limited, which was started in 1986 by the SAMMIE system originators to

continue the consultancy work of the SAMMIE Research Group, U.K. It is approved by

SAE. Its capabilities make it an invaluable tool to designers working on products that are

used by people. The system offers the following advantages:

3D analysis of fit, reach, vision and posture.

Reduced timescale.

Early input of ergonomics expertise.

Rapid interactive design.

Cost effective ergonomics.

The use of this system ensures proper fit, reach, vision and posture for the user.

5.2.1 Fit:

Comfort ability of user in terms of fit is ensured by this system. It can be done for

various age groups using the anthropometric data. It can also create allowances for clothing

and personal equipment.

5.2.2 Reach:

Reach can be assessed by simply positioning hands on a certain position and accordingly

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reach of legs can be seen. The human model will automatically display a geometrically

feasible reach posture .

5.2.3 Posture:

The human model is displayed as a set of 18 joints and 21 straight rigid links

structured hierarchically to represent the major joints and the body segments. Predicted

postures can be quantified in terms of flexion/tension abduction/adduction and lateral/medial

rotation at these joints. The predicted posture is clearly a function of the human model's fit,

reach and vision and a poor posture will usually require modification to the size of the

workstation or the layout of controls and displays.

5.2.4 Vision:

Viewing angles and distances, perspective views, mirrors and reflections, and

spherical aperture projections can all be assessed interactively using the SAMMIE system. A

mirror modelling facility has been developed which has successfully designed mirrors for a

variety of vehicles, meeting both legislative and ergonomics criteria. The focal length,

convexity/concavity, size and orientation of the mirror can all be interactively adjusted to

display the required field of view on the mirror surface

5.3 Specifications:

SAMMIE is a data driven system allowing the user to control the anthropometry and

joint movement limits of the human models from any available set of data. The system

includes a number of male and female, civilian and military data sets as standard. In addition,

SAMMIE allows new data sets to be created from anthropometry found in the literature.

Finally, Human models can be created directly from data taken from human subjects using

the standard methods. Selection of different databases and percentile values is interactive

without the need for direct manipulation of the database. The human models have 23 body

segments and 21 constrained joints and are capable of the full range of normal human

movement. The joint movement ranges can be constrained to reflect acceptable or preferred

comfort ranges inside the normal joint range or to reflect the effects of restrictive clothing or

physical disability. Use of SAMMIE reduces the number of physical mock-up and prototype

tests in a design program by allowing the designer to identify human-workplace interaction

problems and explore a variety of design solutions in a virtual environment.

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5.4 Requirements:

SAMMIE has been solely developed for personal computers on the Windows NT /2000/XP

operating systems.

SAMMIE's hardware requirements are generally modest. A modern PC with Intel Processors

running at 1GHz or better is sufficient. A minimum of 256MB of system RAM and a

compatible graphics card with 64MB of video memory or greater are recommended.

The SAMMIE system is a licensed product. The license is granted in perpetuity and enables

commercial use at a single geographic site on a single Personal Computer. Pricing varies

depending on the number of licenses required and whether the license is commercial or

academic.

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