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ACKNOWLEDGEMENT 

I am thankful to my supervisor Dr. Jerard J Gouw for giving me a real life project to work on

Ergonomic design of a car seat. This project definitely helped me to gain better learning and

understanding of different type of seating position and its impact on human comfort and injury. I

would also like to thank him for rendering all his efforts, supports and encouragement to complete the

project.

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ABSTRACT 

Passenger car seating design and arrangement for driver plays significant role on drivers comfort and

safety while driving. Most drivers are in a high-risk group for spinal disorders including back pain,

neck pain, sciatica, degeneration, and herniated discs, etc. A proper ergonomics design can solve these

problems or reduced the problem significantly, therefore as an engineer we must have to know about

the structure of the vehicle seat. It is necessary to establish ergonomic models of the seating and

analyze the position of the segments of the body when the driver holds a posture of driving.

This project based on popular software CATIA V5 and provides details on human builder and human

measurements components. Major role of the software is to create mankind with different percentile

using Human Builder and Human Measurement Workbench with additional analysis of different

posture. Before designing and analyzing an ergonomic car seat its prime need to design a 3D model of

mankin with necessary view which explains work activities with different posture, including reach

envelop, vision analysis and posture activity. Additionally; and ergonomic car seat and steering wheel

also modeled and assembled with the design. Furthermore; apart from the software recent

technological aspect to design an ergonomic car seat also discussed and analyzed. Based on necessity

and habit, most of the cases a driver is bound to drive a car for long time, therefore because of long

term sitting movement of different body segments such as hand, forearm, leg and eyes are affected

which are the cause of light injuries and affected the task of driver. Because, the postures should be

studied in the research and the designer of the vehicle seat should emphasized on it. The position of

the segment of the body of the driver in driving is also an important parameter in the design of the

vehicle seat. It decides the dimension of the seat and makes the seat more comfort and can be used by

the 95 percent people. An ergonomic seat also designed and compared with flat type back seat. The

result shows ergonomic seat has less impact in trunk than regular seat.

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TABLE OF CONTENTS 

Section Title Page 1. Introduction and Literature Review …………………………………………………. 01

1.1 Ergonomics In The Automotive Industry ………………….…………..….….. 02 1.2 Standards, Guidelines And Recommendations …………..……………………. 02 1.3 Anthropometry And Fundamental Fallacies ………………..……….…………. 03 1.4 Seat Feature Design Assessment ……………………………………………….. 04 1.4.1 Road Test ……….……………………………………………..…………. 05 1.4.2 Simulation ………………………………………………………..……… 05 2 Design Consideration …………………………………………………….…………. 06 3 Designing Passenger Car Seat Travel ………………………………………..……… 06 4 Model Development, Analysis and Discussion ……………..……………..……….. 09 4.1 Create Mankin ……………………………………………………..…………. 10 4.2. Create Different % Ile Mankin …..……………………………………….…... 10 4.3. Steering Wheel Design …..………………………………………………….... 11 4.4. Chair Design ……..…………………………………………………………… 11 4.5. Human Measurement Edition ..………………….……………………………. 12 4.6. Load Parameters ………………………………………………………………. 13 4.7. Create Constraint ……………………………………………………………… 14 4.8. Posture Editor ……………………………………………….………………… 15 4.9. Angular Limitations To Percentage Setting …………………………………… 16 4.10. Object Attachment With The Mankin ………………………………………… 17 4.11 Mankin Reach Envelop ……………………………………………………….. 18 4.12 Inverse Kinematics (IK) ………………………………………………………. 19 5 Ergonomic Analysis ………………………………………………………………… 20 5.1. Vision Analysis ………………………………………………….................... 20 5.2 RULA Analysis using CATIA ………………………………………………… 21 5.2.1. Setting Ergonomics Analysis in CATIA ……………………….. 22 5.2.2. Perform RULA Analysis ……………………………………… 22 5.2.3.1 Posture Related to RULA Analysis …………………... 23

6 REBA Analysis ………………………………………………………………………. 24 7 Biomechanics Single Action Analysis ……………………………………………… 25 7.1. Biomechanics Analysis Result ………………………………………………… 26 8 Comparing Ergonomic And No Ergonomic Seat Effects On Trunk …………….….. 28 9 Some Recommendations Of Correct Sitting, Seat Design And The Drivers …..…… 29 10 Discussion ………………………………………………………..…………..…….. 31 11 Conclusion ………………………………………………………..…………..…….. 32 12 References ……………………………………………………………………..……. 33

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LIST OF FIGURE 

FIGURE No SHORT TITLE PAGE NO

1 Experimental Driving Rig 5

2-4 Seat Travel Distance 6-7

5-8 Mankin 9-10

9 Steering Wheel Design 10

10-12 Chair Design 10-11

13-16 Human Measurement 12-13

17-19 Load Definition 13-14

20-23 Posture 15-16

24 Angular Limitation 17

25-30 Object Attachment 17-18

31 Reach Envelop 19

32 Inverse Kinematics 19

33-34 Vision Analysis 20-21

35-37 RULA Analysis 21-22

38 REBA Analysis 24

39 Biomechanics 27

41-42 Comparing Correct Seating 30

43-44 Recommendation of Seating 31

LIST OF TABLE 

TABLE No SHORT TITLE PAGE NO

1 Result Of Summary Data Tab 28

2 Result of Joint Moment Strength Data Tab 28

3 Result of Segment Positions Tab 28

4 Result of Reaction Forces And Moments 29

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1.  INTRODUCTION AND LITERATURE REVIEW 

Ergonomics has a wide application in human society nowadays. Humans need more comfortable

environment of living and safer working condition. The goal to apply ergonomics technology on the

design of the equipments and systems is to ensure humans with them in complete harmony. So

engineers always put ergonomics in the more important position in the design. The purpose of this

project is to develop a CATIA tutorial to make a full human activity analysis in a sitting position of

vehicle driver. This project deals with developing a step by step CATIA tutorial explaining how the

Ergonomic Design and Analysis module along with its Human Builder and Human Measurements

components are used for creating a manikin with different percentile while changing joint angles

reflecting postural change. These changed postures are then viewed in different planes including in 3D

and analyzed for the driving activity which must include viewing at the display terminal while sitting

on a driving sit.

Firstly, a model is realized using the Human Builder tool available in Ergonomics Design and

Analysis. The model is then tailored to different percentiles using Human Measurements components.

Secondly, two major different percentile models are studied in a step by step tutorial form for their

different postures performing the driving vehicle. The study here means the information generated by

CATIA corresponding to a particular posture of particular model are gathered and observed carefully

to see whether any sitting position for driver performed over a long period of time per day could cause

any health injury resulting from awkward posture.

Finally; the driver can adjust the height of the seat and the angle of the rest back and also can move the

seat along the sliding rack to let it to suit the different size of the drivers. The position of the segments

of the body and posture of driving are most important parameters that the designer should consider and

designed the seat based on the posture so that it can provide a good lumber support of driver. From the

above parameters the designer can find the best posture to reduce the risk of the ergonomic problem

significantly.

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1.1 ERGONOMICS IN THE AUTOMOTIVE  INDUSTRY 

Tools and techniques used by ergonomists in the automotive industry are based on statistical data, Test

drive, and Simulation and computer software. Statistical data analysis and test drive are the primitive

but not considered that much in now a days. In case of simulation and computer software they are

using the same data sources and CAD tools and some simulative hardware. Simulative hardware runs

user trials to evaluate their products; in some cases using only company staff as subjects, in other cases

with members of the general public. They have good correspondence with universities and the

organization is involved in research projects. Normally if there are no ergonomists then the data

sources considered as out of date and user evaluations are rarely conducted. Overall Ergonomics

evaluation depends on the quality of product and the price therefore only few model cars come with

proper ergonomic design of car seat.

1.2 STANDARDS,  GUIDELINES AND RECOMMENDATIONS [3]    

Many areas of ergonomics those are pertinent to automotive design. In case of occupant

accommodation there is wide range of standards, guidelines and recommendations available those are

extremely useful in the early stages of concept design because they are readily available. Some of the

major giant company use their own or modified standard. Some of the standards and their associated

procedures have already been developed or in developing process in the field of ergonomics. USA:

The Society of Automotive Engineers (SAE) has been particularly active in the generation of such

Standards and many of these form part of the legislation which covers automotive design. In case of

human body parts with their relevant posture SAE recommendation to Ergonomist are give below: 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 Eye llipse (ISO 4513/BS AU 176) SAE J1052 Driver and Passenger head position contours SAE J287 Hand controls reach envelopes (ISO 4040/BS AU 199)

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1.3 ANTHROPOMETRY  AND FUNDAMENTAL FALACIES [3 ]  

Design and development of vehicles still now many automotive companies did not have a formalized

structure to identify and deal with ergonomics issues. The main reason behind this is several

misconceptions about ergonomics and lack of knowledge to justify the necessity of it. Pheasant (1996)

and Porter and Porter (1997) in their own experience found that ergonomics in automobile industry

eight fallacies exist to design and implement a product.

1. Ergonomics is expensive and since products are actually purchased on appearance and styling,

ergonomics considerations may conveniently be ignored.

2. The design is not satisfactory for me – it will, therefore, be unsatisfactory for everybody else (a

variation on fallacy 1 above).

3. Percentiles are a very clear and simple way to present and use information concerning body size.

1-3 Fallacies is ignored because we are designing ergonomics sitting.

4. The design is satisfactory for me – it will, therefore, be satisfactory for everybody else.

Not recommended fallacies for this project because the design should fit wide range of people.

5. This design is satisfactory for the average person – it will, therefore, be satisfactory for everybody

else.

Not recommended fallacies for this project because unfortunately for automotive designers, there is no

such thing as an average man or woman, or child for that matter.

6. The variability of human beings is so great that it cannot possibly be catered for in any design – but

since people are wonderfully adaptable it doesn’t matter anyway.

Not recommended fallacies for this project because though we know people are adaptable but we have

to does research has to come up with result that meet requirement for most people.

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7. Ergonomics is an excellent idea. I always design things with ergonomics in mind, but I do it

intuitively and rely on common sense so I don’t need tables of data.

Not recommended fallacies for this project because manual design without using table and standard

data may not fulfill all the requirement of ergonomics car seat design.

8. Designing from 5th percentile female to 95th percentile male dimensions will accommodate 95%

of people.

Recommended and considered fallacies for this project. This will be true if only one dimension is

relevant to the design solution. However, some vehicle requires simultaneous accommodation on a

large number of dimensions because of lot of extra features than regular vehicle. There are poor

correlations between body dimensions it follows that those males who are designed out because of

limited headroom will not necessarily be the same 5% who are designed out for having arms that are

too long or the 5% with legs that are too long, hips too broad etc. Similarly, those females who are not

considered in design their relevant data too small will not just constitute 5% of the females. Therefore

5th percentile stature is a value whereby 5% of the population are shorter and 95% are taller; 50th

percentile stature is the median stature.

Finally; depending on the situation higher and median value conceded for this for this project. For

example, In case of car height definitely we have to consider the highest value of mankin therefore; we

must have to consider 95% ile male height.

1.4 SEAT FEATURE DESIGN ASSESMENT [3]  

In case operation of a seat and drivers comfort, visual requirement and correct posture depends on

optimum design. A good design does not necessarily make sure that the design is correct in terms

drivers ergonomic requirement until it’s not tested or assessed .To asses a design it a challenge for

manufacturer because the result come from mass group of driver after a certain period of use.

Therefore; design should be tested very accurately before marketing. Most cases testing can be

performing by two major ways: 1. Road test 2. Simulation

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1.4.1 ROAD TEST 

One of the experiments of road test conducted by Porter and Gyi (1998) [3]. According to the Vehicle

Ergonomics Group instruction they performed two test videos of 2.5 hour (60 mile) drive in their road

trials. During this test they give driver’s view of the road, with a voice-over of instructions about the

route to guide the driver of when to change gear, slow down other driving instruction. After driving

they collect necessary data from drivers. In this way mental and physical effect of driver can be

assessed before and after the test.

1.4.2 SIMULATION 

Another ways the car manufacturer tests a design by simulation. To accomplish this: Porter and Gyi

(1998) [3] used a highly adjustable driving rig (Figure 01) to identify driving postures and its effects

on a family type driving car. The simulation carried out to obtain the preferred driving

An Experimental Driving Rig.

posture of driver. For this with respect to the

seat they vary the height and horizontal

location of the steering wheel and pedals.

The seat tilt angle was also adjustable. For

each of these adjustments the component

travelled by the experimenter at discrete

increments throughout its range of travel

from one extreme to the other. Then they

temporarily fixed the component and back

again the adjustment in a balanced order

and perform the test again and again to achieve a satisfactory position. Until get a satisfactory result

they fine tuned the adjustment of all controls and positions again and again. Each adjustment a 10–15

minute driving simulation at the rig was then carried out to further confirmation that this posture was

optimum. Each result they document the relevant measures regarding the positions of the controls

from a fixed reference point. To get accurate result they placed the hands on the steering wheel and

Figure - 01

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looking ahead as though they were driving on a road and partially depressing the accelerator. Each

instance of driving posture then measured. They have taken lot of care when using such data for

individual joints and their correlation with the trunk-thigh and knee angles.

2. DESIGN CONSIDERATION 

To perform design we have to assume some factors that are given below:

• During turning of steering wheel, posture of driver was not considered because it happens for

few instances not even 1 turn/min.

• Consider automatic type of car therefore drivers left leg in rest position.

• Car roof height is not considered for design.

• Other minor posture for few instance changes like signal light on/off, Operating Air

conditioner/Radio, Changing gear etc not considered.

• Symmetric data considered for symmetric body parts.

The above design considerations happens only very few instance/minute therefore the driver posture

assume as static all the time and that will not affect any significant factors for design.

3. DESIGNING PASSENGAR  CAR SEAT TRAVEL  [1]       

In case of vehicle seating configuration it’s a challenge for car manufacturer to meet the requirement

of wide range of people. The driver’s seat can move forward and backward. Apart from the driver’s

height, drivers seating habit is also important. Fig - 02 is typical configuration of vehicle seat. In the

figure The dimensions F,S,T,G varies a little with car manufacturer. We assume some standard value to

for those for design to find out seating position other important dimension. Some driver likes to seat

far away as possible from gas/brake pedal and some drivers likes to seat close to the gas/brake pedals.

Since we consider 95% ile Canadian male for the design therefore; now we are trying to find out the

seating configuration for them.

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Assume

Standard Dimension for :

Dash board height F = 32 cm.

Steering Wheel Distance from

Dashboard S = 10 cm

Seating height from Base T = 27 cm.

Fully Pushed and Released Pedal Distance G = 10 cm. Based on the above information, we are going

to determine the follow distances for our design for 95% ile Canadian male:

• A = H2 – H1 = horizontal travel of the seat

• B = H1 – P1 = horizontal distance between the furthest forward position of the hip joint and the

fully pushed pedal

C = vertical distance between the

floor and the bottom of the

dashboard

D = horizontal distance between the

fully pushed pedal and the steering

wheel

Dimension no 15 : K = 460 mm

(95% ile Canadian Male)

2 22 605 270 541.41X mm∴ = − =  Foot Length F = 290 mm (95% ile Male)

Page 1-5 Joint 18 : Ankle flexion (plantar flexion) 95% ile Male is = 580

 

3 2 1 2 3cos18 290 cos 58 153.67 555 541.41 153.67 1250.08X F mm H X X X mm∴ = = = = + + = + + =

2 1 1250.08 1021.65 228.43A H H mm∴ = − = − =  

E

C

F

G

D

B A

S

T

H1

P2P1

H2

270 mm

X X X

K=460 mm

18°/

58°

3 2 1

Figure - 02

Figure - 03

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B = Distance between furthest forward position of the hip joint and fully pushed pedal.

  ( )1021.65 10 10 1121.65 1122B mm mm∴ = + × = →=⎡ ⎤⎣ ⎦     

C = Vertical distance between the floor and the bottom of dashboard. Consider the dashboard height

from bottom seat then its equivalent to the 1.5 times of hip joint height at sitting position from

SRP. Therefore; Segment 14 Hip above SRP

= 4.3” (Male and Female average link length) = 4.3”x25.4 mm = 109.22 mm

1.5 27 10 1.5 109.22 433.83C Height of the seat hip joint height mm= + × = × + × =

D = Horizontal distance between the fully pushed pedal and the steering wheel. [Assume that the hand

griping the steering wheel has a posture of the lower arm making angle of 900 with the upper arm]

The Length of average upper arm [page 1-6 segment 1 Man] = 17.4” = 17.4x25.4 mm= 441.96 mm

The Length of average lower arm [page 1-6 segment 2 Man] = 15.6” = 15.6x25.4 mm = 396.24 mm  

Figure - 04 Here D = B-X

1250.8+(10x10)-593.57 = 757.23 mm [for Men]

WHERE

[ ]2 2441.96 396.24 593.57X mm for Men= + =  

The final Dimension for 95 % ile Canadian

male are :

A =228.43 mm = 23 cm B = 1121.65

mm = 113 cm D = 757.23 mm = 78 cm

 

We will implement the dimension of A, B and D in CATIA for the design of car seat and Mankin

driving posture.

D

B

P1

X

Lower arm

Upper arm

Figure - 04

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4. CATIA MODEL DEVELOPMENT, ANALYSIS AND DISCUSSION. [2] 

4.1    CREATE  MANIKIN 

1. After Loading CATIA, then go to the start

menu, select Ergonomics design &

Analysis work bench and then click

Human Builder.

2. Human Builder work bench select insert

manikin icon located top of Human

Builder Sub Toolbar,

3. The Manikin Dialog Box appears which

consist of two tabs: Manikin and Optional. In

mankind tab Select Father product : In this

case the name is – Product_Maruf. The name

of mankin is ‘Driver’ and select 95% Male as

it described before on this selection.

4. From the ‘Optional’ tab select Canadian as

population and “Whole Body” Model with ‘H-

Point’ Referential. More option available eye

point, right foot, H-Point (default), Left foot,

lowest foot, and Crotch but whole body is

selected because this project intention to

analysis the whole body for a driver.

Figure : 5

Figure : 6

Figure : 7

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4.2. CREATE  DIFFERENT % ILE PERCENTILE MANIKIN 

Although chosen 95% ile

Canadian male for design

and analysis but 10% ile

Canadian Female driver also

created to learn how to

implement different % ile in

same model. The

procedures are same but we

have to choose the Shuttle

icon to separate

manikin in different place,

as requirement of the

Project. Also need to

maintain height of all % ile

mankin based on Foot as

shown in figure. Finally: I

choose 95th percentile

Canadian man manikin.

Two different kind of Mankin – 95% Canadian Male and 10% Canadian Female.

4.3. STEERING WHEEL DESIGN 

The most important part of steering wheel design are Wheel

Diameter and Rod Diameter. It depends on vehicle. The

standard value of Diameter of Wheel varies 325-400 mm and

Rod diameter varies 60-120 mm. Figure – 09 Wheel

Diameter considered 350 mm and Rod Diameter considered

75 mm. Other features do not have effect on human posture

therefore not considered in design.

Figure : 08

Figure : 09

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4.4. CHAIR DESIGN 

Figure –10 design of ergonomic back seat which is

designed for perfect lumber support of mankin. The

dimension of each curve designed in such a way that it is

exactly aligns with thoracic and lumber of 95%

Canadian male mankin. But in case of shorter driver of

5% female Canadian driver the seat back can be adjusted

up and down to get a good posture of lumber and

thoracic. Similarly Figure –11 design of ergonomic seat

base which also designed for perfect thigh support.

Figure -12 Complete Design of

Ergonomic seat with static

posture. Here thickness portion

of the back seat stay over the seat

bottom. Therefore; shorter

Driver(Female 5%) need to

adjust the head set only to get

the posture but won’t be able to

get good lumber support

compare to male 95% because of

height. So an alternative design

needed for shorter driver which

we try to find out after the

biomechanical analysis.

Figure : 10

Figure : 11

Figure : 12

Complete Design of Mankin with Static Driving posture of Mankin.

Horizontals Travel Distance A = 230 mm (Calculated Section-3 Page – 8)

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4.5. HUMAN MEASUREMENTS  EDITION 

Human Measurement of different body parts which are related to create posture is available in Human

Measurements Edition work Bench. To perform the operation selects Icon and the manikin from

the specification tree. After that select the Display the variable list icon which display the list of

different body parts as shown in figure. Those body parts with the dimension generated automatically

based on the % ile chosen before. We don’t need to edit since we already select 95% ile Canadian male

for our project. But in mixed or different case when exact data are not available then according to the

design requirement we can easily EDIT any dimension by selecting the segment length and Select

‘Management - Manual’. The Figure – 13 provides dimension in standing position. The Figure – 14

Relevant data of Figure 13

To get the Figure – 13 click posture editor which will provides dimension in sitting

position. Although all dimension are automatic but in this project sitting

dimensions are the most important factors then standing because the project

Figure : 13

Figure : 14

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is based on sitting position. Major posture of a Driver while driving: Figure -15 and Figure -16.

1. VISION –Line of Sight of driver. Related body parts – Eyes, Head and Neck. 2. STEER - Steer the steering wheel. Related body parts –Hand, Clavicular, and Finger. 3. GAS, BRAKE - Lumbar, Thigh, Leg, Foot and Toes

4.6. LOAD PARAMETERS 

Load parameters are very important for design and analysis

because in software the load data calculate like balance

behavior, center of gravity, and biomechanics. An empty load

node is created in the specification tree figure -17 when the

manikin is created. Empty load parameter does not contain any

data therefore we need input data, for this click on insert a new

Load on the tool bar that will give us Load

Definition Dialog box (Figure - 18). Since the steering wheel

connected with the vehicle therefore driver don’t really carry

the load of steering wheel. Since the driver’s posture is to hold

the steering wheel, so we can consider a small amount of

Figure : 15

Figure : 17

Figure : 16

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load (1 Kg).CATIA Graphical representation shown in figure-19. Elevation depends on the vertical

position of steering wheel. Since the steering wheel for all cars are adjustable therefore we consider

10o standard range of elevation.

The total force and also the forces for each

hand appear in the load node in the

specifications tree. The Load can be edit

anytime: In that case the total magnitude is

set to zero then the load node (with

description) is removed from the load node.

Additionally the Place mode Icon is

needed to move the manikin to a certain

reference point to any location in CATIA

workspace. In this case Both thigh places in

the bottom of seat to make a posture of

sitting.

4.7. CREATIE CONSTRAINT  

Constraint is needed to control the joint between body parts and other objects.

Constraints allow/disallow the degree of freedom of an object. Contact Constraints:

creates a constraint between a segment and a point, line, or plane. Coincidence

Constraint: represented by a line with two coincident circles, arc,

fillet those objects has its own center. It allows two or body parts

movement along the common axis and restricts to move in other axis. Fix Constraints

the unresolved constraint is visually represented by a line with a black square on each

end; one on the segment, one on the H point which makes a body parts fixed so that

other parts are assembled on this. Fix on Constraints: fix a body parts to

disallow movement/rotation in any plane. 

Figure : 18

Figure : 19

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4.8. POSTURE EDITOR:  

Posture Editor Feature’s figure -20 used to

place the relevant posture for sitting of

manikin. This tool bar provides very

precise position of our manikin acting on

each degree of freedom of every joint.

Click the icon then the

following dialog box will appear Figure -

20. We discussed before the necessary

segment creates three Major Posture for a

driver while driving. Based on the

requirement the movement over saggital

plane which are flexion/extension need to

arrange to make a posture so that it seems

like driver is holding the steering. Not only

for flexion/extension but also for

abduction/adduction for Arm, Clavicular,

Fore Arm and Fingers degree of freedom

value put to make the posture. Its note to

mentioned that in this case predefined

posture ‘Sit’ selected and modified for the

mankin of 95% ile Canadian Male.

We know that every segment of body parts has its own angular limitation. We can’t twist our head 360.

This angular limitation depends on certain posture also. For example: If a person in sitting position

then the thigh is constraint in bottom therefore thigh can be move only upward not in downward

because of constraint. In this project based on the drives sitting posture the maximum possible angular

limitation value implemented. To set the angular limitation of different segment of body parts in the

software click the icon (figure -21)

Figure : 20

Figure : 21

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For example: Body thigh angle is 86.437o

but lower value of -18o and upper value of

118o considered figure -22. Same way other

important segment Head, Arm, Forearm,

Finger, Clavicular, Full spine, Thigh, Leg,

Toe and Foot angular limitation value input

in the software.

But this way we can’t be sure that any

angular limitation of a body segment value

meet the design criteria or not. Therefore,

Angular limitation to Percentile conversion

is necessary. Also its need to mention that

inactive and constraint body segments

angular limitation as well as % conversion

is not required figure -23.

4.9. ANGULAR LIMITATIONS TO PERCENTAGE  SETTING 

This feature provides the change of any angular limitations of one or many degrees of freedom at once

according to the percentage choose by the user. The percentage value represents the desired portion of

population that must be able to reach the limit. If we consider 90% then it will meet the requirement of

all the population considered before the design. However some exception of 10% exists but it’s very

rare. In that case car manufacturer or dealer makes a special arrangement for that 10% ile population.

At manikin creation, all angular limitations are set to limits that 90% of the population can reach.

Using the Set Angular Limitations as a Percentage command, we may want to restrict these limits for a

specific requirement of the population study. To perform

Figure : 22

Figure : 23

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click the icon that will Select any segment of the manikin and then Hold down the Ctrl key of

keyboard to select more than one segment at a time.

Click on OK to confirm the modification

of press Cancel to cancel the action. By

clicking OK, both limits (min and max)

of all degrees of freedom selected for

different body parts of mankin converted

to percentile as shown in figure -24.

Degree of Freedom must be checked on

to perform the functions.

4.10. OBJECTS  ATTACHMENT WITH THE MANIKIN 

Ergonomics design and Analysis workbench provide the model of a mankin. Other important model is

also needed because mankin postures are directly related to that model.

In this project besides ergonomic model (mankin) most

important model is ‘Driving Chair’. ‘Steering wheel’ model

is also important. Based on the standard design both model is

designed for the project. To design Steering wheel and Chair

CATIA part design workbench is used. After finishing of the

two model its need to assemble with ergonomics workbench.

After the necessary models imported in Ergonomics Workbench we need to attach the model with

related segment of mankin. To perform this features Click the Attach/Detach icon and

then select the object to attach (in this case selection object - Bottom of

Figure : 24

Figure : 25

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Driving chair) and The body parts related

to that Object Figure – 26,28 (In this case

: Left Thigh). Left Thigh and Right Thigh

any one we can chose. Similarly Seat

Back is attached with Spine of mankin

Figure – 27,29.

Figure -30 Shows Total segments attach with main product.

4.11. MANIKIN REACH ENVELOP 

The feature of Manikin Reach Envelop functions provide to evaluate the manikin body segment reach

ability in 3D space using the manikin’s inverse kinematics capability (IK). It is also important to

determine how much a particular body segment can reach how far while driving since driver may need

to reach some object like: Adjusting Looking Mirror, Manipulate Car Radio or GPS etc. In this case

Figure : 30

Figure : 29

Figure : 26

Figure : 28

Figure : 27

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only hand reach ability is needed and considered for analysis and design. Since the project is based on

Canadian driver therefore right hand activity is more than left hand. Left hand only can be used to

adjust left window and Signal light in most case but those are very near compare to right hand. The

reach envelop surface is that represents all the Possible positions that the manikin can reach using only

the arm and forearm. the motion starts

at the shoulder which literal meaning known as

Clavicular. To perform this function click the

reach envelope icon Then, select any

position of the left/right hand, or any segment

that belongs to the desired hand. The surface that

represents the maximum reach limit is created

figure -31. In this case right hand selected.

Although there is movement of leg but that are

not considered because it has no activity other

than pressing Gas and Brake pedal.

4.12. INVERSE  KINEMATICS (IK) 

Inverse Kinematics is also important

because so far we can adjust each

body segment individually to get a

certain posture but in some cases

more than one body parts segment

adjustment is necessary to get a

posture. For example: grabbing

Figure : 31

Figure : 32

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Steering wheel - Finger, Wrist and hand segments are necessary at the same time. The IK feature

provides to manipulate the manikin to change behaviors of manikin in its environment. This

manipulation will eventually induce motion of several segments to translate and orient the manikin

towards the target to get a certain posture. To perform the IK Click or and adjust the

segments as requirement. After using IK - the result shown in figure-32. Its need to mention that two

modes of IK because of different icon come from the compass orientation on the specified segments

but both provides the same result.

5.  ERGONOMIC  ANALYSIS  

1) Open Vision Analysis. 2) RULA Analysis 3) Biomechanics Single Action Analysis

5.1. VISION ANALYSIS 

Vision analysis is needed to simulate the visual perception of an observer within a virtual illuminated

environment: vehicle Front, Interior, Reachable objects in dashboard. Vision analysis also provides

optical properties to all objects in the virtual scene define the emission of all sources involved and can

be simulate the global lighting environment for detecting glares, stray light, color washout, detection

threshold in order to improve safety and comfort.

Since the timeline constraint of

this project only drivers Vision

angle is considered to know

whether the designed mankind to

see in front of car over the steering

wheel. (Figure – 33)

To perform this function click the Figure : 33

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Vision icon from the Manikin

toolbar and then select a manikin,

Or double-click on the Manikin-

>Profiles->Vision node to get the

same results. Five different kinds

of vision analysis functions are

available in the software. 1.

Binocular 2. Ambinocular 3. Right

Monocular 4. Left Monocular 5.

Stereo. Based on the figure 34

The binocular functions used in this case. Other Important Parameter is Field of View. In this case

Horizontal monocular 100o Horizontal ambinocular 120o, Vertical top and Bottom 35o, Central 6o

selected. The full car model needed to analysis the vision to know whether the driver can see properly

over the dashboard.

5.2. RULA ANALYSIS: 

The RULA (Rapid Upper Limb Assessment) system was developed at the University of Nottingham's

Institute for Occupational Ergonomics. It was developed to investigate the exposure of individual

workers to risks associated with work-related upper limb disorders. (Ref: Lynn Mc Atamney and E.

Nigel Corlett, RULA: A Survey Method for the Investigation of Work-related Upper Limb Disorders).

To perform this analysis figure - 35 click the start menu,

select Ergonomic Design & Analysis then select Human

Activity Analysis. Total Nine parameters exist to perform

the RULA analysis and which can be customized.

In this project default value is taken but value of each parameter can be changed based on the design

requirement because each value of each parameter influences the result of the RULA analysis. Too see

the default value or customizing: - select Tools - > options then select options menu. Select Human

activity analysis bar from the left specification tree. Then RULA Parameters come in the window.

Figure : 35

Figure : 34

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5.2.1. SETTING ERGONOMIC ANALYSIS IN CATIA 

The different values for

these parameters which

define the threshold values

of different degrees of

freedom (Fig: 36 ). Select

the RULA Analysis icon

from the toolbar The

RULA analysis dialog box appears when the Manikin is selected. The dialog box figure -36 shows

the default value of Mankin certain posture. All the values are editable but default value is selected

because we carefully designed the posture for driving in static condition.

5.2.2. PERFORM RULA ANALYSIS  

SIDE: Select the side of the

manikin that will be analyzed.

For our analysis we select Right.

Side segment. (Fig-37)

PARAMETERS - Specify

settings that are not

automatically set.

SCORE - Displays the score

obtained by the analysis.

Figure : 36

Figure : 37

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5.2.3.1  POSTURE RELATED TO RULA ANALYSIS  

Three types of postures are defined in the software:

1. Static 2. Intermittent 3. Repeated

Since most of the time driver hold the steering wheel straight and only few instance driver steer the

wheel left or right which is very less than 4 times/min therefore; based on the situation in this project

for analysis we select static posture. Furthermore; We consider 2 Kg of total weight before.

Considering Factor of safety=2 total weight = 4 Kg. The Figure-37 shows that the final score which

implies “Investigate further and Change soon”. But if we look in figure ‘Details’ section that Writs

and Arm value is 5 and Muscle is 1(red) because of twisting and we can’t change these. Therefore; we

can say the RULA analysis result is accurate in this case and can be considered as perfect design. From

this analysis we did not consider that the arms are supported but in reality when a driver holds the

steering wheel the arms are partially supported.

The RULA method has presented a better sensibility to detect fast and urgent action levels. The REBA

(Rapid Entire Body Assessment) method does a fast evaluation of the whole body. While the RULA

(Rapid Upper Limb Assessment) method makes a fast evaluation of upper body member’s constraints.

To avoid or minimize the risks : both methods, through software or manually present postures

categorizations, having as an analysis result scores that represents the work's risks and indicate

possible actions for a certain posture.

Since the REBA score functions not available in software CATIA Therefore; in this project manually

REBA method used to identify and evaluation of driving posture of 95% ile male Canadian. Finally for

the design and force analysis of body and different segments RULA analysis taken. Figure -39 Shows

Manual REBA Assessment for driving posture in static condition. In terms of scoring and compare

with RULA we can see that REBA assessment for drivers posture is – Medium Risk, Further

investigation/or Change soon.

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6.0  REBA  ANALYSIS   

4 1

1

1

2

2

4

2

7

2

5

Driving Passenger Car 22 11 2009 Maruf Khondker

Figure : 38

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7.0  BIOMECHANICS  SINGLE ACTION  ANALYSIS 

Biomechanics Single Action Analysis used in this project to evaluate the design. The CATIA

ergonomic tool measures biomechanical data on a worker for a certain posture. The single action

analysis functions calculate lumbar spinal loads (abdominal pressure, abdominal force, and body

movements) and forces and moments on different body segment joints etc those are responsible for

different injury of driver. The forces acting on the manikin's hands and body weight taken into account

in the biomechanical analysis; these forces represent the load of carry, push, lift/ lower, or pull,

depending on the scenario.

To perform this operation click

In the Ergonomics Tools

toolbar, select the Biomechanics:

Single Action Analysis function

then in the specification tree

select a manikin for the analysis.

The Biomechanics Single Action

Analysis dialog box (Figure-39).

Each Tab consist details analysis

result. We can capture the result

of each Tab but because of

software limitation (Scroll bar)

multiple captures needed in each

tab. Therefore; Smart way is,

Export the data to a text file and

reorganize the result according to

the requirement. One of the

snapshots given in figure – 40.

Figure : 39

Figure : 40

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7.1  BIOMECHANICS  ANALYSIS  RESULT 

Table – 1 Result of SUMMARY DATA TAB ANALYSIS VALUE GROUND REACTION [N]

L4-L5 Moment 19 [Nxm] Total (X) 8 L4-L5 Compression 1081 [N] Total (Y) 0

Body Load Compression 442 [N] Total (Z) 821 Axial Twist Compression 30 [N] Left Foot (X) -25

Flex/Ext Compression 318 [N] Left Foot (Y) 0 L4-L5 Joint Shear 60 Posterior Left Foot (Z) -2471

Abdominal Force [N] 1 [N] Right Foot (X) 33 Abdominal Pressure 0 [N_m2] Right Foot (Y), (Z) 0, 3392

Table – 2 Result of JOINT MOMENT STRENGTH DATA TAB

JOINT DOF MOMENT [Nxm] % POP.NOT CAPABLE

MEAN [Nxm]

S.D [Nxm]

Right Wrist Flexion-Extension 1 Extention 0.1 8 2 Radial-Ulnar Deviation 0 0.0 18 5

Left Wrist Flexion-Extension 0 0.1 8 2 Radial-Ulnar Deviation 1 Ulnar Deviation 0.0 18 5

Right Elbow Flexion-Extension -4 Flexion 0.0 71 15 Supination-pronation 0 0.0 9 2

Left Elbow Flexion-Extension -4 Flexion 0.0 71 15 Supination-pronation 0 0.0 9 2

Right Shoulder Flexion-Extension -11 Flexion 0.0 69 14

Internal-external rotation 4 Abduction DNA DNA DNA 1 Ext. Rotation 0.2 27 9

Left Shoulder Flexion-Extension -12 Flexion 0.0 69 14

Internal-external rotation 1 Abduction DNA DNA DNA 2 Ext. Rotation 0.2 27 9

Lumbar (L4-L5) Flexion-Extension 19 Extension 0.0 369 69

Right-left lateral bend -15 Left Lateral Bend 0.0 148 40 -4 Left Twist 0.0 72 20

Table – 3 Result of SEGMENT POSITIONS TAB

Segments Proximal Coordinates [mm]

Distal Coordinates [mm]

XZ Plane Angle (deg)

YZ Plane Angle (deg)

Center of Gravity Coordinates [mm]

Length

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Table – 4 Result of REACTION FORCES AND MOMENTS

JOINT Axis Proximal Force [N]

Distal Force [N]

Proximal Moment [Nxm]

Distal Moment [Nxm]

Right Foot X -33 0 143 0 Y 0 0 -353 0 Z -3281 0 -1 0

Right Leg X -33 33 -6 -143 Y 0 0 -1495 353 Z -3243 3281 0 1

Right Thigh X -33 33 44 6 Y 0 0 -2899 1495 Z -3163 3243 0 0

Left Foot X 25 0 79 0 Y 0 0 279 0 Z 2482 0 -1 0

Left Leg X 25 -25 118 -79 Y 0 0 1159 -279 Z 2520 -2482 -1 1

Left Thigh X 25 -25 176 -118 Y 0 0 2276 -1159 Z 2600 -2520 -2 1

Right Hand X 4 0 0 0 Y 0 0 1 0 Z 14 0 0 0

Right Forearm

X 4 -4 0 0 Y 0 0 4 -1 Z 27 -14 0 0

Right Arm X 4 -4 -2 0 Y 0 0 11 -4 Z 49 -27 0 0

Left Hand X 4 0 0 0 Y 0 0 1 0 Z 14 0 0 0

Left Forearm X 4 -4 -1 0 Y 0 0 4 -1 Z 27 -14 0 0

Left Arm X 4 -4 3 1 Y 0 0 11 -4 Z 49 -27 0 0

Head-Neck X 0 0 -1 0 Y 0 0 1 0 Z 65 0 0 0

Pelvis X 8 -8 -25 15 Y 0 0 21 -19 Z 562 -448 0 0

Trunk X 8 -8 -15 -2 Y 0 0 19 -27 Z 448 -163 0 0

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8.    COMAPRING  ERGONOMIC  AND  NON  ERGONOMIC  BACK  SEAT  EFFECT  ON  TRUNK 

Figure – 41 shows an ergonomic design back seat

which has perfect posture of 95% male Canadian

Mankin. Figure – 42 Shows a flat non ergonomic

back seat. Comparing Both figures biomechanics

single action analysis result we found that :

• L4-L5 Moment of Ergonomic Design is ~

40% less than Non Ergonomic Design.

• L4-L5 Compression of Ergonomic Design is

~ 30% less than Non Ergonomic Design.

• Axial Twist Compression of Ergonomic

Design is ~ 30% less than Non Ergonomic

Design.

• Flexural Compression of Ergonomic Design

is ~ 40% less than Non Ergonomic Design. 

The above comparison shows ergonomic design back seat can reduce L4-L5 moment and compression

significantly than non ergonomic design. But here we consider only the back seat. If we consider an

ergonomic design of Seat Base (Page – 10 Section 4.4 – Figure -11) then the compression and moment

can reduce more. However; this design is based for 95% male but other short driver 5% female may not

have exact posture as 95% Male because of height. Therefore Seat back need to adjust to get a good

lumber support which is discussed next section (recommendation).

Figure : 41 Figure : 42

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 9.  SOME  RECOMMENDATIONS  OF  CORRECT  SITTING,  SEAT  DESIGN  AND  THE  DRIVERS  

DESIGN :

Back seat design was

perfect for 95% Male for

perfect lumber support. But

for 5% shorter Female

figure-43 Red mark area:

thoracic level no support.

That case driver has only

choice to adjust the head set.

If we can arrange the seat in

such a way so that Driver

can adjust the back seat Up-

Down figure-44 than we can

provide full lumber support.

As a result it can be access

by wide range of people.

DRIVER HABIT:

• Driver should have a good rest in the interval of driving to regain muscle strength.

• Driver should maintain neutral posture and incline the back seat as requirement so that muscle

should not feel stress all the time.

• When the pedals are fully pressed Driver should adjust spine back until to get contact with the

back of the seat.

• Drivers should adjust the seat in such way that knees are as less bent as possible.

• Driver should adjust the height of seat from floor so that he/she line of sight of eyes over the

steering wheel and have a perfect vision.

Figure : 43 Figure : 44

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SEAT FEATURES:

• All range of Driver should be able to adjust all features of seat with minimum bend and

twisting. Seating adjustable features should be simple in design and handy for driver.

• Head set length and width should be enough to support wide range of people and it can be

adjustable in two directions: Up and Down, Bending in the direction of drivers seating.

• Seat base material should not hard and should not very soft because hard material give

discomfort in thigh and hip and soft material resist muscle to supply enough blood.

• Select good seat base material so that it can not contain any moisture.

• Ensure that the side bolster of the seat should be close enough so that the body supported

comfortably without any pressure at any side.

• Ensure that seat base is not too short and not too long.

• Ensure that seat base little wider than hips and thigh and consider 95% ile male dimension.

• Seating adjustable feature should not exceed angular limitation of human body parts.

• Seat cushion and seat cover if used should be tight enough with seat base and seat back so that

it won’t affect drivers posture while driving.

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10.   DISCUSSION 

To design a passenger car vehicle seat : In terms of ergonomics and as an engineer we must have to

implement human factors and the seat should capable to fit for wide ranges of people with providing

comfort and safety. To meet the requirement of wide range of people proper adjustment of car seat

recommended. Considering the limitation of car space, in this project most important human posture

was analyzed to get a correct sitting and seat. To achieve this three types of analysis-RULA Analysis,

Biomechanics Single Action Analysis and Open Vision Analysis performed. At the end we found that

correct posture and ergonomic seat can reduced the moment and compression of driver significantly. As

a result the driver short term and long term injury can be reduced. Not only reducing injury but also

ergonomic design seat can relax the muscles in the back and also can reduce the stress in the spinal

column which has direct impact on drivers comfort. Furthermore; considering correct sitting

recommendation (Chapter –7) the drivers can reduce the risk of the ergonomic problems.

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11.   CONCLUSION 

During working throughout the project I got in-depth understanding and knowledge of different type

Ergonomics problem and their possible solution. This Project “Ergonomic Car Seat design and

Analysis” is one in of them. But after this project I am confident to execute any kind of ergonomics

related project. Apart from this, I tried my best to implement my ideas and knowledge what I learnt so

far into academic premises and also in real case. At the same time I also got a feeling of the challenges

behind the design and workspace requirement, limitation. Furthermore throughout the project I learned

a lot how to implement and solve ergonomic problem using professional software (CATIA).

Undoubtedly, this project has enhanced my capability to learn and implement it step by step to achieve

a target within a stipulated time line. Certainly this project would increase my level of confidence and

cast ample ray of light to the practical working world outside of the academic premises.

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12.  REFERENCES 

(1) Instructor Class Note and supplied Material: INDU 6411 Fall 2009 Concordia University.

(2) CATIA V5 Help File.

(3) Julian Happen-Smith – “An Introduction to Modern Vehicle Design Chapter 9 “

(4) R.S. Bridger “Introduction to Ergonomics, Third Edition”

(5) Karl Kroemer et al.Prentice Hall, “How to Design for Ergonomics and Efficiency”

(6) H-Point and D-Point in the Pelvis “The Initial Position and Postural Attitude of Vehicle

Operators. Raymond R. Brodeur, Yuntao Cui, Herbert M. Reynolds August 15, 1995

(7) Automobile seat comfort: occupant preferences vs. anthropometric accommodation the Modern

Motor Car.”Department of Industrial & Manufacturing Systems Engineering, University of

Windsor, Ont., Canada