iii VIBRATION INVESTIGATION OF PASSENGER CAR FRONT...

iii

VIBRATION INVESTIGATION OF PASSENGER CAR FRONT

SUSPENSION SYSTEM UNDER VARIOUS ROAD

CONDITION AND DRIVING MANEUVERS

TANTI ZANARIAH BINTI SHAMSHIR ALI

Report submitted in partial fulfillment of the requirements

for the award of the degree of

Bachelor of Mechanical Engineering with Automotive Engineering

Faculty of Mechanical Engineering

UNIVERSITI MALAYSIA PAHANG

DECEMBER 2010

iv

SUPERVISOR’S DECLARATION

We hereby declare that we have checked this thesis and in our opinion this project is

satisfactory in terms of scope and quality for the award of the degree of Bachelor

of Mechanical Engineering with Automotive Engineering.

Signature:

Name of Supervisor: PROFESSOR DR HJ ROSLI BIN ABU BAKAR

Position: DEAN OF FACULTY OF MECHANICAL ENGINEERING

Date: 6 DECEMBER 2010

Signature:

Name of Co-Supervisor: MR GAN LEONG MING

Position: LECTURER


v

STUDENT’S DECLARATION

I hereby declare that the work in this thesis is my own except for quotations and

summaries which have been duly acknowledged. The thesis has not been accepted for any

degree and is not concurrently submitted for award of other degree.

Signature:

Name: TANTI ZANARIAH BINTI SHAMSHIR ALI

ID Number: MH07041


vii

ACKNOWLEDGEMENTS

First of all, I would like to give my grateful to The Almighty, Allah SWT that give a

vision to finish up this project. I also would like to forward my endless gratitude to my

project supervisor, Professor Dr Hj Rosli Bin Abu Bakar, and my co-supervisor Mr Gan

Leong Ming for their supervision, germinal ideas, invaluable guidance, continuous

encouragement and constant support in making this research possible.

Sincere appreciation to my academic advisor, Dr. Md Mustafizur Rahman, for his

support and believe in me during my studies. Very special thanks to the staff and

colleagues in Universiti Malaysia Pahang that always support me with the ideas and

sometimes helping me with the problems that occurred during the project.

I acknowledge my heartfelt recognition to my family Shamshir Ali Bin Abdul Latif,

Norhayati Binti Abd Latif, Tanti Dzeffina Binti Shamshir Ali, Nazri Harris Bin Shamshir

Ali and Wan Asiah Binti Wan Jaafar and for their love, dream and sacrifice throughout

my life and also my siblings for their willingness to help me in this research.

Lastly, my fellow friends especially my group of the test car members, that support

me from the beginning till the end of the project. Thank you again and may Allah bless all

of you.

viii

ABSTRACT

This thesis has the purpose to show the investigation of excitation and vehicle body

movements acting on the two front wheel of the vehicle due to the road profile and driving

maneuvers based on the experiments. This project endeavor to prove the effect road profile

and speed on front suspension and car body movements based on centre of gravity can be

used as representative conditions for ride comfort. It is believed that the front suspension is

moving faster when the vehicle moves at high speed and due to the vehicle movements it

shows that the road surface are irregularity. The procedures constructed on gaining the data

on the front suspension linear motion and vehicle‟s centre of gravity performance in term

of movement. Different kind of road surface irregularity has been considered and dissimilar

driving maneuvers are identified. The study on the apparatus and instruments contributes in

understanding the capabilities of its behavior on going experiments. The test is performed

in Universiti Malaysia Pahang (UMP) and using UMP Test Car which has been installed

with accelerometers and wire potentiometer sensor on the front suspension, Global

Positioning System (GPS) and DEWESOFT software for data acquisition purpose. The

analysis was performed using Flexpro 7. Based on the graphs and explanations, comparison

between the road conditions due to the driving maneuvers and road variation are made.

Thus this study results is comfort ride at all conditions of roads tested except bumpy road

and the vehicle roll and yaw angle is high at roundabout road yet the pitch angle are

increased at the bumpy road due to driving behavior. Based on the analysis it can be

concluded that the front suspension and body of the vehicle are responsive towards the road

profile and driving maneuvers. Consequently, this study contribute in identified the ride

comfort on the track used for the optimization at other speeds. Lastly, this investigation that

been justified in this thesis is only applicable for vehicle passenger.

ix

ABSTRAK

Tesis ini bagi membuktikan kajian perkaitan eksitasi dan pergerakan kenderaan pada dua

roda hadapan kenderaan merujuk kepada jenis profil jalan dan juga cara pemanduan

berdasarkan eksperimen. Kajian ini bertujuan untuk membuktikan kesan perbezaan profil

jalan dan kelajuan kenderaan terhadap sistem suspensi di bahagian hadapan dan pergerakan

kenderaan berdasarkan pusat graviti kenderaan boleh dijadikan pengukuran keselesaan

memandu. Hal ini diyakini bahawa suspensi hadapan bergerak lebih laju pada saat

kenderaan bergerak dengan kelajuan tinggi dan kerana gerakan kenderaan ini menunjukkan

bahawa permukaan jalan yang tidak teratur. Penulisan ini menjelaskan prosedur yang

dibina bagi memperoleh data pergerakan linear suspensi hadapan kenderaan dan pergerakan

kenderaan daripada pusat graviti kenderaan. Kepelbagaian jenis permukaan jalan telah

dipertimbangkan dan cara pemanduan yang berlainan dikenalpasti. Walaupun demikian,

kajian yang dijalankan pada peralatan dan instrumen memberikan sumbangan dalam

memahami kemampuan perilaku pada eksperimen yang dijalankan di Universiti Malaysia

Pahang (UMP) dan data yang digunakan untuk analisis diperolehi menggunakan kereta

pandu uji UMP yang telah dipasang dengan alat pengesan kelajuan dan juga jarak, „Global

Positioning System‟ (GPS) dan perisian DEWESOFT untuk tujuan pengambilalihan

data. Analisis dilakukan dengan menggunakan Flexpro 7. Berdasarkan graf dan penjelasan,

perbandingan antara keadaan jalan dengan cara pemanduan dapat dilakukan. Demikian,

hasil kajian ini adalah keselesaan pada semua profil jalan yang diuji kecuali jalan

berbonggol dan sudut „roll‟ dan „yaw‟ kenderaan adalah tinggi di jalan bulatan manakala

sudut „pitch‟ adalah tinggi di berbonggol berdasarkan cara pemanduan. Berdasarkan

analisis dapat disimpulkan bahawa suspensi hadapan dan pergerakan kenderaan daripada

pusat graviti kenderaan adalah responsif terhadap jenis profil jalan dan juga cara

pemanduan. Kajian ini memberikan sumbangan dalam mengenalpasti kemudahan

memandu pada jalan yang digunakan untuk pengoptimuman pada kelajuan yang lain.

Namun, proses dan data yang telah dinyatakan di dalam penulisan ini hanya boleh

dilakukan dengan kenderaan penumpang.

x

TABLE OF CONTENTS

CHAPTER TITLE PAGE

TITLE PAGE

SUPERVISOR’S DECLARATION ii

STUDENT’S DECLARATION iii

DEDICATION iv

ACKNOWLEDGEMENT v

ABSTRACT vi

ABSTRAK vii

TABLE OF CONTENTS viii

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF SYMBOLS xvi

LIST OF ABBREVIATIONS xvii

CHAPTER 1 INTRODUCTION

1.1 Introduction 1

1.2 Problem Statement 2

1.3 Objectives 3

1.4 Work Scopes 3

1.5 Hypothesis 3

1.6 Flow Chart 4

CHAPTER 2 LITERATURE REVIEW

2.1 Suspension

2.1.1 Types of front suspensions

5

7

xi

2.1.2 Half car model 9

2.2 Vibration Diagnosis

2.2.1 Fast Fourier Transform

2.2.2 Source suspension noise and vibration

2.2.3 Effects suspension noise and vibration

11

14

16

19

CHAPTER 3 METHODOLOGY

3.1 Sensors and Transducers

3.1.1 Type of sensors

3.1.2 Installation of wire potentiometer

26

26

29

3.2 Design Testing Procedure

3.2.1 Purpose of SOP

3.2.2 Scope of SOP

3.2.3 Safety precaution

3.2.4 Experiment statement.

3.2.5 Testing procedures

33

33

33

35

35

36

3.3 Results and Analysis

3.3.1 DEWESoft

3.3.2 FlexPro 7

39

39

40

CHAPTER 4 RESULTS AND DISCUSSIONS

4.1 Variation of Time Response 42

4.2 Front Suspension Vibration Analysis

4.2.1 Road profile

4.2.2 Variation speed on one road

44

44

47

4.3 Car Body Analysis

4.3.1 Roll angle

4.3.1 Pitch angle

4.3.1 Yaw angle

55

55

58

60

4.4 Ride Quality and Comfort 63

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CHAPTER 5 CONCLUSION AND RECOMMENDATION

5.1 Conclusion 66

5.2 Recommendation 67

REFERENCES 68

APPENDICES

A Gantt Chart 72

B Specifications Accelerometer 75

C Specifications Wire Potentiometer 77

D Car Specifications 79

E Fourier Spectral Analysis „Spectrum‟ Properties 80

xiii

LIST OF TABLES

Table No. Title Page

2.1 Types of front suspension 7

2.2 Types of front suspension advantages and disadvantages 8

2.3 Classes of vibration 20

2.4 Approximation indications of acceptability based on the RMS

acceleration values

21

3.1 Types of testing 34

3.2 Types of roads 34

3.3 Maximum speed of gear 36

4.1 RMS acceleration on the various types of roads at different

speed.

65

xiv

LIST OF FIGURES

Figure Title Page

1.1 Flow Chart 4

2.1 MacPherson strut suspension 6

2.2 Spring-mass-damper system 9

2.3 Half-car model. 10

2.4 Stationary response of the suspension 13

2.5 Left spring displacement (blue) and right spring

displacement (red) versus time.

14

2.6 A square wave form and its Fourier spectrum. 15

2.7 Passenger plus driver weighted RMS vertical acceleration

for optimized suspension settings at different speeds over

various roads.

16

2.8 As a car turns a corner (b), centrifugal force causes weight

to transfer from the tires on the inside of the turn to the

outer tires.

17

2.9 As a car brakes, inertia will cause weight to transfer from

the rear tires to the front tires; transfers from the front to the

back during acceleration.

19

2.10 Direction of expose to vibration of a seated human. 20

2.11 Driver plus rear passenger seat ride comfort levels over

gravel highway with suspension setting at optimum,

baseline and 50 km/h measures paving optimum

22

2.12 Driver weighted RMS vertical acceleration for optimized

suspension settings at different speeds over a various roads.

22

2.13 Rear passenger weighted RMS acceleration for optimized

suspension settings at different speeds and the various

roads.

23

xv

2.14 Comparison of vibration characteristics with different

patterns of actuators.

24

2.15 Model validation results for a double lane change maneuver

at 65 km/h.

25

3.1 Kistler 8310B10 26

3.2 8310B standard version with a 4pin position connector. 27

3.3 2D wire potentiometer type SA-WP0760HQ-000. 29

3.4 (a) Mounted at the lower arm parallel and (b) mounted on

the car body parallel to the suspension.

30

3.5 Marking the location to be weld. 31

3.6 Bracket welded to the lower arm. 31

3.7 Calibration of right front displacement sensors. 32

3.8 Proton Persona Sedan 1.6 Manual Transmission (MT) Base

Line (UMP Test Car)

33

3.9 Cone placement for deceleration testing. 37

3.10 Cone placement for cornering testing. 38

3.11 Cone placement for bumpy testing. 39

4.1 Graph of Velocity versus Time during the acceleration test. 42

4.2 Graph of Velocity versus Time during the deceleration test. 43

4.3 Graph of Direction versus Time during the cornering test. 43

4.4 Graph of Velocity versus Time during the bumpy test. 44

4.5 Graph of Acceleration Right Front (RF) Suspension versus

Frequency at constant speed 40 km/h.

45

4.6 Graph of Acceleration Left Front (LF) Suspension versus


45

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4.7 Graph of Displacement Right Front (RF) Suspension versus


46


Frequency on the paved road.

47



48



48


Frequency on the unpaved road.

49



50



50


Frequency on the roundabout road.

51



52



52


Frequency on the bumpy road.

53



54

4.19 Graph of Deceleration Right Front (RF) Suspension versus


54

4.20 Graph of Roll versus Velocity during acceleration test. 56

4.21 Graph of Roll versus Velocity during deceleration test. 56

4.22 Graph of Roll versus Velocity during cornering test. 57

4.23 Graph of Roll versus Velocity during bumpy test. 57

xvii

4.24 Graph of Pitch versus Velocity during acceleration test. 58

4.25 Graph of Pitch versus Velocity during deceleration test. 59

4.26 Graph of Pitch versus Velocity during cornering test. 59

4.27 Graph of Pitch versus Velocity during bumpy test. 60

4.28 Graph of Yaw versus Velocity during acceleration test. 61

4.29 Graph of Yaw versus Velocity during deceleration test. 61

4.30 Graph of Yaw versus Velocity during cornering test. 62

4.31 Graph of Yaw versus Velocity during bumpy test. 62

4.32 Graph of RMS Acceleration Right Front (RF) Suspension

versus Velocity.

63

4.33 Graph of RMS Acceleration Left Front (LF) Suspension

versus Velocity.

64

xviii

LIST OF SYMBOLS

CF centrifugal force in N

CGH center of gravity height in mm

CR rate of acceleration/deceleration in N

centrifugal force in percentage of N

R radius of skid pad in feed mm

W car weight in kg

WB wheelbase in mm

WT lateral weight transfer in kg

T time to complete one lap in seconds

TW track width in mm

acceleration

velocity

aw weighted acceleration time history in m/s2

damping constant for constant, sprung and unsprung respectively

spring constant for constant, sprung and unsprung respectively

length for constant and sprung respectively

, mass for constant, sprung and unsprung respectively

displacement for road, sprung and unsprung respectively

velocity for road, sprung and unsprung respectively

acceleration for road, sprung and unsprung respectively

xix

LIST OF ABBREVIATIONS

2D 2 Dimension

AC Alternating Current

CAN Controller Area Network

CE Common Era

CG Center Of Gravity

CPT Cable Extension Transducer

DC Direct Current

DFT Discrete Fourier Transform

FFT Fast Fourier Transform

FWD Front Wheel Drive

GPS Global Positioning System

ISO International Organization for Standardization

LF Left Front

MT Manual Transmission

N&V Noise and Vibration

PSD Power Spectral Density

RF Right Front

RMS Root Mean Square

SLA Short Long Arm

SOP Standard Operating Procedure

UMP Universiti Malaysia Pahang

1

CHAPTER 1

INTRODUCTION

1.1 INTRODUCTION

The purpose of a vehicle is to transport people or cargo from one place to another.

Embedded in this purpose in doing so, it shall be as little disturbance as possible of who or

what is being carried. For passenger cars, where the cargo is human, the priority of the

suspension system is to provide the optimum environment for comfort of the occupants and

control by the driver. In addition, the suspension system is required to deliver this

performance over a range of load possibilities, from only the driver to a full load of several

occupants plus luggage.

Early years of suspension systems back then, the early wagons were known to have

used elastic wooden poles to reduce the affects of wheel shock. Leaf springs in one form or

another have been used since the Romans suspended a two wheeled vehicle called a

Pilentum on elastic wooden poles. After that, new inventor carriage designs included

rudimentary leaf suspension systems. All through the history, leaf springs would dominate

as the primary suspension design until quite recently (Staniforth, 2006). Leaf springs

presented the profit of simplicity in design and relatively economical cost. By merely

adding leaves or changing the shape of the spring, it could be made to support varying

weights. As a result, major changes primarily tended to revolved around the use of better-

quality materials and making improvement in design modifications.

2

Every vehicle nowadays is equipped with two pair of suspension at the wheels.

Suspension is a term which is specified for the system of springs, shock absorbers and

linkages that connects a vehicle to its wheels. The suspension system is located between the

axles and the vehicle body or frame. For safety purpose, stability, handling and

performance of a vehicle depend on many factors. One of the most important aspects of

these characteristics is the design of the suspension.

1.2 PROBLEM STATEMENT

Generally, automobile frame and the body can be supported by suspension. Besides

that the suspension mechanism is allowing the wheels to “soak up” wrong-doing on the

road surface. The consequence is the wheels will tend to stay in contact with the road, and

the passengers of the vehicle enjoy a ride that is protected from road shock. The suspension

system consists of two basic systems; front suspension and rear suspension. The design of

front and rear suspensions of an automotive may be different.

The front suspension need to focus on support the weight of the front end of the

vehicle, absorb road shocks and cushion the passengers and load against those shocks,

provide steering control and alignment and maintain steering control during severe braking.

Notionally, if a road were perfectly flat, with no abnormality, suspensions wouldn't be

necessary. Unfortunately, roads are far from flat. Without suspension, a motor vehicle

travelling at today‟s speeds would not only be uncomfortable, it would be virtually

uncontrollable. Suspension vibrations are noticed when vehicle speed changes, as when

starting out from a stop, passing, and slowing down or coasting. The perception of ride

quality is corrupted by virtually any disturbance experienced by the drivers or passengers.

Human sensitivity varies according to the nature of the disturbance. Therefore, a „good

ride‟ not just depends on the overall design of the vehicle, but also the design of the

suspension system. Even freshly paved highways have understated imperfections that can

interact with the wheels of a car. It's these imperfections that apply forces to the wheels

(Harrison, 2004).

3

Instead of carry the load from engine compartment, different road condition will

gives different outcomes for the front suspension system. The front suspension system was

designated to perform at certain range of vibration. Yet the drivers and passengers, certain

of them not only used the vehicle on the smooth road but then on the various kind of road

which sometimes the front suspension does not perform on that kind of road. Thus, the

project will investigate the meaning of normal front suspension system performance at

various conditions.

1.3 OBJECTIVES

The aim of this project is to investigate the effect of road profile on front suspension

system. In addition its objective is also to analyze the effect of front suspension system to

car body vibration based on different driving maneuvers.

1.4 WORK SCOPES

The project has to focus on few scopes in order to achieve the objectives:

(i) Literature review on suspension and vibration on the suspension.

(ii) Preparations on the procedures for installation on displacement sensor and

pre-testing.

(iii) Run the experiment based on the procedures.

(iv) Analysis the results gained on the front suspension relates to the road

conditions and body movement at centre of gravity.

(v) Discuss and conclude the project in a final report.

1.5 HYPOTHESIS

Hypothetically, vibration rises at certain speeds or changes in direct proportion to

vehicle speed increment as the road roughness increases. Hence the data obtained may be

consistent by taking into considerations of the influenced parameters.

4

1.6 FLOW CHART

Figure 1.1: Flow Chart

The process of flow chart is explained details in Appendix A.

End

Results & data

analysis

Start

Literature review

Installation sensors at the car

Design procedure for testing

Data collection of front suspension

Final report presentation

Testing on

different road and

driving maneuvers

Yes

Yes

No

No

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CHAPTER 2

LITERATURE REVIEW

2.1 SUSPENSION

For a road vehicle, the suspension system isolates the occupants or cargo from

severe levels of shock and vibration induced by the road surface. This isolation from road-

induced shock and vibration also improves the longevity and durability of the vehicle. Just

as importantly, the suspension system enables the wheels to maintain contact with the road,

assuring stability and control of the vehicle (Bastow et al, 2004).

The front suspension of a vehicle is designed so the steering knuckle and spindle

can pivot on the steering axis to allow steering of the vehicle. The spindle must also rise

and fall, relative to the body, to allow the springs and shock absorbers to reduce bump and

road shock from the vehicle‟s ride. The suspension system allows the springs and shock

absorbers to absorb the energy of the bump, so drivers and passengers can have smooth ride

(Birch, 1999).

While doing these two jobs, the suspension system must not allow loose,

uncontrolled movement of the tire and wheel and must keep the alignment of the tire as

correct as possible (Birch, 1999). Besides that, front suspension also acts to support the

weight of the front end of the vehicle, to provide steering control and wheel alignment and

to maintain steering control during severe braking (Crouse and Anglin, 1993). Figure 2.1

shows front suspension diagram.

http://www.google.com.my/search?tbs=bks:1&tbo=p&q=+inauthor:%22William+Harry+Crouse%22

http://www.google.com.my/search?tbs=bks:1&tbo=p&q=+inauthor:%22Donald+L.+Anglin%22

6

Figure 2.1: MacPherson strut suspension

Source: http://www.hondanews.com (5 July 2010)

http://www.hondanews.com/

7

2.1.1 Types of Front Suspensions

Table 2.1: Types of front suspension

Type of Suspension Descriptions

Solid Beam Axle:

The beam setup both of the front wheels are

connected to each other by a solid axle.

Source: http://www.carbibles.com

(21 July 2010)

Swing Axle:

The axles pivot about a location near the center

of the car and allow the wheels to travel up and

down through the respective arcs.

Source: http://www.corvaircorsa.com

(21 July 2010)

Trailing Link Suspension:

A set of arms located ahead of the wheels to

support the unsprung mass.


(21 July 2010)

MacPherson Strut:

Earle was the one whom patented the idea of

locating the lower end of an inclined strut

system tangentially with transverse link (or

track control arm) and longitudinally by means

of the lever arm of the anti-roll bar.


(21 July 2010)

Equal Length A-arm:

Referred to Double Wishbone suspension as the

A shaped control arms resemble a wishbone.

The suspension is supported by a triangulated

A-arm at the top and bottom knuckle.


(21 July 2010)

Unequal Length Double A-arm:

Implementing upper and lower A-arms of

different length.


(21 July 2010)

Source: Bastow et al (2004)

http://www.carbibles.com/

http://www.corvaircorsa.com/





8

Table 2.2: Types of front suspension advantages and disadvantages

Type of

Suspension Advantages Disadvantages

Solid Beam

Axle

Simplicity in manufacture and

assembly. Strength of the beam axle

is strong for large loads. Camber

control to avoid body roll since both

wheels are tied together.

Unsprung mass hinders the road

holding capability on rough

roads. High mass of the axle and

the wheels connected, not much

ride isolation between unsprung

and sprung mass.

Swing Axle

Simpler than short long arm (SLA)

setup. De-coupling the front wheels

and not mounting the chassis on a

solid beam, there is better ride

isolation.

Can create larger cornering

forces which could raise the car

caused back end lose traction

lead to vehicle losing controls.

Trailing

Link

Suspension

Improvement in ride quality and

road handling. Reduced size of the

suspension components and

reduction in chassis space necessary

to house it.

Tend to bend when significant

loads are subjected to the trailing

links. Control arms very heavy to

support the road loads

transmitted through the wheels.

MacPherson

Strut

Improve in ride quality and road

holding that and independent front

suspension. Extremely compact and

allows smaller chassis dimensions.

Suits for front wheel drive (FWD).

Difficult to increase the tire

width on the car. Very little

camber gain as the wheel moves

up In bump.

Equal

Length A-

arm

Further improvement in ride quality

and road holding. Uses solid, rigid

control arms to mount the knuckle to

the chassis which prevent

deflections during cornering.

No negative camber generates as

the wheel moves into bump

which results the car rolls.

Unequal

Length

Double A-

arm

Gain negative camber keeps the

wheel upright against the road

surface and allows the tire to

generate the maximum possible

cornering force and flexible.

Did not feature by vehicles that

price and space are more concern

than performance.

Source: Bastow et al (2004)

iii VIBRATION INVESTIGATION OF PASSENGER CAR FRONT...

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