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
Date: 6 DECEMBER 2010
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
Date: 6 DECEMBER 2010
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
xii
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
Frequency at constant speed 40 km/h.
45
xvi
4.7 Graph of Displacement Right Front (RF) Suspension versus
Frequency at constant speed 40 km/h.
46
4.8 Graph of Acceleration Right Front (RF) Suspension versus
Frequency on the paved road.
47
4.9 Graph of Acceleration Left Front (LF) Suspension versus
Frequency on the paved road.
48
4.10 Graph of Displacement Right Front (RF) Suspension versus
Frequency on the paved road.
48
4.11 Graph of Acceleration Right Front (RF) Suspension versus
Frequency on the unpaved road.
49
4.12 Graph of Acceleration Left Front (LF) Suspension versus
Frequency on the unpaved road.
50
4.13 Graph of Displacement Right Front (RF) Suspension versus
Frequency on the unpaved road.
50
4.14 Graph of Acceleration Right Front (RF) Suspension versus
Frequency on the roundabout road.
51
4.15 Graph of Acceleration Left Front (LF) Suspension versus
Frequency on the roundabout road.
52
4.16 Graph of Displacement Right Front (RF) Suspension versus
Frequency on the roundabout road.
52
4.17 Graph of Acceleration Right Front (RF) Suspension versus
Frequency on the bumpy road.
53
4.18 Graph of Acceleration Left Front (LF) Suspension versus
Frequency on the bumpy road.
54
4.19 Graph of Deceleration Right Front (RF) Suspension versus
Frequency on the bumpy road.
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
5
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.
6
Figure 2.1: MacPherson strut suspension
Source: http://www.hondanews.com (5 July 2010)
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.
Source: http://www.carbibles.com
(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.
Source: http://www.carbibles.com
(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.
Source: http://www.carbibles.com
(21 July 2010)
Unequal Length Double A-arm:
Implementing upper and lower A-arms of
different length.
Source: http://www.carbibles.com
(21 July 2010)
Source: Bastow et al (2004)
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)