UNIVERSITI TEKNIKAL MALAYSIA MELAKA

IMPROVEMENT OF FRONT WHEEL STEERING SYSTEM

DUE TO SIDE WIND

This report is submitted in accordance with the requirement of the Universiti

Teknikal Malaysia Melaka (UTeM) for the Bachelor of Mechanical Engineering

Technology (Automotive Technology) with Honours

By

TAN SER CHOW

B071210546

920107-08-5983

FACULTY OF ENGINEERING TECHNOLOGY

2015

DECLARATION

I hereby, declare that this thesis entitled “Improvement of front wheel steering

system due to side wind” is the result of my own research except as cited in

references.

Signature : ……………………………………………

Name : ……………………………………………

Date : ……………………………………………

APPROVAL

This report is submitted to the Faculty of Engineering Technology of UTeM as one

of the requirements for the award of Bachelor’s Degree Mechanical Engineering

Technology (Automotive Technology) with Honours. The following are the

members of supervisory committee:

……………………………………………

(Supervisor)

……………………………………………

(Co-Supervisor)

i

ABSTRAK

Satu sistem bantuan pemandu yang dikenali sebagai stereng aktif dinilai semasa

menyimulasikan pelbagai jenis acara memandu. Sistem ini merupakan sistem yang

penting di dalam kenderaan itu. Tujuan utama sistem stereng adalah untuk

membolehkan pemandu mengawal kenderaan secara bebas. Sistem stereng

mengekalkan tayar dengan kenalan jalan. Model kenderaan kereta disimulasi oleh

MATLAB / Simulink dengan 14 DOF termasuk model memandu kenderaan dan juga

model pengendalian.

Sudut stereng adalah input model kenderaan yang harus diberi perhatian. Sudut

sistem stereng antara tayar apabila beralih kenderaan telah difokuskan. Simulasi

dibuat pada keadaan jalan yang berbeza dan juga kesan gangguan angin sampingan.

Nilai yang berbeza digunakan untuk simulasi untuk mengurangkan kesan peristiwa

memandu. Oleh itu, simulasi ini meningkatkan prestasi untuk sistem stereng ini.

Tujuan untuk kerja ini adalah untuk memahami dan meningkatkan respon kenderaan

dalam sistem stereng depan. Peristiwa memandu simulasi ini adalah perekatan jalan

dan sisi gangguan angin sampingan. Semasa pemprosesan simulasi tersebut,

bertambah baik stereng hadapan dapat diperolehi oleh kenderaan ini.

ii

ABSTRACT

A steering aid system called active steering is evaluated by simulating different kinds

of driving events. This system is an important system in the vehicle. The main

purpose of the steering system is to allow the driver control the vehicle

independently. The steering system maintains the tire to the road contact. A full car

vehicle model is simulated in MATLAB/Simulink with 14 DOF of equations which

include the drive vehicle model and also the handling model.

The steering angle is the input of the vehicle model that should be focused on. The

angle of the steering system between the tires when turning the vehicle is taken in

consideration. Simulations are made on different road conditions effect and also side

wind disturbances. Different values are applied to the simulation to reduce the effect

of the driving events. Therefore, these simulations results do provide a better

improvement to the steering system.

The aim for this work is to understand and improve the response of the vehicle in the

front steering system. Specific driving events in these simulations are the road

adhesions and lateral side wind disturbances. Improved front steering is obtained for

vehicle during the processing of the simulations.

iii

DEDICATION

To my beloved parents

Tan Chin Hwee and Teoh Giek Chew

Raise me to become who I am

iv

ACKNOWLEDGEMENT

I would like to express my gratitude to my supervisor, En. Hafiz bin Harun who

guides me through this project. He gave me a lot of advice, ideas and confidence to

complete this project. Besides, I would like to thank Faculty of Engineering

Technology of University Teknikal Malaysia Melaka (UTeM) for helping me in

preparing formal documentations and guidelines for my project report. Not to forget,

my families for their support and blessing.

v

TABLE OF CONTENTS

ABSTRAK ....................................................................................................................... i

ABSTRACT .................................................................................................................. ii

DEDICATION ............................................................................................................. iii

ACKNOWLEDGEMENT ........................................................................................... iv

TABLE OF CONTENTS ............................................................................................... v

LIST OF TABLES ...................................................................................................... vii

LIST OF FIGURES ................................................................................................... viii

LIST OF ABBREVATIONS, SYMBOLS AND NOMENCLATURES ...................... x

CHAPTER 1: INTRODUCTION ............................................................................... 1

1.1 Background .................................................................................................. 1

1.2 Problem Statement ....................................................................................... 2

1.3 Objectives .................................................................................................... 2

1.4 Scope of the study ........................................................................................ 2

CHAPTER 2: LITERATURE REVIEW ................................................................... 3

2.1 Introduction .................................................................................................. 3

2.2 Nonlinear Dynamics .................................................................................... 3

2.3 Dynamic Model & Tire Model .................................................................... 5

2.4 Suspension System in MATLAB ................................................................ 8

2.5 Vehicle Stability Control ........................................................................... 10

2.6 Active Front Steering System .................................................................... 12

2.7 Handling Vehicle ....................................................................................... 14

2.8 Four Wheel Steering System ..................................................................... 17

2.9 Turning Radius .......................................................................................... 18

2.10 Performance of Steering System................................................................ 20

2.11 Functionality of Active Front Steering System ......................................... 22

vi

CHAPTER 3: METHODOLOGY ............................................................................ 24

3.1 Process Flow Chart .................................................................................... 24

3.1.1 Formulation Equation ......................................................................... 25

3.1.2 Equation Blocks in MATLAB & Inserting Values ............................ 25

3.1.3 MATLAB/Simulink ........................................................................... 26

3.1.4 Result Graphs & Side Disturbances & Carsim .................................. 26

3.1.5 Summary ............................................................................................ 26

CHAPTER 4: Development of Full Vehicle Model ................................................. 27

4.1 Introduction ................................................................................................ 27

4.2 Modelling Assumption .............................................................................. 27

4.3 14 DOF system .......................................................................................... 28

4.4 Free Body Diagram .................................................................................... 29

4.5 14 DOF Equation ....................................................................................... 31

4.5.1 Vehicle Ride Model ............................................................................ 31

4.5.2 Vehicle Handling Model .................................................................... 34

4.6 Process Flow .............................................................................................. 37

CHAPTER 5: Discussion ........................................................................................... 52

5.1 Introduction ................................................................................................ 52

5.2 Stability Test .............................................................................................. 52

5.3 Validation Response of 14 DOF Vehicle Model with an Instrumented

Experimental Vehicle ........................................................................................... 53

5.3.1 Lateral Acceleration ........................................................................... 54

5.3.2 Longitudinal Acceleration .................................................................. 56

5.3.3 Yaw Control ....................................................................................... 59

CHAPTER 6: Conclusion .......................................................................................... 62

REFERENCES ........................................................................................................... 63

vii

LIST OF TABLES

Table 2.1: Fixed Parameters of Full Car Model ............................................................ 8

Table 2.2: Vehicle Parameters .................................................................................... 15

Table 2.3: Comparison for Two Wheel Steer and Four Wheel Steer ......................... 18

Table 2.4: Comparison of Four Wheels and Two Wheel Steering System ................ 19

Table 2.5: Application and Safety Function of Hardware and Users.......................... 22

Table 5.1: Data Lateral Acceleration versus Time ...................................................... 55

Table 5.2: Data Longitudinal Acceleration versus Time ............................................ 57

Table 5.3: Data Yaw versus Time ............................................................................... 60

viii

LIST OF FIGURES

Figure 2.1: Frequency Response Diagrams when the Forcing Frequency f is slowly

Increased and Decreased ................................................................................................ 4

Figure 2.2: Modular Architecture of Vehicle Model .................................................... 6

Figure 2.3: Modular Vehicle Model in MATLAB/Simulink ........................................ 7

Figure 2.4: Sprung Mass Displacement (ZCG) vs. Time in Simulink Model ................ 9

Figure 2.5: Sprung Mass Displacement (ZCG) vs. Time using Analytical solutions

(State Space)................................................................................................................... 9

Figure 2.6: Displacement vs Time for K=25000, C=4000 ......................................... 10

Figure 2.7: 7 DOF Complex Model, Dashed Line: Simplified Model ....................... 11

Figure 2.8: Schematic view of AFS system ................................................................ 12

Figure 2.9: (a) Steering Wheel Angle and Front Wheel Angle of Slalom Test; (b)

Pylon Markers of Slalom Test...................................................................................... 14

Figure 2.10: Simulated Lateral Acceleration .............................................................. 16

Figure 2.11: Simulated Roll Angle ............................................................................. 16

Figure 2.12: Designed CATIA Model ........................................................................ 17

Figure 2.13: Power Steering System as Part of the Vehicle’s Close Loop ................. 21

Figure 2.14: Slalom Ride (Cones Distance: 16m and Vehicle Velocity 50 kph) ....... 23

Figure 3.1: Flow Chart Part 1...................................................................................... 24

Figure 3.2: Flow Chart Part 2...................................................................................... 25

Figure 4.1: 14 DOF Full Vehicle Model ..................................................................... 29

Figure 4.2: Vehicle Handling Model .......................................................................... 30

Figure 4.3: Full Car Vehicle Model ............................................................................ 31

Figure 4.4: Launched Carsim Software ...................................................................... 37

Figure 4.5: Vehicle Configuration Sedan E-Class Model Selected ............................ 37

Figure 4.6: Procedure Crosswind Test Selected ......................................................... 38

Figure 4.7: Result 3 deg. Azimuth. Veth. Ref. Selected to Animate .......................... 38

Figure 4.8: Graph Steering Wheel Angle Selected ..................................................... 39

Figure 4.9: Graph Lateral Acceleration of CG’s Selected .......................................... 39

Figure 4.10: Graph Yaw Angle of Sprung Masses Selected....................................... 40

Figure 4.11: Graph Slip Angle Selected ..................................................................... 40

ix

Figure 4.12: Graph Longitudinal Acceleration of CG’s Selected ............................... 41

Figure 4.13: Graph Roll Angle of Sprung Masses Selected ....................................... 41

Figure 4.14: Run Math Model & Animated ................................................................ 42

Figure 4.15: Lateral Side Wind Tested ....................................................................... 42

Figure 4.16: Graph Yaw Angle Vs Time Plotted by Carsim ...................................... 43

Figure 4.17: Graph Lateral Acceleration Vs Time Plotted by Carsim........................ 43

Figure 4.18: Longitudinal Acceleration Vs Time Plotted by Carsim ......................... 44

Figure 4.19: Data Graph by WordPad ........................................................................ 44

Figure 4.20: Data Transferred to Microsoft Excel ...................................................... 45

Figure 4.21: Launched Matlab Software..................................................................... 45

Figure 4.22: Parameter of Vehicle Model E-Class ..................................................... 46

Figure 4.23: Parameter is transferred from Carsim .................................................... 46

Figure 4.24: Run the Simulation ................................................................................. 47

Figure 4.25: Graph Yaw Vs Time Plotted by Matlab ................................................ 47

Figure 4.26: Graph Lateral Acceleration Vs Time Plotted by Matlab ........................ 48

Figure 4.27: Graph Longitudinal Acceleration Vs Time Plotted by Matlab .............. 48

Figure 4.28: Data Compared for Validation Purpose ................................................. 49

Figure 4.29: Data Imported to Vehicle Model ............................................................ 49

Figure 4.30: Validation Graph of Yaw Vs Time ........................................................ 50

Figure 4.31: Validation Graph of Lateral Acceleration Vs Time ............................... 50

Figure 4.32: Validation Graph of Longitudinal Acceleration Vs Time ...................... 51

Figure 5.1 Validation of Lateral Acceleration Vs Time.............................................. 54

Figure 5.2: Validation of Longitudinal Acceleration Vs Time ................................... 56

Figure 5.3: Validation of Yaw Vs Time ..................................................................... 59

x

LIST OF ABBREVATIONS, SYMBOLS AND

NOMENCLATURES

AFS - Active Front Steering

CG - Centre Gravity

DOF - Degree of Freedom

HSRI - Human Services Research Institute

ISO - International Organization for Standardization

MATLAB - Matrix Laboratory

RPM - Rotation per Minute

RAM - Random Access Memory

ROM - Read-only Memory

SBW - Steer-by-Wire

VSC - Vehicle Stability Control

Ffl Suspension force at the front left corner

Zu,fl Front left unsprung masses displacement

Ffr Suspension force at the front right corner

Zu,rr Rear right unsprung masses displacement

Frl Suspension force at the rear left corner

Zu,rl Rear left unsprung masses displacement

Frr Suspension force at the rear right corner

u,fr Front right unsprung masses velocity

Ms Sprung mass weight u,fl Front left unsprung masses velociy

Sprung mass acceleration at the body centre of gravity

u,rr Rear right unsprung masses velocity

Fpfl; Fpfr; Fprl; Fprr

Pneumatic actuator forces at front left, front right, rear right corners, respectively.

u,rl Rear left unsprung masses velocity

xi

Ks,fl Front left suspension spring stiffness

a Distance between front of vehile and C.G. of sprung mass

Ks,fr Front right suspension spring stiffness

b Distance between rear of vehicle and C.G. of sprung mass

Ks,rr Rear right suspension spring stiffness

Pitch angle at body centre of gravity

Ks,rl Rear left suspension spring stiffness

Roll angle at body centre of gravity

Cs,fr Front right suspension damping

Zs,fl Front left sprung mass displacement

Cs,fl Front left suspension damping

Zs,fr Front right sprung mass displacement

Cs,rr Rear right suspension damping

Zs,rl Rear left sprung mass displacement

Cs,rl Rear left suspension damping

Zs,rl Rear left sprung mass displacement

Zu,fr Front right unsprung masses displacement

Zs,rr Rear right sprung mass displacement

Pitch rate at body

centre of gravity

u,fr Front right unsprung

masses acceleration

Zs Sprung mass

displacement at body

centre of gravity

u,fl Front left unsprung

masses acceleration

s Sprung mass velocity

at body centre of

gravity

u,rr Rear right unsprung

masses acceleration

Ks,f

(Ks,fl = Ks,fr)

Spring stiffness of front

suspension

u,rl Rear left unsprung

masses acceleration

Ks,r

(Ks,rl = Ks,rr)

Spring stiffness of rear

suspension

Zr,rl = Zr,fl =

Zr,rr = Zr,rl

Road profiles at front

left, front right, rear

right and rear left tires

respectively

Cs,f = Cs,fl =

Cs,fr)

Damping constant of

front suspension

Steering angle

xii

Cs,r = Cs,rl =

Cs,rr

Damping constant of

rear suspension

r Yaw rate

Pitch acceleration at

body centre of gravity

mt Total vehicle mass

Roll acceleration at

body centre of gravity

x and y Longitudinal and lateral

vehicle velocities

Ixx Roll axis moment of

inertia

f Front side slip angle

Iyy Pitch axis moment of

inertia

r Rear side slip angle

Wheel base of sprung

mass

f Distance between the

front tire to the body

centre

r Angular velocities of

the rear tires

r Distance between the

rear tire to the body

centre

f

Angular velocities of

the front tires

w

Wheel radius

z The moment of inertia

around the z-axis

c The height of the

sprung mass centre of

gravity to the ground

sx The moments of inertia

of the sprung mass

around the x-axes

sy The moment of inertia

of the sprung mass

around the y-axes

1

CHAPTER 1

INTRODUCTION

1.1 Background

In an age of advanced technology, automobile was a life’s necessities for

everyone. It also acts as a transportation to travel for a distance no matter a short or

long journey. Therefore, automobile had become more and more convenience

nowadays. In this competitive field, vehicle must be improved in comfort and safety.

By doing so, development of vehicles should be done to ensure new technology is

implanted into the driving system to enhance driver pleasure.

A vehicle consists of many systems to maintain each of the vehicle parts

function well. The steering system acts as one of the important system in the vehicle.

For commonly known, steering system used to drive the vehicle to different

directions which control by the driver alone. Then, the steering system also provided

the driver a road feel feedback when the vehicle drove through an uneven surface or

facing the wind disturbances. The main purpose of the steering system is to make

contact between the tire and the road surfaces. Therefore, concentrations were mainly

focus on the tire life of the vehicle to achieve better angle of the steering system.

Furthermore, the driver can turned their vehicle with minimum effort by the help of

the steering system which is not so easy to control.

In steering arrangement, the most comfortable position of the hand-operated

steering wheel is placed in front of the driver with the steering column that contained

universal joints. This was to allow the vehicle to deviate from a straight line.

Different kinds of vehicle consist of different kinds of arrangement.

2

1.2 Problem Statement

The problem in this project is the side wind disturbances. This problem could

contribute to vehicle stability. Therefore, this project focused on the improvement of

the front steering system. This study wills focused and highlighted these problems

that become challenges to complete the task. Therefore, simulations between the

Matlab model and Carsim actual model which both consists of 14 DOF equations are

made to improve the front steering system.

1.3 Objectives

The main objective of this project is to focus on the design and development of

mathematical equations, apply them to the MATLAB Simulink and make some

modification on controller design.

1.4 Scope of the study

Scopes of the study are listed as follows:

i) Identifying the effects of the vehicle riding.

ii) Developed mathematical equation with 14 Degree Of Freedom vehicle

model.

iii) Produce a Simulink diagram by using the MATLAB software and

compare with Carsim.

iv) Applied active front steering system in the front system and compare to

conventional system.

3

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

For further process of this research project, literature review made an

important key of it. Literature survey in various fields, such as active steering system,

steering control, handling, vehicle modelling and parameters estimation is carried out

to establish the state of the art.

2.2 Nonlinear Dynamics

First, the dynamic behaviour of a nonlinear seven degrees-of-freedom ground

vehicle model is examined. The nonlinearity occurs due to suspension dampers and

springs. The disturbances from the road are assumed to be sinusoid and the time

delay between the disturbances is also considered. Numerical results show that the

responses of the vehicle model could be chaotic. Using bifurcation phenomenon, the

chaotic motion is detected and confirmed with the Poincare’ maps. The results can be

applicable in dynamic design of a vehicle. [Hajikarami et al, 2009]

As we know, vehicle dynamics is concerned with controllability and stability

of an automobile. Therefore, it was suitable to be design as a ground vehicle. There

were a lot of mathematical models and equations for vehicle and the dynamic

response of them has been examined in large number of previous investigation. In

general, these models can be classified into three types which are the quarter car

model, half car model and also full car model.

4

Because of high nonlinearities of differential equations in the full car model,

the dynamic response of the system is studied numerically using the forth order

Runge-Kuntta algorithm provided by MATLAB.

The frequency responses diagrams are obtained by plotting the amplitude of

the oscillating system versus the frequency of the excitation. This are used to analyse

the dynamics of a system. Bifurcation is the phenomenon of sudden change in the

motion as a parameter is varied. Therefore, the parameter values at which they occur

are called bifurcation points. Poincare’ maps were one of the instruments to analyse

the dynamic system.

In the interval of 4.96< <5.47 Hz, there are two unstable regions caused by

the increasing in frequency, =3.08Hz as a huge jump and a small jump which was

=3.18Hz is observed from the figure 2.1. = 4.76 Hz and = 3.07 Hz is observed

for the decreasing frequency. Besides, 4.99< <5.41 Hz and 2.97< < 3.55 Hz was

the unstable region.

Figure 2.1: Frequency Response Diagrams when the Forcing Frequency f is slowly Increased and Decreased

5

As conclusion from the frequency response diagrams, the number of jumps

and unstable regions of the response were focused. The result of increasing

frequency is different from those for decreasing frequency. This was an ordinary

phenomenon for nonlinear problems but the phenomenon was not observed in the

study of two or four DOF vehicle model.

2.3 Dynamic Model & Tire Model

Most of reference models for chassis controls usually have low level degree of

freedom like a bicycle model. However, these models include some different value in

real vehicle motion and have a difficulty to adapt new technology. In addition, it is

not good for real time that very high degree of freedom like multi-body dynamic

analysis programs because of their long solving time. So, I developed adaptive full

vehicle dynamic model that has 14 degree of freedom with theoretical equations and

experimental data. [Lee et al, 2008]

This paper studies the technology for a thesis of a vehicle dynamics model

based on a full car model with 14 DOF (Degree of Freedom). MATLAB was done

on the 14 DOF full vehicle models which consist of horizontal direction and vertical

direction. 14 DOF model consider of whole direction of the full car vehicle model.

The time used in this software was less compared to commercial program. Therefore,

a more accurate result can be obtained.

The degree of freedom for a full vehicle model consists of 3 horizontal, 7

vertical, and 4 tire model. The procedure and steps were arranged in the modular

architecture of vehicle model. First, the tire model (wheel rotations) has the

longitudinal force at each wheel which relate with the vertical dynamic (vertical,

pitching, rolling motions) and horizontal dynamic (longitudinal/lateral, yawing,

steering motions). The driver model had a steering wheel angle and acceleration and

deceleration torque to the tire model. With this modular vehicle model, clearer

procedure and process can be followed.

6

Figure 2.2: Modular Architecture of Vehicle Model

7

Figure 2.3: Modular Vehicle Model in MATLAB/Simulink

As conclusion, the result of 14 DOF model shows the accuracy of lateral

acceleration and yaw rate in single lane change. This model has difference of 17%

error in roll angle. Therefore, an accuracy of 85-98% is obtained according to the

results. From this simulation, one of the errors that were not reflected on the vehicle

model is the road conditions. By considering effect of suspension's kinematics and

compliance, a more accurate model can be achieved with a better road conditions.

8

2.4 Suspension System in MATLAB

Suspension system design is a challenging task for the automobile designers in

view of multiple control parameters, complex objectives and stochastic disturbances.

For vehicle, it is always challenging to maintain simultaneously a high standard of

ride comfort, vehicle handling under all driving conditions. The objective of this

paper is to develop a MATLAB/SIMULINK model of a full car to analyse the ride

comfort and matrix are to be developed and validation of Simulink model with

analytical solution of state space matrix is to be done elaborately on this paper.

[Mitra et al, 2008]

In this research, mathematical modelling was taken in measure using seven

degree of freedom model of the full car for passive system. There were mathematical

equation formed which include sprung mass and also unsprung mass of a full model

vehicle. Next, the equation was tested with MATLAB/SIMULINK to obtain the

result from the graphs. From the result obtained, vehicle body acceleration was high

at velocity of 10kmph. Therefore, the effect of bump of same amplitude had no effect

on pitch angle and roll angle of the vehicle.

The fixed parameters mentioned in various research papers are taken for the

simulation study. Suspension spring stiffness were considering 55000 N/m, 25000

N/m and damping coefficient 4000 N-s/m, 1000 N-s/m respectively. The

combination of stiffness and damping coefficient were studied in simulation.

Table 2.1: Fixed Parameters of Full Car Model

Ms = 1200Kg Kwr1 = Kwl1 = 30000 N/m a = b = 1.5 m Mwr1 = Mwl1

= 60Kg Kwr2 = Kwl2 = 30000 N/m C = d = 1m Mwr2 = Mwl2 = 60Kg Ixx = 4000 Kg-m2 Iyy = 950 Kg-m2

9

Figure 2.4: Sprung Mass Displacement (ZCG) vs. Time in Simulink Model

Figure 2.5: Sprung Mass Displacement (ZCG) vs. Time using Analytical solutions (State Space)

This validated simulation model was ride comfort and road holding for

different standard road profiles. As results, the speed range of 5 to 10kmph must be

an optimum speed to cross the bump without affecting the Human tolerance zone of

0.315 m/s2 to 0.625 m/s2 as per ISO standard. There was no effect on pitch angle and

roll angle when crossing the bump. The damping coefficient as 25000 N/m and 4000

N-s/m in the result of stiffness may provide better comfort to the driver. MATLAB

simulation was done as shown on both of the graph above. The maximum amplitude

for both graph is approximately 0.38.