development of an active bumper system to reduce vehicle...
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DEVELOPMENT OF AN ACTIVE BUMPER SYSTEM TO REDUCE VEHICLE
CRASH IMPACT
KHAIRUL AZRI BIN AZLAN
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
‘I/We approve that we have read this thesis thoroughly and in my/ our opinion, this
thesis is has fulfilled the criteria covering all the aspects of scope and quality and
satisfied to be awarded for Bachelor of Mechanical Engineering (Automotive).’
Signature :……………………
Supervisor I : Dr. Khisbullah Hudha
Date :...............................
Signature :……………………
Supervisor II : Mr. Mohd Zakaria Bin Mohammad Nasir
Date :...............................
DEVELOPMENT OF AN ACTIVE BUMPER SYSTEM TO REDUCE VEHICLE CRASH IMPACT
KHAIRUL AZRI BIN AZLAN
This report is written as a partial fulfillment of terms in achieving the award for
Bachelor of Mechanical Engineering (Automotive)
Faculty of Mechanical Engineering
Universiti Teknikal Malaysia Melaka
MAY 2009
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“I admit that this report is all written by myself except for the summary and the
article which I have stated the source for each of them.”
Signature :……………………
Writer : Khairul Azri Bin Azlan
Date :...............................
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To my beloved family and friends
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ACKNOWLEDGEMENT
First of all, I would like to thank Allah for giving me blessings to finish up
this project until it is completed. In this segment, I would like to give my
appreciation to all those peoples who were assisted me a lot in order to successfully
end up this project.
I would like to articulate my appreciation to my supervisors, Dr. Khisbullah
Hudha and Mr. Mohd Zakaria Bin Mohammad Nasir for trusting me to implement
this project, guiding me through and giving me all the relevant information and
knowledge regarding to this project. I also would like to forward my gratitude to Mr.
Nur Rashid, Mr. Alif Zulfakar, and Mr. Ubaidillah for giving me useful advices
during the realization of this project.
At last but not least, I would like to express my thanks to everyone especially
to all my beloved family and friends who give their support and contributing their
ideas at all time. Thanks for your kindness. May Allah give his blessing to all of you.
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ABSTRAK
Rekabentuk terbaru “Aktif Bamper” dalam projek ini ialah satu sistem
bamper yang menggunakan peredam magnetorheological (MR) untuk menyerap
daya impak ketika perlanggaran. Beberapa pengilang automotif telah pun
menggunakan sistem penyerapan kejutan yang menggunakan peredam pasif yang
dipasang diantara bamper dan casis kenderaan. Walau bagaimanapun, dengan
menggunakan system ini kebanyakan daya akan di serap melalui pemadatan peredam
dan daya berlebihan akan dipindahkan ke casis kenderaan. Sistem ini biasanya
mempunyai pekali peredam statik yang tinggi dan tidak mampu menyerap daya
perlanggaran berkelajuan tinggi. Di dalam projek ini kami cuba menggunakan
peredam MR yang membenarkan pekali redaman dinamik untuk meminimakan
impak perlanggaran dan mengurangkan pemindahan lebihan daya ke badan
kenderaan. Persamaan matematik, permodelan simulink dan kaedah ujian
perlanggaran kenderaan berskala kecil direka. Keputusan ujian simulasi akan
dianalisis untuk mengkaji potensi sistem aktif bamper.
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ABSTRACT
A new Active Bumper that was designed in this project is a bumper system
that uses magnetorheological (MR) dampers to absorb impact energy during
collision. Some of the automotive manufacturers already use shock absorption
system that consist passive damper located between the bumper and the vehicle
chassis. However, by using this system most of the force will be dissipate by
transmitting all the impact energy through the compression of the damper and the
remaining force will be transferred to the vehicle chassis. This system normally has
very high static damping coefficient and cannot dissipate higher speed collision
force. In this project, MR dampers were used to provide dynamic damping
coefficient and reduced the crash impact and lowering the transmission of the
remaining force to the vehicle body. Mathematical equations, Simulink model, and a
small scale vehicle crash test were designed. The simulation results were analyzed to
determine the potential benefits of the active bumper system.
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TABLE OF CONTENT
CHAPTER TITLE PAGES
DECLARATION
DEDICATION
ACKNOWLEDGEMENT
ABSTRAK
ABSTRACT
CONTENT
LIST OF TABLE
LIST OF FIGURE
LIST OF SYMBOL
LIST OF APPENDICES
CHAPTER 1 INTRODUCTION
1.1 Background Research
1.2 Problem Statement
1.3 Objectives and Scopes
CHAPTER 2 LITERATURE REVIEW
2.1 Active Safety System
2.2 Energy Management of Frontal Collisions
2.2.1 Crash Box
2.2.2 Bumper
2.3 Active Bumper System
CHAPTER 3 METHODOLOGY
3.1 PSM Flow Chart
3.2 Crash Test Method
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3.3 Frontal Collision Test Rig Design
3.4 Equation of Motion
3.4.1 Pendulum and Vehicle Mathematical
Modeling
3.4.2 MR Damper Mathematical Modeling
3.5 Control Strategy for Active Bumper System
3.5.1 Outer Loop Controller
3.5.2 Inner Loop Controller
CHAPTER 4 RESULT AND DISCUSSION
4.1 Result
4.1.1 Test Rig Design
4.1.2 Simulation
4.1.2.1 Light Collision
4.1.2.2 Medium Collision
4.1.2.3 Heavy Collision
4.2 Discussion
CHAPTER 5 CONCLUSION AND RECOMMENDATION
5.1 Conclusion
5.2 Recommendation
REFERENCES
APPENDICES
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LIST OF TABLES
NO. TITLES PAGES
1.1 General Road Accident Statistics and Fatality Index in Malaysia
(Source: www.miros.gov.my)
4.1 Table of Chassis Jerk for All Cases
4.2 Table of Chassis Acceleration for All Cases
4.3 Table of Chassis Speed for All Cases
4.4 Table of Bumper Speed for All Cases
4.5 Table of Relative Bumper-Chassis Speed for All Cases
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Road Accident and Death Cases in Malaysia. (Source:
www.miros.gov.my)
Safety When Driving on Roads. (Source: Bosch, 2006)
Folding Pattern in Quasi Static Test on (a) Bonded Crash Box (b)
Laser Welded Columns. (Source: Peroni et al., 2008)
The Falling Tower Used for the Impact Test (Left) and the
Details Of the Loading Rig (Right). (Source: Peroni et al., 2008)
Bumper System Types. (Source: Butler et al., 2002)
Exemplary Embodiment of a System for Active Control of a
Vehicle Bumper Damper Regarding to the Present Invention.
(Source: Buechele et al., 2004)
Second Exemplary Embodiment of a System for Active Control
of a Vehicle Bumper Damper Regarding to the Present
Invention. (Source: Buechele et al., 2004)
Third Exemplary Embodiment of a System for Active Control of
a Vehicle Bumper Damper Regarding to the Present Invention.
(Source: Buechele et al., 2004)
1.1
2.1
2.2
2.3
2.4
2.5
2.6
2.7
LIST OF FIGURE
NO. TITLES PAGES
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NO. TITLES PAGES
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2.8
2.9
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
3.10
3.11
Forth Exemplary Embodiment of a System for Active Control of
a Vehicle Bumper Damper Regarding to the Present Invention.
(Source: Buechele et al., 2004)
Flow Diagram of Method for Active Control for Vehicle Bumper
damper. (Source: Buechele et al., 2004)
PSM Flow Chart
Crash Test Concept
Fontal Collision Test Rig Assembly
Frontal Collision Test Rig Operation Method
Free Body Diagram of the Crash Test
Free Body Diagram of Vehicle Chassis and Bumper
Configuration of MR Impact Damper. (Source: D. Woo et Al.,
2007)
Hydraulic Model of MR Impact Damper. (Source: D. Woo et
Al., 2007)
Control Structure of an Active Bumper System
Skyhook Modeling
MR Damper Force Tracking Control
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NO. TITLES PAGES
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3.12
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
4.11
4.12
4.13
4.14
Force Tracking Graph of the MR Damper
Picture of (a) Small Scaled Car, (b) Pendulum Set
Complete Test Rig
Graph of Chassis Jerk vs. Time for Light Collision
Graph of Chassis Acceleration vs. Time for Light Collision
Graph of Chassis Speed vs. Time for Light Collision
Graph of Bumper Speed vs. Time for Light Collision
Graph of Relative Speed Bumper-Chassis vs. Time for Light
Collision
Graph of Chassis Jerk vs. Time for Medium Collision
Graph of Chassis Acceleration vs. Time for Medium Collision
Graph of Chassis Speed vs. Time for Medium Collision
Graph of Bumper Speed vs. Time for Medium Collision
Graph of Relative Speed Bumper-Chassis vs. Time for Medium
Collision
Graph of Chassis Jerk vs. Time for Heavy Collision
Graph of Chassis Acceleration vs. Time for Heavy Collision
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NO. TITLES PAGES
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4.15
4.16
4.17
Graph of Chassis Speed vs. Time for Heavy Collision
Graph of Bumper Speed vs. Time for Heavy Collision
Graph of Relative Speed Bumper-Chassis vs. Time for Heavy
Collision
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LIST OF SYMBOL
E = Energy, Nm
m = Mass, Kg
v = Velocity, m/s
e = Coefficient of Restitution
I = Impulse, kgm/s
F = Force, N
= Coefficient of Friction
g = Acceleration of Gravity, m/s2
K = Spring Stiffness, N/m
D = Damping Coefficient Ns/m
j
= Jerk, m/s3
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LIST OF APPENDICES
NO. TITLES PAGES
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A
B
C
Test Rig Drawing
Simulink Model
“Frontal Crash Mitigation Using MR Impact Damper for
Controllable Bumper” Journal of Intelligent Material Systems
and Structure. (Source: D. Woo et al., 2007)
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CHAPTER 1
INTRODUCTION
A road vehicle normally have bumper to absorb an impact from a low
velocity collision. Vehicles bumper are usually designed to withstand an impact of
collision at a relative velocity of 5 to 15 km/h without having major damage
(Buechele et al. 2004). Many conventional bumpers use a stationary impact
absorbing structure that is design to deform permanently in order to prevent
collateral damage to vehicle frame and car components.
A new Active Bumper is a system that reduces the crash impact by
configuring the magnetorheological (MR) dampers that that have been attached
between the car body and the front bumper. The MR dampers are semi-active control
devices that use magnetorheorogical fluid to produce controllable dampers. The
essential characteristic of controllable fluids is their ability to reversibly change from
a free-flowing, linear viscous fluid to a semi-solid with controllable yield strength in
milliseconds when exposed to an electric or magnetic field (Spencer et al. 1996).
When a collision occurs, the data acquisition device will send rapid signals to
the MR dampers controller. The dampers controller in the vehicle central processor
will then analyzing the data before sending appropriate control signal to the bumper
MR damper. The input of the MR dampers is in the form of electrical currents which
will be traveled through coils around the piston heads. This will cause an
electromagnetic field and will effect the MR fluid hence change the damping
coefficient suitably. All this will happen instantaneously during the collision to
reduce the impact force effect.
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1.1 Background Research
Automotive safety is intentionally to avoid vehicle accident or reducing the
effect of accident especially to the human body including the driver, passengers and
pedestrians. Moreover, some of the safety features are also purposely to reduce
vehicle damages in order to minimize the repairing cost.
Active safety in vehicle system uses the information of vehicle external
environment and the system will response accordingly to the situation during the
phase of pre-crash or during the crash event. This is will either avoid the crash from
happen or increase the safety of the vehicle by reducing the crash effect. Passive
safety in the other hand is a system that only works to prevent injury but not change
the vehicle action in response to crash scenario. The examples of the passive safety
are like airbag, crumple zone, seat belt and passive automotive bumper.
A metal or plastic shell that is filled with a foam energy absorbing block of
polypropylene or foam normally used in an automotive low-impact absorbing
bumper construction, and is mounted to the vehicle on a relatively rigid beam
(DePottey et al. 2004). The kinetic energy from the collision will be absorbed by the
foam energy absorbing material through the deformation of the bumper structure.
Many researches have been made regarding to the bumper deformation characteristic
and absorption capability. Usually the research is concentrating on the selection of
the bumper material like aluminum and composites.
In this project, the active bumper system is design to reduce the collision
impact to through the compression of the MR damper that have dynamic damping
coefficient. A vehicle frontal collision test rig was designed and a study on the
collision characteristic is conducted during this project. The test rig was designed to
conduct imitation of heavy, medium and light collision. A control structure was
developed for the active bumper to minimize the jerk on the vehicle chassis. This is
very important in order to avoid huge amount of impact force from transferring to the
passenger compartment hence will probably cause serious injury or fatality to the
vehicle occupants.
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1.2 Problem Statement
Vehicle accidents have become a serious problem in Malaysia and all other
country around the world. Every one of us has the probabilities to be involved in
road accident including the pedestrian. Statistic shows that the numbers of road
accident cases in Malaysia were increased every year in the last 11 years (refer Table
1.1 and Figure 1.2).
Table 1.1: General road accident statistics and fatality index in Malaysia.
(Source: www.miros.gov.my)
Number of Fatality Index
Year Vehicles Registered
Road Length (km) Accidents Death
Per 10,000
Vehicles
Per 100,000
Population
Per Billion VKT
1997 8,550,469 63,382 215,632 6,302 7.37 29.1 33.57 1998 9,141,357 63,382 211,037 5,740 6.28 25.3 28.75 1999 9,929,951 64,981 223,166 5,794 5.83 25.5 26.79 2000 10,589,804 64,981 250,417 6,035 5.7 26 26.25 2001 11,302,545 64,981 265,175 5,849 5.17 25.1 23.93 2002 12,068,144 64,981 279,237 5,887 4.88 25.3 22.71 2003 12,868,934 71,814 298,651 6,282 4.88 25.1 22.77 2004 13,801,297 71,814 326,815 6,228 4.51 24.3 21.1 2005 14,816,407 72,400 328,268 6,200 4.18 23.7 19.58 2006 15,790,732 72,400 341,252 6,287 3.98 23.6 18.69 2007 16,825,150 72,400 363,314 6,282 3.73 22.8 17.6
Figure 1.1: Road accident and death cases in Malaysia.
(Source: www.miros.gov.my)
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In order to reduce the vehicle crash impact that will prevent injury and
fatality, a lot of researches have been made to increase the crashworthiness of a
vehicle structures and bumper. Active bumper is design to assist the absorption of
impact energy through the compression of the MR damper that will reduce the
transmission of the impact energy to vehicle body hence reducing jerk. The use of
MR damper will allow the system to continuously vary the damping mode through a
specific range. This will overcome the disadvantages of the conventional passive
bumper damper.
1.3 Objectives and Scopes
The objectives of this project are as follows:
To develop the equation of motion for front to front crash of vehicle.
To develop the mechanism of an “Active Bumper System” using MR
damper.
The scopes of this project are as follows:
Simulation study on the potential benefits of an “Active Bumper System”.
Development of a small scale vehicle crash test methodology.
To design a frontal collision test rig.
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CHAPTER 2
LITERATURE REVIEW
Automotive safety has become major concern to the car manufacturers and
will always be a subject of interest to the research and development (R&D) centers.
Besides the improvement of drive train performance, safety is also plays an
important role in order to convince customers that the vehicles are safe enough to be
ride. This chapter consists of brief discussions regarding to current automotive safety
technology including any existing technology or on going research that related to
active safety system, energy management of frontal collision, active bumper system
and magnetorheological (MR) damper.
2.1 Active Safety System
There are many factors that affecting the automotive safety. Vehicle safety
can be categories into three main areas as follows (Seiffert and Wech 2007):
a) Accident avoidance – All measures that serve to prevent accident.
b) Mitigation of Injuries – All measures that help to reduce injury during
accident.
c) Pre-Crash measures – All measures to reduce the severity of an accident after
the sensor detect that that severe accident is unavoidable.
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Active safety is more on preventive action to avoid accident (Bosch 2006). The
examples of active vehicle safety system include ABS (Antilock Braking System),
TCS (Traction Control System) and ESP (Electronic Stability Program).
In the field of accident avoidance three main influences are found (Seiffert
and Wech 2007):
a) The human being
b) The technical features of a car
c) The environment
Figure 2.1: Safety when driving on roads
(Source: Bosch, 2006)
Active bumper system is also considered as an active system since it can
respond due to the vehicle external environment condition and can prevent excessive
damage to the vehicle frontal structure. The bumper is also has controller that
capable to receive data and send control signal to configure the bumper MR dampers.
Road safety
Environment Vehicle Human being
Active safety Operational respond Visibility Control
Passive safety
External safety Deformation behavior Exterior body shape
Internal safety Passenger cell equipment Restrain system Steering Column
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2.2 Energy Management of Frontal Collisions
The study on the energy management during frontal collision is very
important. In order to prevent serious injuries, many vehicles are using structural
features like crumple zone to absorb energy from an impact during head on collision
through the compression of the vehicle structures. However, excessive compression
and deformation of the vehicle body will probably affecting the passenger
compartment. Any compression or deformation that involving passenger
compartment may lead to serious injury to the vehicle occupant.
2.2.1 Crash Box
Many car manufacturers use crash box or thin wall as its front rail that can
absorb impact energy through the collapse of the crash box. The materials that used
as crash box are such as strength steel, aluminum alloy or composites.
Figure 2.2: Folding pattern in quasi static test on (a) bonded crash box (b) laser
welded columns
(Source: Peroni et al., 2008)