Hill assist control report

Hill assist is an automatic system that operates brakes to stop rolling back when it is starting on steep hill. When hill assist system senses vehicle is starting from rest on slope, it automatically keeps footbrake even after you release the pedal by accelerated vehicle using parking brake /hand brake. The hill start assist control helps to increase
control on steep grades and prevents from locking. In this hill stop mechanism is also
described to prevent car from rolling back. Another Function is Hill Hold function
which is a highly desirable feature in manual transmission vehicles; it also enhances
the driving experience in automatic transmission vehicles equipped with hybrid
powertrains. The Hill Hold feature supports the Stop and Go performance associated
by holding the vehicle on an incline and preventing undesired motion.
Keywords: Hill

1. A Seminar Report on

“STUDY OF HILL ASSIST CONTROL
FEATURE USED IN DRIVING VEHICLE
ON STEEP GRADE”

By

Ekbote Amey Deepak

T121020876

Guided by


Mr. Y. D. Sonawane






Sinhgad Technical Education Society’s

R.M.D. Sinhgad School of Engineering, Warje, Pune
Department of Mechanical Engineering
Savitribai Phule Pune University, Pune.
[2016-17]

2. Sinhgad Technical Education Society’s
R.M.D. Sinhgad School of Engineering, Warje, Pune






C E R T I F I C A T E


This is to certify that Ekbote Amey Deepak [T121020876 ] has successfully completed the Seminar
entitled “Study of hill assist control feature used in driving vehicle on steep grade” under my
supervision, in the partial fulfillment of Bachelor of Engineering – Mechanical Engineering, of
Savitribai Phule Pune University, Pune.

Date :
Place :




Mr. Y . D. Sonawane Dr. M. V. Nagarhalli
Guide Head of the Department
Mechanical Engineering







External Examiner Dr. C. B. Bangal
Principal


Seal

3. i

Acknowledgement

Every orientation work has imprint of many people and this work is no
different. This work gives me an opportunity to express deep gratitude for the same.
While preparing seminar report received endless help from number of people
this report would be incomplete if I don’t convey my sincere thanks to all those who
were in involved.
First and foremost I would like to thank my respected guide Mr. Y. D.
Sonawane and H.O.D. Dr. M. V. Nagarhalli for giving me an opportunity to present
this seminar and his indispensable support, priceless suggestions and valuable time.
Last but not least I wish to thank my friends and my family for being supportive of
me, without whom this seminar would not have seen the light of day. Every work is
an outcome of full proof planning, continuous hard work and organized effort. This
work is combination of all the three put together sincerely.


Amey Deepak Ekbote
(Third Year Mechanical Engineering)

4. ii

LIST OF FIGURES

Fig No Title Page No
1. Hill start assist control 8
2. Hill assist control Vs without HAC 9
3. Full electric brake system 11
4. Force Analysis of vehicle on inclined plane 14
5. Driving conditions with DAC and without DAC 15

5. iii

NOMENCLATURE

Symbol Meaning
(Full form of Abbreviation)
HAC Hill Assist Control
DAC Down –Hill Assist Control
VECU Electronic Control Unit
ABS Antilock Braking System

6. iv



CONTENTS

Sr. No Title Page No.

Acknowledgement i
List of Figures ii
Nomenclature iii
Contents iv
Abstract v
1. Introduction 1
1.1 Objectives 1
1.2 Scope 1
1.3 History
1.4 Methodology
2
4
2. Literature Review 6
3. Hill Start Assist Control
3.1 Hill Start Components
3.2 Hill Start Assist working
7
7
8
4. Hill Hold Control 10











5.
4.1 Hill Hold Components
4.2 Brake System Used in Hill
Hold Control
4.3Hill Hold Control Working
4.4 Slope Calculations
4.5 Other Hill Holding Devices
4.6 Comparison with HAC and
Without HAC
4.7 Advantages
4.8 Disadvantages
4.9 Applications
Conclusion
References
10
11

11
14
14
15

16
16
16
18

7. v


Abstract

The objective of this topic is to study hill assist control used in vehicles. Hill
assist is an automatic system that operates brakes to stop rolling back when it is
starting on steep hill. When hill assist system senses vehicle is starting from rest on
slope, it automatically keeps footbrake even after you release the pedal by accelerated
vehicle using parking brake /hand brake. The hill start assist control helps to increase
control on steep grades and prevents from locking. In this hill stop mechanism is also
described to prevent car from rolling back. Another Function is Hill Hold function
which is a highly desirable feature in manual transmission vehicles; it also enhances
the driving experience in automatic transmission vehicles equipped with hybrid
powertrains. The Hill Hold feature supports the Stop and Go performance associated
by holding the vehicle on an incline and preventing undesired motion.

Keywords: Hill Assist Control, Hill start assist control, hill hold control

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1. Introduction
In Cars there has been development in technology in last few decades. Day by day
numbers of vehicles are increasing. The major cause is while driving vehicle on off roads
or terrain roads is accident. Many times breakdown of vehicles takes place on hill roads
while driving. So hill assist control is technology which helps in driving vehicle on hill
roads safely. It helps vehicle to stop rolling back from its position.
Hill-Start Assist Control (HAC) is the new mechatronic technology as a safety features
that detect the backward motion of the vehicle on hill or slope, that electronically controls
and increases brake pressure at each wheel.
Downhill Assist Control (DAC) automatically controls the brakes to maintain a constant
low speed when descending slopes, helping reduce wheel lock and keeps good traction to
maintain vehicle control.

A typical problem that is encountered by motor vehicle when they and themselves
stopped on an incline and want to begin moving again, is that the vehicle begins to roll in
the unwanted direction when the brake pedal is released. So hill assist control is new
feature which helps in starting vehicle smoothly and helps to stop rolling back on inclined
roads.

1.1 Objectives
The main objective of this topic is to study :
 To prevent car rolling back on slope roads
 To start vehicle smoothly on slope roads
 To have control on speed

1.2 Scope
This system can be implemented in modern cars with manual transmission and automatic
transmission. By
devising a mechanism of this sort we could make driving more easier.
It is
the new mechatronic technology in brake control system as a safety feature & improves
their off-road capability.

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1.3 History:
An object of the invention is therefore to provide a method for facilitating hill-starting
of a stationary motor vehicle in as simple and intuitive way as possible, and also a device for
implementing the method of the invention. the . In at least one embodiment, the method
comprises (includes, but is not necessarily limited to) applying at least one braking device
using a brake pedal.
A control unit is used to estimate the traveling resistance of the vehicle, as well as
determine a starting gear, a minimum engine torque and a minimum engine speed in order to
overcome the estimated traveling resistance. The driver lets the brake pedal up completely
and the control unit keeps the braking device applied so that the vehicle remains stationary.
The driver operates an accelerator pedal to a position at least corresponding to the
minimum engine speed. A clutch device for the gearbox of the vehicle is activated by the
control unit .When the engine speed has reached the above mentioned minimum engine
speed. The control unit releases the braking device in parallel with the clutch device being
Coupled together so that the brake torque of the braking device decreases as a function of the
increase in the engine torque transmitted by the clutch device. In this connection, it is
important that the braking device be fully released when the driving torque is sufficient to
hold the vehicle stationary on the concerned uphill slope. The vehicle can then be started
without rolling backward at the same time as the brakes are not kept applied for an unnec -
essarily long time.
“Traveling resistance” means primarily the force which has to be overcome by the
engine torque transmitted by the clutch in order for the vehicle to start to roll forward. This
depends mainly on the total Weight of the vehicle and the gradient of the road. In this
connection, it is also important that the control unit maintains the brake pressure only if there
is a risk of the vehicle rolling in the Wrong direction. If the traveling resistance indicates that
the vehicle is standing on a hill road or on a downhill slope, the control unit does not
maintain the brake pressure and start-up takes place in the usual Way. The hill start function
itself is therefore activated only if the vehicle is on an uphill slope. Control unit” preferably
means an electronic control unit that is used for controlling the transmission of the vehicle
and which can (optionally, via other control units arranged in the vehicle) control functions
such as the application of the service brakes.
The control unit preferably first determines a suitable starting gear and then a minimum
engine torque and also a minimum engine speed in order to overcome the estimated Traveling

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resistance. It is of course possible, however, to determine torque and speed first, and then a
suitable starting gear. This can be done by calculating the torque for each Gear and selecting
the lowest gear that satisfies the minimum starting torque requirement.
One advantage of the above method is that the procedure makes it possible that the
control unit does not have to apply the clutch, in spite of the brake pedal being let up and the
Accelerator pedal operated, if the accelerator pedal position and the engine speed are not
sufficient to start the vehicle. Owing to the fact that the clutch is completely disengaged, the
increase in engine speed and turbo pressure can take place more rapidly than if the clutch is
partly coupled together. These advantages mean both increased starting rapidity and reduced
clutch Wear. The procedure is not possible without external application of the service brakes.
Having the brakes applied by a mechanical or electronic arrangement which is not controlled
directly by the driver is usually referred to as “external application”. According to an
alternative embodiment of the invention, the control unit can, in the event of difficulties in
estimating exactly the vehicle Weight and the road gradient, adjust the time of full release of
the braking device, for example in such a Way that the release of the brakes is shifted forward
in time in relation to the calculated balanced position so that the risk of rolling in the Wrong
direction is prioritized ahead of the risk of braking for too long. According to another
advantageous embodiment of the invention, the control unit can, in the event of difficulties in
estimating exactly the vehicle Weight and the road gradient, register the direction of rotation
on one of the rotational speed sensors which register the speed of the vehicle.
The information about the direction of rotation can be used in order to determine Whether the
external application of the service brakes is to be extended or shortened according to
the following steps: (i) the hill start function has been activated as above and the control unit
gradually releases the braking device in parallel With the clutch device gradually
Being engaged, (ii) if the vehicle rolls in the correct direction before the braking device is
fully released, the control unit releases the braking device immediately, and (interconnect
tion) if the vehicle rolls in the Wrong direction before the braking device is fully released, the
control unit extends or increases the external application in order to prevent movement of the
vehicle in the Wrong direction.
By means of the above steps, unnecessary application of the brakes during driving is
avoided at the same time as is movement of the vehicle prevented in the Wrong direction.
This reduces clutch loading, brake loading and the distance the vehicle rolls in the Wrong
direction. According to one advantageous embodiment, the method also comprises the

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following steps which apply if the driver does not operate the accelerator pedal sufficiently:
(i) the hill start function has been activated as above, (ii) the driver lets up the brake pedal
completely, (iii) the driver operates the accelerator pedal but not sufficiently to correspond to
said minimum engine torque and minimum engine speed required in order to activate the
clutch, (iv) the control unit maintains the brake pressure and the car remains stationary,
and (v) the intuitive reaction of the driver is to apply more pressure to the accelerator pedal,
the pedal finally reaching the position which corresponds to said minimum engine torque and
minimum engine speed, the clutch then being activated, and it being possible for the vehicle
to be set in motion according to the method above. In another embodiment, the method also
comprises the following steps in order to prevent the system being used as a parking brake:
(i) the hill start function has been activated as above, (ii) the driver lets the brake pedal up
completely, (iii) the driver does not operate the accelerator pedal, (iv) the control unit keeps
the braking device applied With unchanged brake force for a predetermined time period, and
(v) after this first time period, the control unit Will release the braking device gradually over
a second predetermined time period. The above takes place automatically without
intervention by the driver insofar as the latter does not interrupt the process by reapplying the
braking device using the brake pedal.
According to another advantageous embodiment, the control unit limits the speed of
the engine to a given speed which is a function of the accelerator pedal position When the
Driver has released the brake pedal and operates the accelerator pedal. This function allows
the driver to hold the accelerator pedal fully depressed without the engine speed racing.
According to another embodiment, the control unit informs the driver that the hill start
function is activated by means of, for example, a Warning lamp in the instrumentation of the
vehicle. The driver then knows that he has plenty of time to move the foot from the brake
pedal to the accelerator pedal and that the control unit Will regulate the brake pressure so that
starting can take place Without rolling backward irrespective of how rapidly the driver elects
to operate the accelerator pedal. This takes place on condition that the driver operates the
accelerator pedal within the abovementioned time period so that the function which prevents
the system being used as a parking brake does not start to operate.

1.4 Methodology
The hill-start is very important for the cars. The vehicle will move backward, start with
jerk, or cause engine stalling if failed on the slope road. For the manual transmission, the hill-

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start depends on the driver's skilled driving technology to coordinate the brake pedal, the
clutch pedal and the throttle pedal to achieve a smooth start.

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2. Literature Review
Mohammad Tamimi et al [2] investigated that while driving vehicle on Hill a typical
problem that is encountered by drivers of vehicles with manual transmissions is rollback on
an incline. This occurs when the driver is trying to coordinate the release of the brake
pedal with the release of the clutch pedal and application of the accelerator all at the same
time.
Jiang Xuefeng [3] carried out experiment on starting and stopping vehicle on inclined
road. The vehicle will start with jerk if it fails on inclined road. Therefore it is necessary to
have a system like hill assist control.
Cook George [4] suggested a hill holder mechanism holds the vehicle in slope for 2
seconds by using the brake pressure. A device operable in a transmission of a vehicle for
substantially preventing vehicular rollback on an incline, comprising: a shaft rotatable which
is supported in transmission housing; a gear selectively connected for common rotation with
the shaft, wherein the gear is rotatable in a first rotary direction and a second rotary direction.
A.Arunkumar et al [1] found that while waiting in the traffic, the cars have to move
on step by step very slowly, this situation is a difficult one for the drivers to make their car not
to roll back in the slope. So the mechanism has to be developed to stop the vehicle from
rolling back and it should not stop the vehicle in accelerating forwards. This function can be
achieved by using the ratchet and pawl mechanism.
Zhang L [6] investigated that a Hill Start Control uses a sensor to monitor the wheel
state. If the wheel begins to roll backwards, the ECU controls the brake the system to engage
the brake on the wheel. There have been some experiments with hill-start control strategy.

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3. Hill start assist control
When the vehicle starts off on a steep or slippery hill, the vehicle could
descend backward while the driver switches from the pedal brake to the accelerator
pedal, thus making it difficult for the vehicle to start off. To prevent from
occurring, HAC temporarily (approximately 3 seconds at the maximum) applies the
brakes to the 4 wheels in order to reduce the backward speed of the vehicle. With
HAC however, the driver can start off vehicle easily.

3.1 Hill start components
The components used in hill start control are given below:
a) Hydraulic reservoir
b) Check Valve
c) Hand Brake
d) Electronic Control Unit
e) Engine
f) ABS Valve
g) Gear Box
h) Brake chamber
i) Clutch

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3.2 Hill Start Assist Working
Fig1. Hill Start Assist Control


The hill start was achieved by the brake systems, as can be seen in Figure1. When the
vehicle is prepared to start up on a slope road, the driver push the hill-start pushbutton to
change the vehicle into hill-start mode. The control strategy changes the gear to a proper gear
number by hydraulic actuator. When the driver releases the hand brake, the fluid is prepared
to pass through the ABS valve. However, the abs valve is controlled by the VECU module,
which controlled the ABS valve by engine torque, gearbox, and the hill-start pushbutton. If
the output torque of the engine is not achieved the threshold value, the abs valve does not
open to let the fluid pass through to release the brake chamber. The brake system locks the
wheel to avoid roll back. So the vehicle remains stationary on the slope road, seen in Figure2.

When the driver press the throttle pedal, the output torque of the engine will increase
according to the throttle position. When the engine torque is above the threshold value, the
VECU controls the ABS valve which opens and allows high pressure fluid to pass through
brake chamber and gets released through the brake chamber. So the vehicle will move on the
road. The increase of the engine torque is proportional to the decrease of brake force.

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The advantage of the control strategy is that, firstly, if the engine torque is not achieved
the threshold, the vehicle will remain in the initial position, second, if the driver press the
throttle pedal deeply, the engine torque will increase very fast, then the vehicle will start
quickly.



Fig.2 Hill Assist Control vs. without Hill Assist Control

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4. Hill hold control
The Hill Hold function is a highly desirable feature in manual transmission vehicles;
it also enhances the driving experience in automatic transmission vehicles. The Hill Hold
feature supports the Stop and Go performance by holding the vehicle on an incline and
preventing undesired motion. It prevents rolling back of vehicle and also provides descent
control on slope.
4.1 Hill hold components
The Components used in hill hold control are given below:
 Brake pedal travel sensor
 Master cylinder pressure sensor
 Wheel speed sensors
 Throttle position sensor
 Clutch sensor
 Longitudinal acceleration sensor
 Gear position sensor

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4.2 Brake system used in hill hold control


Fig.3 Full Electric Brake System
Fig.3 shows full electric brake system .During a Hill Hold apply event all four
wheels shall be commanded to a predetermined torque output level with the correct
balance at a specific ramp rate. Once the commanded level is reached, the torque output
level all four wheels will be released at a specific ramp rate. In order to minimize current
draw on the vehicle and manage the thermal state of the electric brake module, a mechanical
latch mechanism shall be engaged on the electric brake module. The latch mechanism shall
be utilized on all four wheels once Hill Hold has been active for a pre-determined amount of
time.The latch mechanism shall maintain the commanded torque level output at the
wheel while allowing the current to the electric brake modules to be reduced. The latching
mechanism shall remain engaged until the Hill Hold conditions are met.

4.3 hill hold control working

The working of hill hold control takes place in three systems as given below:
I) Basic level System :
The goal of the basic level of Hill Hold is to provide the ability for a manual
transmission vehicle driver to maneuver an incline with the use of only the clutch and
accelerator pedals. The working in basic level system is given below:

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 A Hill Hold apply takes place after the driver comes to a full stop with their foot on
the brake.
 A desired Hill Hold torque output level is calculated based on the torque / pressure
level used to stop the vehicle or keep it stationary
 Once the brake pedal is released. Hill Hold will continue to command the same
level of torque / pressure calculated above.
 The Hill Hold criterion is based solely on a Throttle Position command. The
limitation of this approach is that the system will not know the percent grade that the
vehicle is on. Therefore, Hill Hold will be engaged on every grade, even zero percent.
Furthermore, the vehicle will not know the difference between a positive slope and a
negative slope.
 Furthermore, the vehicle will not know the difference between a positive slope and a
negative slope..
II) Mid - level system :
The mid-level system has most of the desired features with a very natural feel to the
driving experience while still minimizing the additional hardware required for
implementation. The working takes place in two stages as given below:
At First Stage
 The vehicle comes to a full stop (regardless of whether the stop is done using the
brake or coast).
 The incline is sufficient to require Hill Hold. The level of incline requiring Hill Hold
is predetermined and is detected using the longitudinal acceleration sensor.
 The clutch pedal is fully depressed (detected by the clutch switch placed very
close to the end of travel).
 The torque output level required is dependent on the slope calculations using the
longitudinal acceleration sensor value.

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At second Stage
 The first is a clear indication that the driver has a desire for the vehicle to move.
 The clutch pedal being released and approaching the gear contact point (2nd
clutch switch)
 An appropriate amount of throttle is being applied for the specific incline. The
appropriate throttle needed would increase with the increase of the gradient of the
incline in the cases of the vehicle moving upwards on a positive incline or vehicle
moving upwards on a negative incline (backing up).
 A minimal amount of throttle would be needed in the other two cases (gravity will
assist with the rest of the needed inertia).
 The clutch condition would be removed from the exit criteria in the case of an automatic
transmission vehicle.
 Another is that the vehicle is stopped on a positive incline and the clutch is released
(indicating Neutral gear is engaged).
 The vehicle is stopped on an incline, the clutch is pressed and the Reverse gear is
engaged
 The vehicle is stopped on a decline (negative slope) and the clutch is released.
 A brake apply by the driver in any of these cases would be a clear indication that the
driver has a desire to let the vehicle roll down in the direction of the slope.
 Once one of the above criteria is met, the latching mechanism in the electric brake
module is de-latched if it was engaged and the torque output level is released at
a rate proportional to the slope.

III) Up level system:
 The addition of a Hill Descent feature that would take control of the vehicle to assist
the driver in rolling down an incline (positive slope) once the reverse gear is engaged.
 The brake system would release and apply torque/pressure to the wheels to control the
descent of the vehicle at very low speeds.
 This would assist the driver maneuver down the hill on such an awkward condition
where rear visibility is restricted and seating position is uncomfortable.
 Active wheel speed sensors would provide a major advantage to make the control of
the Hill Descent at such low speeds comfortable.

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 The exit criteria for Hill Descent could be any or all of the following: A brake apply, a
throttle apply, or a slope value falling below a predetermined threshold.
4.4 Slope calculations:
The longitudinal vehicle road load includes the rolling resistance, aerodynamic resistance,
and uphill resistance. The vehicle model can be described as follows
:
ma = F
r
+ F
t
F =µmgcosƟ + 0.5C
d
AV
2
+ mgsinƟ

Fig4. Force Analysis of vehicle on inclined plane

Where F
t
is the driving force on the vehicle, F
r
is the total resistance, m is the mass of the
vehicle, a is the acceleration ,α is the grade angle, µ is the coefficient of friction of the wheel
,C
d
is the air drag coefficient that depends on the body style and dimension and A is the
frontal area of the vehicle.

4.5 Other Hill holding device:
Ratchet and Pawl mechanism is identified to arrest the backward motion to the car. The
ratchet is placed in the front drive shaft and the Pawl is fitted with the frame. When the
vehicle is moved in the hill road, the lever has to make the pawl to touch the ratchet. If the
vehicle tends to move backward direction, the pawl would stop the ratchet to move Counter
Clock-wise direction with respect to front wheel. As the vehicle is in neutral position, the
pawl engaged the ratchet and the vehicle did not move in backward direction. So the hand
brakes need not to be applied. When the vehicle is in moving condition, the engagement
between the ratchet and pawl is detached.

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4.6 Driving conditions with DAC and without DAC





FIG.5 Driving Conditions with DAC AND Without DAC
The Fig.5 shows comparison between hill assist control and without hill assist control.
Driving vehicle without hill assist control is difficult while it easy to control with hill assist
control. Stable speed can be obtained on hill assist control. Without DAC system wheel lock
takes place while braking. But with DAC while driving it improves Descent control. Vehicle
can be driven safely with hill assist control feature. Controlling of vehicle can be done easily.

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4.7 Advantages
 Prevents accidents while starting the vehicle on slopes
 Cost effective solution
 Stress free driving
 Longer clutch life

4.8 Disadvantages
 Holding of brake may lead to warping of disc.
 Maintenance cost is high.

4.9 Applications
These are cars given below having hill assist control feature in existence:
I) Hill Assist Control
1) Honda CR-V
2) Honda CR-Z
3) Toyota Fortuner
4) Toyota Prius
5) Toyota Land Cruiser
6) Toyota RAV4
7) Chevrolet Trax
8) Volkswagen Touareg
9) Opel Mokka

II) Hill Descent Control
1. Honda CR-V
2. Honda CR-Z
3. Toyota Fortuner
4. Toyota Prius
5. Toyota Land Cruiser
6. Toyota RAV4
7. Chevrolet Trax

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8. Volkswagen Touareg
9. Opel Mokka

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5. Conclusion
The Hill Hold feature itself has proven to be very beneficial to manual
transmission drivers that find themselves on grades that would normally make driving
difficult. In addition to manual transmission vehicles, the driving experience of vehicles with
automatic transmissions can be enhanced. The choice of which method of Hill Hold (basic
level, mid-level, or up-level) to implement is influenced by many factors: desired
performance, system cost and vehicle powertrain. When implemented correctly, the
functionality of the Hill Hold feature seamlessly matches the driver's normal driving habits
and instincts. Hill Hold function makes the driving experience as comfortable and natural
as possible while keeping the system commercially feasible. By using this feature we can
drive vehicle easily.






.

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References:

[1] A.Arunkumar , T. Muthumani , V. Balasubramani , “Design and Fabrication of Anti-
rollback System in Vehicles Using Ratchet and Pawl Mechanism”. International Journal
of Emerging Technology in Computer Science & Electronics (IJETCSE) pp.2015
Volume 12, ISSN: 0976-1353.
[2] Mohammad Tamimi, Deron Littlejohn, Mark Kopka and Gordon Seeley ,“Hill Hold
Moding” pp. 2005 SAE International, volume 3, ISSN: 2005-05-0786
[3] Jiang Xuefeng, Xu Xian, Jin Guodong, Chen Wei , “Research on Hill Start Control”, The
2nd International Conference on Computer Application and System Modeling pp. 2012,
ISSN: 1812-5654
[4] Cook George ,“Anti creep and hill holderbrake system” (US 2938611 A) , International
Conference California pp. 1960, volume12, ISSN :571-656
[5] Ge A., Lei Y., Gao Y., Zhang H. & Fan J., “ A Research on Hill Starting Control of AMT
System of Vehicle”, Automotive Engineering, pp. 1998,volume 3 ISSN: 201302449
[6] Zhang L., Li H.,“Hilling Start-up Control Method Using Accelerometer”. Vehicular
Electronics and Safety, IEEE International Conference, pp.2006, volume 9 ISSN: 1457-
4689