sideslip angle estimation based commercial vehicle stability control

174 Pages·2013·1.86 MB·English

S
IDESLIP ANGLE ESTIMATION BASED COMMERCIAL

VEHICLE STABILITY CONTROL

Ph.D. Thesis
Zoltán Hankovszki

Supervisor: László Palkovics, D.Sc.
External advisor: Roland Kovács

Kandó Kálmán Doctoral School for Multidisciplinary Sciences
Science of Vehicles and Mobile Machines

Budapest University of Technology and Economics
Faculty of Transportation Engineering and Vehicle Engineering
Department of Automobiles and Vehicle Manufacturing
Budapest, Hungary

2013
To my wife, Krisztina
I. Preface
The aim of this work is to investigate commercial vehicle related electronic stability
programs’ possibilities. Special requirements of these vehicles are considered: a deal
had to be done between control theories requirements and the possibilities of these
payload focused transportation vehicles – low series numbers require cheap and ef-
fective solutions. Nevertheless the kinetic energy of these vehicles is much higher
than passenger vehicles’ kinetic energy – it means higher chance for several dam-
ages when this energy can not be kept under control. I used theory based solutions
with everyday based limitations, and I tried to reach the best results that are possible
in this environment.
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II. Contents
I. Preface................................................................................................................ 1
II. Contents.............................................................................................................. 2
1 Introduction.......................................................................................................... 6
1.1 Motivation..................................................................................................... 6
1.2 State of the art.............................................................................................. 7
1.2.1 Law and accordance to this................................................................... 7
1.2.2 Lateral vehicle state observation......................................................... 10
1.2.3 Electronic stability program’s logic...................................................... 15
1.2.4 Steering enhanced electronic stability program................................... 18
1.3 Dedicated aims........................................................................................... 19
1.4 Structure of this work.................................................................................. 19
2 Vehicle models.................................................................................................. 21
2.1 “Complex vehicle model”............................................................................ 22
2.1.1 Tyre model.......................................................................................... 23
2.1.2 Vehicle frame and suspension............................................................ 24
2.1.3 Driveline.............................................................................................. 26
2.1.4 Brake system...................................................................................... 28
2.1.5 Measured signals’ simulation and measurement’s condition .............. 28
2.2 Simplification of vehicle model................................................................... 30
2.2.1 Planar behaviour................................................................................. 31
2.2.2 Two axle vehicle model....................................................................... 33
2.2.3 External (tyre) forces and torque values ............................................. 35
2.2.4 More than two axle vehicle model....................................................... 37
2.3 Lateral vehicle state estimation’s vehicle model, “Estimation model”......... 39
2.4 Lateral vehicle state’s control model, “Control model”................................ 42
3 Parameter identification..................................................................................... 45
3.1 Suspension and brake mechanism characteristics..................................... 46
3.2 Overall steering system ratio and steered wheel angles............................ 47
3.2.1 Steering wheel – Ackermann angle relation........................................ 47
3.2.2 Ackermann angle – steered wheel angles relations............................ 49
3.3 Static tyre characteristics ........................................................................... 51
3.4 Dynamic tyre characteristics ...................................................................... 52
3.5 Sensor error calibration.............................................................................. 54
4 Control techniques ............................................................................................ 57
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4.1 Observability, controllability and stability.................................................... 60
4.2 Models of the investigations....................................................................... 62
4.2.1 Controlled vehicle model parameters.................................................. 63
4.2.2 Ideal vehicle model............................................................................. 64
4.2.3 Controller and observer vehicle models.............................................. 66
4.3 Uncontrolled vehicle model results............................................................. 69
4.4 LQ regulation.............................................................................................. 71
4.5 Adaptive control.......................................................................................... 73
4.5.1 Control performance........................................................................... 75
4.5.2 Simulation results................................................................................ 79
4.6 Conclusion, technique combination............................................................ 80
5 Sideslip estimation ............................................................................................ 83
5.1 Vehicle sideslip angle estimation ............................................................... 83
5.1.1 Structure of the estimation.................................................................. 83
5.1.2 Two step iteration................................................................................ 84
5.1.3 Corrections.......................................................................................... 93
5.2 Requirements of chapter 1.2.2.2.............................................................. 100
5.3 Operation of sideslip estimation method.................................................. 104
6 Control development....................................................................................... 109
6.1 Safe vehicle state..................................................................................... 109
6.1.1 Vehicle state qualifying ..................................................................... 112
6.2 Reference model...................................................................................... 114
6.2.1 Structure of the reference model....................................................... 114
6.2.2 Lateral acceleration limitation............................................................ 116
6.2.3 Test cases for investigation............................................................... 119
6.2.4 Vehicle sideslip angle free play zone................................................ 120
6.3 Control logic............................................................................................. 121
6.3.1 The LQ control part........................................................................... 123
6.3.2 The adaptive control part .................................................................. 127
6.4 Control results.......................................................................................... 131
6.4.1 Simulation based results................................................................... 131
6.4.2 Measurement based results.............................................................. 135
7 Conclusion....................................................................................................... 138
7.1 Thesis 1: Unambiguous danger detection based on vehicle sideslip angle
139
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7.2 Thesis 2: A vehicle sideslip angle estimation method.............................. 141
7.3 Thesis 3: Lateral vehicle control structure................................................ 145
8 Future work ..................................................................................................... 148
9 References...................................................................................................... 149
10 Publications in chronology........................................................................... 156
A Vehicle simulation results................................................................................ 158
A1 General behaviour of the vehicle model....................................................... 158
A2 Simulation’s comparison to measurement results........................................ 160
B Control design results...................................................................................... 163
B1 Uncontrolled vehicle..................................................................................... 163
B2 LQR controlled vehicle................................................................................. 164
B3 Adaptively controlled vehicle........................................................................ 166
B4 Control combination controlled vehicle........................................................ 167
C Final results..................................................................................................... 169
C1 Reference model ......................................................................................... 169
C2 Simulation based stability control................................................................. 170
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Alulírott Hankovszki Zoltán kijelentem, hogy ezt a doktori értekezést magam készítet-
tem és abban csak a megadott forrásokat használtam fel. Minden olyan részt, ame-
lyet szó szerint, vagy azonos tartalomban, de átfogalmazva más forrásból átvettem,
egyértelműen, a forrás megadásával megjelöltem.

Budapest, 2013. május 22.

Aláírás

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1 Introduction
1.1 Motivation
Recently used electronic stability programs (ESP) are effective [1]; they significantly
reduced the number of road accidents with their driver assistance. A system like this
helps the vehicle to realize the directory requested by the driver. Legislations support
the using of these systems. Their dedicated aim is to decrease the number of road
fatalities and accidents in the EU, USA, Japan and everywhere in the world. These
systems ensure one of the best ways of human life’s protection during road trips: with
the keeping of vehicle controllability, lot of accidents could be simply avoided.
Every new vehicle sold in the European Union after November of 2014 has to be
equipped with electronic stability control system – it is the legislation of the European
Parliament [2]. The aim of this mandatory is to reduce deaths and injuries on the
roads of the EU to the half of year 2000 level until 2010 [3]. Figure 1 shows how road
statistic was shaped in the last two decades. In the United States, where high centre
of gravity point sport utility vehicles are popular, the rollover risk was reduced by
nearly 80% in some categories and the number of fatal crashes was decreased with
about 30% in case of vehicle stability control using vehicles [4]. It has to be noticed
that even four-wheel-driving could reach hardly any advantage from the viewpoint of
fatal accidents [5] and the passive vehicle safety has also a limit that is established
by the human body’s abilities (our body is not able to sense velocity but able to sense
acceleration, and this kind of physical effect can even cause injuries [6]).
Fatilites on the roads of the EU
80000
70000
s 60000
e
ti
i
al
at 50000
F
40000
30000
1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012
Years

Figure 1 Fatalities on the roads of the European Union [7]
The role of vehicle stability control systems is primary in this mission. Table 1 shows
Hungarian road accidents of years 2002-2010. Electronic stability controls are not
wide-spread in Hungary yet, so with a harsh approximation when we assume that
single vehicle accidents could be avoided with a good chance when ESP is installed
then it can be seen that the quarter of accidents, serious injuries and fatalities could
be avoided.
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Serious
Single ve- Fatal single
Serious single ve- Fatal acci-
Year Accidents hicle acci- vehicle ac-
accidents hicle acci- dents
dents cidents
dents
2002 19686 5015 6982 1918 1264 271
2003 19976 5289 6904 1970 1135 296
2004 20957 5785 7111 2144 1168 297
2005 20777 5466 7010 1939 1139 301
2006 20977 5651 7075 1975 1173 324
2007 20635 5591 6876 1967 1106 279
2008 19174 5070 6170 1740 890 224
2009 17864 5125 5583 1737 752 219
2010 16308 8722 4941 1424 649 130
Ratio [%] 100.00 29.32 100.00 28.67 100.00 25.24
Table 1 Road vehicle accidents in Hungary between 2002 and 2010 [8]
However, these systems could be better. I investigated primary commercial vehicles’
capabilities, possibilities, problems and electronic stability controls (this category is
important because the using of these vehicles will be more and more important [9]).
To setup a commercial vehicle ESP today, identification measurements are neces-
sary. These measurements result a compromise: a yaw rate (rotational velocity
around the vehicle’s vertical axle) reference model that should be suitable for every
possible platform, load case, adhesion coefficient, tyre type and so on. A golden
mean should be found for every vehicle type. This compromise of the reference
model results that a relative wide free play zone must be defined for the vehicle to
ensure that the controller lets the stable vehicle to operate in every vehicle state that
could happen during operation.
1.2 State of the art
This section has four points: the general state of (commercial vehicle) electronic sta-
bility controls and relevant regulation requirements that defines these systems’ tasks
are listed first. Then vehicle state observation papers, patents and commercial vehi-
cle’s special problems are described. Latter special problems establish so high level
claims to lateral vehicle state estimation in case of commercial vehicles that until now
presented papers and patents don’t give good enough solution. The next section
shows electronic vehicle stability control systems’ state and problems regarding
commercial vehicles. And last but not least active steering systems are investigated.
1.2.1 Law and accordance to this
1.2.1.1 UNECE 13 brake regulation
For heavy duty vehicles even the relevant UNECE brake regulation was modified by
WP29 in 2007 [10]. The modification declares in point 2.32.2.1 and 2.32.2.2 direc-
tional control and roll-over control as functions that have to be performed by an elec-
tronic stability program. In my work I focus on directional control, so previous says:
"Directional control means a function … that assists the driver … in maintaining the
direction intended by the driver …”.
Two types of vehicle directions can be defined – Figure 2:
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- One for the vehicle that is called yaw angle
- One for its heading with respect to vehicle velocity’s direction that is called ve-
hicle sideslip angle.

Figure 2 Directions and coordinate systems of a vehicle in a plane by [13]
Marking Meaning Unit
v horizontal vehicle velocity m/s
h
v longitudinal/lateral vehicle velocity m/s
X/Y
X /Y first/second global coordinate vector m
E E
X /Y longitudinal/lateral vehicle coordinate vector m
V V
β vehicle sideslip angle rad
ν course angle rad
Ψ yaw angle rad
Table 2 Notations of chapter 1.2.1.2
1.2.1.2 Currently used electronic stability programs’ directional control
reference
These two angles together define the direction of the moving. Currently used com-
mercial vehicle stability control systems’ directional control [11], [12] mainly consider
only yaw behaviour of the vehicles, probably because of vehicle sideslip angle and
lateral acceleration measurement difficulties and lack of suitable vehicle sideslip an-
gle estimation method. They are doing that in spite of the fact that yaw angle/rate
based vehicle state observation can’t every time unambiguously define dangerous
vehicle states. It has to be noticed to avoid misunderstandings that today’s commer-
cial vehicle stability control systems are very effective and they realize dangerous
situations mainly in time. The aim is to improve the danger recognition’s accuracy.
Unstable vehicle behaviours could be realized in understeered and oversteered be-
haviours (see definitions later). See Figure 3 that shows constant vehicle velocity
with steering wheel angle increasing. As it can be seen in the figure, lateral accelera-
tion and steering wheel angle can be the base of vehicle state classification (their
proportion’s derivative should be taken into consideration, it is called understeer gra-
dient [13], [14]). Because of the assumed steady-states and because the vehicle ve-
locity is constant, lateral acceleration is proportional to yaw rate – thus yaw rate and
steering wheel angle can be also the base of vehicle state classification.
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