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Haptic feedback on the steering wheel to maximize front axle grip. Joop van Gerwen BioMechanical Design & Precision and Microsystems Engineering, Automotive. Contents. Introduction Methods Concept Experiments Data analysis Results Discussion. Introduction. Introduction. ESC systems. - PowerPoint PPT Presentation
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1/28Challenge the future
Haptic feedback on the steering wheel to maximize front axle grip
Joop van GerwenBioMechanical Design & Precision and Microsystems Engineering, Automotive
2/28Challenge the future
Contents
• Introduction• Methods
• Concept• Experiments• Data analysis
• Results• Discussion
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Introduction
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Introduction
• Reduces loss of control • Effect:
• Reduces fatal single vehicle crashes by [1]• 30-50% among cars and
• 50-70% among SUVs
• Best since seat belt!• Developed from ABS• But: large impact on velocity• Active Front Steering (AFS)
ESC systems
[1] S.A. Ferguson, The Effectiveness of Electronic Stability Control in Reducing Real-World Crashes: A Literature Review, 2007
[2] http://www.guy-sports.com/fun_pictures/95-driving_bd.jpg [3] http://static.howstuffworks.com/gif/28002-rollover-accidents-2.jpg
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Introduction
• Related research on lateral vehicle dynamics guidance• Lanekeeping
• Principle: shared control• Controller is capable of controlling the system• Actuator power not strong enough for full control
Haptic feedback
[1] J. Switkes, E. Rosetter, I. Coe, Handwheel force feedback for lanekeeping assistance: combined dynamics and stability
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Introduction
• Goal :• Use haptic feedback to let the driver take the corrective
AFS action
• Guide to maximum front axle grip
Idea & title explanation
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Methods
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MethodsConcept – Controller structure
• Purpose:• Guide the driver to the proper steering action
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MethodsConcept – Upper controller structure
δ
Desired yaw rate
PD controller
ay
Vx
Limiter
Vx
Tψ_corrective
+ -desψ errorψ
ψ
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• Pacejka combined slip tire model
MethodsConcept – Lower controller structure
δ Tfeedback
δrange
Front axle force rangeVehicle state
Optimum steering
angle
Fy_front_axle
(range)
Tψ_corrective
δdes
Feedback torque
calculationδerror
+ -
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MethodsConcept – How does it feel?
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MethodsConcept – How does it feel?
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MethodsExperiments – Vehicle
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MethodsExperiments – Tracks
[1] http://maps.google.nl
010203040
50
60
70
80
90100110120130
140
150160 170 180 190
200 210 220230
240
250
260
270280
290300
310320
330
340
350360
370
380390
400410420
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• 9 drivers• 2 tracks
• Wet skid-pad• 7 runs of 35 second
• Task: follow inner line as fast as possible
• Adverse track• 3 runs of 70 second (approximately 2 laps)
• Task: take the corners as quick as you can
• NASA Task Load Index• 2 experiment days
MethodsExperiments – Procedures
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MethodsExperiments – Pictures & video
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Methods
• Filtered: Driver torque and accelerations (3Hz anti-causal low pass)
• Removed: unwanted data• Wet skid-pad• RMS data• Adverse track• Translation of data• One full, running lap isolated
Analysis – Filtering & preparation
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Methods
• Performance metrics• Example: velocity
• Driving behavior metrics• Example: steering wheel angle
• Feedback controller metrics• Example: feedback torque
Analysis – Metrics
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Results
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ResultsSignificance
• Two data sets • T-test to calculate chance that data sets originate
from the same source• Chance < 5% is significant• Influence of external factors
• P-value = 5.1874e-007
0
5
10
15
20
January March
Maximum temperature
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ResultsWet skid-pad
0.35
0.4
0.45
0.5
0.55
Wet: FB off Wet: FB on
rms
yaw
rat
e [r
ad/s
]
p-value = 0.035795
0.195
0.2
0.205
0.21
0.215
0.22
0.225
0.23
0.235
0.24
Wet: FB off Wet: FB on
rms
delta
[ra
d]
p-value = 0.0097002
3
3.5
4
4.5
5
5.5
6
6.5
7
7.5
8
Wet: FB off Wet: FB on
rms
driv
er t
orqu
e [N
m]
p-value = 5.1645e-005
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
Wet: FB off Wet: FB on
rms
delta
diff
eren
ce [
rad]
p-value = 0.98408
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ResultsAdverse track – Velocity
0 100 200 300 40020
30
40
50
60
70
80
Position on center line [m]
spe
ed
[km
/h]
10th percentile, no FB
90th percentile, no FB
10th percentile, FB
90th percentile, FBMean, no FBMean, FBSignificantly lowerSignificantly higher
0 100 200 300 40020
30
40
50
60
70
80
Position on center line [m]
spe
ed
[km
/h]
10th percentile, no FB
90th percentile, no FB
10th percentile, FB
90th percentile, FBMean, no FBMean, FBSignificantly lowerSignificantly higher
0 100 200 300 40020
30
40
50
60
70
80
Position on center line [m]
spe
ed
[km
/h]
10th percentile, no FB
90th percentile, no FB
10th percentile, FB
90th percentile, FBMean, no FBMean, FB
0 100 200 300 40020
30
40
50
60
70
80
Position on center line [m]
spe
ed
[km
/h]
Mean, no FBMean, FB
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ResultsAdverse track – One corner
0 100 200 300 400-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
Position on center line [m]
de
lta [r
ad
]
10th percentile, no FB
90th percentile, no FB
10th percentile, FB
90th percentile, FBMean, no FBMean, FBSignificantly lowerSignificantly higher
Steering angle
0 100 200 300 400-1
-0.5
0
0.5
1
1.5
Position on center line [m]
yaw
ra
te [r
ad
/s]
10th percentile, no FB
90th percentile, no FB
10th percentile, FB
90th percentile, FBMean, no FBMean, FBSignificantly lowerSignificantly higher
Yaw rate
0 100 200 300 400-15
-10
-5
0
5
10
15
20
Position on center line [m]
dri
ver
torq
ue
[Nm
]
10th percentile, no FB
90th percentile, no FB
10th percentile, FB
90th percentile, FBMean, no FBMean, FBSignificantly lowerSignificantly higher
Driver torque
Steering angle error
• Significantly lower• Significantly higher
0 100 200 300 400-0.1
-0.08
-0.06
-0.04
-0.02
0
0.02
0.04
0.06
0.08
0.1
Position on center line [m]
de
lta d
iffe
ren
ce [r
ad
]
10th percentile, no FB
90th percentile, no FB
10th percentile, FB
90th percentile, FBMean, no FBMean, FBSignificantly lowerSignificantly higher
0 100 200 300 400-0.1
-0.08
-0.06
-0.04
-0.02
0
0.02
0.04
0.06
0.08
0.1
Position on center line [m]
de
lta
diffe
ren
ce
[ra
d]
10th percentile, no FB
90th percentile, no FB
10th percentile, FB
90th percentile, FBMean, no FBMean, FBSignificantly lowerSignificantly higher
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ResultsAdverse track – Road position
0 100 200 300 4000
0.5
1
1.5
2
2.5
3
3.5
Position on center line [m]
La
tera
l po
sitio
n [m
] va
ria
tion
fro
m m
ea
n
90th percentile, no FB
90th percentile, FBMean, no FBMean, FBSignificantly lowerSignificantly higher
0 100 200 300 400-4
-3
-2
-1
0
1
2
3
4
Position on center line [m]
La
tera
l po
sitio
n [m
]
10th percentile, no FB
90th percentile, no FB
10th percentile, FB
90th percentile, FBMean, no FBMean, FBSignificantly lowerSignificantly higher
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Results
• Variables:• Mental demand• Physical demand• Temporal demand• Performance• Effort• Frustration
• No significant changes• Small test group
NASA Task load index
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Discussion
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Discussion
• Room for improvements:• State estimation & sensing
• Tire model vs. force sensing bearing
• Haptic feedback philosophy• Desired yaw rate determination very simple
• Corrective yaw torque controller
• Possible negative stiffness of steering system
• Do not prevent drivers from steering back to neutral
Conclusions – Improvements
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Discussion
• Haptic feedback caused:• Driving behavior change• Vehicle eager to steer• Higher driver torque• Increased yaw rate• Drivers were drawn to a trajectory
• Potential, but unsafe in current form
Conclusions – Significant changes
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