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Public Defence October 2013
Controllable Suspension Design Using Magnetorheological Fluid
Student: Supervisor:
Co-Supervisor:
Anria Strydom Prof Schalk Els Dr Sudhir Kaul
Outline
Project background
MR damper characterization
Vehicle modeling and model validation
Suspension control
Ride comfort simulation and results
Handling simulation and results
Suspension control results summary
Conclusion
Recommendations and future work
1
Project Background
Ride comfort and Handling Trade-off
2
Handling
Sudden swerve manoeuvres
Hard spring
High damping
Minimize pitch and roll movement
Ride Comfort
Minimize driver fatigue
Soft spring
Low damping
Minimize vertical acceleration
Project Background
Magnetorheological (MR) Fluid Passive, Active & Semi-active Damping
3
Active
Project Background
Baja Vehicle
4
Study Purpose: Mitigate ride comfort and handling
compromise of Baja vehicle
Semi-active suspension control of MR dampers
Tasks: MR damper modeling
Vehicle model development and validation
Implementation of skyhook- and groundhook control
Determination of suspension control settings:
Rough Belgian paving track
Single lane change
MR Damper Characterization
MR Damper Characteristic
5
-0.04 -0.02 0 0.02 0.04-3000
-2000
-1000
0
1000
2000
3000
Displacement ; x ; [m]
Forc
e ; F
MR
; [
N]
Force-displacement relationship of MR damper
-0.5 0 0.5-3000
-2000
-1000
0
1000
2000
3000
Velocity ; x' ; [m/s]
Forc
e ; F
MR
; [
N]
Force-velocity relationship of MR damper
0.50A Measured
0.50A Predicted
1.75A Measured
1.75A Predicted
MR Damper Characterization
MR Damper Models
6
𝐹 = 𝐹𝑐2tan−1 𝑏𝑥
𝜋+ 𝑐𝑥 + 𝐹0
𝐹 = 𝑘𝑥 + 𝑐𝑥 + 𝛼𝑧 + 𝐹0
𝑧 = −𝛾𝑧 𝑥 𝑧 𝑛−1 − 𝛽𝑥 𝑧 𝑛 + 𝐴𝑥
𝑧 = tanh 𝛽𝑥 + 𝛿sgn 𝑥
𝐹 = 𝜎0𝑧𝑣 + 𝜎1𝑧 + 𝜎2𝑥
𝑧 = 𝑥 − 𝜎0𝑎0 𝑥 𝑧 1 + 𝑎1𝑣
𝐹 = 𝛿1𝐼 + 𝛿2 tanh 𝛿3𝑥 + 𝛿4𝑥 + 𝛿5
𝐹 = 𝑏𝑖 + 𝑐𝑖𝐼 𝑥 𝑖
𝑛
𝑖=0
Baja Model Overview
7
Spring-Damper Data
Pneumatic Spring
Characteristic Hydraulic Damper
Characteristic
CAD Centre of Mass Moments of Inertia
ADAMS Model Pacejka ’89
Tyre Model
Test Vehicle
Preparation Baseline
Testing
Baseline
Testing Inputs
RESULTS RESULTS
Model Verified
• Non-linear
• 20 Moving bodies
• 12 unconstrained DOF
• Contains experimentally
determined properties
• Validated using bump
and slalom tests
Bu
mp
Test
Sla
lom
Test
Baja Vehicle Modeling and Model Validation
8
1 1.5 2 2.5 3 3.5 4-30
-20
-10
0
10
20
30
Time ; t ; [s]
Dis
pla
cem
ent
; Z
su4 ;
[m
]
Front left damper displacement
1 1.5 2 2.5 3 3.5 4-30
-20
-10
0
10
20
30
Front right damper displacement
Dis
pla
cem
ent
; Z
su3 ;
[m
]
T ime ; t ; [s]
1 1.5 2 2.5 3 3.5 4-30
-20
-10
0
10
20
30
Rear left damper displacement
Dis
pla
cem
ent
; Z
su2 ;
[m
]
T ime ; t ; [s]
1 1.5 2 2.5 3 3.5 4-30
-20
-10
0
10
20
30
Rear right damper displacement
Dis
pla
cem
ent
; Z
su1 ;
[m
]
T ime ; t ; [s]
Measured
Simulation
Bump Test Simulation Results (1)
9
Suspension deflection
Bump Test Simulation Results (2)
10
1 1.5 2 2.5 3 3.5 4-50
0
50
Time ; t ; [s]
Ro
ll r
ate
;
' ;
[ /s
]
Roll rate of sprung mass
1 1.5 2 2.5 3 3.5 4-100
-50
0
50
100
Pitch rate of sprung mass
Pit
ch
rate
;
' ;
[ /s
]
T ime ; t ; [s]
1 1.5 2 2.5 3 3.5 4-40
-20
0
20
40
Yaw rate of sprung mass
Yaw
rate
;
' ;
[ /s
]
T ime ; t ; [s]
Measured
Simulation
1 1.5 2 2.5 3 3.5 4-50
0
50
Time ; t ; [s]
Ro
ll r
ate
;
' ;
[ /s
]
Roll rate of sprung mass
1 1.5 2 2.5 3 3.5 4-100
-50
0
50
100
Pitch rate of sprung mass
Pit
ch
rate
;
' ;
[ /s
]
T ime ; t ; [s]
1 1.5 2 2.5 3 3.5 4-40
-20
0
20
40
Yaw rate of sprung mass
Yaw
rate
;
' ;
[ /s
]
T ime ; t ; [s]
Measured
Simulation
1 1.5 2 2.5 3 3.5 4-50
0
50
Time ; t ; [s]
Ro
ll r
ate
;
' ;
[ /s
]
Roll rate of sprung mass
1 1.5 2 2.5 3 3.5 4-100
-50
0
50
100
Pitch rate of sprung mass
Pit
ch
rate
;
' ;
[ /s
]
T ime ; t ; [s]
1 1.5 2 2.5 3 3.5 4-40
-20
0
20
40
Yaw rate of sprung mass
Yaw
rate
;
' ;
[ /s
]
T ime ; t ; [s]
Measured
Simulation
Sprung mass angular rates
Slalom Test Simulation Results (1)
11
Suspension deflection
0 1 2 3 4 5 6
-40
-20
0
20
40
Front left damper displacement
Dis
pla
cem
ent
; Z
su4 ;
[m
]
T ime ; t ; [s]
0 1 2 3 4 5 6
-40
-20
0
20
40
Front right damper displacement
Dis
pla
cem
ent
; Z
su3 ;
[m
]
T ime ; t ; [s]
0 1 2 3 4 5 6
-40
-20
0
20
40
Rear left damper displacement
Dis
pla
cem
ent
; Z
su2 ;
[m
]
T ime ; t ; [s]
0 1 2 3 4 5 6
-40
-20
0
20
40
Rear right damper displacement
Dis
pla
cem
ent
; Z
su1 ;
[m
]
T ime ; t ; [s]
Measured
Simulation2
Simulation1
Ideal Skyhook Ideal Groundhook
Skyhook- and Groundhook Control
Control Implementation
𝐹𝑆𝐴 = 𝐺 𝑎𝜎𝑠𝑘𝑦 + 1 − 𝑎 𝜎𝑔𝑛𝑑
12
Passive
damping
Skyh
oo
k C
on
tro
l Passive
damping: 0%
Skyhook gain:
1200 Ns/m
Ride Comfort Simulation: Belgian Paving
13
0
0.2
0.4
0.6
0.8
1
0
1000
2000
3000
4000
0.5
1
1.5
2
2.5
Passive damping factor ; cfac
; [-]
X: 0Y: 1200Z: 0.8827
Weighted RMS acceleration of sprung mass
X: 0.075Y: 0Z: 0.9533
Skyhook gain ; G ; [Ns/m]
X: 1Y: 0Z: 2.047
Acc
eler
atio
n ; Z
s,cm
'' ; [m
/s2]
Weighted RMS vertical acceleration of sprung mass
Ride Comfort Results
14
Passive
Baseline
Ride Comfort
Optimal Passive
Ride Comfort
Optimal Controlled
Skyhook Control
-0.6 -0.4 -0.2 0 0.2 0.4 0.6-800
-400
0
400
800Front left MR damper force
Forc
e ; F
MR
4 ;
[N
]
Velocity ; x' ; [m/s]
FSA
FMR
-0.6 -0.4 -0.2 0 0.2 0.4 0.6-800
-400
0
400
800Front right MR damper force
Forc
e ; F
MR
3 ;
[N
]
Velocity ; x' ; [m/s]
-0.6 -0.4 -0.2 0 0.2 0.4 0.6-800
-400
0
400
800Rear left MR damper force
Forc
e ; F
MR
2 ;
[N
]
Velocity ; x' ; [m/s]
-0.6 -0.4 -0.2 0 0.2 0.4 0.6-800
-400
0
400
800Rear right MR damper force
Forc
e ; F
MR
1 ;
[N
]
Velocity ; x' ; [m/s]
Prescribed damping forces and damper current
Ride Comfort Results
15
7 8 9 10-0.5
0
0.5
1
1.5
2
2.5Front left prescribed current
Time ; t ; [s]
Cu
rren
t ; I 4
; [
A]
7 8 9 10-0.5
0
0.5
1
1.5
2
2.5Front right prescribed current
Time ; t ; [s]
Cu
rren
t ; I 3
; [
A]
7 8 9 10-0.5
0
0.5
1
1.5
2
2.5Rear left prescribed current
Time ; t ; [s]
Cu
rren
t ; I 2
; [
A]
7 8 9 10-0.5
0
0.5
1
1.5
2
2.5Rear right prescribed current
Time ; t ; [s]
Cu
rren
t ; I 1
; [
A]
Skyhook Control
Skyh
oo
k C
on
tro
l G
rou
nd
ho
ok
Co
ntr
ol
Passive damping:
50%
Skyhook gain:
4000 Ns/m
Passive damping:
50%
Groundhook gain:
4000 Ns/m
Handling Simulation: Single Lane Change
16
1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5-50
-25
0
25
50Sprung mass pitch rate
Pitch
Rat
e ;
' ; [/
s]
Time ; t ; [s]
1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5-100
-50
0
50
100
150Sprung mass roll rate
Ro
ll R
ate
;
' ; [/
s]
Time ; t ; [s]
1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5-100
-50
0
50
100Sprung mass yaw rate
Yaw
Rat
e ; '
; [/
s]
Time ; t ; [s]
cfac
= 100%
cfac
= 50%
cfac
= 20%
cfac
= 50% ; G = 4000
cfac
= 50% ; G = 8000
cfac
= 20% ; G = 4000
cfac
= 20% ; G = 8000
1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5-5
0
5
10
15Sprung mass pitch angle
Pitch
An
gle
;
; []
Time ; t ; [s]
1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5-35-30
-15
0
15Sprung mass roll angle
Ro
ll A
ngle
;
; []
Time ; t ; [s]
1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5-20
0
20
40
60Sprung mass yaw angle
Yaw
Ang
le ;
; []
Time ; t ; [s]
cfac
= 100%
cfac
= 50%
cfac
= 20%
cfac
= 50% ; G = 4000
cfac
= 50% ; G = 8000
cfac
= 20% ; G = 4000
cfac
= 20% ; G = 8000
Vehicle body roll angle and yaw rate
Handling Results
17
Groundhook Control
0 2 4 6 8 1050
52
54
56
58
60
Longitudinal displacement ; Xcm
; [m]
Lat
eral
dis
pla
cem
ent
; Y
cm ;
[m
]
Location on grid
cfac
= 100%
cfac
= 50%
cfac
= 20%
cfac
= 50% ; G = 4000
cfac
= 50% ; G = 8000
cfac
= 20% ; G = 4000
cfac
= 20% ; G = 8000
Road-tyre contact
Handling Results
18
Groundhook Control
2 3 4 5 60
1000
2000
3000
4000
Time ; t ; [s]
Ver
tica
l fo
rce
; F
t,z4
; [
N]
Front left tyre vertical force
2 3 4 5 60
1000
2000
3000
4000
Time ; t ; [s]
Ver
tica
l fo
rce
; F
t,z3
; [
N]
Front right tyre vertical force
2 3 4 5 60
1000
2000
3000
4000
Time ; t ; [s]
Ver
tica
l fo
rce
; F
t,z2
; [
N]
Rear left tyre vertical force
2 3 4 5 60
1000
2000
3000
4000
Time ; t ; [s]
Ver
tica
l fo
rce
; F
t,z1
; [
N]
Rear right tyre vertical force
0 2 4 6 8 1050
52
54
56
58
60
Longitudinal displacement ; Xcm
; [m]
Lat
eral
dis
pla
cem
ent
; Y
cm ;
[m
]
Location on grid
cfac
= 100%
cfac
= 50%
cfac
= 20%
cfac
= 50% ; G = 4000
cfac
= 50% ; G = 8000
cfac
= 20% ; G = 4000
cfac
= 20% ; G = 8000
1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5-50
-25
0
25
50Sprung mass pitch rate
Pitch
Rat
e ;
' ; [/
s]
Time ; t ; [s]
1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5-100
-50
0
50
100
150Sprung mass roll rate
Ro
ll R
ate
;
' ; [/
s]
Time ; t ; [s]
1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5-100
-50
0
50
100Sprung mass yaw rate
Yaw
Rat
e ; '
; [/
s]
Time ; t ; [s]
cfac
= 100%
cfac
= 50%
cfac
= 20%
cfac
= 50% ; G = 4000
cfac
= 50% ; G = 8000
cfac
= 20% ; G = 4000
cfac
= 20% ; G = 8000
1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5-5
0
5
10
15Sprung mass pitch angle
Pitch
An
gle
;
; []
Time ; t ; [s]
1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5-30
-15
0
15Sprung mass roll angle
Ro
ll A
ngle
;
; []
Time ; t ; [s]
1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5-20
0
20
40
60Sprung mass yaw angle
Yaw
Ang
le ;
; []
Time ; t ; [s]
cfac
= 100%
cfac
= 50%
cfac
= 20%
cfac
= 50% ; G = 4000
cfac
= 50% ; G = 8000
cfac
= 20% ; G = 4000
cfac
= 20% ; G = 8000
Vehicle body roll angle and yaw rate
Handling Results
19
Skyhook Control
0 2 4 6 8 1050
52
54
56
58
60
Longitudinal displacement ; Xcm
; [m]
Lat
eral
dis
pla
cem
ent
; Y
cm ;
[m
]
Location on grid
cfac
= 100%
cfac
= 50%
cfac
= 20%
cfac
= 50% ; G = 4000
cfac
= 50% ; G = 8000
cfac
= 20% ; G = 4000
cfac
= 20% ; G = 8000
Road-tyre contact
Handling Results
20
Skyhook Control
2 3 4 5 60
500
1000
1500
2000
2500
3000
Time ; t ; [s]
Ver
tica
l fo
rce
; F
t,z4
; [
N]
Front left tyre vertical force
2 3 4 5 60
500
1000
1500
2000
2500
3000
Time ; t ; [s]
Ver
tica
l fo
rce
; F
t,z3
; [
N]
Front right tyre vertical force
2 3 4 5 60
500
1000
1500
2000
2500
3000
Time ; t ; [s]
Ver
tica
l fo
rce
; F
t,z2
; [
N]
Rear left tyre vertical force
2 3 4 5 60
500
1000
1500
2000
2500
3000
Time ; t ; [s]
Ver
tica
l fo
rce
; F
t,z1
; [
N]
Rear right tyre vertical force
0 2 4 6 8 1050
52
54
56
58
60
Longitudinal displacement ; Xcm
; [m]
Lat
eral
dis
pla
cem
ent
; Y
cm ;
[m
]
Location on grid
cfac
= 100%
cfac
= 50%
cfac
= 20%
cfac
= 50% ; G = 4000
cfac
= 50% ; G = 8000
cfac
= 20% ; G = 4000
cfac
= 20% ; G = 8000
Suspension Control Results Summary
21
Control Gain Passive
Level Result
Baseline
Result
Ride Comfort
Skyhook 1200Ns/m 0%
0.88m/s2 RMS
vertical
acceleration. 2.1m/s2 RMS
vertical
acceleration. Optimal Passive 7.5%
0.95m/s2 RMS
vertical
acceleration.
Handling
(Conventional
off-road
vehicles)
Skyhook 8000Ns/m 50%
Up to 6%
contact loss at
1 wheel. Body
roll reduced.
Up to 12%
contact loss at 3
wheels.
Handling
(Test vehicle) Optimal Passive 20%
Yaw rate of
88°/s
obtained.
Yaw rate of
62°/s obtained.
58%
55%
42%
Conclusion
12 DOF full vehicle model developed using ADAMS View software and validated
Various MR damper models developed and superior model combined with vehicle model
Ride comfort improved using skyhook control
Directional response of test vehicle improved using low passive damping
Body roll and road-tyre contact of conventional off-road vehicle improved using skyhook control and high passive damping
22
Recommendations
Recursive MR damper modeling with force feedback
Vehicle model improvement
Suspension characteristics for other handling manoeuvres
Future Work
Combined ride comfort and handling
Suspension control algorithms: focus on vehicles without differentials
Hardware-in-the-Loop tests to measure MR damper force
23
Recommendations & Future Work
Thank You