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