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Active Steering Project Active Steering Project Andrew Odhams Richard Roebuck David Cebon 2 nd April 2009

Active Steering Project

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Active Steering Project. Andrew Odhams Richard Roebuck David Cebon 2 nd April 2009. Contents. Control concept Low speed testing High speed testing Conclusions. ACTIVE STEERING. Lead Point. Follow Point. Controller Low speed High speed Conclusions. - PowerPoint PPT Presentation

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Page 1: Active Steering Project

Active Steering ProjectActive Steering ProjectActive Steering ProjectActive Steering Project

Andrew OdhamsRichard Roebuck

David Cebon2nd April 2009

Page 2: Active Steering Project

ContentsContentsContentsContents

1. Control concept2. Low speed testing3. High speed testing4. Conclusions

Page 3: Active Steering Project

ACTIVE STEERINGACTIVE STEERINGACTIVE STEERINGACTIVE STEERING

– Define Lead point and follow point– Calculate articulation angle of a perfect tracking

trailer– Steer in relation to difference between real and ideal

articulation angle– Set individual wheel angles to equalise tyre forces

Lead Point

Follow Point

•Controller

•Low speed

•High speed

•Conclusions

Page 4: Active Steering Project

PATH FOLLOWING TESTSPATH FOLLOWING TESTSPATH FOLLOWING TESTSPATH FOLLOWING TESTSUK Roundabout Test

5.3m

8.9m11.25m

12.5m

•Controller

•Low speed

•High speed

•Conclusions

Page 5: Active Steering Project

LOW SPEED LOW SPEED ROUNDABOUTROUNDABOUTLOW SPEED LOW SPEED ROUNDABOUTROUNDABOUT• Unsteered:

•Controller

•Low speed

•High speed

•Conclusions

Page 6: Active Steering Project

LOW SPEED LOW SPEED ROUNDABOUTROUNDABOUTLOW SPEED LOW SPEED ROUNDABOUTROUNDABOUT• Command Steer:

•Controller

•Low speed

•High speed

•Conclusions

Page 7: Active Steering Project

0 10 20 30 40 50 60 70 80 90 100-5

-4

-3

-2

-1

0

1

Time [s]

Off

trac

king

: F

ront

Tra

ctor

- 5

th W

heel

[m

]

Tail Swing

Cut In

LOW SPEED ROUNDABOUTLOW SPEED ROUNDABOUTLOW SPEED ROUNDABOUTLOW SPEED ROUNDABOUT• Offtracking of 5th Wheel:

Locked

Command CVDC

•Controller

•Low speed

•High speed

•Conclusions

Page 8: Active Steering Project

0 10 20 30 40 50 60 70 80 90 100-5

-4

-3

-2

-1

0

1

Time [s]

Off

trac

king

: F

ront

Tra

ctor

- R

ear

Tra

iler

[m]

Tail Swing

Cut In

LOW SPEED ROUNDABOUTLOW SPEED ROUNDABOUTLOW SPEED ROUNDABOUTLOW SPEED ROUNDABOUT• Offtracking of Trailer Rear:

Locked

Command

CVDC

•Controller

•Low speed

•High speed

•Conclusions

Page 9: Active Steering Project

LOW SPEED ROUNDABOUTLOW SPEED ROUNDABOUTLOW SPEED ROUNDABOUTLOW SPEED ROUNDABOUT• Tail Swing:

Locked Command Path Following

• Tail swings into blind spot

•Controller

•Low speed

•High speed

•Conclusions

Page 10: Active Steering Project

• Unsteered:LATERAL TYRE FORCESLATERAL TYRE FORCESLATERAL TYRE FORCESLATERAL TYRE FORCES

•Controller

•Low speed

•High speed

•Conclusions

Page 11: Active Steering Project

LATERAL TYRE FORCESLATERAL TYRE FORCESLATERAL TYRE FORCESLATERAL TYRE FORCES• Unsteered:

• FIXED TRAILER: 36.6 kN

•Controller

•Low speed

•High speed

•Conclusions

Page 12: Active Steering Project

LATERAL TYRE FORCESLATERAL TYRE FORCESLATERAL TYRE FORCESLATERAL TYRE FORCES• Path following Strategy:

• CT-AT TRAILER: 6.1 kN

•Controller

•Low speed

•High speed

•Conclusions

Page 13: Active Steering Project

Rollover PreventionRollover PreventionRollover PreventionRollover Prevention

• Rationale– Reduce the risk of rollover by controlling the path

of the trailer

• Optimal linear control strategy– Minimise lateral acceleration– Maintain acceptable path error

• Virtual Driver Model– Original path following controller is nonlinear– ‘Virtual driver model’ performs same function using

linear control

•Controller

•Low speed

•High speed

•Conclusions

Page 14: Active Steering Project

Virtual Driver ModelVirtual Driver Modelof Trailer Steeringof Trailer Steering

Virtual Driver ModelVirtual Driver Modelof Trailer Steeringof Trailer Steering

TractorSemi-trailer

Current position of 5th wheel

Y

O X

Snapshot of tractor semi-trailer and path of 5th wheel at time instant k

try

0ry 1ry 2ry rhy

uT

tre

•Controller

•Low speed

•High speed

•Conclusions

Page 15: Active Steering Project

Optimal Control StrategyOptimal Control StrategyOptimal Control StrategyOptimal Control Strategy

0 11 0 0

1 0 0 0d d d

ri

x k x kA B By u k k

y k y kD E

Discrete-time equations for vehicle and path of 5th wheel

1 1 1 1 2 2 2 2 2 2

Tx y

0 1 2

T

r r r rhy y y y y

xz

y

The control objectives

where and2

tr

y

eCz Du

a

tru

The cost function

2

22 2

1 20

tr yk

J Q e k Q a k R u k

Path error Lateral Accel’n Steering effort

•Controller

•Low speed

•High speed

•Conclusions

Page 16: Active Steering Project

Results continuedResults continuedResults continuedResults continued

Manoeuvre: Lane changeVehicle speed: 88km/hFixed value of Q1/R=0.05

•Controller

•Low speed

•High speed

•Conclusions

Page 17: Active Steering Project

Selection of weighting valueSelection of weighting valueSelection of weighting valueSelection of weighting value

Q2/R=0.005

Manoeuvre: Lane changeVehicle speed: 88km/hFixed value of Q1/R=0.05

25% reduction

Conventional

•Controller

•Low speed

•High speed

•Conclusions

Page 18: Active Steering Project

Path errors in lane changePath errors in lane changePath errors in lane changePath errors in lane change

0 20 40 60 80 100 120 140 160 180-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

X distance [m]

Path

trac

king

err

or [

m]

Locked [TO=0.35]

PFC(q2/r=0) [TO=0.15]

RSC(q2/r=0.025) [TO=0.31]

RSC(q2/r=0.1) [TO=0.72]

RSC(q2/r=0.0025) [TO=0.07]

q1/r=0.05•Controller

•Low speed

•High speed

•Conclusions

Page 19: Active Steering Project

After lane changeAfter lane changeAfter lane changeAfter lane change

V=88km/h

Locked Path Following Control

•Controller

•Low speed

•High speed

•Conclusions

Page 20: Active Steering Project

PERFORMANCE MEASURESPERFORMANCE MEASURESPERFORMANCE MEASURESPERFORMANCE MEASURES

Performance Measure

Locked

Comm.

SteerPFC RSC

Hig

h

speed

Transient Off-tracking [m] 0.35 -0.15 0.31

Rearward Amplification 1.18 1.05 0.86

•Controller

•Low speed

•High speed

•Conclusions

Low

speed

Steady State Off-tracking [m] 4.3 1.6 1.2

Tail Swing (Entrance) [m] 0.17 0.61 0.0

Peak Tyre Force [kN] 36.6 5.3 6.1

Exit Settling Distance [m] 23.5 8.8 0.6

Page 21: Active Steering Project

ConclusionsConclusionsConclusionsConclusions

• Improved low-speed manoeuvrability– Improved productivity (LCV)– Improved safety

• Reduced tyre scrub– Reduced tyre wear– Reduced vehicle wear

• Improved high-speed stability– 25% LTR reduction with no increase of PE– Important for LCV