Improving Off-Road Vehicle Handling Using an Active Anti-Roll

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Imppgroving off-road vehicle handling using an active anti-roll bar

PH Cronjé Supervisor: Prof PS Els

1 Table of contents

• Statistics

• Problem statement

• Theory

• Proposed solutions

• Simulations

• Design, manufacturing and testing

• Results

• Conclusion

2 Rollover accident statistics

• Number of rollover fatalities per million registered vehicles, averaged from 1985 to 1990 in the United States

3 Rollover accident statistics

• Passenger vehicles involved in fatal accidents, by vehicle body type in the United States

4 Problem statement

• SUVs are growing in popularity

• Poor handling due to off-road capabilities

• Problem statement: Can the handling of an off-road vehicl e b e i mproved with out th e sacrifi ce of rid e comf ort?

5 Theory: Steady state cornering

6 Theory: Vertical load distribution

7 Theory: Static stability factor

t SSF = 2hCG

• Determines if the vehicle will slide before it will roll

• To improve the safety of the vehicle, the following relationship must hold:

t μ < 2hCG

8 Theory: Conclusion

• If th e l atera l acce lerat ion is use d as t he opt im iz ing variable, the vehicle will roll

• Previous work showed that body roll angle is a desired variable to optimized when improving handling for a predefined road and manoeuvre

•To imppgrove handling: o Lower the CG point o Increase suspension stiffness and/or damping o Add additional system which increases the roll stiffness

9 Solutions proposed in literature

• Passive suspension

• Semi-active suspension

• Active anti-roll bar

• Active suspension

• Tilting vehicles

Each of these solutions will now be discussed

10 Passive suspension

• No energy is put into the system and no adjustments are made during operation

11 Semi-active suspension

• Only a small amount of energy is put into the system with which adjustments are made to the system according to external inputs

12 Active anti-roll bar

• Anti-roll bar actuated by an actuator which is actively controlled according to external inputs

13 Active suspension

• A great amount of energy is put into the system and controlled by external inputs

14 Tilting vehicles

• Vehicle leans into the turn

• Works only on narrow vehicles

15 Selected solution

Question 1 2 3 4 5 6 Solution Weighting 0.2 0.1 0.2 0.2 0.1 0.2 Total Position 1. Passive suspension 10 9 4 2 10 7 6.5 4 2. Semi‐active damping 10954887.1 3 3. Active anti‐roll bar 1097.55697.8 1 4. Active suspension 10 8 8 7 3 8 777.7 2

• The solutions was weighted according to the selection criteria

• Selected solution: Active anti-roll bar

16 Active anti-roll bar (AARB)

17 Simulations

• Full non-linear vehicle model in ADAMS 2005

• Simulation uses Simulink and Matlab

• Adjustments to obtain correlation:

– Spring and damper characteristics

– Tyre characteristics

– CG height

– Chassis torsional stiffness

18 Correlation of baseline model

6 Measured Simulated

2 g) ee

0 Body roll angle (D -2

-4

-6 3 4 5 6 7 8 9 10 11 Time (s)

19 Model proposed solution

• Proposed solution was modelled in ADAMS

• Simulations was used to obtain specific design variables and predict results

• Proposed solution

predicts 80%

improvement in

bodyyg roll angle

20 Simulate proposed solution

Body roll angle: Base vehicle vs AARB vehicle on flat road 6 Base vehicle AARB vehicle

2 (Deg) ee

0 age body roll angl rr -2 Ave

-4

-6 0 1 2 3 4 5 6 7 8 9 10 Time (s)

21 Design, manufacturing and testing

22 Vehicle implementation

23 Tests

• Tests was performed as Gerotek Test Facilities, West of Pretoria

• The tests consisted of: o Steady state handling test: Constant radius test o Dynamic handling test: DLC manoeuvre o Ride comfort test: Drive over the Belgian paving at constant speed

Each of these test will now be discussed

24 Constant radius test

• Accelerate slowlyyg from standstill while following a

constant radius around a point until the vehicle is

unable to

maintain a

constant radius

25 Double-lane-change-manoeuvre

• Enter fffirst lane at a predefined speed

• Swerve to offset lane

• Return to original lane

26 Ride comfort test

• Dr ive over the Be lg ian pav ing in a s tra ig ht line w ith a constant speed

27 Results: Constant radius test

4 e (Deg)

rage bodyrage roll angl 2 Ave

0 Soft suspension, ARB disconnected Soft suspension, ARB connected Soft suspension, AARB -1 -1 0 1 2 3 4 5 6 7 8 Lateral acceleration (m/s2)

28 Results: DLC manoeuvre

6 Without ARB

5 With ARB With AARB

)) 2

Roll angle (Deg 0

-1

-2

-3

-4 5 6 7 8 9 10 11 12 13 Time (s)

29 Results: Ride comfort test

• Vertical acceleration weighted according to the BS 6841 : 1987 standard for vertical vibration on a seated person

• RMS was calculated from weighted vertical acceleration

TtTest run SiSuspension ARB setti ng: WihtdWeighted no.: setting: RMS: 1 Soft Disconnected 143m/s1.43 m/s2

2 Soft Connected 1.41 m/s2

3 Soft Active 1.44 m/s2

30 Conclusion

• The AARB system shows a 74% improvement in maximum body roll angle during a DLC manoeuvre with the soft suspension over the base line vehicle

• The AARB system showed no detrimental effect on the ride comfort of the vehicle

• AARB system can dramatically improve the handling of an off-road vehicle without the sacrifice of ride comfort.

• Thank you for your time and safe driving!