Jean-Christophe FAUROUX
[email protected]
Guillaume DOUARRE LaMI / IFMA / UBP Clermont-Ferrand, France
Improving Skid-steering Fauroux / Vaslin / Douarre Laboratoire de Mécanique & Ingénieries
Philippe VASLIN
[email protected] LIMOS / UBP Clermont-Ferrand, France
Improving skid-steering on a 6x6 all-terrain vehicle A preliminary experimental study
KOKOON project www.kokoon.fr.st
IFToMM 2007, The 12th World Congress in Mechanism and Machine Science
IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE June 1721, Besançon, FRANCE
1
Introduction to the problem Two existing principles for steering a wheeled vehicle Improving Skid-steering Fauroux / Vaslin / Douarre
Introduction Vehicle
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Ackermann steering
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Skid-steering
Our purpose ●
To keep the robustness and mechanical simplicity of skid-steering vehicles
Experiment ●
Results Conclusion Future work
Trying to minimize the energy consumption of such vehicles during steering
A complex phenomenon, difficult to model Preliminary experimental results to check consistency ●
Evaluate the ripping forces
●
Try to minimize them...
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...by adjusting normal contact forces
IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE
2
Ackermann steering
Improving Skid-steering Fauroux / Vaslin / Douarre
Introduction ●
Ackermann
●
Skid-steering
Ackermann (1817) / Jeantaud (1870) For wheeled vehicles that steer with minimal skid With N axles, (N-1) axles must steer at least Mostly for hard ground
Vehicle Experiment Tricycle scooter, Piaggio MP3
Results
C Mobile crane, Liebherr 15008.1 6 steering axles out of 8
Conclusion Future work Power lift truck, Manitou M26
Mobile mortar, Patria NEMO
Minimal skid vs. complexity IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE
Semitrailer 1 steering axle out of 5 + 1R
3
Skid-steering
Improving Skid-steering Fauroux / Vaslin / Douarre
Introduction ●
Ackermann
●
Skid-steering
For wheeled and tracked vehicles Mechanical simplicity (no steering mechanism, only suspension) Wheels cannot roll laterally Mostly for low friction / soft grounds
Vehicle Experiment Results
Two versions of the same mobile mortar Ackermann and Skidsteering tracked, Patria AMOS
C
Conclusion Future work Amphibian ATV, Oasis LLC Max 6x6
Tracked tractor, Caterpillar D6R III
Mobile robot, Pioneer 3 AT
Simplicity vs. turning resistance IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE
AT wheelchair, Modul Evasion
4
Overview of the 6x6 Kokoon vehicle
Improving Skid-steering Fauroux / Vaslin / Douarre
Introduction
An ATW (All-Terrain Wheelchair) 6x6 transmission and 2x1330W electric engines Oleo-pneumatic suspension on all wheels Climbing capacity: 20cm obstacles, 36% slopes Speed: 8 km/h Autonomy: 4h
Vehicle ●
Overview
●
Transmission
●
Suspension
Experiment Results Conclusion Future work
IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE
Designed at IFMA from 1999
5
Overview of the 6x6 Kokoon vehicle Multiple functions Improving Skid-steering Fauroux / Vaslin / Douarre
Introduction
Sliding sport seat Top case or transporting platform
Overview
●
Transmission
●
Suspension
Experiment Results Conclusion Future work
Safety harness
Improved access: sliding seat
Controlled by joystick
Vehicle ●
Roll bar
Lead batteries 24V 160Ah Transport position 2 DC electric engines of 1330W each 6x6 allterrain vehicle
Independent oleopneumatic suspensions
Skid steering for robustness and allterrain mobility A reconfigurable vehicle A research platform with sensors IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE
Research configuration with onboard camera, double acquisition laptop and suspension sensors 6
Vehicle transmission
Improving Skid-steering
Belt transmission: 3 wheels at the same speed Compatible with suspension displacements Good efficiency Clutching
Fauroux / Vaslin / Douarre
Introduction Vehicle ●
Overview
●
Transmission
●
Suspension
Experiment Results Conclusion Future work
IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE
7
Vehicle suspension 5 17
6 Independent wheels Improving Skid-steering
● ●
10 3
cm
cm
Length = 175 cm Width = 103 cm
7
cm
Fauroux / Vaslin / Douarre
Introduction
● ●
Track width = 93 cm Wheel base = 47 cm 40 cm
Vehicle ●
Overview
● ●
●
●
Transmission Suspension
Experiment
93
●
●
47
cm
Trailing arm suspensions ●
Results
Wheel diam. = 40 cm Wheel width = 7 cm
47
cm
cm
Robust Easy to adjust Oleo-pneumatic shock-absorber
Conclusion Future work
IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE
8
The force plate Steadystate circular turning A force plate to measure contact reaction forces Improving Skid-steering
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Fauroux / Vaslin / Douarre
●
●
Rx Ry Rz
longitudinal force provided by the engines lateral force due to ripping normal force due to mass dispatching
Introduction Z
Vehicle
Cir cu
Experiment ●
Force plate
●
Mass
●
Suspensions
●
Turning
Results
lar t
X
raje
cto
ry
Gro
und
For
ce
pla
Y te
Conclusion Future work IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE
9
The force plate
60cm
A sixcomponent force plate (TSR, France) Force measurement ranges: Improving Skid-steering Fauroux / Vaslin / Douarre
Introduction Vehicle Experiment ●
Force plate
●
Mass
●
Suspensions
●
Turning
Results Conclusion Future work
Rx: 1000N
Ry: 900N
80cm
Rz: 2000N
3 twocomponent strain gauge transducers at 120° 3 tangential components (RxRy) 3 normal components (Rz) Acquisition chain: 6 channels, 16 bits, 100Hz, Labview Wrench = 6x6 Calibration matrix x Tensions
Fx Fy Fz =[ C ] Mx My Mz
V1 V2 V3 V4 V5 V6
Wooden box
Z
Wooden box
Force transducers
Ground level
Top plate Base plate
X
IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE
Y
10
Mass dispatching
Improving Skid-steering
Centre of mass is computed with the CAD model Hypothesis : uniform density in each part Empty mass: 367 kg
Fauroux / Vaslin / Douarre
Introduction Vehicle Experiment ●
Force plate
●
Mass
●
Suspensions
●
Turning
Results Conclusion Future work IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE
11
Mass dispatching
Improving Skid-steering Fauroux / Vaslin / Douarre
Experimental measurement 6 scales with the same height
Introduction Vehicle Experiment ●
Force plate
●
Mass
●
Suspensions
●
Turning
CAD CM
Central axle axis
Real CM Lifting rectangle
Results Conclusion Future work
Good correlation Experiment / CAD IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE
12
Suspension reconfiguration Reconfigurable suspension Improving Skid-steering Fauroux / Vaslin / Douarre
● ●
●
Reference configuration Three identical suspensions Includes a 83kg driver 108 kg
Introduction Vehicle Experiment ●
Force plate
●
Mass
●
Suspensions
●
Turning
Results
● ●
●
●
Future work
183 kg
Modified configuration Differentiated suspensions Central suspension becomes more loaded 80 kg (26%)
A new mass dispatching
250 kg (+58%) z
Reference dimensions ●
Conclusion
158 kg
Adjustment with hs
●
Initial
hs = 145mm
●
New
hs = 045mm
x Parameter
Value
vs
180 mm
hs std
145 mm
hs mod
45 mm
ls
210280 mm
l2
170 mm
la
350 mm
e
15 mm
IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE
120 kg (35%)
hs
O
S1 θs
vs
Fs ls
B θa
C l2
Fw
e la
S2
13
Turning experiment Three types of trajectories for the external wheels Radius R Improving Skid-steering Fauroux / Vaslin / Douarre
Infinite ( => straight line)
6m
3m
Acquisition at 100Hz is enough for low speed (around 45 kph) Duration: from 1.5s (straight line) to 2.5s (3m turn)
Introduction Vehicle Experiment ●
Force plate
●
Mass
●
Suspensions
●
Z
Y
3m
R =
Turning
Results Conclusion Future work
X
m
6
= R
Li ne
s dr
aw
n
wi
th fl
ou r
IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE
14
Typical curves
Improving Skid-steering Fauroux / Vaslin / Douarre
Introduction
Curves of Rx, Ry, Rz are provided One or two wheels on the force plate at the same time Five zones appear on the time axis Average values on each zone (vibrations on gravel and electric perturbations) Rz1 = 627N Rz2 = 972N Rz3 = 905N (one side only) Main results: Wheels 2 and 3 prevail for Rz > confirms weight dispatching ● ● ●
Vehicle
2000 Reaction forces (N)
Wheel 1
Standard suspension
Experiment
Wheels 1 and 3 prevail for Ry and turning moment Wheel 2 generates most of the traction force Rx (belt sliding ?) Wheels 1+2
Wheel 2
Wheels 2+3
Wheel 3
Rx (N) Ry (N)
Turn R = 6m
Rz (N)
1500
Results ●
Curves
●
Reference
●
Modified
●
COP
●
Explanation
1000
500
0
Conclusion Future work
500 0
0,5
1
Time (s)
1,5
IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE
2
15
2000
Wheels 1+2
Reaction forces (N) Standard suspension Straight line
Wheels 2+3
1500 Wheel 1
Wheel 2
Wheel 3
Results for reference vehicle
Rx (N) Ry (N) Rz (N)
1000 Rz
Influence of radius R Rz does not changes with R
500
Improving Skid-steering Fauroux / Vaslin / Douarre
Rx 0 Ry
Ry is quasi null in straight line Ry increases when R decreases
500 0
0,5
Time (s)
1
1,5
2000
Introduction
Reaction forces (N) Standard suspension Turn R = 6m
1500
Vehicle
Rx is quasi null in straight line Rx increases when R decreases This phenomenon was experienced by the driver
1000
Experiment
Rz 500
Results
Rx 0
●
Curves
●
Reference
Ry 500
●
0
0,5
1
Time (s)
1,5
2
2000 Reaction forces (N) Standard suspension Turn R = 3m
Modified
1500 ●
COP 1000
●
Explanation Rz 500
Conclusion Rx 0
Future work
Ry
IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE
500 0
0,5
1
Time (s)
1,5
2
2,5
16
2000 Reaction forces (N) Standard suspension Straight line 1500
Wheels 1+2
2000
Wheels 2+3
Results for modified vehicle
Wheel 1
Wheel 2
Wheel 3
Reaction forces (N) Modified suspension Straight line
Rx (N) Ry (N) Rz (N)
1500
1000
1000 Rz
500
Improving Skid-steering Fauroux / Vaslin / Douarre
Rx
Rx 0
0 Ry
Ry
500
500 0
0,5
Time (s)
1
1,5
0
2000 Reaction forces (N) Standard suspension Turn R = 6m
Rz
500
Results
Rx
Rx
0
0 Ry
Ry
500
500 0
0,5
1
Time (s)
1,5
0
2
2000 Reaction forces (N) Standard suspension Turn R = 3m
Modified
0,5
1
Time (s)
1,5
2000 Turn is shorter on modified vehicle
Reaction forces (N) Modified suspension Turn R = 3m
1500 A 36% decrease of Ry on Wheel 3
1500
COP 1000
●
Rz 500
●
1000
Experiment
●
1,5
A 38% decrease of Rx on Wheel 2
1000
Reference
1
1500
Vehicle
●
Time (s)
Reaction forces (N) Modified suspension Turn R = 6m
1500
Curves
0,5
2000
Introduction
●
Rz
500
1000
Explanation
Rz
Rz 500
500
Conclusion Rx 0
Rx
0
Future work
Ry
Ry IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE 500
500 0
0,5
1
Time (s)
1,5
2
2,5
0
0,5
1
Time (s)
1,5
17
Centre of pressure (COP) COP = the point where the moment of contact wrench is null Phases are visible (one or two wheels on the force plate) The COP follows circles => Trajectories were correct Improving Skid-steering
60
X (cm)
Fauroux / Vaslin / Douarre
Introduction
50
Vehicle Experiment Results ●
Curves
●
Reference
●
Modified
●
COP
●
Explanation
Conclusion Future work
Going straight
40
Turn R=6m
Turn R=3m
30 20 10 Y (cm)
0
0
10
20
30
40
50
IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE
60
70
80 18
Physical explanations Strong influence of mass dispatching on turning ability Analogy with the behaviour of a road tire Improving Skid-steering
● ●
Fauroux / Vaslin / Douarre
Introduction
Lateral force Ry increases with normal force Rz Lateral force Ry depends also on slip angle s
●
Linear behaviour up to sl
●
During skidsteering, two slip angles s1 and s3 appear on wheels 1 and 3
Forceplatform
Vehicle Experiment
Lateral force RY
X
s1
Results ●
Curves
●
Reference
●
Modified
●
COP
●
Explanation
Conclusion Future work
RZ1 > RZ2 > RZ3
V1
V2
V3
s3
RZ1 RZ2
RZ3 Slip angle
Y
s sl
Circular trajectory of radius R
IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE
19
Conclusion
Improving Skid-steering Fauroux / Vaslin / Douarre
Introduction
Skid-steering can be greatly improved... ...only by minor adjustments on the suspensions 10cm adjustments only decreased normal force of 30% on front and rear axles Propulsion forces decreased of 30% when steering Multi-axles vehicles without steering systems are robust. They can now be efficient when skid-steering
Vehicle Experiment Results Conclusion Future work
IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE
20
Future work
Improving Skid-steering Fauroux / Vaslin / Douarre
Introduction Vehicle Experiment
Replace belts by chains to suppress sliding Add 6 force sensors inside the wheels for continuous measurement Build analytical model Towards an active correction system
TSR force sensor in a wheel
Results Conclusion Future work
Acknowledgement ANVAR : French National Agency for Development of Research TIMS Research Federation Mobility pole
Michelin Company
...and many more on www.kokoon.fr.st
IFToMM 2007, The 12th World Congress in Mechanism and Machine Science June 1721, Besançon, FRANCE
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