analyzing tire performance via wheel and contact patch ... 2012.pdf · integrate 6-component wheel...

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Slide 1

Analyzing Tire Performance Via Wheel

and Contact Patch Force Measurements

Dr. Rahul Ahlawata, Dr. Michael Smitha & Mr. Tatsuo Ichigeb

a A&D Technology, Michigan, USA b A&D Company, Tokyo, Japan

Tire Technology Expo 2012

February 14-16, Cologne, Germany


Slide 2

Objective

Integrate 6-component wheel force sensor with 3-component tire footprint force sensor to provide unparalleled state-of-the-art tire performance data

Force Matrix Sensor (FMS)

Wheel Force Sensor (WFS) Wheel Posture Sensor (WPS)

Tire Measurement System


Slide 3

Interest in Tire Footprint Force Measurement

Study vehicle dynamics with tires as a combined system

Tire design & tread wear

Tire-pavement interaction

Model validation data

NASA, 1991[2]

CSIR, 2004[5]

Smithers, 1999[4]

Smithers, 1999[4]


Slide 4

A&D’s Force Matrix Sensor (FMS)

Tire path

Force sensor

Road embedded

Measurement directions

Sensor unit

Installation


Slide 5

FMS Overview

Sensor size: 7.5mm x 7.5 mm (each sensor), 10 sensors/unit Maximum number of units: 96 (total 960 sensors)

Speed/sampling rate: 20kHz (simultaneous), 0-300 km/hr Input force range per sensor: 100N (Fz), 50N(Fx), 50N(Fy)

FMS can be used indoors or outdoors (dry conditions only) Advantages of outdoor testing: o Testing conditions are closer to real world conditions o Presence of contaminants is important for tread wear testing o Obtain driver feel and conduct combined vehicle & tire

development Advantages of indoor testing: o Faster testing o More controlled conditions o Easy to study the influence of variables

One Unit


Slide 6

Wheel Force Sensor/Wheel Position Sensor

Wheel Force Sensor (WFS) Measures three component forces (Fx, Fy and Fz) and moments (Mx, My and Mz) acting at the wheel hub Wheel Position Sensor (WPS) Measures the movement of wheel in all six degrees of freedom

WFS Design: o Distributed force bridges with model based

decomposition to get orthogonal force components

o Very low cross sensitivity, low interference and high sampling rate Distributed force bridges


Slide 7

Outdoor Testing Setup Test Vehicle: Mini

Cooper S, Front Wheel drive

Default conditions: Weight of test vehicle (with equipment & crew) 1426kg (front 870kg, rear 556 kg), tire pressure 250kPa

FMS data recorded at 20kHz, Logger data at 10 kHz, WFS data

at 2kHz


Slide 8

Advancements in the Last 50 Years

South African Council for Scientific & Industrial Research (CSIR), Pretoria (1959) [1]

A&D Research and Development Center, Tokyo, Japan (2011)


Slide 9

FMS Coordinate System

FMS records the forces exerted BY the tire ON the road

(as per the following coordinate system)

Fx’ Fy’

Fz’

Fz

Fx

Fy

All results in this presentation are the forces exerted BY the

road ON the tire (as per the ISO coordinate system shown below)

The relationship between the recorded forces {Fx’,Fy’,Fz’} and plotted forces {Fx,Fy,Fz} is: Fx= -Fx’, Fy= Fy’, Fz= Fz’


Slide 10

Fz

Fx

Fy

WFS Coordinate System WFS records the forces exerted

ON the tire hub (as per the following coordinate system)

Fx’ Fy’

Fz’

Axes are converted to be consistent with FMS data

(as per the ISO coordinate system shown below)

The relationship between the recorded forces {Fx’,Fy’,Fz’} and plotted forces {Fx,Fy,Fz} is: Fx= -Fx’, Fy= Fy’, Fz= -Fz’


Slide 11

Recording Tire Footprint Forces

Direction of Travel

Front Right (FR) tire passes over FMS during motion

X Y

X

Y


Slide 12

Orientation of the Results

This recorded data are reorganized to comply with this orientation

Inside Shoulder

Crown

Leading Edge

Trailing Edge

Outside Shoulder

Local Force (N)

Local Fz for 40km/hr coast-down test


Slide 13

Variation of Forces in X Direction

X axis

40 curves

X

Y 1

2

40

Sensors 1-40

3 4

Each sensor records {Fx,Fy, Fz} forces as the vehicle travels in

X direction

Sensors are stacked up

along Y axis

Sum of 40 curves gives total forces in Y direction plotted along the length of the contact patch


Slide 14

Variation of Forces in Y Direction

Y axis

X

Y

8mm Resample data to account for the width of the sensor

Total forces in X direction plotted along the width of the contact patch

Each tread is in contact with the sensor until it travels 8mm


Slide 15

Analysis of Fx during Coast-down

Straight line 20 km/hr coast-down Test

Leading edge has positive & trailing edge has negative forces due to change in relaxation cord tension as the footprint tries to narrow itself [3]

Toe-in results in higher forces on the shoulder corresponding to outer edge

Test Tires: Yokohama BluEarth 205/55R16

Fx Fx


Slide 16

Analysis of Forces along X axis


Sanity check: Total Fz (FMS)= 4372N Fz (WFS)=4315N 50% of static front weight of the car =4268N

Fz peaks in the leading edge resulting in a positive rolling resistance moment

Fz



Slide 17

Analysis of Fx during Acceleration

Straight line 20% acceleration Test

Due to application of external torque, trailing edge shows positive peaks [7]

Shoulders produce more force than the crown [4,8]


Fx Fx


Slide 18

Analysis of Forces along X axis


Sanity check: Total Fz (FMS)= 4154N Total Fz for coast-down test (FMS)=4182N 50% of static front weight of the car=4268N

Effect of weight transfer can also be seen in Fz peaks

Fz

Straight line 20% acceleration Test


Slide 19

Effect of Braking on Fx

20km/hr coast-down

20km/hr Light-braking

20km/hr High-braking

Test Tires: Bridgestone Sneaker 205/55R16 91V

Fx Fx

Fx Fx

Fx Fx

Σy Fx

Σy Fy

Σy Fz

Total Fz(FMS)=3974N Total Fz(WFS)=4280N




Slide 20

Effect of Braking on Footprint Forces

Straight line 20km/hr coast-down test

Test Tires: Bridgestone Sneaker 205/55R16 91V

Note: Total Fz increases due to load transfer Contact patch area also increases with braking Fz peaks in leading edge, Fx peaks in trailing edge

Σy Fx

Σy Fy

Σy Fz


Fz(FMS)=4633N Fz(WFS)=4682N

Straight line 20km/hr light-braking test

Total Fx(FMS)= -102N Total Fx(WFS)= -104N


Total Fx(FMS)= -1518N Total Fx(WFS)= -1526N


Slide 21

Comparison of Different Tires B

rid

geSt

on

e

Snea

ker

20

5/5

5R

16

91

V

Bri

dge

Sto

ne

R

egn

o G

R-X

T 2

05

/55

R1

6 9

1V

Bri

dge

Sto

ne

B

lizza

k R

EVO

2

20

5/5

5R

16

91

Q

60 km/hr coast-down Test

Fx

Fx

Fx

Fx

Fx

Fx

Σx Fx Σx Fy

Σx Fz

Total Fz(FMS)=4200N

Total Fz(FMS)=4144N

Total Fz(FMS)=4270N


Slide 22

Comparison of Different Tires B

rid

geSt

on

e

Snea

ker

20

5/5

5R

16

91

V

Bri

dge

Sto

ne

R

egn

o G

R-X

T 2

05

/55

R1

6 9

1V

Bri

dge

Sto

ne

B

lizza

k R

EVO

2

20

5/5

5R

16

91

Q

60 km/hr coast-down Test

Fx

Fx

Fx

Fx

Fx

Fx

Σx Fx Σx Fy

Σx Fz

Total Fz(FMS)=4200N

Total Fz(FMS)=4144N

Total Fz(FMS)=4270N

Tires with same specifications but different tread patterns have different shapes of contact patches and produce different force distributions

Low rolling resistance Higher peak Fz Smaller contact patch

High rolling resistance Lower peak Fz Larger contact patch


Slide 23

Analysis of Fy during Coast-down Forces oppose the narrowing of the footprint in Y direction

Shoulders have higher forces. Asymmetry in Y direction reflects the residual aligning torque as well as the camber effect [3,4]


Fy Fy



Slide 24

Analysis of Fy in Coast-down & Acceleration

20km/hr coast-down

100% acceleration

Tire experiences (-)ve Fy during acceleration resulting in a side-pull towards outside

Fy is asymmetric about Y axis due to tire alignment and manufacturing defects


Fy

Fy

Σx Fx Σx Fy

Σx Fz

Σy Fx

Σy Fy

Σy Fz

Total Fz(FMS)=3508N Total Fy(FMS)= -729N

Total Fz(FMS)=4372N Total Fy(FMS)=83N


Slide 25

FMS Assisting in Tread Wear Analysis

Test: Straight-line 20% acceleration with two different pressures (250kPa & 200kPa)

WFS Data: 250kPa 200kPa Fz 4182N 4167N Fx 639N 422N

Gives information about performance but NOT about tread wear


Slide 26

FMS Data Shows Distribution of Forces 2

50

kPa

Straight line 20% acceleration test

20

0kP

a


Fx Fy Fz

Fx Fy Fz


Slide 27

FMS Data Shows Distribution of Forces 2

50

kPa

20

0kP

a

Inside shoulder treads experience MUCH higher peak forces and are likely to wear much faster. Complete footprint measurement can provide this analysis


Slide 28

Summary

Wheel Force Sensor (WFS) Measures transient forces at the wheel hub: Wheel speed Time history of total Fx, Fy, Fz, Mx,

My, Mz Movement of wheel via WPS

Force Matrix Sensor (FMS) Measures the distributions of forces in the contact patch: High resolution of tire footprint

forces Fx, Fy & Fz at preselected locations

Footprint size and shape analysis

Aid in tire/vehicle/pavement design

Obtain inputs and parameters for models

Study tire-vehicle-road as a complete system

Vehicle/tire performance Vehicle/tire safety Tire wear


Slide 29

Acknowledgements

• R&D Center, Division 7 team members:

– Takayasu Sasaki

– Yuuki Sakurai

– Masaaki Banno

– Hiroki Yamaguchi

• Kenji Sato, A&D Company, Japan

• Claude Rouelle, OptimumG, USA

• Marion Pottinger, M’gineering LLC, USA


Slide 30

References

1. “Dynamic forces exerted by moving vehicles on a road surface”, Bonse & Kuhn, Highway Research Board Bulletin, No. 233, pg 9-32, 1959

2. “Static footprint local forces, areas and aspect ratios for three type VII aircraft tires”, Howell, Tanner & Vogler, NASA technical paper 2983, 1991

3. “The three-dimensional contact patch stress field of solid and pneumatic tires”, Pottinger, Tire Science & Technology, 20(1), 1992

4. “Effect of suspension alignment and modest cornering on the footprint behavior of performance tires and heavy duty radial tires”, Pottinger & McIntyre, Tire Science & Technology, 27(3), 1999

5. “Towards the application of stress-in-motion (SIM) results in pavement design and infrastructure protection”, De Beer, Fisher & Kannemeyer, Heavy Vehicles, Weights and Dimensions: 8th International Symposium, Gauteng, South Africa, 14-18 March, 2004

6. “The pneumatic tire”, U.S. Department of Transportation, National Highway and Traffic Safety Administration, 2004

7. “Theory of ground vehicles”, Wong, Third edition, Wiley Inderscience, 2001

8. “Evaluation of tire tread and body interactions in the contact patch”, Koehne, Matute & Mundl, Tire Science & Technology, 31(3), 2003

9. “Towards realistic simulation of deformation & stresses in pneumatic tyres”, Pelc, Applied Mathematical Modeling, 31(3), 2007


Slide 31

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