Partial squeeze-film levitation modulates fingertip friction - - PowerPoint PPT Presentation

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Partial squeeze-film levitation modulates fingertip friction - - PowerPoint PPT Presentation

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Partial squeeze-film levitation modulates fingertip friction Controlling macroscopic friction in vivo Michal Wiertlewski, Rebecca Fenton Friesen, J. Edward Colgate why does touch matter? low friction Courtesy of R. Johansson, Umea University

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Michaël Wiertlewski, Rebecca Fenton Friesen, J. Edward Colgate

Partial squeeze-film levitation modulates fingertip friction

Controlling macroscopic friction in vivo

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low friction

why does touch matter?

2

Courtesy of R. Johansson, Umea University

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SLIDE 3

low friction

the role of shear force

3

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low friction

haptic interfaces

4

Controlling forces on the user via manipulandum

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SLIDE 5

5

flickr/ChaochaoX

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low friction

ultrasonic friction modulation

6 Watanabe and Fukui, 1995

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SLIDE 7

low friction

amplitude dependency

7

vibration amplitude

(µm)

friction coefficient 2 1

typical participant

1 2 3

artificial finger

α

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SLIDE 8

low friction

vibration modulation

8

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low friction

previous hypotheses : squeeze film

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Watanabe and Fukui, 1995 Winfield et al. 2007 Biet et al. 2007

∂ ∂x ✓ ¯ u3p 12µ ∂p ∂x ◆ = ∂(p¯ u) ∂t

p

vibration lift air ow

α sin ωt u

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SLIDE 10

low friction

previous hypotheses : squeeze film

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Watanabe and Fukui, 1995 Winfield et al. 2007 Biet et al. 2007

µ0 µ = 1 − fsq fn ∂ ∂x ✓ ¯ u3p 12µ ∂p ∂x ◆ = ∂(p¯ u) ∂t fsq = Z

S

p0 @ s u2 + 3

2α2

u2 − α2 − 1 1 A

p

vibration lift air ow

α sin ωt u

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SLIDE 11

low friction

near-field acoustic levitation

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Chu and Apfel 1982 Hashimoto et al 1996

u ∝ s β fp α

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low friction

structure of the fingertip

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skin collagen fjbers network bone

Persson et al. 2013 Pasumarty et al. 2011

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low friction

surface topography

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3 4 5 6 7

  • 30
  • 28
  • 26
  • 24
  • 22
  • 20
  • 18
  • 16

log q (1/m)

red: dry 1 green: dry 2 blue: wet 1 H=0.75

log C (m

4)

Persson et al. 2013

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SLIDE 14

low friction

measurement real area of contact

13

Wiertlewski, M., Fenton Friesen R., Colgate, E., PNAS 2016

evanescent wave scattering ~300 nm

brightness friction force (N) 0.5 1 0.5 1

Wiertlewski, M., Fenton Friesen R., Colgate, E., PNAS 2016

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SLIDE 15

low friction

setup

14

Wiertlewski, M., Fenton Friesen R., Colgate, E., PNAS 2016

t stroboscopic illumination

camera

  • 30 kHz resonance frequency
  • pixel size of 10 µm
  • green light to limit diffusion
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low friction

variable friction

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low friction

contact mechanics

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asperities height distribution

u0

urms

ps pr

Greenwood & Williamson 1966 Persson 2007

pr = pc e−u/urms

pc = 0.375 q0 urms E 1 − ν2

with

E = 20 MPa urms = 2.5µm q0 = 104m−1

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low friction

squeeze-film levitation

17

∂ ∂x ✓ ¯ u3p 12µ ∂p ∂x ◆ = ∂(p¯ u) ∂t

Reynold’s lubrication equation for laminar flow:

α small α large u u0

pa = p0 @ s u2 + 3

2α2

u2 − α2 − 1 1 A ≈ 5 4 p0 α2 u2

leads to : Salbu 1964 Minikes et al. 2004

if σ = 12ωµL2 p0u2 > 36

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SLIDE 19

low friction

equilibrium

18

p(r) p(r) α sin(ωt)

fjngertip applied pressure reaction from support squeeze fjlm pressure pa

pr

ps − pr = pa ps ⇣ 1 − e

−u+u0 urms

⌘ = 5 4 p0 α2 u2

2 4 6 8 10 initial gap

u0/urms u/urms

normalized film thickness

5

10 15

fixed pressure pr normalized amplitude α/urms

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low friction

relation to friction

19

Bowden and Tabor 1939 Persson 2007

apparent area

  • f contact

true area of contact

A = A0 e

−u+u0 urms

≈ A0 e

−α2 2Γ

ft = τ0 A

A/A0

0.2 0.4 0.6 0.8 1

relative area

0.2 0.4 0.6 0.8

1

normalized amplitude α/urms

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low friction

real area of contact

20

Wiertlewski, M., Fenton Friesen R., Colgate, E., PNAS 2016 Wiertlewski, M., Fenton Friesen R., Colgate, E., PNAS 2016

radial coordinate (mm) estimated pressure (kPa) 2 4 6 applied pressure 0.5 µm 1 µm 1.5 µm 2 µm squeeze film 5 10

  • 5

5 interfacial separation (µm)

A B

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low friction

model vs data

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vibration amplitude

(µm)

friction coefficient 2 1

typical participant

1 2 3

artificial finger

α

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low friction

effect of moisture

22

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low friction

strobing

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light strobe plate motion

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low friction

micro-second stroboscopy

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low friction

dynamic of the contact area

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  • 2
  • 1

1 2 4 8

ωt

brightness plate displacement (µm)

π

0.6 0.7 0.8 0.9 1 2π RMS brightness variation (%)

m

fingertip dynamic vibrating plate x1 = α sin(ωt) squeeze film & asperities bt kt x2 = u + x1

brightness

∝ exp − u urms

2π/ω

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low friction

artificial fingers

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Fenton Friesen R. Wiertlewski, M., Peshkin M.A, Colgate, E., Worldhaptics 2015

rigid skin backing alumium core

Rebecca Fenton Friesen

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low friction

artificial fingers

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50 100 relative friction reduction (%) 0.3 0.7 1.1 linearized stifgness (N/mm) 0.4 0.2 0.1 coeffjcient of restitution 0.3 TangoPlus human fjnger BioTac DragonSkin

Fenton Friesen R. Wiertlewski, M., Peshkin M.A, Colgate, E., Worldhaptics 2015

Rebecca Fenton Friesen

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low friction

influence of damping in the tissues

27

nonlinear squeeze film asperity tips creating gap

α sin(ωt) ps

displacement (µm) −1 1 2 1 ms high damping factor

ζ = 0.1 ζ = 2.5

low damping factor

g >0 g

Fenton Friesen R. Wiertlewski, M., Colgate, E., Haptic Symposium 2016.

1 0.6 1.2 Average gap (µm)

ζ

0.1 10 damping ratio under-damped regime

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low friction

friction modulation under vacuum

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amplitude (um) 0.5 1 1.5 2 2.5 3 relative friction 0.2 0.4 0.6 0.8 1 1 atm 0.5 atm 0.1 atm 0.02 atm experimental conditions

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 44 45 46 47 48 49 50 51 52 amplitude (um) aligned motor current (mA) atmospheric vacuum stalled motor 1 0.5 estimated relative friction

Fenton Friesen R. Wiertlewski, M., Peshkin M.A, Colgate, E., Worldhaptics 2017

force sensor motor vacuum gauge vacuum pump actuating piezos sensing piezo nodal lines camera vacuum chamber finger

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low friction

lastest hypothesis : partial levitation

29

5µm throw cushioned impact max separation descent

30 µs time

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what can we do with it?

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ultrasonic actuators glass plate

  • ptical sensor

led controller

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low friction

high-fidelity rendering

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  • fast non-contact position sensor (8 µm - 5 kHz)
  • 6.25 points per cycle with vc = 250mm/s
  • 12 bit dac and linear amplifier
  • compensation filters

Daniele Leonardis

David Meyer

Wiertlewski, M., Leonardis D., Meyer, D., Peshkin, M., Colgate, E., Eurohaptics 2014.

modulation signal carrier friction force ultrasonic fjnger friction

a(t) ft(t) sin 2πf0t

driving signal

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low friction

vibration of texture

33

5 10 15 20 25 30 fjnger position (mm) −100 100 0.1 10 1 4 8 interaction force (mN)

  • spat. freq. (1/mm)
  • ampl. (mN)

Wiertlewski, M., Lozada,J., Hayward, V. IEEE Transactions on Robotics, 2011

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low friction

normal force modulation

34

  • J. Monnoyer, E. Diaz, C. Bourdin, M. Wiertlewski. Eurohaptics 2016

low friction high friction

Johansson & Flanagan 2009

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SLIDE 38

low friction

normal force modulation

35

  • J. Monnoyer, E. Diaz, C. Bourdin, M. Wiertlewski. Eurohaptics 2016.


falling friction normal force

5 10 0.5 1

n=14

normal force rising friction

0.5 1 5 10

n=9 no correlation

5 10 0.5 1

n=5 correlation p<5% friction variation (a.u)

Jocelyn Monnoyer

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low friction

conclusion

  • Friction carries rich tactile

information

  • Multi-scale model is useful to

capture the behavior of ultrasonic levitation

  • ongoing work to understand

sliding friction force fluctuations

  • in vivo friction is messy
  • large variability
  • multi-physics

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conclusion

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low friction

acknowledgments

37

  • Stéphane Viollet
  • Jocelyn Monnoyer, Xi Lin
  • Viviane Gleizes, Nicolas Huloux, Di Chen

michael.wiertlewski@univ-amu.fr

  • Ed Colgate
  • Michael Peshkin
  • Rebecca Fenton Friesen
  • David Meyer,