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

Partial squeeze-film levitation modulates fingertip friction Controlling macroscopic friction in vivo Michaël Wiertlewski, Rebecca Fenton Friesen, J. Edward Colgate

why does touch matter? low friction Courtesy of R. Johansson, Umea University 2

the role of shear force low friction 3

haptic interfaces Controlling forces on the user via manipulandum low friction 4

flickr/ChaochaoX 5

ultrasonic friction modulation low friction Watanabe and Fukui, 1995 6

amplitude dependency 2 typical friction coefficient participant artificial finger 1 low friction 0 0 1 2 3 vibration amplitude (µm) α 7

vibration modulation low friction 8

previous hypotheses : squeeze film lift air ow u p vibration α sin ω t ✓ ¯ u 3 p ◆ = ∂ ( p ¯ u ) ∂ ∂ p 12 µ ∂ x ∂ x ∂ t low friction Watanabe and Fukui, 1995 Winfield et al. 2007 Biet et al. 2007 9

previous hypotheses : squeeze film lift air ow u p vibration α sin ω t ✓ ¯ u 3 p ◆ = ∂ ( p ¯ u ) ∂ ∂ p 12 µ ∂ x ∂ x ∂ t 0 1 s u 2 + 3 2 α 2 Z f sq = p 0 u 2 − α 2 − 1 @ A S low friction µ 0 µ = 1 − f sq Watanabe and Fukui, 1995 f n Winfield et al. 2007 Biet et al. 2007 9

near-field acoustic levitation s low friction β Chu and Apfel 1982 u ∝ α Hashimoto et al 1996 f p 10

structure of the fingertip bone collagen fj bers network skin low friction Pasumarty et al. 2011 Persson et al. 2013 11

surface topography -16 H=0.75 red: dry 1 -18 green: dry 2 blue: wet 1 -20 4 ) log C (m -22 -24 -26 low friction -28 -30 3 4 5 6 7 log q (1/m) Persson et al. 2013 12

measurement real area of contact evanescent wave ~300 nm scattering 1 friction force (N) 0.5 low friction 0 1 0.5 brightness Wiertlewski, M., Fenton Friesen R., Colgate, E., PNAS 2016 Wiertlewski, M., Fenton Friesen R., Colgate, E., PNAS 2016 13

setup stroboscopic illumination t camera • 30 kHz resonance frequency low friction • pixel size of 10 µm • green light to limit di ff usion Wiertlewski, M., Fenton Friesen R., Colgate, E., PNAS 2016 14

variable friction low friction 15

contact mechanics p s p r u 0 u rms asperities height distribution p r = p c e − u/u rms low friction E p c = 0 . 375 q 0 u rms with 1 − ν 2 E = 20 MPa u rms = 2 . 5 µ m Greenwood & Williamson 1966 q 0 = 10 4 m − 1 Persson 2007 16

squeeze-film levitation u u 0 α small α large Reynold’s lubrication equation for laminar flow: ✓ ¯ u 3 p ◆ = ∂ ( p ¯ u ) ∂ ∂ p 12 µ ∂ x ∂ x ∂ t low friction σ = 12 ω µL 2 if p 0 u 2 > 36 leads to : 0 1 s u 2 + 3 2 α 2 α 2 A ≈ 5 p a = p 0 u 2 − α 2 − 1 4 p 0 @ u 2 Salbu 1964 Minikes et al. 2004 17

equilibrium applied pressure fj ngertip p s − p r = p a p ( r ) p ( r ) α sin( ω t ) α 2 = 5 ⇣ − u + u 0 ⌘ 1 − e p s urms 4 p 0 u 2 reaction from squeeze fj lm p r pressure p a support fixed pressure p r 15 10 normalized film thickness low friction u/u rms 2 5 initial gap 4 u 0 /u rms 6 8 10 0 normalized amplitude α /u rms 18

relation to friction apparent area of contact true area of contact 1 Bowden and Tabor 1939 0.8 Persson 2007 relative 0.6 area A/A 0 f t = τ 0 A 0.4 low friction − u + u 0 A = A 0 e 0.2 urms − α 2 ≈ A 0 e 2 Γ 0 0 0.2 0.4 0.6 0.8 1 normalized amplitude α /u rms 19

real area of contact A estimated pressure (kPa) 6 applied pressure 4 squeeze film 2 0 10 0.5 µm B interfacial separation (µm) 1 µm 1.5 µm 2 µm 5 low friction 0 -5 0 5 radial coordinate (mm) Wiertlewski, M., Fenton Friesen R., Colgate, E., PNAS 2016 Wiertlewski, M., Fenton Friesen R., Colgate, E., PNAS 2016 20

model vs data 2 typical friction coefficient participant artificial finger 1 low friction 0 0 1 2 3 vibration amplitude (µm) α 21

effect of moisture low friction 22

strobing light strobe low friction plate motion 23

micro-second stroboscopy low friction 24

dynamic of the contact area 1 0.9 8 brightness 0.8 0 0.7 0.6 0 2 π 4 -2 -1 0 1 2 π RMS brightness plate displacement (µm) variation (%) ω t 2 π / ω brightness u fingertip low friction b t k t ∝ exp − dynamic u rms m x 2 = u + x 1 squeeze film & asperities x 1 = α sin( ω t ) vibrating plate 25

artificial fingers Rebecca Fenton Friesen rigid skin low friction backing alumium core Fenton Friesen R. Wiertlewski, M., Peshkin M.A, Colgate, E., Worldhaptics 2015 26

artificial fingers Rebecca Fenton Friesen TangoPlus DragonSkin BioTac human fj nger relative friction reduction (%) 100 50 low friction 0 0.3 0.7 1.1 0 0.1 0.2 0.3 0.4 linearized sti fg ness (N/mm) coe ffj cient of restitution Fenton Friesen R. Wiertlewski, M., Peshkin M.A, Colgate, E., Worldhaptics 2015 26

influence of damping in the tissues 1.2 under-damped regime p s Average gap (µm) nonlinear asperity tips 0.6 squeeze film creating gap 0 α sin( ω t ) 0.1 1 10 damping ratio ζ low damping high damping factor factor ζ = 0 . 1 ζ = 2.5 2 displacement (µm) 1 low friction g > 0 0 g 0 −1 1 ms Fenton Friesen R. Wiertlewski, M., Colgate, E., Haptic Symposium 2016. 27

friction modulation under vacuum vacuum vacuum pump gauge actuating piezos force sensor 52 atmospheric vacuum camera motor finger 51 aligned motor current (mA) 1 50 estimated relative friction nodal lines 49 sensing piezo vacuum chamber 48 47 1 46 0.8 45 stalled motor relative friction 0.5 0.02 atm 44 0.6 experimental 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 conditions low friction amplitude (um) 0.4 0.2 0.1 atm 1 atm 0.5 atm 0 0 0.5 1 1.5 2 2.5 3 amplitude (um) Fenton Friesen R. Wiertlewski, M., Peshkin M.A, Colgate, E., Worldhaptics 2017 28

lastest hypothesis : partial levitation 5µm throw descent cushioned impact max separation low friction time 30 µs 29

what can we do with it? 30

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controller led ultrasonic actuators glass plate optical sensor 31

high-fidelity rendering David Daniele Meyer Leonardis carrier modulation ultrasonic fj nger friction friction force signal sin 2 π f 0 t f t ( t ) a ( t ) driving signal low friction • fast non-contact position sensor (8 µm - 5 kHz) • 6.25 points per cycle with v c = 250mm/s • 12 bit dac and linear amplifier • compensation filters Wiertlewski, M., Leonardis D., Meyer, D., Peshkin, M., Colgate, E., Eurohaptics 2014. 32

vibration of texture 100 interaction 0 force (mN) − 100 10 spat. freq. (1/mm) 1 low friction 0.1 8 4 0 0 5 10 15 20 25 30 ampl. (mN) fj nger position (mm) Wiertlewski, M., Lozada,J., Hayward, V. IEEE Transactions on Robotics, 2011 33

normal force modulation low friction high friction low friction Johansson & Flanagan 2009 J. Monnoyer, E. Diaz, C. Bourdin, M. Wiertlewski. Eurohaptics 2016 34

normal force modulation 1 0.5 falling friction Jocelyn 0 Monnoyer n=14 0 5 10 normal force no correlation 1 n=9 0.5 0 rising friction 0 5 10 low friction correlation p <5% 1 normal force 0.5 n=5 0 0 5 10 J. Monnoyer, E. Diaz, C. Bourdin, M. Wiertlewski. Eurohaptics 2016. 
 friction variation (a.u) 35

conclusion 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 low friction • large variability • multi-physics 36

acknowledgments • Ed Colgate • Michael Peshkin • Rebecca Fenton Friesen • David Meyer, • Stéphane Viollet • Jocelyn Monnoyer, Xi Lin • Viviane Gleizes, Nicolas Huloux, Di Chen low friction michael.wiertlewski@univ-amu.fr 37