Principles for climbing with dry adhesion - Stanford...

Stryker Interaction Design Workshop September 7-8, 2005

1 3/24/13

Principles for climbing with dry adhesion

2. Directional adhesives

1. Hierarchical compliance

3. Distributed force control


2 3/24/13

Spatular shaft

2!m

Spatula

200nm

Setal shaft

100!m

Lamella

Cushions 1cm

1mm

Conforming to surfaces: hierarchy of compliant structures in the gecko


3 3/24/13

Directional gecko adhesion

25 mN of Adhesion

Gecko setae dragging with curvature

-30

-20

-10

0

10

20

30

40

50

0 1 2 3 4

Time (s)

Forc

e (m

N)

Colored: Normal force Gray: Shear force

Dragging against curvature

No Adhesion

Time (s)

Forc

e (m

N)

-30

-20

-10

0

10

20

30

40

50

0 1 2 3 4


4 3/24/13

Gecko Force-Space Results

Load, then pull off at various angles, and measure force

-10 0 10 20

-10

0

10

20

Tangential Force (mN/stalk)

Normal Force (mN/stalk)

500µm

-10 0 10 20

-10

0

10

20



500µm600µm

-10 0 10 20

-10

0

10

20



500µm600µm700µm

loaded with stalk angle: adhesion ~ tangential stress

loaded against stalk angle: Coulomb friction

safe region

Autumn et al. JEB 2006

Fn

Ft

compression

adhesion


Directional adhesion: loading cycle determines adhesion

5 3/24/13

microscope video, side view with trajectory shown

normal and shear stress trajectory versus limit curve


Directional adhesion: loading cycle determines adhesion

6 3/24/13

microscope video, side view with trajectory shown

normal and shear stress trajectory versus limit curve

Stickybot foot adhesion limit surface

7 3/24/13 D. Santos, et al.Gecko-Inspired Climbing Behaviors on Vertical and Overhanging Surfaces, IEEE ICRA 2008.


Biomimetics Laboratory Stanford University

Daniel Santos

Adhesion limit surface implications

Johnson-Kendall-Roberts

FNormal

FTangential

Gecko “Frictional Adhesion”

FNormal

FTangential

Autumn, et al.; Journal of Experimental Biology; Volume 209, 2006


9 3/24/13

Force Control optimal strategy for inverted surface

Frictional Adhesion Johnson-Kendall-Roberts

Rear Foot Flipped

FN

FT

FN FN FN

FT FT FT

Generalization: Formulate as linear programming problem to control foot orientation & internal forces for arbitrary loading conditions [Santos, JAST09].


Biomimetics Laboratory Stanford University

Daniel Santos

Force Control: vertical surfaces consequences of adhesion model

Frictional Adhesion

FNormal

FTangential

3/24/13 11

-0.01 0

0.01

0.02

0.03

Gecko wall reaction forces F

orce

(N)

Left Fore

Right Fore

Right Hind

Left Hind

Lateral -0.04

-0.02

0

0.02

0.04

N=7 N=6

N=5 N=8

Normal -0.01

-0.005

0 0.005 0.01

N=7 N=6 N=5 N=8

Fore-aft N=7 N=6 N=5 N=8

K. Autumn R.J. Full


12 3/24/13

Control foot orientation + internal forces


13 3/24/13

Directional adhesion facilitates control of forces for smooth, efficient locomotion

Tangential force

Nor

mal

For

ce

Contact force limits

Safe force region

Desired loaded state

Desired attach/detach state


14 3/24/13

Directional

Directional vs. non-directional One front leg cycled with three feet attached (tripedal crawl). 3 successive steps shown

Preload Adhesion Detach

Non- directional


15 3/24/13

Dynamic Directional Adhesion

Hypothesis: directional adhesion ! gentle loading + lift-off ! long life

! Directional behavior similar to gecko and larger Stickybot stalks

! Adhesion maintained, while sliding.

! Provides non-catastrophic failure mechanism.


16 3/24/13

Adhesive structure analysis for optimization of performance

•  Behavior occurs at multiple scales – Suspension scale (mm)

•  Commercial software is viable –  Preload path only

– Terminal features scale (µm) •  Custom FE code •  Semi-analytic models

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Machining Process Overview Control blade trajectory to get desired shape and dense packing of features

MOLD

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E. Eason et al., "Micro-Wedge Machining for the Manufacture of Directional Dry Adhesives," ASME Journal of Micro and Nano-Manufacturing, 2013 (in press)


Angle control: micromachining process

Key Design Parameters •  ()$*+,-.$/0$12.3$•  4)$5+6.35/3$12.3$*+,-.$•  7)$12.3$7.5,76$•  8)$12.3$89*:5+,$•  ;)$#*6.35*-$</=+,>8$?/@=-=8

18

! "

h

E. Eason


Machined vs lithographic microwedge performance

19

Increased adhesion

Better low-shear

performance


Test results with unfilled PDMS

20 psi

previous results (40kPa normal)

10 psi

Large scale results: 17 psi in pure shear over 1x1 in


Loading on the wall is different from benchtop tests; geometry affects limit surface

Different pull locations (structure is rigid between

pull location and contact points)

FT FN

h

h

r = 0 r = 0.1h r = 0.5h r = h r = 2h

r

!°

! =10°

Maximum |F| at the structure geometry

angle

Red r=0 lines match the original contact limit

surfaces

20° = contact limit surface angle

Alan Asbeck

unless one can pull from the red dot

location, any deviation from ideal angle produces

a moment and uneven pressure


How to get nearly uniform loading over the entire toe, with tolerance to a range of loading angles?

Lamella

Bio-Inspiration

Phalanges

Lamellae

Fluid-filled sac

Lateral digital tendon

Lateral digital tendon

(Russell J. Morphology 1982)

Stryker Interaction Design Workshop September 7-8, 2005 23

Loading angles: alignment compensation

4 leg version of RiSE platform

4 kg gross loads


Scaling to larger areas and loads: tiled arrays

adhesive

rigid tile

pressurized

sac

pressure

plate

main tendontile tendon

compliant

supportstructure

pulley

40 kg

Approx. 80cm2

Stryker Interaction Design Workshop September 7-8, 2005 25

Scaling to larger areas and loads: results

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32

Role Team Members Section

PI Aaron Parness 347

Co-I Mark Cutkosky Stanford

Co-I George Studor JSC

Co-I Victor White 389

Co-I Carl Seubert 344

Task Objectives: 1. Develop full capture head using

current gecko adhesive and leveraging small-scale two pad gripper prototypes

2. Mock up compliant robotic arm and integrate with capture head for floating object capture demonstration on RoboDome testbed

Infusion Path: option A: Small Sat Demo (partner with

Qinetiq and Aerospace Corp) option B: ISS experiment or inspection

(partner with JSC)

Critical Milestones Date

Demo of capture head on stiff mount Apr 2013

Completion of mock-up compliant arm Jun 2013

Demo of floating object capture Sep 2013

Gecko-Inspired ON-OFF Adhesives For Orbital Debris Mitigation

Primary Technical Hurdles: •  Scaling 2-pad prototypes to full capture head

•  Correctly sizing compliance in robotic arm •  Integrating elements for demo

Technical Approach / Expected Accomplishment: Develop Robotic Capture Head Mock up compliant robotic arm

Demo floating object capture

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•  [3.8.+6$Z/=3$5@.*$/+$P7=38@*Z$MFG"[email protected]$


This work has been supported by the RiSE program (DARPA BioDynotics N66001-03-C-8045) with additional support from NSF NIRT (ID 0708367) and COINS (UCB)

Robots in Scansorial Environments (RiSE)

Acknowledgements

Principles for climbing with dry adhesion - Stanford...

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