copyright © april 20, 2006 mark r. cutkosky, stanford university 1 rise consortium members...

Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University

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RiSE Consortium MembersRiSE Consortium Members

DARPA/SPAWAR N66001-03-C-8045

RiSE isfunded by

With additional support from the Intelligence Community Postdoctoral Fellowship Program


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Requirements for climbing with dry adhesion

Requirements for climbing with dry adhesion

Hierarchical complianceHierarchical compliance over scales from 10over scales from 10-2 -2 to 10to 10-7-7m.m.ReasonReason:: obtain large contact areas and uniform loading on materials obtain large contact areas and uniform loading on materials ranging from glass to bark.ranging from glass to bark.ConsequenceConsequence: need compliances at limb, toe, lamellar and setal scales; : need compliances at limb, toe, lamellar and setal scales; need integrated macro/micro fabrication solutions.need integrated macro/micro fabrication solutions.

Anisotropic adhesion and frictionAnisotropic adhesion and frictionReasonReason:: control adhesive stresses and attachment/detachment. control adhesive stresses and attachment/detachment.ConsequenceConsequence: : need asymmetric, fully 3D micro structures that are need asymmetric, fully 3D micro structures that are difficult to fabricate with current MEMS and nanofabrication technologiesdifficult to fabricate with current MEMS and nanofabrication technologies

Distributed Control of ForcesDistributed Control of ForcesReasonReason:: increase stability, prevent contact stress concentrations increase stability, prevent contact stress concentrations ConsequenceConsequence:: need heterogeneous and anisotropic structures behind the need heterogeneous and anisotropic structures behind the contact surface for shear load transfer; need compliant under-actuated contact surface for shear load transfer; need compliant under-actuated mechanisms and feedback for internal force control.mechanisms and feedback for internal force control.


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Gecko hierarchical complianceGecko hierarchical compliance

Spatular shaft

2µm

Spatula

200nm

Setal shaft

100µm

Lamella

Cushions1cm

1mm


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Stickybot hierarchical complianceStickybot hierarchical compliance

10m

10m

Berkeley

600nm

U. Dayton

1mm

1mm

Multimaterial toes: 3 grades of urethane polymer with embedded fabric for shear load transfer

5 mm

sandwich of pillars & membranes

3 cm3 cm

anisotropicelastic features

1m

300m

10-2 m

10-3 m

10-4 m

10-5 m 10-6 m

10-7 m


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Pre

ssur

e se

nsiti

ve a

dhes

ives

Fat

Aga

rose

gel

Sof

t ins

ect c

utic

leP

MM

A

Rub

ber

Pol

yeth

ylen

eE

poxy

Alu

min

um

Car

bon

nano

tube

s

Dia

mon

d

Car

tilag

e

Bon

e, F

iber

com

posi

tes

102 104 105 107 108 109

tacky nontacky

-keratin

Young’s Modulus (Pa)

polypropelene(bulk)

setal array80-110 kPa

polypropelene fiber array

Effective modulus of setal array Effective modulus of setal array

Dahlquist criterion~100 kPa for tack

elastomer(bulk)

elastomer comb array

larger features, more sensitivity to tip geometrylarger features, more sensitivity to tip geometry

increased resistance to fouling, faster dynamicsincreased resistance to fouling, faster dynamics

1012106

length = 110mdiameter = 4.5m

Substrate

backingPSA


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Anisotropic AdhesionAnisotropic Adhesion

25 mN ofAdhesion

Gecko setae dragging with curvature

-30

-20

-10

0

10

20

30

40

50

0 1 2 3 4

Time (s)

Fo

rce

(m

N)

Colored: Normal forceGray: Shear force

Dragging against curvature

No Adhesion

Time (s)F

orce

(m

N)

-30

-20

-10

0

10

20

30

40

50

0 1 2 3 4

Synthetic elastomer -combs: optimize geometry for directionaladhesion and uniform tip stress.(Stickybot 4-1-06 movie)

100m


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Mechanisms for active load distributionMechanisms for active load distribution

Russell: Gecko and lizard tendon routing -- consistent solutions seen across many species.Zani: Geckos and lizards that excel on rock always have claws in addition to lamellae.

tendons with multiple attachmentsites ensure load distribution

active toes with small distal clawsKey challenge:

Given n adhesive patches (+ spines), how can we ensure even loading for an n-fold increase in adhesion & traction? tuned, passive compliance for decoupling and to minimize stress concentrations at wall surface active deployment to increase probability of establishing good attachments route loads through tendons to prevent “premature unpeeling”

lamellaeload path


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Control of foot orientation and internalforces for using directional adhesion

Control of foot orientation and internalforces for using directional adhesion

unstable

stable

Optimization: stability vs foot orientationfor inverted clinging

(optimal if all feetpull toward COM)

Inverted: feet pull toward COM () for max. adhesion ().

Climbing: feet pull upward ()and inward () for adhesion + stability

Directional adhesion can be realigned to

enhance perturbation rejection.

Toe orientation is altered as feet

change function.

Observations

Model predictionsContact constraint model

Ft > 0 (preferred direction):

Ft ≤ Fmax, Fn ≥ - Ft

Ft ≤ 0 (non-preferred):

|Ft| < Fn (Coulomb), Fn ≥ 0


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StickyBot: advanced platform for

investigation of adhesive climbing

StickyBot: advanced platform for

investigation of adhesive climbing

Test vehicle for directional adhesives

Selectively compliant: 4 grades of polymer, carbon fibers and fabric for directional stiffening

Highly under-actuated: 12 servos, 38 DOF.

Double differential toe mechanism for conforming and peeling

Limb sensors for force control.

Government purpose rights. ContractN66001-03-C-8045. Contractor: StanfordUniversity. Exp date: Nov. 30, 2008


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Method II: polymer fiber patches (2m dia, 20m long) with 100m backing embedded in compliant (Shore 20A) substrate.

+

Method I: Patterned array of nano-tubes or fibers is aligned & bonded with elastic, directional combs; connecting regions are removed.

LoadingLoading

Integration methods for directional multiscale

contact

Integration methods for directional multiscale

contact

SDM pallet (sacrificial material)

Government purpose rights. ContractN66001-03-C-8045. Contractor: StanfordUniversity. Exp date: Nov. 30, 2008


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StickyBot manufacturing processStickyBot manufacturing process

[Movie: gecko_sor3.mov]

Manufactured via SDMManufactured via SDMwith multiple materialswith multiple materials

and embedded and embedded componentscomponents


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Deposit (part)

Shape

EmbedDeposit (support)

Shape

Part

Embedded Component

Support

Shape Deposition Manufacturing Shape Deposition Manufacturing


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Study biological materials, components, and their roles in locomotion.

Study Shape Deposition Manufacturing (SDM) materials and components.

Models of material behavior and design rules for creatingSDM structures with desired properties

Example: mapping from passive mechanical properties of insects to biomimetic robot structures

Example: mapping from passive mechanical properties of insects to biomimetic robot structures

ServoMotor

Roachleg

Displacement InputForce Output

stiff material

viscoelasticmaterial


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Fabrication sequence for leg flexuresFabrication sequence for leg flexures

Cut pocket for casting 1stlayer of hard material


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Cast hard material andcut pockets for flexures


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Cast material forsoft flexures


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Add next support layerand machine for casting


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cast and machinehard material struts


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Cast and machinesupport for top layer


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Cast and machine toplayer of hard material


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Cast top layer softmaterial for flexures


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Plane top surface andremove support material


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MicrocombsMicrocombs

Sandwich the combs around a spacerSandwich the combs around a spacer Use as a positive for a moldUse as a positive for a mold


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A note on Tip GeometryA note on Tip Geometry

1mm 100um 10um 1um 100nm

Tip Contact Diameter

Microcombs CNTs

MicroCNC Berkeley HairsProposed Silicon

Combs

Optimal geometry is achieved when stress is uniformly distributed at pull- off, i.e. no peeling (H. Gao and H. Yao 2004)

Shape Insensitive Range Foptimal / Fsingular =1

Foptimal / Fsingular ~1000

Foptimal / Fsingular ~106


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Method II: polymer fiber patches (2m dia, 20m long) with 100m backing embedded in compliant (Shore 20A) substrate.

+

Method I: Patterned array of nano-tubes or fibers is aligned & bonded with elastic, directional combs; connecting regions are removed.

LoadingLoading

Integration methods for directional multiscale contact

Integration methods for directional multiscale contact

SDM pallet (sacrificial material)


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Mold configurationMold configuration

20mm

33mm

Hole diameter:

0.015 in (~400um)

Tip angle : 20o

* This is a mold for one toe pad. Final mold design should have more than 16 of this.


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DimensionsDimensions

20o

1.4 mm

0.4 mm

0.4 mm

• The angled surface does not need to be straight. Concave arc might be better in terms of reducing effective stiffness

• Angle needs to be small. ~20deg is a good number to start

• Lower side height (0.4mm) needs to be small to minimize clumping. But It makes the mold fragile.

copyright © april 20, 2006 mark r. cutkosky, stanford university 1 rise consortium members...

Documents

stanford university

anisotropic adhesion

shear force

psa slide

adhesion time s force

directional adhesion

mn of adhesion gecko

shear load transfer