Upload
tanner-beller
View
218
Download
3
Tags:
Embed Size (px)
Citation preview
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
1
RiSE Consortium MembersRiSE Consortium Members
DARPA/SPAWAR N66001-03-C-8045
RiSE isfunded by
With additional support from the Intelligence Community Postdoctoral Fellowship Program
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
2
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.
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
3
Gecko hierarchical complianceGecko hierarchical compliance
Spatular shaft
2µm
Spatula
200nm
Setal shaft
100µm
Lamella
Cushions1cm
1mm
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
4
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
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
5
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
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
6
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
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
7
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
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
8
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
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
9
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
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
10
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
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
11
StickyBot manufacturing processStickyBot manufacturing process
[Movie: gecko_sor3.mov]
Manufactured via SDMManufactured via SDMwith multiple materialswith multiple materials
and embedded and embedded componentscomponents
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
12
Deposit (part)
Shape
EmbedDeposit (support)
Shape
Part
Embedded Component
Support
Shape Deposition Manufacturing Shape Deposition Manufacturing
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
13
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
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
14
Fabrication sequence for leg flexuresFabrication sequence for leg flexures
Cut pocket for casting 1stlayer of hard material
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
15
Fabrication sequence for leg flexuresFabrication sequence for leg flexures
Cast hard material andcut pockets for flexures
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
16
Fabrication sequence for leg flexuresFabrication sequence for leg flexures
Cast material forsoft flexures
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
17
Fabrication sequence for leg flexuresFabrication sequence for leg flexures
Add next support layerand machine for casting
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
18
Fabrication sequence for leg flexuresFabrication sequence for leg flexures
cast and machinehard material struts
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
19
Fabrication sequence for leg flexuresFabrication sequence for leg flexures
Cast and machinesupport for top layer
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
20
Fabrication sequence for leg flexuresFabrication sequence for leg flexures
Cast and machine toplayer of hard material
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
21
Fabrication sequence for leg flexuresFabrication sequence for leg flexures
Cast top layer softmaterial for flexures
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
22
Fabrication sequence for leg flexuresFabrication sequence for leg flexures
Plane top surface andremove support material
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
23
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
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
24
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
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
25
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)
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
26
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.
Copyright © April 20, 2006 Mark R. Cutkosky, Stanford University
27
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.