bio inspired design - lecture 3. mechanical stiffness and motion
TRANSCRIPT
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Vermelding onderdeel organisatie
Bio-Inspired DesignMechanical Stiffness and Motion
Faculty of Mechanical, Maritime, and Materials EngineeringDepartment of BioMechanical Engineering
Just Herder
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© 2008 Just L. Herder
Lecture 2: BioconstructionBiostructure & bioenergy (muscle configurations)
• Contents 1st hour (Just): mechanical stiffness & motion: strength at low weight, redundant structures, etc.
• Contents 2nd hour (Paul): hydrostatic stiffness & motion: energetically efficient muscle configurations, stiffness with soft structures.
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© 2008 Just L. Herder
• Engineering: System, Shape, Material
• Are there any differences between human engineering and nature, in terms of:• System• Construction elements• Material
Bioconstruction
Raptor by Kraft Telerobotics
Cool JC, 1976
?
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© 2008 Just L. Herder
Biomaterials
• Tensile materials (Crystalline Polymers, Silk, Collagen, Cellulose, Chitin)
• Flexible materials (Protein Rubbers, Mucopolysaccharides, Pliant Composites, Mesoglea, Uterine Cervix, Skin, Arterial Wall, Cartilage)
• Rigid materials (Bone, Keratin, Cell wall, Wood, StonyMaterials)
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© 2008 Just L. Herder
Biomaterials
• Tensile materials (Crystalline Polymers, Silk, Collagen, Cellulose, Chitin)
• Flexible materials (Protein Rubbers, Mucopolysaccharides, Pliant Composites, Mesoglea, Uterine Cervix, Skin, Arterial Wall, Cartilage)
• Rigid materials (Bone, Keratin, Cell wall, Wood, StonyMaterials)
• No metal!
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© 2008 Just L. Herder
Biocomponents
• Tensile components (Skin, Tendon, Fibre)• Compressive/bending components (Skeleton)• Relative motion components (Joints, Compliance)• Active components (Muscle)
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© 2008 Just L. Herder
Biocomponents
• Tensile components (Skin, Tendon, Fibre)• Compressive/bending components (Skeleton)• Relative motion components (Joints, Compliance)• Active components (Muscle)
• No multirev bearings, no wheels, no fasteners!
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Vertebrates: joints
• Synarthroses: hardly movable (sutures in human skull)• Amphiarthroses: slightly movable (cartilage attachments in
ribs and vertebrae disks)• Diarthroses: Larger motion range:
• Ball-and socket (e.g. hip, GH-joint)• Ellipsoidal (e.g. fingers)• Condyloid (e.g. knee joint)• Saddle (e.g. part of the wrist joint)• Pivot (e.g. radius/ulna joint)• Hinge (e.g. elbow joint)• Plane/gliding (e.g. scapula joint)
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© 2008 Just L. Herder
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Bio-inspired joints
www.aclsolutions.com
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Bio-inspired joints
www.aclsolutions.com
Rolling/sliding contact
Cross-wise arranged bands
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Bio-inspired joints
Bands
Rollers
Springs
www.aclsolutions.com
J Verbeek, JL Herder
www.aclsolutions.com
Rolling/sliding contact
Cross-wise arranged bands
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© 2008 Just L. Herder
Bio-inspired joints
Bands
Rollers
Springs
www.aclsolutions.com
J Verbeek, JL Herder
www.aclsolutions.com
Rolling/sliding contact
Cross-wise arranged bands
Nature does not label…
You hypothesize, investigate, and design.
Physical principles.
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© 2008 Just L. Herder
Minimal Access Surgery
• Reduced dexterity• Reduced sensation• Reduced view
Just Herder
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© 2008 Just L. Herder
Bio-Inspired rolling joints
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© 2008 Just L. Herder
Bio-Inspired rolling joints
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Bio-Inspired rolling joints
Band is compromise between bending and tension
Most vulnerable parts take highest forces!
1:
2
F MyA I
d MBernouilli EulerR ds EI
F Ey F EdA R bd R
σ
θκ
σ
= +
− = = =
= + = +
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© 2008 Just L. Herder
Force directed design
M Horward, JL Herder
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© 2008 Just L. Herder
Low friction forceps
• Rolling joint• Flexible band
• Negligible friction• No backlash• No need for
lubrication
M Horward, JL Herder
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© 2008 Just L. Herder
Low friction forceps
Six rolling joints
One-on-onemoment transfer
Herder et al.
Patent pending: US 6447532 M Horward, JL Herder
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© 2008 Just L. Herder
Low friction forceps
Mechanicalefficiency 96%
10 mm shaft
Herder and Horward, 1997Patent pending: US 6447532
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© 2008 Just L. Herder
Low friction forceps
K den Boer et al. (1999)
Pulse in artificial artery can be perceived clearly
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© 2008 Just L. Herder
BioDesign
• Unknown loads• Long or short period• Suddenly or slowly• Once or repeatedly• Move while transmitting considerable forces• Accidental overload• Energy-efficient
• Design Principles• Real Organisms
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© 2008 Just L. Herder
BioDesign
• Unknown loads• Long or short period• Suddenly or slowly• Once or repeatedly• Move while transmitting considerable forces• Accidental overload• Energy-efficient
• Design Principles• Real Organisms
We cannot see physical principles, we have to hypothesize. From real organisms we can at best find that it might be right
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BioDesign Principles
• Lightweigth: only tension or compression• Reduce tension members to wires, maximize I in other
members• Minimize use of compression members and maximize
use of tensile members, isolate compessive members• In composite material, the stiffer element used to
control strain and maximize resistance to stress• Thin-walled cylinders effectively reinforce against
explosion and buckling by cross-helical fibres• Either resist or permit great forces/deflections
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BioDesign
Linear beam theory: M=Fh, with =σMy/I and I=πr4/4:
σ=4Fh/πr3 hence rmin=(4Fh/πσ)1/3 non-prismatic trunk
Note: in reality many more factors than aerodynamic drag
F
h
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Compliance in design
B Trease, S Kota, Univ of Michigan at Ann Arbor
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© 2008 Just L. Herder
Compliance in design
B Trease, S Kota, Univ of Michigan at Ann Arbor
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Compliance in design
F vd Berg, JL Herder
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BioDesign
M
V
N
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BioDesign
M
V
N
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BioDesign
M
V
N
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BioDesign
M
V
N
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BioDesign: Stuctural Optimization
• Other static loading: cross-sectional shape and material properties, deflection by EI
• Careful with maximizing I, e.g. wall thickness in tubes• Minimum weight/strength ratio: minimize density
(since modulus generally fixed), especially wrt buckling• Energy absorption dominant: uniform cross-section, no
local stress raisers, preferably solid round rod• Pure tension: governed by specific strength and
maximum allowable deformation, any shape rods
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Tensegrity on cell level
D.E. Ingber
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Tensegrity on cell level
D.E. Ingber
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Tensegrity on tissue level
• Linear stiffening: stiffness increases with elongation(non-linear stiffness)
• Similar to biological tissue (pull your skin!)• Stress in all members varies
D.E. Ingber
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Tensegrity on organ level
D.E. Ingber, K. Snelson
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Tensegrity in growth…
• Deployable• Disjointed struts• Axially stiff• Axial stiffening• Weak in bending• Bending softening
A.G. Tibert, S. Pellegrino, K. Snelson
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Tensegrity in Delft
Mark Schenk, Simon Guest, Just Herder
9 cables 9 springs
Tensegrity Mechanism
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Conclusion
• Different materials• Different components• Different concepts• Different perspective• Big gap• Lots to do