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Technische Universität München
Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures
SHAPE MORPHING OF FLEXIBLE SURFACES AND ACTUATOR INTERACTION
Horst Baier, Leri Datashvili
Institute of Lightweight Structures (LLB)Technische Universität München, Germany
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Technische Universität München
Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures
Membrane and reflector structures
Advanced fiber composites / hybridmat. & structures
Smart Structures Multidisc. design optimization and procedures
Research areas at LLB / TU München
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Technische Universität München
Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures
„Classical“ adaptive structures: dyn. load alleviation
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Technische Universität München
Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures
Low speed
High speed
Human eye
Morphing biological systems
Flight systems Optical (RF) Systems
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Technische Universität München
Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures
high loads and stiffness… and morphing
high shape precision… and morphing
Morphing Aerospace StructuresMassive change in geometry
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Technische Universität München
Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures
Morphing wing: rereference mission
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Technische Universität München
Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures
Morph. param. influence on diff. criteria
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Technische Universität München
Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures
Spoke concept
Skin integrated actuators Pneumatic concept
Wing morphing machanisms
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Technische Universität München
Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures
Institute for Lightweight Structures LLB
Morphing wing
Morphing actuators Morphing surfaces
?
Friswell, Swansea
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Technische Universität München
Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures
Massively morphing sat reflectors …
... to achieve non-isotropic RF beam radiationin (space) antennas
requires actuators and a morphing surface with• low in-plane and shear stiffness
• moderate bending stiffness
• very low CTE
• good thermal and electr. conductivity
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Technische Universität München
Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures
Micro-mech. FE model(stiffness, CTE, …)
Simul and test results
Triax C-fibre shell-membrane material (soft silicone matrix): CFRS
Structural and reflector material
• excellent thermo-mechanical properties• good RF properties• moderate - good morphing behavior
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Technische Universität München
Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures
Triax CFR-matrices with different Young‘s moduli
Mat. properties and level of anistropy depend on specimen size
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Technische Universität München
Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures
Possible actuator types
Stroke: 20mmForce: 15N
Low mass actuators with high strokes; space compatibility = ?
EAP „bubble“ actuator
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Technische Universität München
Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures
Actuator – structure interface
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Technische Universität München
Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures
Lab demonstration model
“Proper” concept also requires ..
…proper actuator length + alignment + smooth load introduction into morphing surface
Refl. membrane
Manually driven actuators in lab model
Actuator i/f toreflect. surface
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Technische Universität München
Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures
Determination of actuator strokes
… typically 50 – 100 actuators per m2 of reflecting surface
Discretized goal shape generated shape
(step-wise sol. incase of nonlin. behav.)
with uij
displacement at dof
i from unit stroke at actuator j
xj
actual strokes to be determined from optim. problem
i= 1, .. N, N: number of dofs
of FEM
J= 1, .. m , m: number of actuators
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Technische Universität München
Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures
Some typical results
•Surface rms deviation of actual shape vs. goal (required) shaperms < 0.15 mm (for 1 m diam. reflector)
•Surface rms deviation between simalation vs. test resultsrms < 0.1 mm
shape morphing amplitudes of 10-15 mmwith high spatial frequency possible
concurrent mechanical and RF simulation and optimization preferable / feasible? simultaneous determination of design (+mat.!) parameters preferable / feasible ? other / better mech. design options e.g. by higher integration level ?
Further open points:
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Technische Universität München
Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures
Morphing in biol. cells flexible cell walls with morphable reinf.
Morphing in biology
lense
Actuating muscles
Human eye
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Technische Universität München
Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures
Integrated Integrated displdispl. . fieldfield identification identification
Measurement of strain at
many positions
Reconstr. model using.
• modal data
• Krylov vectors
• other FEM data
• exp. data
[C]
0100200300400500600700800900
0
500-10
-8
-6
-4
-2
0
2
x 10-3
y [mm]
x [mm]
disp
lace
men
t[mm
]
real displacement fieldestimated displacement field
Displacement field
Real and reconstructed displ. field
FOS in CFRS
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Technische Universität München
Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures
• high forces (many tons)
• high strokes
• moderate resolution
• low spatial frequency
• high reliability
• low mass / volume
• self locking
• moderate temp. range
•low frequency
• small forces
• small or high strokes
• high resolution (µm range)
• high spatial frequency
• good reliability
• low mass / volume
• self locking
• extreme temperature range
• quasi-static
Morphing requirements
Aero-elasticity RF-elasticity
Coupling Aeodyn. Coupling RF. structureModelling:
Struct.