u. of pennsylvania, jan. 2000 university of pennsylvania, philadelphia project goal methodologies...
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U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
Project goal
Methodologies and tools for interface between design and manufacturing for Micro-Electro-Mechanical Systems (MEMS)
NSF Grant CISE #9617997
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
Optimal topology design of compliant mechanisms Automatic image interpretation and creation of solid
model from optimized topology image Image capturing of fabricated devices Image processing for edge-extraction and object-
finding Writing image data as an IGES file for Pro-Engineer Vision-based metrology for meso-scale ceramic
devices
Past accomplishments
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
PerformanceSpecifications
SynthesisSolution
Refined DesignSolution
Meshed Modelfor Analysis
Solid Model fromthe OptimizedDevice
Digital Formatfor SFF or CNC
Mask Layoutfor Microfab.
MicroPrototype
MacroPrototype
RefinedPrototype
CAD model fromthe macro prototype
Fabrication/Prototyping
Digital Interface
Design
Reverse Engineering
Solid model frommicroscopic images
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
From optimized compliant topology image to a solid model
IGES model with line and arc segments
Optimized compliant topology using material density design parameterization
Image processing, edge extraction, and object finding
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
Image from the optical microscope After edge extraction
The lack of sharp edges corresponding to the actual structure poses a challenge in extracting the correct topology.
Edge extraction from 2-D images
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
From fabricated MEMS device to a solid modelOptical microscope image of a compliant micro crimper After edge extraction
5 µm
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
From fabricated MEMS device to a solid model
IGES model exported into Pro-E with line and arc segments
Extruded solid model ready for behavioral simulation
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
Macro prototype of a micro wedge motor
(Allen, 1998)The micro prototype was made using Sandia’s SUMMiT process.
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
Lithography masks for a micro wedge motor
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
Premise:Assuming material behavior and properties, forces can be estimated from underformed and deformed geometry of a flexible structure.
Vision-based force sensing
Goal:Non-contacting, non-interfering force sensor based on vision and computation.
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
Image capturing beforeand after deformation
Displacements
Strains
Stresses
Forces
Materialproperties
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
Inverse elastic analysis problem.
Linear (small deformations) problem is trivial.
Large deformation, small/large strain problem is of interest here.
yKf Stiffness matrix
Forces Displacement
Assumption: Correspondence between undeformed and deformed geometries is known.
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
y
z
At time t = 0(Undeformed)
At time t(Deformed)o
1 2
34
1 2
34
x
Computing the deformation gradient
y
y
x
yy
x
x
x
X tt
tt
00
00
Deformation gradient
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
Computing the large strain
)ln(VLogarithmic strain
21
CV
TXXC *
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
Computing the stress and element forces
Material properties for plane-stress condition
2
100
01
01
1 2
E
M
*M
eV
Te dVBF
qB
Stress
Element forces
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
Force recovery
Large strain case Small strain case
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
Macro-scale experiment
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
Corner detection
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
Comparison of computed and measured displacements
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
Recovered forces (experimental displacements)
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
Recovered forces (numerical displacements)
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
The procedure for computing strains from displacements is prone to numerical error.
The computed strain is very sensitive to even small perturbations in displacement data.
The sensitivity is worse for small strains than large strains.
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
Sensitivity analysis
U. of Pennsylvania, Jan. 2000
University of Pennsylvania, Philadelphia
Sensitivity analysis