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© Maximillian A Perez 2005
Max Perez
MicroSystems LabMechanical and Aerospace Engineering
University of California, IrvineIrvine, CA
[email protected]://mems.eng.uci.edu
Micromachined Optical Accelerometers for Serial Sensor Networks
University of California - IrvineUniversity of California - Irvine
IM-SURE
Irvine, CA 6.29.05
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© Maximillian A Perez 2005
Micro-Opto-Electro-Mechanical Systems(MOEMS)
Manipulating the world at the level of the wavelength
For Optical Communications For Consumer Electronics
MotivationMotivation
IM-SURE
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© Maximillian A Perez 2005
Project Goals
Light OSAPower DAQ
• Conventional Systems– Electrical– Multiple power /detection lines– Subject to EM interference
– Low Sensitivity
A Distributed Acceleration SensorDistributed Acceleration Sensor network
100mVg
• Proposed System– All Optical– Single source/signal line– Immune to EM interference
– High Sensitivity 15Vg
Monitor
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© Maximillian A Perez 2005
Applications
A system of arrayed inertial sensors that are:
•Highly Sensitive Highly Sensitive •Spatially DistributableSpatially Distributable
•SimpleSimple•RobustRobust
Vibration Monitoring
Structure System Identification
Structural Health Monitoring
MotivationMotivation
Could be used for:
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© Maximillian A Perez 2005
FPI-based Accelerometer Concepts
Broadband Light
INi f OUTcSignal
Ao
I I
A
Ao
FPI-Based Accelerometer•Proof mass (m) suspended (stiffness k) relative to reference plate (damping c)•Reference plate attached to measured structure
System Operation•Interferometric fringe peak placement indicates inertial load (acceleration)
BackgroundBackground
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© Maximillian A Perez 2005
Device Fabrication
FabricationFabrication
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PDMS Elastomeric Suspension
Elastomeric Suspension: •Low Stress
Minimize plate bowing•No surface deposited mechanical layers
Minimize surface roughness
PDMS Elastomer: •High Compliance (E ~ 1MPa)•Stable (Tg ~ -125C)•Cleanroom compatible•Tough
Unstreched / Stretched PDMS Elastomer
FabricationFabrication
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The Trunnion Mode
Reference
Sense
Sense Mode•Normal or ‘out-of-plane’ mode
•Desire low stiffness for sensitivity
Trunnion Mode•Out-of-plane tosional mode•Activated by:
•Asymmetric suspensions (sense mode coupled)•Rotational Acceleration
I
Reference
Sense
highk highk
lowklowklowk
lowk
BackgroundBackground
Most Pressing Concern => Dynamic parallel plate error
IM-SURE
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© Maximillian A Perez 2005
Composite Fabrication
~ACV
FAiMTa: •Field-Aided Micro-Tailoring technology•Electrically aligned particles in a polymer matrix act as short fibers
•Developed by Geun Hyung Kim and Yuri M. Shkel (U. Wisconsin-Madison)Polymeric composites tailored by electric fieldsJournal of Materials ResearchVol. 19, #4, No. 4, Apr 2004
FabricationFabrication
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Composite Results
Alignment: •Simple application of voltage results in particle alignment with structure geometry
•Iron fillings •500-900V, ~0.5mm gap, 5Hz•10% Fe : PDMS
~
500-900V @5Hz
ResultsResults
=> 8000X increase in 8000X increase in trunnion stiffness trunnion stiffness
=> 2X increase in 2X increase in sense stiffness sense stiffness
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Serialization Concepts
Serialized Operation: •Define sensor channels of R-high for each FPI •Creates an Intrinsic Wavelength Division sensor Network
INi f OUTcSignals
I I
A B
Ao B
oR
Ao B
o
R
Ao B
o
Sensed VibrationsBackgroundBackground
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© Maximillian A Perez 2005
Funding/Acknowledgments
•The National Science Foundation Grant CMS-0223050, program manager Dr. Shih-Chi Liu.
•Duration: Three years (Currently at 2/3 completion)
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Questions?
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© Maximillian A Perez 2005
The Composite Shear Suspension
Characteristics•Low volume fractions
=>greatest effects!•Minimal effect on sense axis stiffness
torsional v Hk k k
BackgroundBackground
0.5 mm
0.25 mm 1.0 mm
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.40
1
2
3
4
5
6x 10
4
Inclusion volume fraction
k Mo
de/k
Mo
de
(vf=0
)
Fractional Change in Modal Stiffness
In-Plane
Out-of-Plane
Trunnion