NASA Technical Reports Server (NTRS) 20160001157: Fiber Optic Sensing System (FOSS) Technology - A New Sensor Paradigm for Comprehensive Structural Monitoring and Model Validation Throughout the Vehicle Life-Cycle

5.7 MB·English

by  NASA Technical Reports Server (NTRS)

Fiber Optic Sensing System (FOSS)
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A New Sensor Paradigm for Comprehensive Structural

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aa Monitoring and Model Validation throughout the Vehicle
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Life-Cycle
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uu Francisco Peña, Dr. Lance Richards, Allen. R. Parker, Jr.,
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Anthony Piazza, Patrick Chan, and Phil Hamory
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oo NASA Armstrong Flight Research Center
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Edwards, CA
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January 20th, 2015
The FOSS Team
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Structures
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Francisco Pena Structural Test and Analysis

s Engineer
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AFRC Structures Test and Analysis
Structural Test and Analysis Products
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n • Experimental methods
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i • Structural testing from coupon, subcomponent, component, qual-unit, flight component, full
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sr vehicle (for aircraft of all Mach no’s, launch vehicles, spacecraft applications)
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ns • Ground testing (structural labs, wind tunnels, cryogenic labs)
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i • Flight testing
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Ad • Mechanical: Load frames, custom designed test setups, load introduction hardware, restraints,
eA • Thermal: high & low temperature (radiant quartz lamps and cryogenic cooling, resp)

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• Aero
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p • Structural measurement methods
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• Strain (stress), temperature, displacement, load, heat flux, discrete, full-field
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nn • Strain gage technology, fiber optic sensors, load cells, LVDTs, potentiometers, TCs, digital
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s s image correlation, thermal imaging, Interferometry, Moire,
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ci • Experimental Stress Analysis, measurement uncertainty (temperature compensation methods)
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u • Correlation of experimental / analytical results
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no • Collaborate with analysts to correlate experimental results with analytical predictions
or • Analytical, computational, empirical
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laan • Validated structural analysis from coupon, subcomponent, component, qual-unit, flight
no component, full vehicle (for aircraft of all Mach no’s, launch vehicles, spacecraft applications)
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ia • Collaborate with experimentalists to correlate real-time structural monitoring (comparison of
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structural performance vs analytical predictions)
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• Post-test, post flight, correlation of analytical/experimental results
• Tuning of B/Cs, mat props, loads (mech/thermal, i.e applying measured data to analysis
models)
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NASA Focused Structural Health Monitoring
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Key Drivers Enabling
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r Vehicle-focused Technologies
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in Real-time, Advanced Sensing
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decision-making - Multi-parameter
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Online processing - Sensor arrays

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c Onboard systems Advanced Systems
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p Lightweight, and Processing
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d Small size, SHM - Solid state
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a Low power, - Rugged

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c System solutions Materials NDE - High Speed
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u Ultra-Efficient
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Background and Inspiration
Biological Inspiration of Fiber Optic Smart Structures
n One Square-Inch of Human Skin
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i • Four yards of nerve fibers
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it • 600 pain sensors
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• 1300 nerve cells
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Sp • 75 pressure sensors
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• 100 sweat glands
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s s • 3 million cells
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ittu • 3 yards of blood vessels
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eA Smart Structure Human Body
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lan Fiber Optic Pain, temp,
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Piezo’s, SMAs Muscles
IVHM, Smart
Brain
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Courtesy: Airbus 5
Why Fiber Optic Sensors?
One Of These Things (is Not Like The Others)
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(Light, small, easy)
(Complex)
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Fiber Optic System Operation Overview
Fiber Optic Sensing with Fiber Bragg Gratings
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• Immune to electromagnetic / radio-frequency interference and
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a radiation
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s • Lightweight fiber-optic sensing approach having the potential of Grating region
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embedment into structures
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• Multiplex 100s of sensors onto one optical fiber
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• Fiber gratings are written at the same wavelength
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• Uses a narrowband wavelength tunable laser Tuning
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direction
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• Typically easier to install than conventional
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• In addition to measuring strain and temperature these sensors
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n 2 R – spectrum of ith grating
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r I  R Cos(k2nL ) k  n – effective index
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A l L – path difference
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l k – wavenumber
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Reflector L L L
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Reflected light
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How it Works: FBG OFDR Overview
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t Tunable Laser Signal Conditioning and A/D Perform FFT
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S/C A/D
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Domain Domain

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Perform iFFT
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Wavelength
Length
Domain
Domain
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Armstrong’s FOSS Technology
Current Capabilities
Current system specifications
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n • Fiber count 16
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rit • Max sensing length / fiber 40 ft
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it • Max sensors / fiber 2000
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imin • Total sensors / system 32000
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• Max sample rate (flight) 100 sps
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ac • Power (flight) 28VDC @ 4.5 Amps
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• User Interface Ethernet
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• Weight (flight, non-optimized) 27 lbs
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ua • Size (flight, non-optimized) 7.5 x 13 x 13 in
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• Altitude 60kft at -56C for 60 min
• Temperature -56 < T < 40C
Predator -B in Flight
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Fiber Bragg Grating (FBG)
Optical Frequency Domain Reflectometry (OFDR)
FBG-OFDR can dramatically improve structural and system
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1/100 the total sensor weight
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s s • Reducing data system integration time and cost
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n launch vehicles
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• Providing an unprecedented understanding about
system/structural performance throughout space Shape sensing for
vehicle control
craft and mission life cycle ISS COPV strain & temp
monitoring
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