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Fiber Optic Sensing
Presented by: Jason Kiddy (Aither)
Alan Turner (Micron Optics)
May 13, 2008
Sandia Wind Blade Workshop
Aither Engineering, Inc.4865 Walden LaneLanham, MD 20706(240) [email protected]
Micron Optics, Inc.1852 Century PlaceAtlanta, GA 30345(281) 334-3793 [email protected]
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Aither Engineering, Inc.
• Maryland Corporation, formed July 2006 as a spin-off from Systems Planning and Analysis (SPA).
• Annual Revenues: $750k-$1M
• Staff: 9 Total, 6 Full Time Engineers
• Secret Facility Security Clearance
• Location: Lanham, Maryland (Washington DC Metro area)
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Background
Fiber Optic Monitoring of Wind Turbines - Phase I SBIR -
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Instrumented Blade System Concept
• Improve turbine blade reliability through an integrated monitoring system based on fiber Bragg grating sensors
• Predict blade deflections for real-time control to reduce stresses and avoid tower strikes
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Phase I SBIR Objectives
• To analyze an existing turbine blade design (TPI CX-100) to determine sensor density and optimal sensor locations for deflection measurements
• Retrofit an existing blade with fiber optic sensors to measure flap bending
• Verify accurate strain measurements and shape prediction during quasi-static load to failure test
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Bragg Grating Sensors
• Sensor operates by optically monitoring changes in the grating structure
• Localized, variable length (~ 1 cm)
• Multiplexible
• Sensitive to strain and temperature
P
Λ
CoreCladding
P
Reflected Transmitted
Broadband Source
P
e, T2x2 Coupler
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Time Division Multiplexing (TDM)
• Multiplexing occurs based on sensor return time
• Low reflectivity FBG sensors
• Must have a minimum distance between FBG sensors to resolve individual sensors
#1 #2 #3 #n-1 #nPulsedSource Coupler Sensor Array
time
time
#1 #2 #3 #n-1 #n Interrogator
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Wavelength Division Multiplexing (WDM)
• Optical filtering based on wavelength of sensors
• Number of sensors limited by channel spacing of WDM— Must consider overall wavelength shift response of sensors
#1 #2 #3 #n-1 #nSource Coupler Sensor Array
1530 1560Wavelength (nm)
Pow
er (a
.u.)
Determines Maximum Measurement Range
l1
l2
l3l4
l5
l8Spectrum Analyzer
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Static Deflection Test• FBG sensor data taken throughout load
profiles— 0%-100% in 25% increments
— Above 100% until failure in 10% increments
• Blade failed at ~120% design load at root trailing edge
• All FBG sensors survived test — Low pressure (top) sensors recorded
greatly reduced strains
— Post-test inspection revealed poor epoxy adhesion for unknown reasons
— High pressure (bottom) sensors recorded accurate strains and were used for deflection processing
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Static Deflection Results
-0.2
0
0.2
0.4
0.6
0.8
1
0 1 2 3 4 5 6 7 8 9 10
Distance Along Blade (m)
Def
lect
ion
(m)
25% Load50% Load75% Load100% Load120% Load25% Load50% Load75% Load100% Load120% Load
Maximum Error @ 120% Load: 2.4 cm or 3.5%Maximum Error @ 100% Load: 0.53 cm or 0.86%
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FBG SensorFiberSplice ProtectorFurcation TubingConnectorFault Detector
Distance Along Blade (m)0.653 1.8 2.55
-1.147- -0.75-
-1934-1591-1428295,593Load 3
-1773-1458-1309500,000Load 2
-1611-1325-11901,010,000Load 1
FBG 3FBG 2FBG 1# Cycles
Fatigue Test Results
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Sensor Blade Project
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Project Objectives
• Replace retrofitted FBG strain sensors with integral sensors that are embedded in the blade
• To demonstrate the usefulness and robustness of the Micro Optics instrumentation as mounted in the rotating frame
• To demonstrate the accuracy of the tip deflection measurement during operational use
• To test the performance of commercially available strain and temperature sensor from Micron Optics
• To investigate data handling issues
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Aither Sensor Layout
• Two arrays of 8 FBGs will be embedded in both HP and LP skins• Two additional redundant strain sensing arrays will be embedded
with the primary arrays• 3 temperature sensors will be retrofit on inside of skin surface
Trailing Edge
0.05 1.2 2.35 3.50 4.65 5.80 6.95 8.10
-1.15-
Distance Along Blade (m)
-1.15- -1.15- -1.15- -1.15- -1.15- -1.15-
Embedded Strain Sensors(8 in LP and HP skins)
Temperature Sensors (x3)
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Embedded Sensor Location
• Optical fibers will be embedded in the SARTEX carbon/fiberglass hybrid material
• Six layers of SARTEX at root. Three layers end near center of blade. Three layers end near tip.
• Fiber will egress near the tip at a ply drop off• Fiber return to the root of the blade will occur underneath a single
layer of glass
SARTEX
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Composite Sample Test
• 4 point bending samples created to test strain transfer in SARTEX material
• Excellent correlation between FBG and surface-mounted RSG
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Aither Temperature Sensor Design
• Conventional ‘loose-tube’design
• FBG sensor will remain strain free inside of SS tube
• Individual sensors will be fusion spliced together to reduce power loss
• SS tubes will be bonded to inside of turbine blade surface after layup and curing
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Micron Optics Confidential Slide 18
MICRON OPTICSCompany Profile
• Founded April 1990.• Based in Atlanta, GA.• Manufacturing Facility includes 24,000 sq.
ft. and multiple Clean Rooms.• Consistently won multiple annual US
National Research & Development Awards. • In-House Mirror Coating Operation for Filter
Development & Manufacturing.• Unique, Well-Developed, Seminal,
Core Component and Embedded Opto-Electronics Technology.
• 27 MOI Patents & 3 Trademarks Issued, Additional 5 MOI Patents Pending. Owner of another 32 Patent Licenses.
• 86 Journal and Conference Publications.• Financially Self-Supported.
• Founded April 1990.• Based in Atlanta, GA.• Manufacturing Facility includes 24,000 sq.
ft. and multiple Clean Rooms.• Consistently won multiple annual US
National Research & Development Awards. • In-House Mirror Coating Operation for Filter
Development & Manufacturing.• Unique, Well-Developed, Seminal,
Core Component and Embedded Opto-Electronics Technology.
• 27 MOI Patents & 3 Trademarks Issued, Additional 5 MOI Patents Pending. Owner of another 32 Patent Licenses.
• 86 Journal and Conference Publications.• Financially Self-Supported.
2006 Sales by Territory
54%
21%
25% USEuropeAsia
2006 Sales by Market
52%35%
13%SensingTelecomBioTech
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Micron Optics Fiber Bragg Grating Sensor Layout
Fiber Bragg Grating Temperature Sensor (surface mounted) Micron Optics os4300 ( * ≡ optional)T
SS
TT
SS S SS
High Pressure (HP) Skin, Internal Surface
Low Pressure (LP) Skin, Internal SurfaceS
LE
TE
S S T T Te
Fiber Bragg Grating Temperature Sensor (surface mounted) Micron Optics os4200Te
TeSS T
SS S SSS S T T
S
*
* *
Fiber Bragg Grating Strain Gage Sensor (surface mounted)Micron Optics os3200 ( * ≡ optional)S
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Micron Optics Fiber Optic Sensing Cable Layout
High Pressure (HP) Skin, Internal Surface
Low Pressure (LP) Skin, Internal Surface
Mounted on the interior surface of the HP skin, Micon Optics will have one fiber optic sensing cable terminating at 8.9-m.
Mounted on the interior surface of the LP skin, Micon Optics will have one fiber optic sensing cable terminating at 8.9-m.
LE
TE
Cable Diameter = 3.0 mm
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Strain Gage to be Surface Mounted on Bladeos3200 - Dielectrically Packaged Design
Optical fiber inProtective braided jacket
FBG underneathInside protective groove
Protective plastic carrier& epoxy molding preform
FBGGroove
FiberBonding cavity
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Fibergroove
Plastic carrier
Venting holes
Epoxy Filling hole
Top View
CrossSection
Adhesive Backing
Strain Gage to be Surface Mounted on Bladeos3200 - Dielectrically Packaged Design
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Temperature Sensor to be Mounted on Blade Tipsos4200 – Temperature Sensor
• Operating temperature range -40 to 120 deg. C
• Temperature Coefficient 9.9 pm/deg. C (+\-10pm)
• Response time 0.3 seconds
• Long Term Accuracy +\-5 deg. C
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Equipment to be Utilized in Blade Monitoring
• SP130 utilized to control the SM130 remotely enabling power saving, data logging and web serving capability.
• SM130 interrogates the FBG sensors. Available from 1 to 16 channels. Has a dynamic bandwidth of up to 2 Khz
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SP130 Specifications
• SP130 has a 1.4 GHz Pentium, 512 MB DDR, a 100GB 2.5 inch HD and windows XP operating system.
• Peripheral interfaces include USB, Ethernet, RS232/422/485 and a user configurable digital I/O.
• Provides power management through wake-on-LAN and wake-on-clock functions.
• Small foot print, mounts directly onto the SM130.
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SM130 Specifications
• 4 channels with a spectral width of 1510 to 1590 nm. Available from 1410 to 1590 nm.
• 1 khz scanning frequency, available to 2 khz.
• Wavelength repeatability 1pm@1khz, 0.05 pm with 1,000 averages.
• Power consumption 25 watts, 50 watts max.
• Operating temperature 0 to 50 degrees C.
• External triggering capability.
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Data Acquisition Architecture
• Sandia’s Atlas data system to provide TTL trigger input, to SM130, to synchronize data sets.
• SP130 will host the software that will control the SM130.
• An Ad-Hoc wireless network between the laptop, located in the control room and the SP130 in the hub, will allow for the retrieval of data files through shared resources in the “Wind 2” workgroup.
• SP130 will be configured as a web server allowing for remote control of SM130 software.
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Active X container in IE for remote control of SM130