noncontact sesnsing of rotating structures with …...noncontact sensing with rotary optical radial...

Noncontact Sensing with Rotary OpticalNoncontact Sensing with Rotary OpticalRadial Coupler (RORC) using CRadial Coupler (RORC) using C--lenslensRadial Coupler (RORC) using CRadial Coupler (RORC) using C lenslens

Khazar Hayat Prof Sung Kyu HaKhazar Hayat, Prof. Sung Kyu Ha

Motivation

Structural Health Monitoring (SHM) of Critical Rotary Components

Rotating StructureSHM Goals:SHM Goals:

SHM

ComponentsSensing Mechanism

Data acquisition &

SHM Goals: SHM Goals:

Condition Assessment

Damage Evaluation

Service Life Prediction

Management Catastrophic Failure Prevention

osts

Cost Savings trend 

Predictive

Co

SHM

SHM Advantages:

• Ensure Structural Integrity Scheduled

Predictive

Unscheduled

Time

Unscheduled(Today)

PredictivePredictiveSHMg y

•“Maintenance on demand”• Lower unscheduled inspections

Slide 2

< SHM Benefits (Source: Holger Speckmann, AIRBUS)>

Motivation

Composite Rotating Structures

<Composite High Speed Rotor (HSCL Lab)>

SHM A li ti

< Wind Turbine blade ><Composite Fan Blade

SHM Applications

< Wind Turbine blade > ( Model: GE90-115B)>

H li t Bl d (S Sik k Ai ft C )

Slide 3

<  Helicopter Blades (Source: Sikorsky Aircraft Corp) > 

Problem Statement

Structural integrity can be assessed by monitoring strainsStructural integrity can be assessed by monitoring strains

Difficult to receive strain data from Rotating Structure

“Development of a Noncontact Strain MeasurementDevelopment of a Noncontact Strain Measurement Method using Rotary Optical Radial Coupler

(RORC)”

Slide 4

Previous Strain Measurement Methods

Strain Gauges with Slip Ring / Telemetry system

•High signal to noise ratio

•Data transmission limitation

•Not applicable to higher speedNot applicable to higher speed

•Need power supply

•Sensitive to electromagnetic (EM) interference

Slide 5

Previous Strain Measurement Methods

FBG Sensor with Telemetry System•Power Supply Problempp y

•Imbalance of Rotating Structure at Higher Speed

< Wireless signal transmission between Signal Process Unit (SPU) & FBG sensorsattached on wind turbine blade>

Slide 6

Ref: Kerstin S., Wolfgang E., Jorg A., Elfrum L. and Gerhard L. A fibre bragg grating sensor system monitors operational load in a wind turbine blade. Meas. Sci. Technol. 2006: (17) 1167-1172

Previous Strain Measurement Methods

Fiber Optic Rotary Joint

•Optical signal transmissionOptical signal transmission

•Insensitive to EM interference

•Tight mechanical tolerance for optical alignment•Tight mechanical tolerance for optical alignment

•Limited speed & durability due to mechanical parts

< Working Principle of Fiber Optic Rotary Joint >

Slide 7

Ref: Jing W., Jia D., Tang F., Zhang H., Zhang Y., Zhou G., Yu J., Kong F. and Liu K. Design and implementation of a broadband optical rotary joint usingC-lenses. Opt. Express: (2004) 12 4088–93

Previous Strain Measurement Methods

Fiber Optic Coupler•Free-space coupling

•Require machining of for installation, weakening the Shaft

• Space Installation Problems in real structuresSpace Installation Problems in real structures

< Arrangements of a rotary optical coupler and FBG sensors >

Radial Optical Rotary Coupler (RORC)

(Over come above problems associate with Fiber Optic Coupler)

Slide 8

( p p p )

Theory

Fiber Bragg Grating (FBG) Sensor•Reflect particular (i.e. Bragg) wavelength of light and transmits others

Strain-included shift =

n0 : refractive index of the airn1 : refractive index of the claddingn2 : refractive index of the coren3 : refractive index of the grating

λΔλΔ

•Strain & Temperature Measurements

Slide 9

Theory

Wavelength Division Multiplexing (WDM)

•Many FBG sensors on single optical fiber can be address simultaneously•Many FBG sensors on single optical fiber can be address simultaneously

•Sensing Network

< Representation of a WDM interrogation of FBG sensor array >

Slide 10

Experiment

Experimental Arrangement for RORC Feasibility

Slide 11

< Sketch of experiment test fixture to show feasibility of rotary optical radial coupler (RORC) >

Experiment

Alignment of Collimators

•Tedious and Time Consuming (i e 06 DOF’s )•Tedious and Time Consuming (i.e. 06 DOF s )

•Use of marked Collimators< 06 DOF manipulation >

V-groove block pre-alignmentfor marking

< Optical alignment b/t stationary side and rotary side collimators >

Fi l li t ith k d lli t (i k t hi )

< Circumferential marking of C-lens Collimators pair at proper optical alignment position >

Slide 12

Final alignment with marked collimator (i.e. mark matching)

Experiment

Equipment Specification & SetupFBG Sensor Spec.:

• Qty: 01l l h• Central Wavelength: 1552.10 nm

< Pair of C-lens Collimators used as RORC >

Slide 13

< Experimental setup >

Preliminary Results & Conclusions

• Optical signal pike per each rotation of disk appeared onsi-425 Optical Sensing Interrogator (as expected )

th

• As speed increases, the timespace between wavelength signalspikes decreases and vice versa(see region A & C )

Wav

elen

gt

• Increase in speed sometimescauses misalignment that result in

Time

missing signal spikes(see region B)

Slide 14

< Signal spikes appearing on si-425 interrogator >Time

Preliminary Results & Conclusions

• For max. test speed of 1350 RPM, strain modulatedwavelength signal was observed

Wavelength Signal

Strain Measurement

•Wavelength signal value (i.e.1552 10 nm) remained constant up

Strain Measurement

1552.10 nm) remained constant upto 1350 rpm, because negligibledeformation / strain of steel disk

Slide 15

< Wavelength signal measurement on si-425 optical sensing interrogatorat different rotating disk speeds >

Future Work

• Multiple points strain signal measurement( i.e. For 0o ~ 360o varying strains)

• High Sampling Data Acquisition System< signal measurement four times per revolution

at required rotation angles >

• Optical Loss across RORC

Minimize by precise alignment & use of better quality Collimators

Overcome by Higher Laser Source

• Real-time applications(i.e. on wind turbine blade, composite flywheel rotor, helicopter blade, Composite fan blades etc.)

Slide 16

Thank You for Your Attention

sungkha@gmail.comkhazarhayat@yahoo com

Slide 17

khazarhayat@yahoo.com