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Advanced Instrumentation for Acousto-Ultrasonic Based Structural
Health Monitoring
Joel Smithard, Steve Galea,
Stephen van der Velden, Ian Powlesland,
Cedric Rosalie, and Nik Rajic
Aerospace Division
UNCLASSIFIED – Approved For Public Release
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Outline
▪ AUSAM+ overview
▪ Hardware
▪ Firmware and Software
▪ Operational Modes
▪ First-Of-Class Assessment
▪ System Demonstration
▪ MatLab Scripting
▪ Array of 16 sensing elements
▪ Acousto-Ultrasonic ‘fingerprint’
▪ Wrap-up
UNCLASSIFIED – Approved For Public Release
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AUSAM overview
115 x 65 x 20 mm; size comparison to IPhone
• Instrument Bandwidth 50 kHz – 5 MHz for actuation and response
– High order Lamb waves provide a richer source of AU information
• Interrogate using PZTs and FBGs
UNCLASSIFIED – Approved For Public Release
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AUSAM Hardware ▪ USB 2.0: power and communications
▪ High Voltage PZT Amplifier
▪ 50 KHz to 5 MHz frequency
▪ Drive on any channel(s)
▪ Receive on any channel(s)
▪ 1 to 1024 synchronous averages
▪ External isolated trigger in/out
▪ External Temperature and Strain measurements
▪ Connect up to 62 units
Drive:
• Maximum 200Vp-p drive pulse• Arbitrary function generator• Drive capacitive loads up to 10nF
• Monitoring of drive load voltage and current
Receiver:
• 4 independent low noise receiver channels• 4 independent optical PIN diode channels• 4 Optical DC power measurements
• Independent gain control from -4.5dB to 55dB
UNCLASSIFIED – Approved For Public Release
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AUSAM Firmware and SoftwareCan replace
with Raspberry Pi; connect over
wireless
Can replace with Python; wireless to
Raspberry Pi
UNCLASSIFIED – Approved For Public Release
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AUSAM+ MatLab Object
UNCLASSIFIED – Approved For Public Release
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%%Setup
ausam_master = AusamModel( 'bitfile', ‘..\aushmiv.bit', 'serial', '1606000DLL');
ausam_slave1 = AusamModel(……
ausam_slave2 = AusamModel(……
…….
ausam_slave1.Hardware.Unit(2).Leds='hhhhhhhh'; %LEDs driven by hardware function, eg LED1=trigger
ausam_slave1.Hardware.Unit(2).TriggerControl = 11363; % one wire mode;
…….
% set channel gains (dB)
gain = 43.5;
ausam_master.Hardware.Unit(2).Channel(1).Gain = gain;
ausam_master.Hardware.Unit(2).Channel(2).Gain = gain;
…….
skew = 11.51e-3;
ausam_master.Hardware.Unit(2).Channel(1).Skew = skew;
ausam_master.Hardware.Unit(2).Channel(2).Skew = skew;
-----
AUSAM+ Scripting (setup)
UNCLASSIFIED – Approved For Public Release
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%%Trigger done get/use the data
ausam_master.Hardware.Unit(2).Channel(1).RequestADC;
ausam_master.Hardware.Unit(2).Channel(2).RequestADC;
…….
% Data has now been moved from actual hardware to the MatLab object.
PVDF_Array_element_16 = ausam_master.Hardware.Unit(2).Channel(4).Data;
PVDF_Array_element_15 = ausam_master.Hardware.Unit(2).Channel(3).Data;
……..
PVDF_Whole_Array = [PVDF_Array_element_1; PVDF_Array_element_2; ...
figure(5),imagesc(fliplr(PVDF_Whole_Array'))
% Plot all channels
figure(1)
subplot(2,2,1)
plot(ausam_master.Hardware.Unit(2).Channel(1).Data)
subplot(2,2,2)
……
%Do some magic with it☺
factor = ((2/2^12)/(10^(ausam_master.Hardware.Unit(2).Channel(4).Gain/20))); %gets ADC counts to volts
[HT] = AUSAM_GenerateHilbertTransform(ausam_master.Hardware.Unit(2).Channel(4).DataCounts*factor);
…….
AUSAM+ Scripting (get the data)
UNCLASSIFIED – Approved For Public Release
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The AUSAM+ operates in three typical modes.
1. Generating an excitation drive signal
2. Performing an EM impedance sweep
3. Active interrogation• pulse-echo
• pitch-catch
The first two modes focus on acquiring large excitation signals while the active interrogation modes focus on acquiring small AU responses.
Operational Modes
UNCLASSIFIED – Approved For Public Release
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▪ Acquisition system
▪ Drive amplifier
▪ Noise/Crosstalk
▪ ElectroMechanical (EM) Impedance
▪ Photodiodes
▪ Auxiliary functions
▪ User functionality
UNCLASSIFIED – Approved For Public Release
First-Of-Class Testing (FOCT)
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Drive amplifier (FOCT)
UNCLASSIFIED – Approved For Public Release
Frequency sweep using a five cycle Hanning windowed
sinusoidal signal, at maximum amplitude, applied to a 1 nF
precision capacitor
Improvement
possible; not
limited by
hardware
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UNCLASSIFIED – Approved For Public Release
Drive amplifier (FOCT)
The PSD of the AU response of a
PZT element on an aluminium
plate, in a pitch-catch
configuration, when the actuator
element is excited at 500 kHz
1.2 MHz 100 Vp
excitation signal
applied to a 1 nF
capacitor
PSD of 500kHz response AUSAM and LeCroy
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UNCLASSIFIED – Approved For Public Release
Noise/Crosstalk (FOCT)
Cha has 1 nF capacitor using
100 mm long twisted pair wire,
other channels open circuit
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ElectroMechanical (EM) Impedance (FOCT)
UNCLASSIFIED – Approved For Public Release
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3 mm thick aluminium plate with 10 and 6.3 mm diameter PZT discs.
All the data collected were from a single Hanning windowed sinusoidal drive pulse (ie. no averaging was applied)
PZT System Demonstration
UNCLASSIFIED – Approved For Public Release
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Impedance magnitude
10mm element
UNCLASSIFIED – Approved For Public Release
6.3mm element
Reduction indicating good bond
Reduction indicating good bond
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UNCLASSIFIED – Approved For Public Release
150 kHz pulse-echo and pitch-catch
Drive Pulse Unfiltered Filtered
pulse-echo
10mm
pitch-catch
6.3mm
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UNCLASSIFIED – Approved For Public Release
1.5 MHz pulse-echo and pitch-catch
Drive Pulse Unfiltered Filtered
pitch-catch
6.3mm
pulse-echo
10mm
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4 AUSAM+ units: 16 Element Sensor
UNCLASSIFIED – Approved For Public Release
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AUSAM+ Sensitivity vs LeCroy DSO
LeCroy
AUSAM+
UNCLASSIFIED – Approved For Public Release
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16 Element Sensor Array: Wave Front
UNCLASSIFIED – Approved For Public Release
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UNCLASSIFIED – Approved For Public Release
‘Fingerprint’ Ball Impact 100mm From Array (2D FFT)
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frequency-thickness (MHz-mm)
wavenum
ber
(rad/m
)
A0
SH0
S0
A1
S1
S2
0 0.5 1 1.5 2 2.5 3 3.5 4 4.50
500
1000
1500
2000
‘Fingerprint’ Active Acousto-Ultrasonic Drive
UNCLASSIFIED – Approved For Public Release
Acousto-Ultrasonic sweeps 0.1–2.5MHz, 100kHz steps
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• A new small, robust, flexible instrument for Acousto-Ultrasonic interrogation.
• Excite and monitor Lamb waves at frequencies up to 5 MHz.
• Sinusoidal excitations of 200 Vp-p in the frequency range 200 kHz to 1.5 MHz while providing usable drive strength at frequencies 50-200kHz & 1.5-5 MHz.
• The device was shown to have a relatively low noise floor and low electrical crosstalk between acquisition channels.
• The performance of an in-built EM Impedance capability compared well to that of a commercial Impedance Analyser.
• The module provides the ability to undertake strain and temperature measurements.
• The compact AUSAM+ is small and light enough to find SHM application in a vast array of situations.
• The Matlab hardware object provides enormous versatility allowing the user to easily interface with the hardware functionality thus permitting the development of customised in-house GUIs for a wide variety of activities and applications.
UNCLASSIFIED – Approved For Public Release
Wrap-up
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UNCLASSIFIED – Approved For Public Release
Questions
stephen.vandervelden@dst.defence.gov.au
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