industrial panel meeting may 13 2008 pg group research portfolio patrick gaydecki and bosco...

Industrial Panel MeetingMay 13 2008

PG Group Research Portfolio

Patrick Gaydecki and Bosco Fernandes

School of Electrical and Electronic EngineeringUniversity of Manchester

PO Box 88Manchester M60 1QD

United Kingdom

Tel: [UK-44] (0) 161 306 4906

[email protected]

www.eee.manchester.ac.uk/research/groups/sisp/research/dsp

mailto:[email protected]

http://www.eee.manchester.ac.uk/research/groups/sisp/research/dsp

http://www.eee.manchester.ac.uk/research/groups/sisp/research/dsp

Inductive Scan Imaging

• Inductive scan imaging systems generate images of embedded steel by analysing the response of a time-varying magnetic field that is impressed on the material by resonant transmitter coils.

• Since 1996 the team has published over 40 papers to journals and conference proceedings

• By exploiting both the changes in impedance and inductance of the coil, corrosion can be imaged.

• The team is now developing a system to detect corrosion in the pre-stressing wire of concrete pipes.

peakpeakdetectordetector ripple filterripple filter precisionprecision

offset nulloffset null

filter/filter/gaingain

referencereferenceoscillatoroscillator

phasephasedetectordetector

frequency tofrequency tovoltagevoltage

converterconverter

Sensing Sensing CoilCoil

DACDAC ADCADC

processor forprocessor forfiltering andfiltering and

controlcontrollocallocal

memorymemory

com

ms

com

ms

po

rtp

ort

real-timereal-timeDSP systemDSP system

TheImaging Sensor

precisionprecisionoffset nulloffset null

filter/filter/gaingain

tunedtunedoscillatoroscillator

Early Experimental Configuration

Image from Sensorbar diameter = 16mm, upper bar depth = 20mm

scan height = 20mm above surface

-0.01

0.01

0.03

0.05

0.07

0.09

0.11

0.13

0.15

0.17

0 50 100 150 200 250 300

Scan Distance (mm)

Sen

sor

Res

pons

e (V

olt)

Measured Signal

Fitted Pearson VII Function

-0.01

0.01

0.03

0.05

0.07

0.09

0.11

0.13

0.15

0.17

0 50 100 150 200 250 300

Scan Distance (mm)

Sen

sor

Res

pons

e (V

olt)

Measured Signal

Fitted Pearson VII Function

Peak Position, xp

Peak Intensity, vPeak Intensity, v

Full Width at Half Height, w

Determination of Scan Profile Parameters

Curve Fitting Approach

• Fit a curve to the sensor response (Pearson VII function).

• Extract the peak parameters: peak value and full width at half height.

• Use a curve-fitting model or train a neural network on the extracted peak parameters to estimate the bar dimensional information.

741195230 031560 ./.. ))(.(.),( vwvwvd

5501650020 .. )(.),( vwwv

390230 0331326 .. ).(.),( vvd

2

cosx

2

siny

dz

3-D Bar Visualisation

3x3 bar mesh using 16mm bar size. The top layer is at depth of 30 mm.

Calculated Items Top Layer Bottom Layer

1 (v1, w1) 16.40 16.61

2 (v2, w2) 16.39 16.54

3 (v3, w3) 16.65 16.54

d1 (v1, =16) 29.65 45.70

d2 (v2, =16) 29.75 46.01

d3 (v3, =16) 30.26 45.42

d1 (v1, w1) 29.77 46.26

d2 (v2, w2) 29.88 46.52

d3 (v3, w3) 30.55 45.92

Dimensional Result : 16mm Bars, Scan Depth 30mm

Image Result : 16mm Bars, Scan Depth 30mm

Imaging of Steel Bars Located behind a Ferrous Steel Layer

subtractionsubtraction

amplificationamplification

power power amplifieramplifier

functionfunctiongeneratorgenerator

3 Coil Configuration

Coil Arrangement

Bars placed under a 0.5mm thick mild steel plate

Broken bar placed under a 2 mm thick mild steel plate

Corrosion Detection, Imaging and Quantification

Corrosion Quantification: Experimental Setup

The accelerated corrosion system

The bar samples

3x2 samples from each bar size

solution concentration of 0.2%

Corrosion Quantification: Initial Results

Image of steel bar and of corrosion product (Q-detection)

Image of corrosion product and steel bar(phase-detection)

Image from Heterodyne output

bar diameter = 20mm, scan height = 30mm above surface

Qualitative corrosion estimation

bar diameter = 20mm, bar length = 200mm, scan height = 25mm

Corrosion thickness (R.H.S) = 0.1mm

Corrosion thickness (R.H.S) = 1mm

The Solid State Magnetic Field Camera(mFIC)

System Configuration

• Previous studies have shown that a 2D array with a minimum 33 x 33 sensor elements will provide sufficient information to allow the generation of a high resolution images using image interpolation techniques.

• It has also been shown that in a 3D spatial orientation, the vertical component of the magnetic flux density (Bz) is the most favourable for image generation, since the image is easy to interpret and can readily be applied to reconstruct the object’s geometry.

• In these experiments we have deployed a 1D linear array of 33 fix solid-state sensors oriented along the Bz axis, in conjunction with a 300 x 40 mm rectangular coil, to produce line scan readings similar to those obtained previously in a traditional 2D scan comprising a single sensor.

• A third generation mFIC has also been constructed, which comprises a 2D array of 33 x 33 sensor elements, which scans electronically and has no moving parts (discussed at the end of this report). However, it was deemed that the system was not optimised for the present feasibility tests and was therefore not used.

Linear Array (1D) System Design

• The PCB sensor array was constructed using 33 MI solid-state sensors (PNI Corp. PNI Sen-s65) spaced with a pitch of 9.325 mm and aligned in a sensor probe that was vertically mounted in order to measure the magnetic flux density along the Z axis (Bz).

• Each sensor has a total field range from –11 to +11 gauss, with a typical resolution of approximately 0.015 µT.

• The readings from each sensor were acquired and digitised sequentially by using an Application Specific Integrated Circuit (ASIC) module, controlled from a central DSP microprocessor unit. The DSP unit also coordinated the multiplexing and data acquisition via an SPI interface.

• Data were stored in memory during the scan and finally transmitted to a computer via an RS 232 interface.

S 8S 8S 8S 8

S 2S 2S 2S 2

S 7S 7S 7S 7

S 6S 6S 6S 6

S 5S 5S 5S 5

S 4S 4S 4S 4

S 3S 3S 3S 3

S 1S 1S 1S 1

S 33S 33

Linear Array Design

ASICASICcontrol and control and

excitation circuitexcitation circuit

ASICASICcontrol and control and

excitation circuitexcitation circuit

DSPDSPdatadata

controllercontroller

DSPDSPdatadata

controllercontroller

DC currentDC currentsystemsystem

DC currentDC currentsystemsystem

Linear Array Design

Version 1.1

Version 2.1

Experimental Setup

X-Y-Z scanner systemX-Y-Z scanner system

CoilCoil

Motor Motor controllercontroller

Power generatorPower generator

PC Control and PC Control and Data AcquisitionData Acquisition

Sensor ArraySensor Array

TargetTarget

Experimental Setup

300 x 300 mm Coil300 x 300 mm Coil1 1 ΩΩ resistance, 2.5 A resistance, 2.5 A

Variable height supportVariable height support

50 t

o 1

20 m

m50

to

120

mm

Bar mesh targetBar mesh target

Sensor arraySensor array

reference levelreference level

Arm supportArm support

Image Pre-Processing

The raw image generation process proceeds as follows:

• An initial scan is taken without the target and with the excitation current switched on, to calibrate the sensors.

• A second scan is taken of the target with the excitation current switched off, to estimate the target’s residual magnetic field.

• A final scan is taken of the target with the excitation current switched on.

• The final scan is corrected for variations in the sensor response and the residual magnetic field of the target.

Scan #1: No Scan #1: No target, field target, field

onon

Scan #1: No Scan #1: No target, field target, field

onon

Scan #2: Scan #2: With target, With target,

field offfield off


field offfield off


field onfield on


field onfield onCompensationCompensationCompensationCompensation

Pre-Pre-processedprocessed

Image Image

Pre-Pre-processedprocessed

Image Image

Multistage image processing algorithm to separate the different layers and to de-blur the composite image

1 2 3 4 5 6

Benitez et al., Efficient image enhancement algorithm for images of steel reinforcing bars in concrete obtained by a new solid-state sensor-based system, IET Science, Measurement & Technology , Volume 1, Issue 5, p. 255-260, 2007.

11 MOVING AVERAGEMOVING AVERAGEFILTERINGFILTERING

MOVING AVERAGEMOVING AVERAGEFILTERINGFILTERING

DE-TRENDINGDE-TRENDINGROWSROWS

DE-TRENDINGDE-TRENDINGROWSROWS

DE-TRENDINGDE-TRENDINGCOLUMNSCOLUMNS

DE-TRENDINGDE-TRENDINGCOLUMNSCOLUMNS

HILBERT HILBERT TRANSFORM TRANSFORM

BASEDBASEDPEAK PEAK

ENHANCEMENTENHANCEMENT


BASEDBASEDPEAK PEAK


MOVING MOVING AVERAGEAVERAGEFILTERINGFILTERING

MOVING MOVING AVERAGEAVERAGEFILTERINGFILTERING

REFERENCE REFERENCE LEVELLEVEL

CORRECTION CORRECTION ROWSROWS


CORRECTION CORRECTION ROWSROWS


CORRECTION CORRECTION COLUMNSCOLUMNS


CORRECTION CORRECTION COLUMNSCOLUMNS


BASEDBASEDPEAK PEAK



BASEDBASEDPEAK PEAK


FINAL FINAL IMAGEIMAGE

FINAL FINAL IMAGEIMAGE

1 3 4 5 6

RAW RAW IMAGEIMAGE

RAW RAW IMAGEIMAGE

2

Image Post-Processing

Validation of Modelling: Optimum Number of Sensors

Experimental results Model predictions

Experimental outcomes confirmed simulated predictions

Image Processing Results

Scanner images: bar mesh located at 100 mm depth

Image Processing Results Images of 12mm bar mesh at 100 mm depth

original

processed

original

processed

original

processed

Results: Concrete Block Scanning

Rebar configuration within the block Scanned image

Complete Linear Array Scanner System

Scan of Target under Ceramic Tile and Foil

Scan of Hammer under Plasterboard

Scan of Hammer under Plasterboard and Foil

Target

/

Barrier

Air

Foil in

air

Ceramic Tile

Tile and

foil

Plaster

board

Plaster

board

and foil

Wire strippers Yes Yes Yes Yes Yes Yes

Pliers Yes No No No Yes Yes

Hammer Yes Yes Yes Yes Yes Yes

Kitchen knife No No Yes Yes Yes Yes

Steel disc Yes Yes Yes Yes Yes Yes

Test Matrix

Notes:

All plasterboard 9.5 mm thicknessAll ceramic tiles 8 mm thickness

Metal Object Imaging in Air, 25 mm

Results:Images of Wire-Strippers

Air, 35 mm

Foil in air, 35 mm

Ceramic tile, 35 mm

Ceramic tile and foil, 35 mm

Plasterboard, 30 mm

Plasterboard and foil, 30 mm

Plasterboard, 25 mm

Results:Images of Pliers


Results:Images of Hammer

Air, 30 mm

Foil in air, 30 mm

Ceramic tile, 30 mm

Plasterboard and foil, 50 mmCeramic tile and foil, 30 mm


Plasterboard, 42 mm

Sample Post-Processed Image

Magnetic Field Imaging of a Ring Coilwith DC Current Excitation

dd

configuration

model experiment

17 mmdepth

67 mmdepth

117 mmdepth

2D mFIC Configuration

• A solid state mFIC has now been fabricated which comprises an array of 33 x 33 magneto-inductive sensors and a square DC excitation coil.

• Three sub-controllers, each of which is responsible for handling the data from eleven linear arrays, feed data to a master controller, which in turn communicates with the host computer.

• Scanning is performed entirely electronically and involves no moving parts.

• An image is generated within three seconds; future developments will enable a data rate of five frames (images) per second.

• At present the device is optimised for imaging steel bars embedded in concrete. Modifications of the system will be required to enable it to detect and image metal weaponry concealed behind walls.

• However, it should be noted that a modified linear mFIC, scanned manually, may be more appropriate for the imaging of concealed weaponry.

2D Array Design

DSP Sub-controller #3DSP Sub-controller #3DSP Sub-controller #3DSP Sub-controller #3

DSP Sub-controller #1DSP Sub-controller #1DSP Sub-controller #1DSP Sub-controller #1

DSP Sub-controller #2DSP Sub-controller #2DSP Sub-controller #2DSP Sub-controller #2DSP MainDSP MainControllerController

DSP MainDSP MainControllerController

Line Sensor Array #1 (1 x 33)Line Sensor Array #1 (1 x 33)Line Sensor Array #1 (1 x 33)Line Sensor Array #1 (1 x 33)




Completed Solid State2D Array Scanner

Development of a Large BorePrestressed Pipe Inspection System

DigitalDigitalFunction generatorFunction generator

InstrumentationInstrumentationamplifieramplifier

Power amplifierPower amplifier

DC power supplyDC power supply

TransmitterTransmittercoilcoil

DSP phase/amplitudeDSP phase/amplitudesystemsystem

ComputerComputer

DigitalDigitalfilter systemfilter system

OscilloscopeOscilloscope

InstrumentationInstrumentationamplifieramplifier

Receiver coilReceiver coil

Hardware

Early Rotational Line-scan SystemPipe testing

0

50000

100000

150000

200000

250000

300000

350000

400000

450000

500000

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350

Angle (Degree)

Am

plit

ude

(DS

P o

utpu

t)

0

50000

100000

150000

200000

250000

300000

350000

400000

450000

500000

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350

Angle (Degree)

Am

plit

ude

(DS

P o

utpu

t)Rotational Line-scan Result

Tx over broken wires

Rx over broken wires

Brega Plant Tests

1.6m Pipe Rotational scans

15

25

35

45

55

65

75

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320

Angular Position (Deg)

Se

nso

r O

utp

ut

(mV

)

3 wire breaks 5 wire breaks 5 wire breaks 7 wire breaks 9 wire breaks

Brega Plant: 1.6 m Pipe Rotational Scan

Rx over breaks

Tx over breaks

Brega Plant: 4m Pipe Wire Break Spot Tests

Wire break spot test

200

220

240

260

280

300

320

340

360

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Number of wire breaks

Se

nso

r O

utp

ut (

mV

)

Brega Plant: 4m Pipe Line Scan Tests

Line scans on 4m pipe

10

60

110

160

210

260

310

360

410

0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400

Scan position (mm)

Sen

sor

Out

put (

mV

)

17 wire breaks 22 wire breaks

17 wire breaks22 wire breaks

Digital Signal Processing and its Application to

Low Level Signal Recovery

Characteristics of DSP Systems

• DSP offers flexibility, allowing a single platform to be rapidly reconfigured for different applications

• Operations such as modulation, phase shifting, signal mixing and delaying are simply performed in software

• System performance is far more accurate than equivalent analogue systems

• However, for real time operation, considerable intellectual investment is required to design and program DSP platforms

DSP Hardware and Software Specifications(Signal Wizard Systems, Developed at UoM)

• 24-bit codec resolution (1 part in 16777216, or 144 dB)

• Variable sample rate extending to 196 kHz

• Processor power of 100 - 550 million multiplication-accumulations per second (MMACS)

• Dual channel/ eight channel operation for signal referencing and mixing with digital audio inputs/outputs

• Non-volatile memory for retention of settings

• Standard PC interfacing: USB, JTAG, serial and parallel

• Easy FIR, and IIR filter design, with other processing functions including mixing and phasing

Final Realized HardwareFinal Realized Hardware(Signal Wizard 2)(Signal Wizard 2)

Signal Wizard 3Signal Wizard 3

550 million 550 million multiplications multiplications andand additions per secondadditions per second

FIR and IIRFIR and IIRdesign areadesign area

Graphical Graphical display of filterdisplay of filter

Hardware control: download, Hardware control: download, gain, adaptive, delay, mixing etc.gain, adaptive, delay, mixing etc.

Signal Wizard 2 Software

Adaptive Filter Software

C:\NPL Workshop\Programs\adaptive_true.exe

Signal Shape ReconstructionEssential Equations Describing Time Domain Deconvolution (Inverse Filtering)

for Real-Time and Off-Line Processing

)()()()(*)()( HXYthtxty

)(

)()( 1

H

YFtx

)()(*)()( tsthtxty

)(

)(

)(

)()( 1

H

S

H

YFtx

otherwisesH

ifs

,10)(

1,0

sHFth

)(

1)(

~ 11

)(~

*)()( 1 thtytx

Simple Fourier domain scheme (rarely successful):

Fourier domain scheme with noise estimate:

Time domain scheme with noise estimate (surprisingly useful):

Finally:

Signal Shape Reconstruction in Practice

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

-0.003 -0.002 -0.001 0 0.001 0.002 0.003 0.004

time (s)

volts

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

-0.003 -0.002 -0.001 0 0.001 0.002 0.003 0.004

time (s)

volts

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

-0.003 -0.002 -0.001 0 0.001 0.002 0.003 0.004

time (s)

volts

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

-0.003 -0.002 -0.001 0 0.001 0.002 0.003 0.004

time (s)

volts

Signal comprising three impulses

Signal after inverse filtering in real-timeSignal after low-pass distortion

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

-0.003 -0.002 -0.001 0 0.001 0.002 0.003 0.004

time (s)

volts

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

-0.003 -0.002 -0.001 0 0.001 0.002 0.003 0.004

time (s)

volts

Detection of AC magnetic fieldspropagated through a ferrous steel boundary:

The Skin Effect

)(.

d

tjd

s eeJJ

r0

2

The strength of both the eddy currents and the associated magnetic field fall rapidly with depth in ferrous materials. The equation which describes the fall in current density is given by:

Where Js is the current density on the surface, d is the depth within the material, is the skin depth, is the angular frequency and J is the is the current density at depth d. The skin depth for a given material is governed by the relationship:

where is the conductivity of the conductor or target, r its relative permeability and 0 is the absolute permeability of a vacuum.

digital functiondigital functiongeneratorgenerator

InstrumentationInstrumentationamplifieramplifier(x 400)(x 400)

DigitalDigitalOscilloscopeOscilloscope

powerpoweramplifieramplifier

super super narrowbandnarrowband

filterfilter

digital gaindigital gain(x 4096)(x 4096)

DSPDSP

Frequency, Frequency, kHzkHz

TransmittedTransmittedfluxfluxdensity, Tdensity, T

Skin depth, Skin depth, mmmm

AttenuationAttenuation ReceivedReceivedfluxfluxdensity, Tdensity, T

4.54.5 3.1 3.1 10 10-4-4 0.1940.194 3.33 3.33 10 10-5-5 1.03 1.03 10 10-8-8

9.09.0 1.73 1.73 10 10-4-4 0.1370.137 4.57 4.57 10 10-7-7 7.89 7.89 10 10-11-11

13.013.0 4.09 4.09 10 10-4-4 0.1140.114 2.20 2.20 10 10-8-8 8.99 8.99 10 10-12-12

Steel properties:

Relative permeability: 250Conductivity: 6.0 106 Sm-1

Mild steel plate

Mild steel enclosure

Experimental Configuration

Laboratory System

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

0 5000 10000 15000 20000 25000

Frequency, Hz

Am

plitu

de,

dB

Pole locations for two IIR filtersPole locations for two IIR filters

Centre Frequency, kHzCentre Frequency, kHz pp00, real, real pp00, imaginary, imaginary pp11, real, real pp11, imaginary, imaginary

4.54.5 0.831460.83146 0.555560.55556 0.831460.83146 -0.55556-0.55556

9.09.0 0.382680.38268 0.923870.92387 0.382680.38268 -0.92387-0.92387

IIR Filter Frequency Response at 9 kHz

Line Scan Results at 4.5 kHz and 9 kHz

0

100

200

300

400

500

600

700

800

900

0 200 400 600 800 1000

Distance across plate, mm

mV

(R

MS

)

1.00E-07

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

0 5000 10000 15000 20000 25000

Frequency, Hz

Log

ampl

itude

0

200

400

600

800

1000

1200

1400

0 200 400 600 800 1000

Distance across plate, mm

mV

(R

MS

)

1.00E-07

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

0 5000 10000 15000 20000 25000

Frequency, Hz

Log

ampl

itude

4.5 kHz 9 kHz

Detection of low amplitude ultrasonic pulses propagated through seawater via a steel structure

7 m structure being lowered into the dockat Liverpool, UK

Location of transmitter

InstrumentationInstrumentationamplifieramplifier(x 400)(x 400)

DigitalDigitalOscilloscopeOscilloscope

super super narrowbandnarrowband

filterfilter

digital gaindigital gain(x 2048)(x 2048)

DSPDSP

MicrocontrolledMicrocontrolledpulserpulser

TransmittingTransmittingtransducertransducer

ReceivingReceivingtransducertransducer

100 m100 m

Signal typeSignal type Tone burstTone burst

Frequency Frequency 40 kHz40 kHz

Transmission Transmission amplitudeamplitude

20 V20 V

Divergence angleDivergence angle hemisphericalhemispherical

AttenuationAttenuation Geometric (1/Geometric (1/rr22))

Peak received signalPeak received signal 650 nV650 nV

Experimental Configuration

Time

Am

plitu

de

Time

Am

plitu

de

Time

Am

plitu

de

Typical Results

(a) Detail of original received signal degraded by noise.

(b) Detail of received signal, recovered by super narrowband filter.

(c) Complete tone burst signal detected after transmission through water, recovered using a super narrowband IIR filter.

(a)

(b)

(c)

Intelligent Clothing Development

Analogueelectronics

DigitizationBT

wirelessTx

Sensor Electronics

volumedisplay

HRdetection

DSP

DSP

Channel splitting

BTwireless

Rx

COM PORT

ECG

respiration

Data Acquisition and DSP

Standard medical equipment and the SmartLife system: A comparative study

• Comparison of the responses from standard Silver/Silver Chloride (Ag/AgCl) electrodes and yarn electrodes using hospital monitoring equipment

• Comparison of the above responses using the Smartlife electronics and software system

• Analysis of the data from Holter Monitors and Loop Recorders

Standard ECG methods have been compared against the SmartLife system in the following ways:

Comparative study : Results

Holter monitor

Loop recorder

Vest

Standard hospital equipmentAg/AgCl

Smartlife electronics and software

Signal comparison: yarn and standard electrodes

Signal from standard Ag/AgCl Gel electrodes Signal from SmartLife® Health Vest electrodes

Signal Section

Amplitude (mV) Duration (ms)

Ag/AgCl Vest Ag/AgCl vest

P wave 0.2 0.3 120 120

QRS complex 2.0 2.5 80 80

T wave 0.5 0.5 240 240

industrial panel meeting may 13 2008 pg group research portfolio patrick gaydecki and bosco...

Documents

quantification slide

surface slide

coil configuration slide

d bar visualisation

inductive scan imaging

ferrous steel layer

image of steel bar

thick mild steel plate