kent wei - magnetic induction tomography current development and potential industrial applications

Magnetic induction tomography –

current development and potential industrial

applications

Presented in Kuwait,

Electronics and Electrical Engineering Faculty

4th October 2011

Presenter: Kent Wei,

on behalf of Dr. Manuchehr Soleimani

Magnetic Induction Tomography (MIT) work in Bath

Outline

• Introduction to Magnetic Induction Tomography (MIT)

– Background

– MIT Theory

– System Design

– Software Design

– Image Reconstruction Algorithm

– Rotational MIT

– MIT in Pipeline imaging

– Other tomography techniques

Background (MIT)

• Feature:

– Most recently explored electrical tomography

technique, compare with other electrical tomography

systems, such as EIT and ECT

– Contactless Electromagnetic Imaging.

• Application:

– Metal detection

– Industrial non-destructive testing (NDT)

– Medical application

MIT Theory

• Mutual Inductance

• Sensor response

MIT System Design

Bath MIT

Mk-I and Mk-II

MIT Instrumentation Design

• LabView

• NI-USB 6259

Image Reconstruction

Forward Model (MIT)

Conductivity Distribution Sensor Measurement

Inverse Model (MIT)

Sensor Measurement Conductivity Distribution

Forward Model

Inverse Model

Forward Problems

Object

eddy current

H-field (d/dt)

H-field (d/dt)

1

E

i( i )E iJe

excitation coil

measuring coil

Inverse Problems

Solving Linearised Inverse Problem:

does not exist, as A is generally under-determined, i.e. not symmetrical

Inverse Problem with Tikhonov Regularisation

Solving Inverse Problem:

Regularisation

Parameter

Imaging Result

Images are reconstructed using a linearised reconstruction method based on inversion of a sensitivity Jacobian matrix with Tikhonov regularisation

More Imaging Result

Suitable for metallic object imaging!

HY Wei, M Soleimani, A simple magnetic induction tomography system and the image reconstruction (Published: The 4th World Congress on Industrial Process Tomography)

Rotational MIT (RMIT)

• Electrical Tomography – low imaging resolution

• Coil array can be rotated with respect to the central axis

• Better Image Quality with the same amount of sensors HY Wei, M Soleimani, Theoretical and experimental evaluation of rotational magnetic induction

tomography (Accepted: IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT)

No rotation: 28

measurements

One rotation: 28x2=56

measurements

Two rotations: 28x3=84

measurements

Rotational MIT

0 10 20 30 40 50 60 70 80 9010

-3

10-2

10-1

100

Measurement number

Nor

mal

ised

sin

gula

r va

lues

No rotation

One rotation with 22.5 degree

Two rotations with 15 degrees

RMIT Image Result

No rotation One rotation Two rotations

RMIT Image Result

No rotation One rotation Two rotations

Pipeline Inspection

• Pipeline Inspection is important in industry:

– undiscovered damaged pipelines => huge

operational cost + environmental disaster

• Current Techniques

– Non-destructive testing (NDT)

– In-service testing: pipeline inspection gauges (PIG)

– High Cost and Highly skilled technicians required

MIT in Pipeline Imaging

• Low cost, but yet provide a satisfactory imaging

• In-situ imaging

Narrow Band-pass MIT in Pipeline Imaging

• Narrowband filtering is a technique that can

increase the image quality at the area of interest

Reconstructed Image

without narrowband

filtering

Reconstructed Image

with narrowband

filtering

More narrowband filtering MIT result

Damaged Tube

with small

opening

Damaged Tube

with large

opening

Damaged Tube

with medium

opening Hollow Tube

with no opening

3D Industrial MIT - Simulation

Sensitivity Map

Movement of the centre of mass - Result

Copper bar Predefined

pattern

Movement of the center of

mass extracted from the

image reconstructions

Movement of the centre of mass (Simulated Result)

Woods metal

phantom

Movement of the centre of

mass extracted from the

image reconstructions

Flow Imaging Result

Reconstructions of the boundaries

for every 2 consecutive images

Reconstructions of the boundaries

for every 2 consecutive images

Aluminium cone-

shaped phantom

Conclusion

• MIT is a suitable technique for conductive

material imaging and NDT testing

• Low cost

• Image quality can enhance further by

implementing different measuring techniques or

reconstruction algorithms

• Satisfactory Imaging Result

• Close to commercialisation state

Improved FEM Model for 3D ECT

an outer screen

an insulation (15mm)

a mounting pipe (3mm)

imaging volume

a top view of sensor

Electrical Capacitance Tomography

4D 3D 2D

Question? Kent Wei: H.Wei@bath.ac.uk

Manuchehr Soleimani: M.Soleimani@bath.ac.uk