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