Veera SundararaghavanAt NDE Laboratory, Michigan State University

Special thanks: Prof. L. Udpa, Prof. P. Ramuhalli2002

Summer research work

Development of data acquisition, signal processing and visualization software for a Portable Ultrasound

thickness gauge

NEED• To develop a manual portable ultrasound

thickness gauge and a data visualization software

• Present sensors - Position data??– Tee and Elbow sections ??

• Gridding and measurement

Pulser/Receiver

Flock of Birds

Transmitter

To A/D card

Panametric P/R

Receiver

To Serial Port

Flock of Birds (FB) Sensor• Pulsed DC magnetic tracking.• Advantages over acoustic,optical and mechanical

tracking are,– Full six degrees-of-freedom tracking without limits

in angular coverage.– Small form factor. Sensors ranging from 25mm to

5mm wide for tracking even instruments inserted into the human body.

– Unlimited range of motion without mechanical or line-of-sight limits.

– Real time tracking of multiple sensors. Wireless sensors can now track up to 100 sensors simultaneously for real time animation of characters.

Applications of FB

• Virtual reality games• Simulation - Entertainment -

Motion Capture• Medical 3D imaging• Biomechanical measurements • Scientific visualization• Telerobotics

Functioning of FB

Transmitter Electronics

Signal processing

Signal timing

Data Acquisition• Point by point acquisition using drivers written in

MATLAB 6.0 & Instrumentation and DAQ Toolboxes are used

• STEPS: – Load bird settings (COM Port, Baud rate etc.)– Set up bird hardware by writing bytes to the

serial port– Data acquisition of bird position as bytes– Convert bytes to position data– Use DH matrix to transform the coordinates– Examine bird settings ..reset and close serial

port when error occurs

Denavit-Haartenberg(DH) Matrix

• X S = X B + X O * M(1,1) + Y O * M(2,1) + Z O * M(3,1)

• Y S = Y B + X O * M(1,2) + Y O * M(2,2) + Z O * M(3,2)

• Z S = Z B + X O * M(1,3) + Y O * M(2,3) + Z O * M(3,3)

XS,,YS, ZS

XB,,YB, ZB

0,,0, 0 X

Y

Z

XO

YO

ZO

M =

COS(Y)*COS(Z) COS(Y)*SIN(Z)

-SIN(Y)

-COS(X)*SIN(Z) +SIN(X)*SIN(Y)*COS(Z)

COS(X)*COS(Z) +SIN(X)*SIN(Y)*SIN(Z)

SIN(X)*COS(Y)

SIN(X)*SIN(Z) +COS(X)*SIN(Y)*COS(Z)

-SIN(X)*COS(Z) +COS(X)*SIN(Y)*SIN(Z)

COS(X)*COS(Y)

Ultrasound DAQ

• DAQ using Matlab DLL drivers provided by GAGE APPLIED Inc

• TOF measurement• Low pass filtering

• Hilbert envelope is found

• Smoothing using gaussian convolution

• Thresholding and Peak detection

• Testing of results for a calibrated block

Software• Specify Geometry

• Specify parameters (material,velocity of sound etc)

• Start/stop scan (online acquisition and imaging)

• Generation of a tomographic image

• Save data as x,y,z and TOF (not thickness??)

• Compare Data from previous runs

Software

Steps towards a portable device

• Use of multiple transmitters in order to test complex geometries

• Design of a mechanical fixture/Clamps in order to hold and move the transmitters

• Squirt devices for couplants• Software : 3D Curve fitting of points to

create the required surface during testing itself (instead of warping)