Amorphous Wire LocalizationCheckpoint Presentation

April 18, 2001

Matthew Foy

Richard Kao

Matthias Ziegler

Hardware Project Overview

• Objective– To create a system in which we can detect

the amorphous wire to the highest accuracy that will allow us to test our software

• Deliverables– A system that is based on 16 sensors that

returns a single location of the wire

Proposed Dates

• Research Magnetic Fields and 2/26

appropriate hardware• Research current oscilloscope 3/1

software and localization techniques• Develop triangulation software 3/8• Develop software for sine wave 3/12

data analysis

Proposed Dates (cont.)

• Hardware Completion 3/16

(Magnetic Field Hardware)• Create sensors 3/26• Get signal on oscilloscope 4/6• Integrate software and hardware 4/13• Test with one sensor 4/15

Proposed Dates (cont.)

• Amplify signal of oscilloscope 4/17

and reduce noise• Integrate computer boards to 4/23

accept 15 signals• Perfect Localization of wire 5/3

with these signals

Magnet Types

• Permanent Magnets

• Resistive Magnets

• Superconducting Magnets

• The type we will be concentrating on will be resistive magnets

Permanent Magnets

• Typical Kitchen Magnets• Two ends – North and South• Overall Properties:

• This provides an additive effect, producing a stronger magnetic field

• Attract steel and iron• Opposites attract and Likes

repel

Current produces magnetic field

• Current flowing through a wire also produces a magnetic field

• Differs from permanent magnet because it is temporary (lasts only while current is running)

Resistive Magnets (Electromagnets)

• Resistive magnets consist of many windings or coils of wire wrapped around a cylinder or bore through which an electric current is passed

Magnetic Field

Wire

Sensors Computer

Data Analysis

Oscilloscope

HardwareHardware Software Software

Hardware – Software Integration

Setup

Magnetic Field of 7-12 Gauss

Amorphous Wire

Sensor

(250 coils) Oscilloscope

30 coils of wire

Software Overview

• Expected Deliverables– Input amplitude and phase for each sensor– Compute distance from the wire to 3

separate sensor arrays– Determine the location and approximate

orientation of the wire in 3 space

Software Overview Cont...

• Sensor Class– Member Variables

• Array of benchmark amplitudes from calibration• Current amplitude being recorded• Current phase being recorded• Sensor Coefficient

Software Overview Cont...

• Sensor Array Class– Member Variables

• Front and Rear Sensor Objects• 3 Triplet Sensor Objects

– Member Functions• Compute Sensor Array Coefficient• Compute distance to wire

Software Overview Cont...

• Main function– Creates 3 Sensor Array Objects– Calibrates each Sensor Array– Computes each Sensor Array Coefficient– Computes distance to wire from each Array– Localizes wire in 3-space

Our Results

• On top is what our results should like

• Our result is the bottom graph

• The point where the wire should be magnetized is too small and in the wrong location

Our Results (cont.)

• The problem was that the wire was not long enough so the signal it gave off was not strong or what we were looking for

• It turned out the wire wasn’t 50 microns as expected but 150 microns, which threw the calculation off

Revised Dates

• Hardware/software integration 4/23• Test with one sensor 4/25• Amplify signal of oscilloscope 4/27

and reduce noise with 1 signal• Integrate computer boards to 5/2

accept 12 signals• Perfect creation of signals 5/7

                                                                                                      

Analog Input Board

Low Cost High Speed 16 Channel 12-& 16-Bit Analog Input Board

16 Single-Ended/8 Differential Analog Inputs  

Models with 12-or 16-Bit Analog Input Resolution

160K Samples/Second A/D (DAS-1400-12)

512 Sample FIFO

8-Bits Digital I/O

System Calibration

• The wire is rotated through the tilt plane and about the central axis in 10 degree increments, with the amplitude recorded at each step

• The phase of the wire is recorded• Each sensor array coefficient (k) is computed

based on the calibration distance and the change in signal amplitude from the front to rear sensor in the array

System Calibration Cont...

x

y - tilt axis

z - central axis

rotation about central axis(yz plane)36 readings

wire

x

y - tilt axis

z - central axis

rotation about tilt axis (xz plane)18 readings

wire

36 readings/sensor * 18 readings/sensor = 648 benchmarks/sensor

Wire Distance

• Distance– The rear sensor in the array is a known

distance (d) behing the front sensor– With the coefficient known for each sensor

array (k) along with the signal amplitude at the front (Af) and rear (Ar) sensors, we can compute the distance to the sensor array (d#)

Distance Equations

1df

3

1dr

3-Af - Ar = k( )

dr = df + d d - known distance from front sensor to rear sensor in arraydf - distance from front sensor to wiredr - distance from rear sensor to wireAf - amplitude at front sensorAr - amplitude at rear sensork - sensor array coefficient

Wire Localization

• Wire is a known radius (r#) from each sensor array, creating a sphere of possible locations around each array

• Intersection of 3 spheres is the location of the wire, computed by simultaneously solving 3 distance equations for the 3 unknown variables (x,y,z)

Localization Equations

d2 = (x2-x1)2 + (y2-y1)2 + (z2-z1)2

z = sqrt( r12 - x2 - y2 )

r12 - r2

2 - cd2

2 cd

y =

r12 - r3

2 + cd2 + 0.5( r1

2 - r22 + cd

2 )

2sqrt( cd2 - (0.5cd)2 )

x =

r1 - distance from sensor array 1 to wirer2 - sensor array 2 to wirer3 - sensor array 3 to wirecd - calibration distancex,y,z - the coordinates of

the wire

Sensor Array Coordinatess1 = ( 0, 0, 0)s2 = ( 0, cd, 0)s3 = ( sqrt( cd

2 - (0.5cd)2), cd/2, 0)

Software Problems

• Noise in the signal sometimes causes irregular readings in the signal amplitude

• Removing Noise– Input the 3 peak points from one phase of the sine

wave and sum them for one amplitude– This process is repeated for 60 sine waves (1sec)– Total sum is the signal amplitude for the sensor

What’s Next?

• Complete hardware-software interface• Use the triplet sensors to estimate the

orientation of the wire– By examining how the amplitude measured

at each triplet sensor in the array deviates from a mean value during the calibration, we hope to estimate the approximate orientation of the wire

• Localize multiple wires at the same time

Dependencies

• Finished– Creation of Magnetic Field– Creation of Sensors

• Still Working on– Signal Amplifier– Input Computer Board– Need Perfected Signal to Finish Software