1. Amorphous Wire Localization Checkpoint Presentation April 18, 2001 Matthew Foy Richard Kao Matthias Ziegler

2. 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

3. Proposed Dates Research Magnetic Fields and 2/26 appropriate hardware Research current oscilloscope 3/1 software and localization techniques Develop triangulation software3/8 Develop software for sine wave 3/12 data analysis

4. Proposed Dates (cont.) Hardware Completion 3/16 (Magnetic Field Hardware) Create sensors3/26 Get signal on oscilloscope4/6 Integrate software and hardware4/13 Test with one sensor4/15

5. 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

6. Magnet Types Permanent Magnets Resistive Magnets Superconducting Magnets The type we will be concentrating on will be resistive magnets

7. 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

8. 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)

9. 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

10. Magnetic Field Wire SensorsComputer Data Analysis Oscilloscope Hardware Software Hardware – Software Integration

11. Setup Magnetic Field of 7-12 Gauss Amorphous Wire Sensor (250 coils) Oscilloscope 30 coils of wire

12. 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

13. Software Overview Cont... Sensor Class –Member Variables Array of benchmark amplitudes from calibration Current amplitude being recorded Current phase being recorded Sensor Coefficient

14. 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

15. 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

16. 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

17. 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

18. Revised Dates Hardware/software integration4/23 Test with one sensor4/25 Amplify signal of oscilloscope 4/27 and reduce noise with 1 signal Integrate computer boards to 5/2 accept 12 signals Perfect creation of signals5/7

19. 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

20. 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

21. 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

22. 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 (A f ) and rear (A r ) sensors, we can compute the distance to the sensor array (d # )

23. Distance Equations 1 df3df3 1 dr3dr3 -A f - A r = k() d r = d f + d d - known distance from front sensor to rear sensor in array d f - distance from front sensor to wire d r - distance from rear sensor to wire A f - amplitude at front sensor A r - amplitude at rear sensor k - sensor array coefficient

24. 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)

25. Localization Equations d 2 = (x 2 -x 1 ) 2 + (y 2 -y 1 ) 2 + (z 2 -z 1 ) 2 z = sqrt( r 1 2 - x 2 - y 2 ) r 1 2 - r 2 2 - c d 2 2 c d y = r 1 2 - r 3 2 + c d 2 + 0.5( r 1 2 - r 2 2 + c d 2 ) 2sqrt( c d 2 - (0.5c d ) 2 ) x = r 1 - distance from sensor array 1 to wire r 2 - sensor array 2 to wire r 3 - sensor array 3 to wire c d - calibration distance x,y,z - the coordinates of the wire Sensor Array Coordinates s 1 = ( 0, 0, 0) s 2 = ( 0, c d, 0) s 3 = ( sqrt( c d 2 - (0.5c d ) 2 ), c d /2, 0)

27. 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

28. 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

29. Dependencies Finished –Creation of Magnetic Field –Creation of Sensors Still Working on –Signal Amplifier –Input Computer Board –Need Perfected Signal to Finish Software