1. High Resolution AMR Compass Honeywell Advisor Dr. Andy Peczalski Advisor Professor Beth Stadler Pat Albersman Jeff Aymond Dan Beckvall Marcus Ellson Patrick Hermans

2. Abstract Honeywell This project’s purpose is to improve the accuracy of a digital compass by using multiple compass IC’s. These will work together to collectively improve the accuracy of the overall system.

3. Project Motivation Magnetic ICs in High Demand Navigation HDD Proximity sensing Position sensing Increasing Accuracy is Required Decreasing Size is also Beneficial Honeywell Images from http://phermans.com/w/images/e/e2/HMC105X.pdf

4. Current Technology Anisotropic Magnetoresistance Wheatstone bridge Honeywell Images from http://phermans.com/w/images/9/9f/Appl_note_for_position_sensing.pdf

5. Current Technology Analog –1–1, 2 or 3 axes sensing –D–Direct access to bridge –N–Navigational accuracy depends on ability to read voltages Digital –2–2 or 3 axes –I–Internal heading calculation –A–Accurate to 1 degree Honeywell

6. Future Technology Honeywell What is the next step? Nanowires AMR sensing abilities Decreased size Decreased sensitivity Images from Prof. Beth Stadler

7. Project Description Honeywell Feasibility study for the use of nanowires Not actually working with nanowires Trying to increase accuracy by using multiple bridges as would be required with nanowires Providing Honeywell with a new use for nanowires

8. Project Description Honeywell One benchmark is to try to increase the accuracy of the system by the number of sensors used. Increased precision and repeatability is also desired.

9. Project Description Honeywell Customized hardware is necessary to implement the multiple sensor system. Customized software will be required to manage the implementation.

10. Chosen IC: HMC 6352 Honeywell Digital 2-axis compass On board ADC Modifiable sensing range Speaks I2C Small package Improvable accuracy Barber pole bridges Image from http://phermans.com/w/images/9/9d/HMC6352.pdf

11. Software & Algorithms Modeling & Simulations Matlab Firmware MPLab & CCS Compiler User Interface Visual Basic (VB) Honeywell

12. Sensor Modeling Goal: Parameters-> M-file -> Sensor Data Honeywell Consists of Many Sub-functions Noise, Bridge, OpAmp, A2D Needs to model real world situations

13. MATLAB Honeywell Successfully used to simulate single and multiple sensors before our hardware could be designed Provided a vehicle to test the performance of our heading calculation algorithms Totaled 1702 lines of MATLAB code

14. Sensor Placement The placement of the sensors must create a system accurate across 360 degrees Each individual bridge of each sensor can be simulated independently in MATLAB Multiple arrangements can be simulated to determine the best implementation Honeywell

15. Orientation Simulations Single IC Senor Output Wave Form: Honeywell Data Appears Evenly Spaced ICs at: 0, 36, 72, 108, 144, 180, 216, 252, 288, 324 Degrees

16. Orientation Simulations Single IC Senor Output Wave Form: Honeywell Data Evenly Spaced ICs at: 0, 9, 18, 27, 36, 45, 54, 63, 72, 81 Degrees

17. MicroController C Code Written in MPLab – Version 8.0 CCS complier – Version 4 Run on PIC 18f4550 1326 Lines of C – 2532 Lines of Assembly Honeywell

18. Sensor Communication Sensor Commands – Heading Adjusted voltages Raw voltages – Calibrate – Re-address – Number of Summed measurements Honeywell

19. Serial Communication Allows Compass to display results Very helpful in debugging Allows for VB to control sensor Easy to implement in CCS 115200 Baud allowable from the 20Mhz crystal Honeywell

20. Weighted Averaging Honeywell

22. Visual Basic (VB) Interface Provides an end-user interface Synchronizes the compass and the rotation table used to accurately measure moves Allows for automated data acquisition Provides a repeatable test benching system Requires a third board to handle adjusted ground on PMC Total of 4733 Lines of Code Honeywell

24. Visual Basic (VB) Interface Commands to perform repeatable data acquisition and benchmark tests.

25. Honeywell Personal Computer (VB) PIC18F4520 (C) PMC Controller Rot. Table Sensors Serial I2C Parallel

26. Hardware: Abstract One compass, two boards – Main Board Microcontroller – Daughter Board Sensors Honeywell

27. Hardware: Main Board Essentially a controller board – Microcontroller – RS-232 Communication – I 2 C Communication – Interfacing Daughter Board Front Panel Honeywell

28. Initial Design: Daughter Board Three functional systems – Sensor array – Power MUX – Laser Constraint: One of the dimensions must be less than 3.5” – Opening of zero-gauss chamber is 3.5” in diameter Honeywell 3.492” 3.132”

29. Honeywell Daughter Board I 2 C Bus Data Clock

30. Design challenge: – Need to assign unique address to each sensor – Each sensor is factory installed with address 0x42 – In order to change addresses, a command must be sent to a sensor on the bus – This command message contains: – How to change address of individual sensor if every sensor is receiving the command? Honeywell Daughter Board Power MUX StartAddress[Ack]Command[Ack]Stop

31. Solution: Need to isolate communication to individual sensor How? – Burn-in Socket – Use a network of jumpers – Multiplex I 2 C to each sensor – Multiplex power to each sensor Honeywell Daughter Board Power MUX Photo taken from http://www.locknest.com/newsite/products/qfn/index.htm

32. We chose to multiplex power – Advantages Saves power Simplifies troubleshooting – Disadvantages Signal loss through MUX Other unknowns… Honeywell Daughter Board Power MUX

33. Problems with Initial Design Problems – Main Board None – Daughter Board I 2 C bus – When powered off, the sensors interfere with I 2 C bus – 5V data signal is pulled down to 2.5V – Therefore communication will not work – Problems not related to design Sensor 3 will not communicate Will not hinder project; algorithm will still work Slight loss of sensitivity at sensor 3’s axes of sensitivity (27° and 117 °) Honeywell

34. Changes to Initial Design I 2 C bus fix – Remove MUX and feed power to all sensors – Cut I 2 C traces – Add jumpers to I 2 C vias and address them one by one – Connect all jumpers to I 2 C bus Honeywell

35. Changes to Initial Design Other changes – No laser mount Laser mounted directly to plexi-glass case Saves cost ($25) Honeywell

36. Proposed Final Design Due to I 2 C bus issues, our current design does not work Two options 1.Power all sensors and use burn-in or jumpers socket to isolate sensors 2.Multiplex I 2 C bus 3.Add Physical Jumpers to the I 2 C bus to individual connect one sensor at a time Honeywell

37. Testing Honeywell Prototype Final

38. Test Setup Honeywell

39. Accuracy Honeywell Precision Repeatability Compare ß field Compare

40. Prototype Testing Honeywell Given one sensor CCS compiler

41. Final Testing Honeywell Elements of Final testing Pretesting to determine zero gauss values Pretesting to determine IC positional offsets Testing to obtain compass specs Accuracy, Precision, Repeatability

42. Pre-testing (zero gauss) 1.Place sensors in the zero gauss chamber 2.Rotate 360 deg. while taking readings 3.Analyze data and get zero gauss values This determines what value we should see when the IC is experiencing zero gauss, aka: parallel to the field direction. Honeywell

43. Pre-testing (offsets) 1.Place sensors in artificial magnetic field 2.Run VB script that finds sensor locations Uses the zero gauss value of each chip Works using relativity, sensor 1 = 0, sensor2 = ? From 1 Bang bang control 3.Analyze data and find chip placements 4.Hardcode this to software Honeywell

44. Raw voltage readings with offsets

45. Honeywell Raw voltage readings with offsets

46. Accuracy Test Procedure 1.Determine the B field Find the zero crossing on each axis B field should be 90 degrees from zero crossing Average the 20 axes results 2.Take measurement 3.Compare result to actual 4.Rotate to different position 5.Repeat steps 2-5 Honeywell 23 deg 113 deg

47. Results Honeywell Results Comprise of: Determining Specs Comparison of Specs to Controls Ways to improve Future for Nanowires?

48. Results: Control Comparisons First Control is the Sensor Heading output – We Don’t know how they compute this Second Control is performing arctan(x/y) on a single designated sensor These will be compared with our computation of arctan(x/y) of multiple sensors averaged Honeywell

49. Results: Specs - Repeatability Comprised of 5 readings taken at 0, 90, 180,270 Our Product: Min = +- 0.015 Max = +-0.089 Control: Min = +- 0.033 Max = +-0.051 Honeywell: Min = +- 0.030 Max = +- 0.120 Honeywell

50. Results: Specs - Precision Honeywell

51. Results: Specs - Accuracy Honeywell

52. How Can We Improve Currently using arcTan(x/y) to compute heading – This assumes we have X and Y which need to be 90 degrees apart – In practice this is not true, we found this is actually only within +-8 degrees Use different algorithms, better weighting More Sensors Honeywell

53. Future For Nanowires? Nanowires are inherently less accurate Means greater room for improvement Small enough to use more than 10 bridges Weighting should have more of an effect Will have completely different obstacles All in all, from the results of this feasibility test they look very promising Honeywell

54. Conclusion Honeywell Questions/ Comments? Thanks for your Attention and Time!