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High Resolution AMR Compass

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

  2. Introduction/Abstract – Marcus E • MATLAB Simulations – Marcus E • Software – Pat H • Hardware – Jeff A • Testing – Pat A • Results – Dan B Agenda Honeywell

  3. 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. Abstract Honeywell

  4. 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. Abstract Honeywell

  5. Customized hardware is necessary to implement the multiple sensor system. Customized software to manage the implementation is also necessary. Abstract Honeywell

  6. MATLAB • Used to simulate single and multiple sensors before our hardware was complete • Provided a vehicle to test the performance of our heading calculation algorithms • 1702 lines of MATLAB simulations Honeywell

  7. 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

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

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

  10. Three software realms involved with this project: • MATLAB • C • VB Software Honeywell

  11. C • Written in MPLab • Version 8.0 • CCS complier • Version 4 • Run on PIC 18f4550 • 1326 Lines of C • 2532 Lines of Assembly Honeywell

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

  13. 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

  14. Honeywell

  15. Honeywell

  16. Weighted Averaging Honeywell

  17. Honeywell

  18. VB • Provides an end-user interface • Synchronizes the compass and the rotation table • Allows for automated data acquisition • Provides a repeatable test benching system • Requires a third board to handle adjusted ground on PMC • 4733 Lines Honeywell

  19. Honeywell

  20. Honeywell

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

  22. Final Hardware • Abstract • Initial Design • Problems with Initial Design • Changes Made • Proposed Final Design Honeywell

  23. Abstract • One compass, two boards • Main Board • Microcontroller • Daughter Board • Sensors Honeywell

  24. Initial Design Main Board Honeywell

  25. Main Board • Essentially a controller board • Microcontroller • RS-232 Communication • I2C Communication • Interfacing • Daughter Board • Front Panel Honeywell

  26. Initial Design Daughter Board Honeywell

  27. Daughter Board • Three functional systems • Sensor array • Power MUX • Laser Honeywell

  28. Daughter Board Dimensions • Constraint: One of the dimensions must be less than 3.5” • Opening of zero-gauss chamber is 3.5” in diameter 3.132” Honeywell 3.492”

  29. Daughter Board Dimensions • Constraint: One of the dimensions must be less than 3.5” • Opening of gauss-free chamber is 3.5” in diameter 0.73” 3.132” The Daughter Board meets size requirements Honeywell

  30. Daughter Board HMC6352 Feedback Networks Power LED Clock Ground Data Decoupling Capacitor Honeywell

  31. Daughter Board I2C Bus Clock Data Honeywell

  32. Daughter Board Power MUX • 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

  33. Daughter Board Power MUX • Solution: Need to isolate communication to individual sensor • How? • Burn-in Socket • Use a network of jumpers • Multiplex I2C to each sensor • Multiplex power to each sensor Honeywell Photo taken from http://www.locknest.com/newsite/products/qfn/index.htm

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

  35. Problems with Initial Design • Problems • Main Board • None • Daughter Board • I2C bus • When powered off, the sensors interfere with I2C 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

  36. Changes to Initial Design • I2C bus fix • Remove MUX and feed power to all sensors • Cut I2C traces • Add jumpers to I2C vias and address them one by one • Connect all jumpers to I2C bus Honeywell

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

  38. Changes to Initial Design • Other changes • Main Board Layout Before After Honeywell

  39. Proposed Final Design • Due to I2C bus issues, our current design does not work • Two options • Power all sensors and use burn-in or jumpers socket to isolate sensors • Multiplex I2C bus Honeywell

  40. Proposed Final Design • Option 1: Power all sensors and use socket/jumpers • Advantages • No MUX needed • Reduces surface area of board • Reduces signal loss of MUX • Sleep mode on sensors • Save power • I2C bus has not been tested in this mode Honeywell

  41. Proposed Final Design • Option 1: Power all sensors and use socket/jumpers • Disadvantages • Sockets can be expensive • Footprint of HMC6352 is not common • Hard to find socket • No disadvantages if we add jumpers Honeywell

  42. Proposed Final Design • Option 2: Multiplex I2C bus • Advantages • No need for a socket • Sleep mode to save power (not tested) • Disadvantages • Side effects of multiplexing I2C unknown Honeywell

  43. Testing • Prototype Final Honeywell

  44. Test Setup Honeywell

  45. Precision Accuracy Repeatability Compare Compare ß field Compare Honeywell

  46. Prototype Testing • Given one sensor • CCS compiler Honeywell

  47. Final Testing • Elements of Final testing • Pretesting (zero gauss values) • Pretesting (offsets) • Testing (accuracy, precision, repeatability) Honeywell

  48. Pre-testing (zero gauss) • Place sensors in the zero gauss chamber • Rotate 360 deg. while taking readings • Analyze data and get zero gauss values Honeywell

  49. Pre-testing (offsets) • Place sensors in artificial magnetic field • Run VB script that finds sensor locations • Finds zero gauss value of each chip • Works using relativity • Bang bang control • Analyze data and find chip placements • Hardcode this to software Honeywell

  50. Raw voltage readings with offsets Honeywell