Worcester Polytechnic Institute A Major Qualifying Project AURORA Autonomous Unpowered Recovery of Radiosonde Aircraft Submitted By: Richard Eberheim, Robotics Engineering Nicholas Hassan, Robotics Engineering and Electrical & Computer Engineering Joshua O’Connor, Mechanical Engineering Advised By: Kenneth Stafford, Professor Robotics Engineering, Mechanical Engineering Fred Looft, Professor Electrical Engineering This report represents the work of WPI undergraduate students submitted to the faculty as evidence of completion of a degree requirement. WPI routinely publishes these reports on its website without editorial or peer review. For more information about the projects program at WPI, please see http://www.wpi.edu/academics/ugradstudies/project-learning.html Abstract This project developed an autonomous radiosonde glider that actively steers itself from the apex of its flight to safe recovery locations on the ground. This enables easy and reliable recovery, reducing costs and offering new capabilities to atmospheric researchers. The glider integrates the essential weather sensors used on current radiosondes with those needed for autonomous flight in a durable, easy to manufacture airframe capable of multiple data gathering flights with minimal repairs between each flight. 1 Acknowledgments This project was made possible through the support, guidance, and assistance of the staff and students of Worcester Polytechnic Institute. We would like to thank Professors Ken Stafford and Fred Looft for advising the project. We would also like to thank Keshuai Xu for assisting us with soldering, Bill Jones from Intermet Systems for his help on the radiosonde design, and Raymond Ranellone for loaning us a regulator for our helium tank. 2 Table of Contents Abstract ............................................................................................................................... 1 Acknowledgments............................................................................................................... 2 Table of Contents ................................................................................................................ 3 Table of Figures .................................................................................................................. 6 Table of Tables ................................................................................................................... 9 1. Introduction ................................................................................................................... 10 2. Background ................................................................................................................... 11 2.1. Introduction ............................................................................................................ 11 2.2. Current Radiosonde Technology and Operations .................................................. 11 2.3. Sounding Data ........................................................................................................ 11 2.4. Current Recovery Efforts ....................................................................................... 13 2.5. Acquisition of Background Information ................................................................ 13 2.6. The Atmosphere ..................................................................................................... 13 2.7. Conditions to Expect .............................................................................................. 14 3. Project Goals and Requirements ................................................................................... 15 3.1. Goals for Project Success....................................................................................... 15 3.2. Develop Flight Controller with Radiosonde Abilities ........................................... 15 3.3. Develop Software Capable of Selecting Landing Site ........................................... 15 3.4. Develop Unpowered Aircraft Capable of 7:1 Glide Ratio..................................... 15 3.5. Able to Land and Return to Flight with Little Maintenance .................................. 16 3.6. Use Materials Safe for Jet Engine Consumption ................................................... 16 3.7. Test Glider from 1000 Feet .................................................................................... 16 3.8. Unit Cost Under 200% of Current Radiosondes .................................................... 16 3.9. Cost per Launch Equivalent to Current Radiosondes ............................................ 16 3.10. CONOPS .............................................................................................................. 16 4. Flight Controller Implementation ................................................................................. 17 4.1. Introduction ............................................................................................................ 17 4.2. Flight Controller Requirements ............................................................................. 17 4.3. Overall Design Considerations .............................................................................. 17 4.4. Selecting PCB Design Software ............................................................................ 18 3 4.5. Selecting Major Components ................................................................................. 19 4.6. Designing the Flight Controller PCB ..................................................................... 25 4.7. Designing the GSM Module PCB.......................................................................... 35 4.8. Designing the Radio Module PCB ......................................................................... 39 4.9. Sourcing Components ............................................................................................ 42 4.10. Weighing the Components and Soldering the PCBs ........................................... 42 4.11. Low Level Coding and Debugging ...................................................................... 43 4.12. Assembling the Modules and Attaching to Airframe .......................................... 52 4.13. Breadboard Flight Controller for Initial Test Flights ........................................... 53 4.14. Changing ATmega328P to Cortex-M4 ................................................................ 53 4.15. Results .................................................................................................................. 54 4.16. Future Design Considerations .............................................................................. 54 5. Airframe Development ................................................................................................. 55 5.1. Introduction ............................................................................................................ 55 5.2. Overall Design Considerations .............................................................................. 55 5.3. Preliminary Concepts ............................................................................................. 55 5.4. Initial Tests............................................................................................................. 60 5.5. Designing the First Rigid Airframe (Pink Foam) .................................................. 62 5.6. Designing the Second Rigid Airframe (Small Foam Board) ................................. 63 5.8. Developing the Fourth Airframe ............................................................................ 67 5.9. Final Test Revisions ............................................................................................... 71 5.10. Final Airframe Results and Analysis ................................................................... 72 6. Software Development.................................................................................................. 76 6.1. Introduction ............................................................................................................ 76 6.2. Flight Mode State Machine .................................................................................... 76 6.3. Radiosonde Code ................................................................................................... 77 6.4. Navigation Code .................................................................................................... 77 6.5. Autopilot Code ....................................................................................................... 79 6.6. Final Software Design and Results ........................................................................ 96 7. Conclusion .................................................................................................................... 98 Works Cited ..................................................................................................................... 99 4 Appendix A: Bill of Materials ........................................................................................ 104 Appendix B: PCB Schematics ........................................................................................ 107 Appendix C: Procedure for Building the Airframe......................................................... 109 Appendix D: Preparing the Weather Balloon ................................................................. 114 Appendix E: Airframe Component Schematics .............................................................