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Final Design

Robby Allbritton . Peter DeRoche. Alison Goodwin . Salina Songha. Autonomous Lawnmower. Final Design. Fall '05 - Spring '06. Sponsored by: Air Force Research Laboratory at Eglin Air Force Base. FAMU-FSU College of Engineering. Agenda.

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Final Design

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  1. Robby Allbritton . Peter DeRoche Alison Goodwin . Salina Songha Autonomous Lawnmower Final Design Fall '05 - Spring '06 Sponsored by: Air Force Research Laboratory at Eglin Air Force Base FAMU-FSU College of Engineering

  2. Agenda • Motivation for the project • Scope and needs • Lawnmowing Aspects • Prototype • Specifications • Navigation • OOPic • GPS • Wheel Encoders • Competition Program • Issues Encountered • Conclusions

  3. Project Sponsor Air Force Research Laboratory at Eglin Air Force Base Contacts: Martin Eilders and Javier Escobar

  4. Autonomous Lawnmower Competition • Objective • Mow a 150m2 field of grass without human interaction • Use any available navigation technology • Must operate safely • Must be all weather capable • Judged based on time and accuracy

  5. Project Scope • Solve the design problems from previous year • GPS not integrated • Excessive motor vibrations • Corroded materials • Hazardous edges

  6. Needs • Integrate GPS technology • Eliminate vibration problem • Safe operation • Compete in the Annual Autonomous Lawnmower Competition • Use as much existing equipment as possible • Keep the total cost production under $2000

  7. Final Pro/E Prototype

  8. Actual Prototype

  9. Prototype Specifications • Dimensions = 42” x 31.5” x 14” • Total Weight = 86 lbs. • Cutting width = 31” • Variable cutting height • Manual and Autonomous Operation • Speed range = 0 to 6.4 km/hr

  10. Power Specifications • Available power = 13.8 Ahr • Battery voltage = 25 - 30 volts • Estimated run time = 25 minutes per charge • Charging time = 4+ hrs. • Drive motor specs • 1.6 HP • 13 lbs.

  11. Cutting Mechanism • String trimmers motor assembly • Trimmer head assembly

  12. Safety Specifications • Kill switches • Bump switch

  13. OOPic Microcontroller • All hardware is controlled by same microprocessor • Can multitask hardware objects • Virtual Circuits are created to link hardware objects together • Event subroutines can interrupt the regular program when a specified criterion occurs

  14. Global Positioning System • Uses triangulation from satellites to determine position, speed, and heading of unit • First used A12 by Thales Navigation • Switched to DS-GPM since it is built and designed for use with the OOPic

  15. Output from GPS

  16. Wheel Encoder • Track how much each wheel turns • 10 “Clicks” = 1 Revolution

  17. Competition Program • Main Program • Uses waypoint guidance • Applies different inputs to drive motors • GPS provides positional information • Events • If encoder values are not equal • Will direct mower back to original heading • If bump switch is depressed • Kills drive motors immediately • Will resume regular program when switch is released

  18. Issues Encountered

  19. A12 GPS • Output data is not in a consistent format • Speed and time was not accurately captured • A12 Initializes at 600 Baud Rate while OOPic only allows a choice between 31500, 1200, 2400, or 9600 • Requires special cord • 9-pin to 4-pin • 12 Volts to 5 Volts • Switch to DS-GPM since it is made for use with OOPic

  20. DS-GPM • Time Constraints • GPM unexpectedly on backorder • Data not storing and displaying correctly • Attempted different physical configurations • Attempted different programming options • Problem pinpointed to I2C connection between GPM and OOPic • Manufacturer recommended returning the GPM to the distributor for replacement

  21. Lawnmower Path • Drive motor outputs different for same input • Causing mower to drive in circular path • Experimentally able to apply different inputs to each motor for same output • Environment affects inputs necessary • Shorter distances lessen error in path • Heading output from GPS can be used to correct errors in path

  22. Conclusions • Did we achieve our main goals • What did we accomplish with the project • Does the mower go straight

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