Sponsored by: Air Force Research Laboratory at Eglin Air Force Base FAMU-FSU College of Engineering

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

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

Autonomous Lawnmower Competition Objective –Mow a 150m 2 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

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

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

Final Pro/E Prototype

Actual Prototype

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

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

Cutting Mechanism String trimmers motor assembly Trimmer head assembly

Safety Specifications Kill switches Bump switch

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

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

Output from GPS

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

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

Issues Encountered

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

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

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

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