LawnBot

1. LawnBot Senior Design Project, EE 481 Monday, November 26th, 2012

2. Team Members • Corey Kimble • Electrical Engineering Major • Steel of West Virginia, Inc. • Colleen Morgan • Electrical Engineering Major • Johnson Controls • Erin Radtke • Electrical Engineering Major • Naval Air Systems Command (NAVAIR) • David Smith • Electrical Engineering Major • Allegheny Design Services • Zachary Taylor • Electrical Engineering Major • R&E Electric Company Inc.

3. Outline • Design Achievements • Changes in Original Design • Hardware Design • Software Design • Test Results • Safety • Reflections

4. Design Achievements • Remote Control • Bumper • Invisible Fence • RoboRealm

5. Changes in Original Design • Had different designs to choose from • Went with dog fence boundary system • Stated to use 2 12v batteries in series for mower power • 24v Battery that came with mower is sufficient • Mentioned roll over sensor • Not enough time to implement • Added bumper system • Increases the safety of the mower and foreign objects

6. Hardware Design • Push Mower Body Frame/Plexiglass Cover • Basis for Lawnbot construction • Plexiglass covers mowers and has components mounted on top • 24 Volt Battery/Safety Switch • Safety switch toggles the 24V battery supply on/off • Battery supplies electricity for the three motors and other components • Motors • 2 24V 33 RPM motors for driving the mower • Motor Blade • Motor Controller • Allows the two driving motor to be controlled with remote control or software program

7. Hardware Design • Remote Control • Allows to manually control Lawnbot • Remote Control Receiver/Antenna • Receives input from remote • Relay Switches • First relay is specifically for remote controls • Second relay rated for high current • Invisible Fence Receiver • Detects when Lawnbot approaches boundary • Computer • Stores program and interacts with Lawnbot

8. Bumper System • PVC Pipe Design • Provides a basis for the bumper • Spring/Bolts • Bolts hold outside component to inner square • Spring loaded to compress when object is hit • Sheet Metal • Attached to outside component to take the hit from object • Push Buttons • Outside component engages pushbutton when compressed

9. Bumper Design

10. RoboRealm • Robotic programming software • Group lacked programmer • Mainly used for visual robotics • Easy GUI Interface • Inconsistency in program operations

11. Difficulties • VBScript or C? • Lack of programming skills lead to VBScript • Some VBScript methods not accepted in RoboRealm • RoboRealm continuously loops… • Could not create just one script file… • USB to TTL Connection • +5V, GND, TX, RX • Created virtual Comm. Port

12. Difficulties Continued • Initializing motor driver • RoboRealm already had a setup! Kind of… • Serial connection for object avoidance/boundary detection • Very tricky • USB would not allow TX and RX… • Had to order another cable • Creating a timed loop command • Sounds simple… • Took the most time • Most vital part of program

13. Software Design Finally… • Variables initialized • Communication established with motor driver • Serial communication established • Mower drive motors initialized to stop • Computer battery checked. • Button interface that would start/stop mowing process

14. Software Design Continued • Bumper Switch/Boundary Detection • Read into serial cable • Both situations warrant same process • Object/Boundary Process • Mower Needs to stop immediately • Back away • Rotate in different direction • Continue mowing

15. Program Flow • Simplistic Design • Designed to perform basic necessities • Time • Level of difficulty • Reliability

17. Little Bugs Still Present • Bumper switches and dog fence interference • Random program glitches • When dog fence and bumper switches connected together to read into computer • Switches are very sensitve • Little movements set off switch • When dog fence is removed from same connection as bumper switches • Program runs fine, only have of the switches work • When dog fence is connected and switches are removed • Program runs fine

18. Mower Maintenance • Electric mower = Easier maintenance • Battery charge • Blade sharpening • Check wheel tread and cotter keys • Check wire connections • Relays functionality • Contact retailer for any other issues

19. Electric mower • Gas mower • Many moving parts, combustion, need for oiled components, rust • Electric mower • Charged battery, mower motor

20. Battery charge • Charge battery for full length before each use • Replace battery if there is any damage/lose of charge • Contact Worx for proper replacement

21. Dull blade • Like any regular lawn mower, electric mower has regular mower blade • Mower use = dull blade • Loosen nut holding blade in place and remove blade • Either buy new blade or sharpen old blade • Replace blade and tighten nut

22. Wheel tread and cotter keys • Wheels are held onto motors via cotter key • Check for key strength and wear and tear • Replace if damaged • Tire tread is low • Remove cotter key, take wheel off, put new wheel on, re-insert cotter key

23. Wire Connections • Loose connections = bad communication • Make sure all terminals are tight and no wires are damaged. • Replace damaged wires with size 12 wire (power connection) or size 20 wire (communication connection)

24. Relays Functionality • If mower blade will not turn on • Check for clicking noise when relay is energized • No click = bad relay • Replace large relay with 24v DC 12 amp ice cube relay • Replace small relay with dimensions engineering RC battle switch

25. Test Results • Indoor, Remote Control • Most testing for RC stage done indoors • Each component of LawnBot independently, then system as a whole with all components • First issue: relay, added a second relay which handles higher current • Still needed first relay for the remote control capability • Outdoor, Remote Control • Worked well, no issues

26. Test Results • Indoor, Autonomous Stage • Tested to see if software could control mower • Tested detection components • Boundary detection, invisible fence • Interference detection, push buttons

27. Test Results • Outdoor, Autonomous Stage • Bumper system fell apart within 20 minutes of use • Caster wheels in high grass, “bogged down” • Remote control receiver and cables connecting to computer both connected to motor driver caused communication issue, additional switch added • Needed an additional serial cable, with only one cable, unable to read push buttons and invisible fence into the program and control the motors at the same time

28. Safety Features • Mower blade kill switch • Manual switch on remote control • Overall kill switch • Manual switch on lawn mower • Boundary detection • Invisible fence • RoboRealm • Bumper • Detects foreign objects • Stops and reroutes • RoboRealm

29. User and Future Builder Precautions • Even with safety features, users still must take precautions when using this lawn mower • Should not be operated by children • Remove any objects from the lawn that may cause interference to the mower before use • Users should not use this lawn mower around pets or children • Users should not operate electric lawn mower in standing water or during inclement weather • The lawn mower should only be used on a grassy area • Users should take precautions when installing invisible fence • Do not operate lawn mower unsupervised • Future builders must take precaution when assembling mower • Blades are sharp and could cause harm to assemblers • The sheet metal bumper has sharp edges and could cause injury • Disconnect from voltage source when connecting wires • Carefully solder, extreme heat

30. Reflections • Five Electrical Engineers • Needed computer science students and a computer engineering student • Software • RoboRealm mainly used for digital image processing purposes, image analysis, etc. • The LawnBot only used the software to provide output commands given only a few input commands • Better Budgeting • Better tools, better construction of materials for bumper system • GPS, cosmetically would have made the lawn itself appear better • GPS, more accurate

31. Questions, Comments, Concerns