1. Milestone #2 Line Following Using Photo-transistors

2. Presentation Overview Moe’s New Body Sensors and Electronics New Code Milestone Results Questions 2

3. Moe’s New Body Original Body 20.4cm x 25.4cm = 518.16cm 2 New Body 17.2cm x 21.2cm = 364.64cm 2 Reduction of ~30% 3

4. Moe’s New Body Small and more compact still lots of room Bolt more stable than caster 85% of weight over rear axle Wheels protected from snagging 4

5. Moe’s New Tires Increase of ~675% in Surface Area 6.75cm x 0.5cm2cm x 0.5cm = 1cm 2 5.25cm x 3.0cm2.25cm x 3.0cm = 6.75cm 2 SizeTraction Area Old New 5 Less slipping Better performance climbing slopes

6. Moe’s New Wheelbase Original Wheelbase 24.5cm wide* New Wheelbase 17cm wide* Reduction of ~30% 6 *As measured from outside of wheels Tighter, faster turning Turning harder to control

7. Moe’s Electronics 7 Kill Switch - cuts power to the H-bridge Auto-Start Button - resets program stored in memory Photo-Transistor Arrays - detects line using 4 emitter-sensor pairs

8. Moe’s Electronics 8 Electronics stacked to fit smaller footprint build high rather than wide concentrate weight over back wheels

9. Moe’s Sensor Design 2 - 2.5cm wide strips of balsa 1 - 1cm 2 square balsa Sensors mounted perpendicular to each other Steering bolt adjusted to obtain proper height from table (2cm) 9

10. Moe’s Sensors I Sensor arrays mounted in a line Pros: - simplicity Cons: - we only used inside two pairs - tells us very little about the line 10

11. Moe’s Sensors II 11 Sensors mounted at ~45 o Pros: - detect upcoming turns using front-most pairs - basic line following with inner two pairs Cons: - slightly more complex logic - and …

12. Moe’s Sensors II 12 Turning corners on short section of track often placed front sensor pairs past next turn. Moe then believes that there is no corner and ends up missing next turn. Testing showed this happened on 33-50% of turns on the short track section

13. Moe’s Sensors II 13 Move sensor arrays back 2cm. This doubles our error margin, meaning that our turns need not be as accurate. Moe successfully negotiates corners on the short track with 95-99% accuracy.

14. Moe’s Sensors III Sensors moved 2cm towards servos Previously: recognized 50-66% of short track turns Now: recognizes 95-99% of short track turns ~85% increased sensitivity 14

15. Moe’s Sensor Trouble However, we often had trouble with this turn. For some reason, the sensors would seem to randomly miss it. We have yet to determine the reason for this. 15 Missing this turn occurs ~25% of the times Moe attempts to negotiate it.

16. Moe’s New Code INIT - define constants, ports, pins and delay timers CONTROL - define motion directions, speeds, and variables LINE - define line-following instructions - differentiate between hard and short turns - short turns used to perform small corrections to line-following - compensates for our servos operating at different rates - hard turns used to make 45 o turns AUTO_START - loads line-following routines into memory 16

17. Moe’s Motion Logic Outside Left 17 0000Straight 1000 0100Short Left 1100Hard Left 0010Straight 0001Short Right 0011Hard Right Inside Left Outside Right Inside Right Direction

18. Milestone Results Last Place, again… 18 Moe seems to have performance issues when it comes to the milestone challenges. During testing: - averaged ~21 seconds per lap - however, he only averaged 2-3 laps before failing - battery level ~9.30V to ~9.48V Our battery level dropped between trials during Friday’s test because we switched of the servos, but the sensors were still drawing power. We want to either run the sensors off a separate power source, or wire the kill switch to cut power to the sensors as well as the servos.

19. Milestone Time Log 19 Hardware: 22+ hours Software: 18 hours Documentation: 18 hours Total: 52+ man hours

20. Questions ? 20