1. Critical Design Review Group A3: HMS “Bloodhound” Matt Morris Matt Prygoski Jay Slaggert Fred Thwaites Dan Zibton Tuesday, April 22, 2008 Thursday, April 24, 2008

2. Project Overview Autonomous Hazardous Material Seek-and-Identify Vehicle Use GPS to locate general area of potentially hazardous material Use infrared sensor to detect if material is hazardous Return to starting position when detection is complete

3. Independently Driven Rear Wheels –Two 24V Gear Motors Front Wheel Casters HDPE body PVC Boom with Infrared Sensors GPS Navigation System Key Features

4. Abstract Purpose: to design a hazardous material seek and identify vehicle that is capable of autonomously locating, sampling, and identifying a target that could possibly be hazardous material Important Goal: Simple and Durable Target customers: Military Law enforcement agencies HazMat clean-up crews

5. Design Requirements Powered by at most 20V battery Move to a location within +/- 1m specified by provided coordinates Travel on grass, dirt, concrete, and asphalt Body no larger than 2m in any direction Complete search in under 5 minutes

6. Accurate –Capable of moving to with in +/- 1 m of a target. Robust –Capable of movement over all-terrain Maneuverable –Easily moves in small spaces of 20 square meters. Simple –Minimal parts for easy implementation. Objectives of Drive System

7. Option 1

8. Option 2

9. Option 3

10. Option 3 was Chosen Key Advantages Identified in Option 3: Zero Degree Turning Radius Minimal Wheel Slip Possible Technical Challenges: Account for Minimal Wheel Slip Provide Enough Power to Rear Wheels Implementation of a Robust Drive System

11. Technical Challenges Control Wheel Slip –Position CoG close to Rear Wheels –Acceleration should not exceed a = μ s g/2 –μ s,min, = 0.7 –a max =3.5 m/s 2 Provide Enough Power –ω = 225 rpm –T = 1 N-m

12. Robust Drive System

13. Prototype Considerations

14. Key Aspects Zero degree turning radius capability allows vehicle to traverse search path Sensors in front of vehicle Ability to guide a vehicle with GPS Direct drive would be simple to control with feedback loop

15. Materials Purchased large pneumatic casters and rubber wheels similar to final design HDPE used for body – strong, lightweight, machinable, and cheap PVC used for boom – Strong and stiff – Easily reconfigurable

16. Fabrication Limitations Rear wheels should have better tread but the hub was useful L-Brackets are not ideal Center of gravity should be moved toward rear of vehicle – Reduces caster drag – Increases drive traction

17. Next Generation Prototype Use more powerful motors and battery – Determine caster performance at high speed – Analyze repeatability of maneuvers (with a focus on caster performance) Explore better designs for shouldering and fastening body panels

18. Circuit Diagram

19. 12V Motors, 355 oz- in torque failed due to unpredictable dynamic forces 24V Motors without specs used in place Determined feasible based on in-robot testing

20. Circuit Diagram MOSFET transistors used as a gate to close circuit, allowing the motors access to ground Can handle 100V, 12A

21. Vehicle Operation Record Start and Hazard Location (Sample the GPS Receiver)

22. GPS Uncertainty

23. Vehicle Operation Two Phases: - Traverse. Use GPS to guide vehicle within 10m of hazard - Search Algorithm. Systematically search area around hazard

24. Traversing Considerations: - Speed. Travel fast but allow GPS to acquire accurate readings - Position/Orientation. Need to know position and orientation - Can’t Rely on Angles. GPS error too great to accurately calculate angle of orientation

25. GPS Error vs. Vehicle Speed Minimum Error at 2.6 m/s At 1.8 m/s Only 6% greater error

26. Traversing N W S H Drives forward Record location Pivots and reorients if x or y distance to hazard is increasing Stops when within 10m of hazard

27. Search Algorithm - Square Spiral - Never necessary to retrace path - Covers greater than 90% of area - 40% faster than back and forth pattern

28. Results - Traversing

29. Results – Search Algorithm

30. Results Part 2 Vehicle can travel at 1.8 m/s (4 mph) Video: When starting in wrong direction, ‘Bloodhound’ can correct course Locate hazardous material 30-40 m away in less then two minutes Stop within 2.7 m of original target

31. Feasibility / Recommendations Proves GPS technology is feasible for the use Without extra technology, reckoning system is crude but effective Electronic compass should be investigated for future models to refine drive system Casters / Rear Driven wheels allow easy navigation Motors for this type of application are readily available Both possible motors provided enough torque Higher quality motors available to increase speed to 2.0+ m/s Stationary boom adequate to search large area

32. Lessons Learned Compass can be combined with GPS to create useful and accurate system. GPS on it’s own can be very precise but is not as repeatable Infrared sensors can pick up false positives based on reflections of the sun or other objects, including the IR emitter even when the emitter is out of range

33. Thank you. Questions?