1. The JAviator Quadrotor An Aerial Software Testbed
Rainer Trummer
Department of Computer Sciences
University of Salzburg, Austria
August 20, 2010

2. Introduction The JAviator Project The JAviator Quadrotor
Airframe Construction
Avionics Components
Computer System
Quadrotor Dynamics
Control System Design
Control System Performance
Software Architecture
Conclusions

3. The JAviator Project Project goals: Real-time programming in Java:
Develop high-payload quadrotor model helicopters
Develop high-level real-time programming abstractions
Verify solutions on JAviator (Java Aviator) helicopters
Real-time programming in Java:
Write-once-run-anywhere also for real time (time portability)
Exotasks vs. Java threads (collaboration with IBM Research)
Real-time programming in C:
Time-portable software processes (CPU, I/O, Memory)
Real-time operating system Tiptoe: tiptoe.cs.uni-salzburg.at

4. The JAviator Quadrotor
Jan 2006 – Aug 2007: JAviator V1
Entirely hand-fabricated CF, AL, and TI components
Total diameter (over spinning rotors): 1.1 m
Empty weight (including all electronics): 1.9 kg

5. The JAviator Quadrotor

6. The JAviator Quadrotor

7. The JAviator Quadrotor
Since February 2007: JAviator V2
CNC-fabricated, flow-jet-, and laser-cut components
Total diameter (over spinning rotors): 1.3 m
Empty weight (including all electronics): 2.2 kg

8. Airframe Construction

9. Airframe Construction

10. Airframe Construction

11. Airframe Construction

12. Airframe Construction

13. Airframe Construction

14. Airframe Construction

15. Airframe Construction

16. Avionics Components

17. Avionics Components

18. Avionics Components

19. Avionics Components

20. Computer System

21. Quadrotor Dynamics
Climb
Yaw
Roll
Pitch

22. Quadrotor Dynamics
X-Y-Z Cartesian Coordinates versus Z-Y-X Aircraft Coordinates
Roll: −π ≤ Φ ≤ π Pitch: −½π ≤ θ ≤ ½π Yaw: −π ≤ Ψ ≤ π

23. Control System Design

24. Control System Design

25. Control System Design

26. Control System Design

27. Control System Design

28. Control System Design

29. Control System Design

30. Control System Design

31. Control System Design

32. Control System Performance
Initial Status
Many problems with automatic altitude control
Very unsatisfying attitude stability and response
Current Status
Excellent stability with extended Kalman filters
Perfectly tuned and working control system
Position Control
RFID accuracy varies from 20 cm to > 50 cm
On-demand control to improve position hold
Robustness
Very fault tolerant in regard to timing issues
Highly sensitive to lost or dropped sensor data

33. Control System Performance

34. Control System Performance

35. Software Architecture

36. Conclusions Hardware Software
Helicopter development was least time-consuming
Custom-built hardware increased production costs
But unique platform with high demonstrative impact
Software
No way around embedded programming and writing individual low-level driver software
Great amount of time was spent solving pure control engineering problems
Complexity increased rapidly but raised interesting computer science challenges

37. Thank You!
Questions?