Developing of a Softwall Controller to avoid No-Fly-Zones in an existing Autopilot System

1. Developing of a Softwall Controller to avoid No-Fly-Zones in an existing Autopilot System Christoph Bruno Ruetz Departamento Engenharia Electrotécnica e Computadores Faculdade de Engenharia da Universidade do Porto R. Dr. Roberto Frias, 4200 465 Porto, Portugal E-mail: cruetz@gmx.de

2. Structure • Motivation • Apollo System • Softwall System • Goals • Requirements • Approaches • Implemented System • Goals • Software structure • Problems • Future Developments

3. Motivation • After 9/11, more than ever safety in and around air vehicles is needed • Ever since, several ideas appeared: • to forecast if a plane will fly into a building • to prevent a pilot from flying into a building • Control Commands should not be directly sent to the airplane steering • to design a System, it has to be between the control and steering

4. Apollo System • UAV controller component of the AsasF control hierarchy, developed in FEUP • Decouples detailsof UAV control fromorganization ofexternal controllers

5. Softwall System [Goals] • Define a system that avoids detected Softwalls • The System should be a part of Apollo  Modularity • But anyway there should be a possibility to decide whether the module will be used or not

6. Softwall System [Requirements / Environment] • Language was C++, because Apollo is written in C++ • modularity  good planning of Object structure • SVN for developing both projects (Apollo and Softwall) at the same time • Defining softwalls • Algorithms that meet requirements to detect and avoid softwalls

7. Approaches (I) • Reachability Sets from Ian Mitchell [1] • Backward calculation from a obstacle from where it‘s possible to reach it • heavy calculations • Existing matlab sources but no c++  giving up this approach

8. Approaches (II) • 2D-Softwall graphical approach from J. Adam Cataldo [2] • Base: Critical measurement 1/T • Depends on the direction, the distance and the max turning rate of the airplane • Safe!!! Tested in a Research Project [3]

9. Approaches (III) • Using Airplane Model • s := speed; := heading; t := time; p := position

10. Approaches (IV) • How does it work…? No-Fly-Zone Waypoint Avoid window collision radius collision collision

11. Approaches (V) • Checking the critical time every 100 ms • In an avoiding window… • the pilot will be informed about a potential collision • starts at 4th and ends at 6th times of the min turn radius • If missing, evasive action with the max. turn rate initiates • After a certain time the airplane tries to follow the old plan • Checking begins again  Like a POTENTIAL FIELD ALGORITHM

12. Approaches (VI) • This approach is the basis of the Avoiding system • Problems: Calculation only during the flight not smoothed enough • Solution: pre-calculation of a possible trajectory as a second algorithm set upon the first algorithm • Trajectory calculation is needed • A lot of different kind of algorithms from Industrial robot sector, like… • Roadmaps (Voronoi, Visibility Graphs, Decomposition…) (just good for 2D Environments  • A* (discretize the C-Space)  • PRMs (unpredictable)  • …  Baginsky algorithm

13. Approaches (VII) • Why Baginsky? • Geometrical Approach from Boris Baginsky • Heuristic • Short search time in low dimension <= 3D • Good path quality • Good solutions in 2D or 3D environments • How does it work…?

14. No-Fly-Zone Waypoint radius

15. No-Fly-Zone Waypoint radius

16. Deepest intrusion point No-Fly-Zone Waypoint radius

17. Deepest intrusion point No-Fly-Zone Waypoint radius Middlepoint to move

18. Collision Moving t-times No-Fly-Zone Waypoint radius Middlepoint to move

19. Collision No Collision Moving t-times No-Fly-Zone Waypoint radius Collision Middlepoint to move

20. Collision No Collision Moving t-times No-Fly-Zone Waypoint radius Collision Middlepoint to move

21. Collision No Collision Moving t-times No-Fly-Zone Waypoint radius Collision Middlepoint to move

22. No Collision Collision Moving t-times No-Fly-Zone Waypoint radius Collision Middlepoint to move

23. No Collision Collision Moving t-times No-Fly-Zone Waypoint radius Collision Middlepoint to move

24. No Collision Collision Moving t-times No-Fly-Zone Waypoint radius Collision Middlepoint to move

25. Implemented System [Goals] • Apollo decides if the Softwall System will be in use • Just activate the module in Apollo or not • Apollo and Softwalls should have access to the same information of the Airplanes • Softwalls and Apollo should work as a module of its own. • Adapter Classes docking on the module to communicate with the environment  That will guarantee independence by changing Autopilot Systems

26. Implemented System [Architecture] Apollo Softwall Filter System Config File Softwall Airplane Pathplanner Config File Baginsky CollisionManager 2D-Approach Generic Autopilot Interface

27. Implemented System [Software] • Define softwall • Neptus - Config file - SoftwallS [Circle 1] alt = 100 ;altidude in meters lon = 0.6565 ;longitude in radians lat = -2.1342 ;latitidue in radians radius = 100 ;in meters if should be a circle [Halfspace 1] alt = 100 ;altidude in meters lon = 0.6565 ;longitude in radians lat = -2.1342 ;latitidue in radians heading = 3.159 ;in radians, defines the direction of the ;halfspace if it‘s a halfspace

28. Implemented System [Problems] • Reachabillity Sets not practicable  2D Approach • Apollo modularity was changed • Execution of Apollo had to be stopped if the airplane was following a trajectory

29. Future developments • Reachability sets translate in C++ code • 3D Softwalls calculation • Define airplanes as moving softwalls  currently there are only static softwalls • Implement softwalls in other Vehicles • Safety and a real environment should be tested • Testing intersection Halfspaces • Make the plane follow a softwall • Send all calculated points at the same time

30. Developing of a Softwall Controller to avoid No-Fly-Zone in an existing Autopilot System Christoph Bruno Ruetz Departamento Engenharia Electrotécnica e Computadores Faculdade de Engenharia da Universidade do Porto R. Dr. Roberto Frias, 4200 465 Porto, Portugal E-mail: cruetz@gmx.de Obrigado!