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December 2, Projects
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  • 1. Mothership-Daughtership Coverage Control Problem Jason Durrie 12/2/2009
  • 2. Outline • Coverage Problem • Reactive Algorithms • MS-DS Concept • MS-DS and Coverage • Simulation • Conclusion
  • 3. Coverage Problem • Cover designated area with sensor/actuator • Multiple robots with single sensor and single-pass over area for this project • Examples: • Roombas vacuuming the floor • Satellite imaging • Turbine blade inspection
  • 4. Reactive Algorithms • Directly couple perception to action • Simple and Robust • Distributed • Decentralized • Scalable • Examples: http://correll.cs.colorado.edu/www/Research/Entries/2007/11/1_Inspecti on_using_a_Swarm_of_Miniature_Robots.html • Braitenberg vehicles – light sensor coupled to motors • Turbine blade inspection – circumnavigates blades • Ants – pheromones used to find shortest route • Wifi deployment – maximize wifi coverage
  • 5. Reactive Algorithms • Hierarchical Decomposition Cover Area • Subsumption Architecture Move • Decompose behavior into modules • Layer modules into goals Avoid Obstacles • Upper layers subsume lower layers • Difficult to design/organize as behaviors and goals become more complex
  • 6. MS-DS Concept • Heterogeneous set of robots • Mothership (MS) and Daughtership (DS) are not usually the same types of robots • MS typically have more computational power available for planning • DS (local decisions) • MS (global decisions) • Examples: • Cluster scheduling by proxy • Large aircraft dropping small aircraft Reliable Coverage Control using Heterogeneous Vehicles, Islam I. Hussein, Dusan Stipanovic, Yue Wang
  • 7. MS-DS Coverage Hypothesis Hypothesis: A hierarchical mothership (MS) – daughtership (DS) system can be applied to coverage control problems and is more efficient and scalable than a team of all MS or all DS.
  • 8. MS-DS Coverage • DS are iCreates • Basic hardware • Have 2 states: move and cover • MS are down-looking, abstract computers • Can command DS to change states • Performs look-ahead simulation to determine best DS state
  • 9. MS-DS Teams • Can be split into designated teams • Each MS controls a team • Requires MS to communicate coverage updates
  • 10. MS-DS Regions • Can be split into teams by region • Each MS controls DS within its region • Requires MS coordinate to assign regions initially
  • 11. Test Cases 1) Single DS only moving 2) Single DS probabilistically changing state 3) Tests 1 and 2 with multiple DS 4) Multiple DS with single MS 5) Multiple DS in designated teams with multiple MS 6) Test 5 in teams by region
  • 12. Simulation Master Controller Action Command Sim Master Sim Sim Topic Topic Sensor Sensor Topic Topic Sim IF Sim IF Sim IF Sim IF Sim IF Algorithm Algorithm Algorithm Algorithm Algorithm DS-1 DS-2 DS-N MS-1 MS-K
  • 13. Simulation Master Controller Sim Master Sim Action Sensor Topic Topic Sim IF Algorithm Robot-X
  • 14. Simulation Master Controller Sim Master Sim Action Sensor Topic Topic Sim IF VTALRM Algorithm WAIT(STOPPED) STOP Robot-X
  • 15. Simulation Master Controller Sim Master Sim Action Topic Sensor Topic [ ] cos  cos  Sim IF −sin  2 2 [] [] x ˙ 0 sin  sin  Algorithm y = cos ˙ vL CONT ˙ 2 2  vR −1 1 0 d d Robot-X d v Rv L turn radius= 2 v R−v L
  • 16. Sim Issues • Collision detection and handling is non- trivial • ROS does not play nice with signals and signal handling • Cannot run a full simulation • One of 3 errors occurs: • ROS messaging stops • One of the processes terminates • One of the processes will not continue
  • 17. Future Work • For this project: • Resolve signaling issues • Run test cases • For after the class: • Evaluate test case data • Run some test cases on hardware to validate simulation data • Modify to simulate aircraft
  • 18. Questions?