1. Multiple Robot Systems: Task Distribution, Coordination and Localization Sameer Singh 83 ECE 2000 Final Year NSIT

2. Problems with Single Robots Application Specific – Thus cannot be used for different tasks Expensive Features – Require large amount of sensors Fault Intolerant Heavy computation power required

3. MRS Advantages Not Application Specific Easy on the controller High Fault Tolerance Comes out cheaper for complex tasks Can carry out Tightly Coupled Tasks

4. Mobile Robot for MRS Pioneer 3DX Robot from ActivMedia Robots

5. Specs of Pioneer 3DX 250 Watt hours of hot swappable batteries 8 forward sonar ring Payload up to 23 kgs Speeds up to 1.6 m/s Dimensions: 44cm X 38cm X 22cm

6. Internal Behaviors Drive – controlled by keys or joystick Plan Paths Display map of sonar Communicate Data – Sensor and Control Run C/C++ Program Simulation Software

7. Accessories for Pioneer 3DX Wireless Ethernet Laser Mapping Robotic Arm Pan-Tilt-Zoom color Camera Stereo Range-Finding Camera Compasses and Tilt Sensors Infra Red Ranging Sensors Bumpers and Grippers

8. Task Distribution Distribution of Tasks to different robots Ensure Fault-free operation in dynamic, noisy environment Ensure Cooperation Suitable for Heterogeneous Environment Non-deterministic Polynomial complete problem

9. Task Distribution Tasks are divided into sub-tasks, which further into sub-subtasks, and so on… hence, a task tree is generated. Responsibility of Parent to allocate child tasks to other robots and ensure completion Uses broadcast communication Auction based Task distribution

10. Steps for Task Distribution 1.Task Announcement 2.Metric Evaluation 3.Bid Submission 4.Auction Close 5.Progress/Contract Renewal Resources required includes features (camera, gripper, etc.) and/or capabilities (mobile, carry heavy, open doors, etc.) and/or current state (idle, charging, pushing box, etc.)

11. Task Distribution Tightly Coupled Task Watcher with ranging sensors and camera Pusher with grippers and camera

13. Localization Absolute and Relative Localization GPS or some model-based to be used for Absolute, thus expensive Absolute better for single robots Relative more pertinent for MRS since formations require relative, not absolute Can develop absolute coordinates from relative

14. Localization Each robot is the origin Contains probability distribution of all robots All robots broadcast their observations Distributions are updated according to the observations from self and other robots Thus robots even know where other robots are which have not even been seen

16. Spatial Interference Basic avoidance method fails Conflict Resolution should take place In nature, there is aggression, we shall emulate it

17. Spatial Interference Each robot has a fear threshold, which decides how close it shall let the other robot come. Robot is brave or afraid depending on if the other robot is outside or inside the fear threshold. Fear threshold – Personal Space, Previous Wins, Fixed Hierachy, Priority

18. Spatial Interference

19. Other issues Performance v/s Population Dynamic Population? Anonymity or Identities Communication

20. References Vaughan, R.T., Stoy, K., Sukhatme, G.S. and Mataric, M.J. - Go ahead, make my day: Robot Conflict Resolution by Aggressive Competition Howard, A., Mataric, M.J. and Sukhatme, G.S. – Cooperative Relative Localization for Mobile Robot Teams: An Egocentric Approach Batalin, M.A. and Sukhatme, G.S. – Spreading Out: A Local Approach to Multi-Robot Coverage Gerkey, B.P. and Mataric, M.J. – Sold!: Auction Methods for Multirobot Coordination Mataric, M.J. – Coordination and Learning in Multirobot Systems ActiveMedia Robotics – www.activrobots.com

21. Thank You I would like to mention the USC Robotics Research Lab for the source of the inspiration and the source of these references. Most diagrams and figures I have used are from their publications.