Multiple Robot Systems: Task Distribution, Coordination and Localization Sameer Singh 83 ECE 2000...
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Transcript of Multiple Robot Systems: Task Distribution, Coordination and Localization Sameer Singh 83 ECE 2000...
Multiple Robot Systems:Task Distribution, Coordination and Localization
Sameer Singh83 ECE 2000
Final YearNSIT
Problems with Single Robots
Application Specific – Thus cannot be used for different tasks
Expensive Features – Require large amount of sensors
Fault IntolerantHeavy computation power required
MRS Advantages
Not Application SpecificEasy on the controllerHigh Fault ToleranceComes out cheaper for complex tasksCan carry out Tightly Coupled Tasks
Mobile Robot for MRS
Pioneer 3DX Robot
from ActivMedia Robots
Specs of Pioneer 3DX
250 Watt hours of hot swappable batteries8 forward sonar ringPayload up to 23 kgsSpeeds up to 1.6 m/sDimensions: 44cm X 38cm X 22cm
Internal Behaviors
Drive – controlled by keys or joystickPlan PathsDisplay map of sonarCommunicate Data – Sensor and ControlRun C/C++ ProgramSimulation Software
Accessories for Pioneer 3DX
Wireless EthernetLaser MappingRobotic ArmPan-Tilt-Zoom color CameraStereo Range-Finding CameraCompasses and Tilt SensorsInfra Red Ranging SensorsBumpers and Grippers
Task Distribution
Distribution of Tasks to different robotsEnsure Fault-free operation in dynamic,
noisy environmentEnsure CooperationSuitable for Heterogeneous EnvironmentNon-deterministic Polynomial complete
problem
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 communicationAuction based Task distribution
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.)
Task Distribution
Tightly Coupled Task Watcher with ranging sensors and camera Pusher with grippers and camera
Localization
Absolute and Relative LocalizationGPS or some model-based to be used for
Absolute, thus expensiveAbsolute better for single robotsRelative more pertinent for MRS since
formations require relative, not absoluteCan develop absolute coordinates from
relative
Localization
Each robot is the originContains probability distribution of all
robotsAll robots broadcast their observationsDistributions are updated according to the
observations from self and other robotsThus robots even know where other robots
are which have not even been seen
Spatial Interference
Basic avoidance method fails
Conflict Resolution should take place
In nature, there is aggression, we shall emulate it
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
Spatial Interference
Other issues
Performance v/s
Population Dynamic
Population? Anonymity or
Identities Communication
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
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.