autonomous multi-robot exploration
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Autonomous Multi-Robot Exploration inCommunication-Limited Environments
Stephen Cameron, Julian de Hoog and Arnoud Visser
University of Oxford
University of Amsterdam
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Mobile Robots Today
• reconnaissance, surveillance
• mapping, exploration
• search and rescue
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• using the
RoboCup Rescue scenario asinspiration
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Typical Challenges
• Engineering
• Localisation and Mapping
• Team Coordination
•Communication
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The Exploration Problem
• Team of robots exploring unknown environment
• Assume reasonable SLAM (particle filters / scan matching)
• Central base station
• Possibly communication drop-out or failure
• How to:
• explore as quickly as possible
• relay as often and as efficiently as possible
• currently assuming paths are easily found and stay found!
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Existing Approaches
• Line of sight
• Frontiers / Utilities
• Robot packs
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- information gain- path cost- communication likelihood
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Role-based Exploration
Relays Explorers
Ferry information back andforth between teammates
Explore far reachesof the environment
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Hierarchy
• control commands
• new information
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Both centralisedand distributed
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Demo
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Where to Rendezvous?
• open space
• junctions
• large comm range
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Path Edges and Nodes
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More Examples
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Dynamic Environments
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A problem
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Swap roles?
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Another Common Scenario:
Loops
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The “Role Swap” Rule
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• Two robots, A and B
• A wants to go to DA, B to DB
• Let γ(u,v) be path cost from u to v
• If max{ γ(A,DA), γ(B,DB)} > max{ γ(A,DB), γ(B,DA)}...
• ... then let A and B swap(role, state, location in hierarchy, everything)
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The “Role Swap” Rule
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Demo
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Which is better?
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Opportunistic exploration Dynamic role-based exploration
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Knowledge at BaseStation
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Opportunistic exploration Dynamic role-based exploration
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Control over team
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Opportunistic exploration Dynamic role-based exploration
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Dynamic Role-based Exploration
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• Simple, easy to implement
• Not dependent on communication
• Speed of exploration is equivalent toopportunistic frontier / utility based exploration
• Information is returned to the BaseStation muchfaster and more frequently
• Greater control over the team
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Another Example(showing hierarchy and role changes)
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The Same Example(showing comm links)
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Dynamic Role-based Exploration
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• Simple, easy to implement
• Not dependent on communication
• Speed of exploration is equivalent toopportunistic frontier / utility based exploration
• Information is returned to the BaseStation muchfaster and more frequently
• Greater control over the team
• Dynamic adjustment to various environmenttypes
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Realistic?
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Future Work
•Theoretical Description of the Role SwapRule
• Extensive testing of emergent behaviour
• Additional roles: static relays?
• Testing on real robots / third partysimulation platform
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Credits
• UAV video: microdrone GmbH (http://www.youtube.com/watch?v=Y4jtguSF0n4)
• Mapping robot: Tsubouchi Laboratory, University of Tsukuba
• Search and rescue Kenaf robot: Tadokoro Laboratory, Tohoku University
• Search and rescue robot on rubble: NIST, http://www.nist.gov/public_affairs/techbeat/tb2007_0608.htm
• Rescue robot entry hole: researchchannel.org, http://www.researchchannel.org/
prog/displayevent.aspx?rID=3820
• Thinning example: Danielle Azar, http://cgm.cs.mcgill.ca/~godfried/teaching/projects97/azar/skeleton.html
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