Theory of Computing Systems

, Volume 62, Issue 5, pp 1223–1240 | Cite as

Collaborative Exploration of Trees by Energy-Constrained Mobile Robots

  • Shantanu DasEmail author
  • Dariusz Dereniowski
  • Christina Karousatou


We study the problem of exploration of a tree by mobile agents (robots) that have limited energy. The energy constraint bounds the number of edges that can be traversed by a single agent. We use a team of agents to collectively explore the tree and the objective is to minimize the size of this team. The agents start at a single node, the designated root of the tree and the height of the tree is assumed to be less than the energy bound B of the agents. The agents have local vision and communication capabilities; two agents can exchange information only when they are collocated at the same node. We provide an exploration algorithm for visiting all nodes of the unknown tree and we compare our algorithm with the optimal offline algorithm that has complete knowledge of the tree. Our algorithm has a competitive ratio of O(log B), independent of the number of nodes in the tree. We also show that this is the best possible competitive ratio for exploration of unknown trees.


Collective exploration Mobile agents Energy-constrained Synchronous tree Local communication Competitive ratio 



This work was partially supported by the ANR projects MACARON (anr-13-js02-0002) and ANCOR (anr-14-CE36-0002-01), and by the Polish National Science Center grant DEC-2011/02/A/ST6/00201. The second author would like to thank Krzysztof Kwaśniewski for interesting discussions on the subject.


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© Springer Science+Business Media, LLC 2017

Authors and Affiliations

  1. 1.Aix-Marseille University, CNRS, LIFMarseilleFrance
  2. 2.Faculty of Electronics, Telecommunications and InformaticsGdańsk University of TechnologyGdańskPoland

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