Self-Assembly Strategies in a Group of Autonomous Mobile Robots


[ Abstract ] [ Control ] [ Video ] [ Contact ]


  Abstract


Robots are said to be capable of self-assembly when they can autonomously form physical connections with each other. By examining different ways in which a system can use self-assembly (i.e., different \emph{strategies}), we demonstrate and quantify the performance benefits of (i) acting as a physically larger self-assembled entity, (ii) letting the system choose when and if to self-assemble, (iii) coordinating the sensing and actuation of the connected robots so that they respond to the environment as a single collective entity. Our analysis is primarily based on real world experiments in a hill crossing task. The configuration of the hill is not known by the robots in advance---the hill can be present or absent, and can vary in steepness and orientation. In some configurations, the robots can overcome the hill more quickly by navigating individually, while other configurations require the robots to self-assemble to overcome the hill. We demonstrate the applicability of our self-assembly strategies to two other tasks---hole crossing and robot rescue---for which we present further proof-of-concept experiments with real robots.



  Control


Details of the distributed control used to implement the self-assembly strategies for the hill crossing task can be found
here. Details of the robot rescue experiments can be found here.



  Video



3 real robots use the basic self-assembly response strategy to overcome the difficult hill (wmv). This is footage from one of the experimental trials described in our paper.

2 real robots fail to collectively overcome a hill due to an inappropriate hill approach orientation (wmv). The robots self-assemble in response to the difficult hill, then approach the hill with the random orientation that resulted from the stochastic self-assembly process. This random orientation proves overly parallel to the orientation of the hill, the center of gravity escapes the footprint of the connected robotic entity, and the robots topple over. This is footage from one of the experimental trials described in our paper.

2 robots use the connected coordination strategy to overcome the difficult hill. The robots self-assemble in reponse to the difficult hill, then rotate as a collective entity to arrive at an appropriate group orientation (wmv). The connected robots rotate to prevent toppling, choosing an orientation perpendicular to that of the hill. This is footage from one of the experimental trials described in our paper.

Basic self-assembly response strategy as seen on German national television (h264 / wmv). Extracted from programme "Quarks and Co." shown on german television channel WDR.

6 real robots use the basic self-assembly response strategy to overcome the difficult hill (wmv).

6 real robots use the basic self-assembly response strategy to overcome the difficult hill (wmv). Two robots independently seed separate self-assembly processes. The seeds do not detect each other because the distance between them is too great. The result is a simple form of stochastic, distributed group size regulation.

3 pre-assembled robots use the connected coordination strategy to overcome the difficult hill (wmv). The robots in this video were manually assembled by the experimenter. This video shows how instructions propogate along the line of robots in this implementation of the connected coordination strategy.

3 robots use the basic self-assembly response strategy to overcome a 3cm hole (wmv). The robots detect that the hole is narrow, and cross individually.

3 robots use the basic self-assembly response strategy to overcome a 10cm hole (wmv). The robots detect that the hole is too wide to be crossed individually, so they self-assembly and cross as a connected entity.

2 rescue robots use the connected coordination strategy to rescue two broken robots in parallel. (wmv). The first rescue robot to attach recognises that it can transport by itself the broken robot to which it has attached, and repels the second rescue robot, thus ensuring that the second rescue robot attaches to the other broken robot and thus that the tasks get carried out in parallel.

2 rescue robots use the connected coordination strategy to rescue a larger composite broken swarm-bot (wmv). The first rescue robot to attach recognises that it is unable to transport the broken swarm-bot, and calls for assistance. The second rescue robot attaches, and together they succeed in transporting the broken swarm-bot.

2 rescue robots use the connected coordination strategy to rescue a larger composite broken swarm-bot (wmv). The first rescue robot to attach recognises that it is unable to transport the broken swarm-bot, and calls for assistance. The second rescue robot attaches. The initial connected morphology is not successful in transporting the broken swarm-bot. The rescue robots stochasticallly reconfigure until they find a successful morphology. Then together they succeed in transporting the broken swarm-bot.




  Contact


Webpages:

Swarm-bots: www.swarm-bots.org
Swarmanoid: www.swarmanoid.org
Rehan's homepage: http://iridia.ulb.ac.be/~rogrady
Roderich's homepage: http://iridia.ulb.ac.be/~rgross
Anders' homepage: http://iridia.ulb.ac.be/~alyhne
Marco's homepage: http://iridia.ulb.ac.be/~mdorigo

Address:

IRIDIA - ULB
50 Avenue F. Roosevelt - CP 194/9
1050 Bruxelles
Belgium