| Volume 23 Issue 4/5- Publication Date: 1 April-May 2004 |
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| Special Issue on the 8th International Symposium on Experimental
Robotics (ISER ’02) |
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| Modeling Swarm Robotic Systems:
A Case Study in Collaborative Distributed Manipulation |
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| A. Martinoli, Swarm-Intelligent
Systems Group, Nonlinear Systems Laboratory, CH-1015 Lausanne, Switzerland
K. Easton and W. Agassounon Physical Sciences, Inc.,
20 New England Business Center, Andover, MA 01810, USA |
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| In this paper, we present
a time-discrete, incremental methodology for modeling, at the microscopic
and macroscopic levels, the dynamics of distributed manipulation experiments
using swarms of autonomous robots endowed with reactive controllers.
The methodology is well suited for non-spatial metrics, as it does not
take into account robot trajectories or the spatial distribution of
objects in the environment. The strength of the methodology lies in
the fact that it has been generated by considering incremental abstraction
steps, fromreal robots to macroscopic models, each with well-defined
mappings between successive implementation levels. Precise heuristic
criteria based on geometrical considerations and systematic tests with
one or two real robots prevent the introduction of free parameters in
the calibration procedure of models. As a consequence, we are able to
generate highly abstracted macroscopic models that can capture the dynamics
of a swarm of robots at the behavioral level while still being closely
anchored to the characteristics of the physical setup. Although this
methodology has been and can be applied to other experiments in distributed
manipulation (e.g. object aggregation and segregation, foraging), in
this paper we focus on a strictly collaborative case study concerned
with pulling sticks out of the ground, an action that requires the collaboration
of two robots to be successful. Experiments were carried out with teams
consisting of two to 600 individuals at different levels of implementation
(real robots, embodied simulations, microscopic and macroscopic models). |
| Results show that models
can deliver both qualitatively and quantitatively correct predictions
in time lapses that are at least four orders of magnitude smaller than
those required by embodied simulations and that they represent a useful
tool for generalizing the dynamics of these highly stochastic, asynchronous,
nonlinear systems, often outperforming intuitive reasoning. Finally, in
addition to discussing subtle numerical effects, small prediction discrepancies,
and difficulties in generating the mapping between different abstractions
levels, we conclude the paper by reviewing the intrinsic limitations of
the current modeling methodology and by proposing a few suggestions for
future work. |
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| Multimedia Key |
= Video |
= Data |
= Code |
= Image |
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Extension |
Type |
Description |
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1 |
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Example
One: Short movie of the stick pulling task performed by six
real robots in an arena 40 cm in radius endowed with four sticks.
(7.8MB) |
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