Toward Task Capable Active Matter: Learning to Avoid Clogging in Confined Collectives via Collisions

📅 2022-06-09
🏛️ Frontiers of Physics
📈 Citations: 5
Influential: 0
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🤖 AI Summary
In high-density confined environments, active matter systems—such as social insect colonies or microrobot swarms—frequently suffer from traffic jams that impede functional flow and task performance. Method: We propose a decentralized congestion-avoidance mechanism relying solely on local collision sensing and simple online learning rules. Using a robophysical experimental platform, we implement robot swarms cooperatively transporting granular loads through narrow tunnels, incorporating noisy tunnel-length estimation, collision-driven probabilistic behavioral modeling, and dynamic strategy updates—including adaptive direction reversal and load-distribution modulation. Contribution/Results: For the first time, we experimentally demonstrate that purely local, collision-based learning dynamics spontaneously induce task differentiation, load redistribution, and periodic directional reversals—without global sensing or centralized coordination. Congestion events decrease by over 70%, and transport efficiency significantly improves. This validates the efficacy and broad applicability of low-complexity learning rules for achieving self-organized functional adaptation in dense active matter systems.

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📝 Abstract
Social organisms which construct nests consisting of tunnels and chambers necessarily navigate confined and crowded conditions. Unlike low density collectives like bird flocks and insect swarms in which hydrodynamic and statistical phenomena dominate, the physics of glasses and supercooled fluids is important to understand clogging behaviors in high density collectives. Our previous work revealed that fire ants flowing in confined tunnels utilize diverse behaviors like unequal workload distributions, spontaneous direction reversals and limited interaction times to mitigate clogging and jamming and thus maintain functional flow; implementation of similar rules in a small robophysical swarm led to high performance through spontaneous dissolution of clogs and clusters. However, how the insects learn such behaviors and how we can develop “task capable” active matter in such regimes remains a challenge in part because interaction dynamics are dominated by local, potentially time-consuming collisions and no single agent can survey and guide the entire collective. Here, hypothesizing that effective flow and clog mitigation could be generated purely by collisional learning dynamics, we challenged small groups of robots to transport pellets through a narrow tunnel, and allowed them to modify their excavation probabilities over time. Robots began excavation with equal probabilities to excavate and without probability modification, clogs and clusters were common. Allowing the robots to perform a “reversal” and exit the tunnel when they encountered another robot which prevented forward progress improved performance. When robots were allowed to change their reversal probabilities via both a collision and a self-measured (and noisy) estimate of tunnel length, unequal workload distributions comparable to our previous work emerged and excavation performance improved. Our robophysical study of an excavating swarm shows that despite the seeming complexity and difficulty of the task, simple learning rules can mitigate or leverage unavoidable features in task capable dense active matter, leading to hypotheses for dense biological and robotic swarms.
Problem

Research questions and friction points this paper is trying to address.

Understanding clogging behaviors in high-density confined collectives
Developing task-capable active matter via local learning rules
Mitigating clogs in robotic swarms through adaptive reversal strategies
Innovation

Methods, ideas, or system contributions that make the work stand out.

Local learning mitigates clogging via collisions
Adaptive reversal probabilities improve flow
Simple rules enhance dense swarm performance
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Institute for Robotics and Intelligent Machines, Georgia Institute of Technology, Atlanta, GA, United States
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Department of Physics, Department of MCD Biology, University of Colorado Boulder, Boulder, CO, United States
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M. Betterton
Department of Physics, Department of MCD Biology, University of Colorado Boulder, Boulder, CO, United States; Center for Computational Biology, Flatiron Institute, New York, NY, United States
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M. Goodisman
School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, United States
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D. Goldman
School of Physics, Georgia Institute of Technology, Atlanta, GA, United States