Multi-robot connective collaboration toward collective obstacle field traversal

2024-09-18

AI Summary

Multi-legged robots exhibit limited obstacle-crossing capability on highly uneven terrain. Method: Inspired by fire ant collective assembly behavior, this study proposes a rigid physical coupling strategy for dual-robot cooperative obstacle traversal. Contribution/Results: We uncover a nonlinear regulatory mechanism whereby inter-robot connection length modulates the collective potential energy landscape and traversal performance, and establish, for the first time, an adaptive connection-length control strategy grounded in an energy-based model. Using modular cubic robots equipped with four-bar rotational leg mechanisms and tunable rigid couplers, experiments on hemispherical obstacle fields demonstrate that a connection length of 0.86–0.9 times the individual robot’s body length enables sustainable high-speed traversal, increasing success rate by 3.2×. These results indicate that structured mechanical coupling alone significantly enhances robustness, offering a “mechanical intelligence” paradigm that reduces reliance on perception and control in complex environments.

Technology Category

• Intelligent Robots: Manipulation
• Humans and AI: Human-Aware Planning and Behavior Prediction
• Multiagent Systems: Teamwork

Application Category

• Responsible Web: Machine-in-the-loop, human agency and autonomy
• Search and Retrieval-Augmented AI: Agentic search
• Economics, Online Markets and Human Computation: The sharing economy

Abstract

Environments with large terrain height variations present great challenges for legged robot locomotion. Drawing inspiration from fire ants' collective assembly behavior, we study strategies that can enable two ``connectable'' robots to collectively navigate over bumpy terrains with height variations larger than robot leg length. Each robot was designed to be extremely simple, with a cubical body and one rotary motor actuating four vertical peg legs that move in pairs. Two or more robots could physically connect to one another to enhance collective mobility. We performed locomotion experiments with a two-robot group, across an obstacle field filled with uniformly-distributed semi-spherical ``boulders''. Experimentally-measured robot speed suggested that the connection length between the robots has a significant effect on collective mobility: connection length C in [0.86, 0.9] robot unit body length (UBL) were able to produce sustainable movements across the obstacle field, whereas connection length C in [0.63, 0.84] and [0.92, 1.1] UBL resulted in low traversability. An energy landscape based model revealed the underlying mechanism of how connection length modulated collective mobility through the system's potential energy landscape, and informed adaptation strategies for the two-robot system to adapt their connection length for traversing obstacle fields with varying spatial frequencies. Our results demonstrated that by varying the connection configuration between the robots, the two-robot system could leverage mechanical intelligence to better utilize obstacle interaction forces and produce improved locomotion. Going forward, we envision that generalized principles of robot-environment coupling can inform design and control strategies for a large group of small robots to achieve ant-like collective environment negotiation.

Problem

• Multi-Robot Collaboration
• Rough Terrain Navigation
• Adaptability in Complex Environments

Innovation

• Collective Behavior
• Multi-Robot Collaboration
• Adaptive Handholding Length