Three-dimensional hydro-cluttered locomotion by an undulatory robot

2026-06-04

AI Summary

This study addresses the challenge of locomotion for underwater robots in complex, cluttered hydrodynamic environments characterized by mixed rigid and compliant obstacles. The work proposes AquaMILR, a limbless bioinspired robot that innovatively leverages environmental complexity as a motion resource. By integrating programmable body compliance, three-dimensional depth control, and coordinated environmental contact, the system achieves efficient and robust 3D maneuverability. Its design features bilateral cable actuation, distributed buoyancy regulation, corrosion-resistant encapsulation, and an onboard power-electronics architecture. Notably, inertia-induced rolling emerges as a spontaneous self-recovery mechanism from entanglement. Experimental results demonstrate that AquaMILR can rapidly traverse, circumnavigate obstacles, and autonomously recover from jams in intricate habitats such as mangrove forests, enabling visual inspection of root zones inaccessible to conventional underwater platforms.

Abstract

Aquatic robots have expanded human access to underwater environments, yet many underwater spaces contain obstacles that can disrupt open-water locomotion. In "hydro-cluttered" environments, water is interspersed with rigid and flexible clutter, making body-obstacle contact unavoidable. Operating in these spaces requires robots that can regulate and exploit contact, but this regime remains difficult to model or simulate. Building on recent advances in mechanical intelligence in terradynamically capable limbless robotics, we develop principles for 3D aquatic locomotion using AquaMILR, an elongate limbless robot that combines bilateral cable-driven actuation, programmable body compliance, distributed depth regulation, corrosion-resistant enclosures, and onboard power and electronics for untethered field operation. Systematic robophysical experiments reveal that programmable body compliance regulates body deformation and converts body-environment interactions into fast, robust, forward progression across increasing hydro-clutter constraint strength. Depth regulation provides three-dimensional access, allowing the robot to bypass clutter, recover from obstruction, and continue through otherwise inaccessible routes. In potential jamming scenarios, emergent inertia-induced rolling acts as a spontaneous recovery mechanism, freeing the robot from clutter that would otherwise lead to failure and allowing locomotion to continue without additional control. Tests of the robot in an aquatic mangrove field demonstrate that these principles transfer to practical operation, enabling navigation and onboard visual inspection of inaccessible root zones. These results establish principles for hydro-cluttered locomotion and a design paradigm in which aquatic robots exploit environmental complexity as a locomotor resource.

Problem

• hydro-cluttered locomotion
• aquatic robotics
• obstacle-rich environments
• 3D underwater navigation
• body-environment interaction

Innovation

• hydro-cluttered locomotion
• programmable compliance
• undulatory robot
• mechanical intelligence
• 3D aquatic navigation