A Bioinspired Underwater Robot with a Latch-Mediated Soft Bistable Mechanism

2026-05-26

AI Summary

This study addresses the challenge of limited energy density in conventional power sources for miniature underwater robots, which hinders simultaneous achievement of efficient propulsion and agile maneuverability. Inspired by the mantis shrimp, this work proposes a soft bistable actuator based on a latch-mediated spring actuation (LaMSA) mechanism that enables asymmetric energy storage and release using a single motor, integrated with a tunable fin-angle propulsion system. The compact design requires no complex control yet supports multimodal locomotion, including stable periodic flapping, precise turning, vertical ascent, diagonal forward motion, and lateral translation. Experimental results demonstrate a peak thrust of 0.528 N, an impulse of 0.147 Ns, and a vertical displacement of 30 mm, significantly enhancing both maneuverability and energy efficiency in miniature underwater robotic systems.

Abstract

Underwater robotics has advanced significantly over recent decades. however, the development of miniaturized underwater robots remains limited by low energy densities of traditional power sources. Nature offers compelling solutions-organisms like mantis shrimps and fleas utilize latch-mediated spring actuation (LaMSA) systems that achieve rapid movements through a decoupled energy storage and release mechanism. Despite extensive studies of LaMSA, replicating such rapid, asymmetric actuation within simple, compact structures remains challenging. In this work, we introduce a bioinspired, soft bistable actuator with an integrated latch mechanism that enables asymmetric energy input and release using a single motor. Coupled with fin structures, this design facilitates efficient underwater propulsion and maneuverability. Experimental results demonstrate stable periodic flapping, precise steering, and a maximum thrust of 0.528 N, impulse of 0.147 Ns, and vertical displacement of 30 mm. By modulating fin angles, the robot achieves versatile motions, including vertical ascent, diagonal forward movement, and lateral translation. This study presents a novel, energy-efficient approach for controlling motion in compact underwater robots, paving the way for advanced biomimetic designs with potential applications in exploration, environmental monitoring, and inspection.

Problem

• underwater robotics
• energy density
• latch-mediated spring actuation
• soft bistable mechanism
• bioinspired actuation

Innovation

• Latch-Mediated Spring Actuation
• Soft Bistable Actuator
• Bioinspired Underwater Robot
• Asymmetric Actuation
• Energy-Efficient Propulsion