Self-Sustained And Coordinated Rhythmic Deformations With SMA For Controller-Free Locomotion

TL;DR

This paper introduces a novel, fully onboard, electronics-free control method for SMA-based soft robots that uses mechanical circuits to generate and synchronize rhythmic deformations for autonomous crawling locomotion.

Contribution

It presents a new mechanical control strategy that amplifies SMA actuation and synchronizes multiple modules without electronics, advancing autonomous soft robot locomotion.

Findings

Achieved self-sustained rhythmic deformation cycles using mechanical circuits.

Demonstrated synchronized crawling locomotion with two robotic modules.

Enabled fully onboard control with a simple DC power supply.

Abstract

This study presents a modular, electronics-free, and fully onboard control and actuation approach for SMA-based soft robots to achieve locomotion tasks. This approach exploits the nonlinear mechanics of compliant curved beams and carefully designed mechanical control circuits to create and synchronize rhythmic deformation cycles, mimicking the central pattern generators (CPG) prevalent in animal locomotions. More specifically, the study elucidates a new strategy to amplify the actuation performance of the shape memory coil actuator by coupling it to a carefully designed, mono-stable curve beam with a snap-through buckling behavior. Such SMA-curved beam assembly is integrated with an entirely mechanical circuit featuring a slider mechanism. This circuit can automatically cut off and supply current to the SMA according to its deformation status, generating a self-sustained rhythmic deformation cycle using a simple DC power supply. Finally, this study presents a new strategy to coordinate (synchronize) two rhythmic deformation cycles from two robotic modules to achieve efficient crawling locomotion but still use a single DC power. This work represents a significant step towards fully autonomous, electronics-free SMA-based locomotion robots with fully onboard actuation and control.