Mechanics of soft-body rolling motion without external torque

TL;DR

This paper investigates the mechanics behind soft-body rolling motion, revealing that sequential muscle actuation, not gravity imbalance, drives rolling, and demonstrates this through biological experiments, modeling, and a soft robot prototype.

Contribution

It introduces a new mechanics model explaining larval rolling via sequential muscle actuation and validates it with a soft robotic system, advancing understanding in biological and robotic contexts.

Findings

Sequential muscle actuation is critical for rolling.

Rolling is not driven by gravity or ground reaction forces.

A soft robot successfully mimics larval rolling behavior.

Abstract

The Drosophila larva, a soft-body animal, can bend its body and roll efficiently to escape danger. However, contrary to common belief, this rolling motion is not driven by the imbalance of gravity and ground reaction forces. Through functional imaging and ablation experiments, we demonstrate that the sequential actuation of axial muscles within an appropriate range of angles is critical for generating rolling. We model the interplay between muscle contraction, hydrostatic skeleton deformation, and body-environment interactions, and systematically explain how sequential muscle actuation generates the rolling motion. Additionally, we constructed a pneumatic soft robot to mimic the larval rolling strategy, successfully validating our model. This mechanics model of soft-body rolling motion not only advances the study of related neural circuits, but also holds potential for applications in soft robotics.