Soft Pneumatic Actuator Capable of Generating Various Bending and Extension Motions Inspired by an Elephant Trunk

TL;DR

This paper introduces a novel soft pneumatic actuator inspired by an elephant trunk, capable of complex bending and extension motions through superimposing simple tube movements, validated by models and experiments.

Contribution

The paper presents a new flexible pneumatic actuator design that achieves complex motions by superimposing simple tube movements, validated through modeling and experiments.

Findings

Successfully modeled tip position changes in various motions.

Validated models with experimental data.

Demonstrated practical grasping and pouring actions.

Abstract

Inspired by the dexterous handling ability of an elephant's trunk, we propose a pneumatic actuator that generates diverse bending and extension motions in a flexible arm. The actuator consists of two flexible tubes. Each flexible tube is restrained by a single string with variable length and tilt angle. Even if a single tube can perform only three simple types of motions (bending, extension, and helical), a variety of complex bending patterns can be created by arranging a pair of tubes in parallel and making the restraint variable. This performance takes advantage of the effect of the superposition of forces by arranging two tubes to constructively interfere with each other. This paper described six resulting pose patterns. First, the configuration and operating principle are described, and the fabrication method is explained. Next, two mathematical models and four finite element method-based analyses are introduced to predict the tip position changes in five motion patterns. All the models were validated through experiments. Finally, we experimentally demonstrated that the prototype SEMI-TRUNK can realize the action of grabbing a bottle and pouring water, verifying the effectiveness of the proposed method.