Understanding Legged Crawling for Soft-Robotics

TL;DR

This paper models soft-robotic legged crawling using an articulated robot approximation, analyzes gait performance and sensitivity, and validates findings through experiments with a fluid-driven soft robot.

Contribution

It introduces a hybrid-quasitatic analysis for soft-robotic crawling and demonstrates its effectiveness in optimizing gait parameters and predicting real-world robot behavior.

Findings

The model accurately predicts crawling performance.

Optimal gait parameters improve efficiency.

Experimental results match theoretical predictions.

Abstract

Crawling is a common locomotion mechanism in soft robots and nonskeletal animals. In this work we propose modeling soft-robotic legged locomotion by approximating it with an equivalent articulated robot with elastic joints. For concreteness we study our soft robot with two bending actuators via an articulated three-link model. The solution of statically indeterminate systems with stick-slip contact transitions requires for a novel hybrid-quasitatic analysis. Then, we utilize our analysis to investigate the influence of phase-shifted harmonic inputs on performance of crawling gaits, including sensitivity analysis to friction uncertainties and energetic cost of transport. We achieve optimal values of gait parameters. Finally, we fabricate and test a fluid-driven soft robot. The experiments display remarkable agreement with the theoretical analysis, proving that our simple model correctly captures and explains the fundamental principles of inchworm crawling and can be applied to other soft-robotic legged robots.