A Terradynamics of Legged Locomotion on Granular Media

TL;DR

This paper introduces a new 'terradynamics' model for predicting legged locomotion on granular media, providing insights into how leg shape and movement affect performance on flowable substrates.

Contribution

It develops a force model for arbitrarily-shaped legs in granular media and applies it to predict robot locomotion, filling a gap in existing terrestrial locomotion models.

Findings

Granular media stresses depend on depth, orientation, and movement direction.

Leg morphology and kinematics significantly influence locomotion efficiency.

The model accurately predicts robot movement on granular substrates.

Abstract

The theories of aero- and hydrodynamics predict animal movement and device design in air and water through the computation of lift, drag, and thrust forces. Although models of terrestrial legged locomotion have focused on interactions with solid ground, many animals move on substrates that flow in response to intrusion. However, locomotor-ground interaction models on such flowable ground are often unavailable. We developed a force model for arbitrarily-shaped legs and bodies moving freely in granular media, and used this "terradynamics" to predict a small legged robot's locomotion on granular media using various leg shapes and stride frequencies. Our study reveals a complex but generic dependence of stresses in granular media on intruder depth, orientation, and movement direction and gives insight into the effects of leg morphology and kinematics on movement.