The effect of limb kinematics on the speed of a legged robot on granular media

TL;DR

This study investigates how limb kinematics influence the speed of a legged robot on granular media, developing a predictive model to optimize gait parameters for improved mobility on such challenging terrains.

Contribution

The paper introduces a combined kinematic and granular force model to predict robot speed and identifies optimal gait parameters for locomotion on granular media.

Findings

High performance occurs only in a small parameter space.

The model accurately predicts speed based on gait parameters.

Optimal gaits minimize body acceleration and limb interference.

Abstract

Achieving effective locomotion on diverse terrestrial substrates can require subtle changes of limb kinematics. Biologically inspired legged robots (physical models of organisms) have shown impressive mobility on hard ground but suffer performance loss on unconsolidated granular materials like sand. Because comprehensive limb-ground interaction models are lacking, optimal gaits on complex yielding terrain have been determined empirically. To develop predictive models for legged devices and to provide hypotheses for biological locomotors, we systematically study the performance of SandBot, a small legged robot, on granular media as a function of gait parameters. High performance occurs only in a small region of parameter space. A previously introduced kinematic model of the robot combined with a new anisotropic granular penetration force law predicts the speed. Performance on granular media is maximized when gait parameters minimize body acceleration and limb interference, and utilize solidification features of granular media.