Granular Media Friction Pad for Robot Shoes—Hexagon Patterning Enhances Friction on Wet Surfaces

Halvor T Tramsen,Stanislav N Gorb,Lars Heepe

doi:10.3390/app112311287

Abstract

For maximizing friction forces of robotic legs on an unknown/unpredictable substrate, we introduced the granular media friction pad, consisting of a thin elastic membrane encasing loosely filled granular material. On coming into contact with a substrate, the fluid-like granular material flows around the substrate asperities and achieves large contact areas with the substrate. Upon applying load, the granular material undergoes the jamming transition, rigidifies and becomes solid-like. High friction forces are generated by mechanical interlocking on rough substrates, internal friction of the granular media and by the enhanced contact area caused by the deformation of the membrane. This system can adapt to a large variety of dry substrate topologies. To further increase its performance on moist or wet substrates, we adapted the granular media friction pad by structuring the outside of the membrane with a 3D hexagonal pattern. This results in a significant increase in friction under lubricated conditions, thus greatly increasing the universal applicability of the granular media friction pad for a multitude of environments.

Highlights

Generating large friction forces on unknown substrate geometries requires high adaptability when approaching the substrate, combined with high energy dissipation when applying transversal load. This is why we recently proposed the granular media friction pad (GMFP) as a potential universal solution for friction enhancement on a wide range of substrates [1]
Friction forces are generated by the mechanical interlocking of the solid-like granular material and the substrate asperities, as well as by high internal friction of the granular media [6,7,8,9,10,11]
The granular media friction pad (GMFP) was composed of loose granular material that was encased by a thin, elastic membrane

Summary

Introduction

Generating large friction forces on unknown substrate geometries requires high adaptability when approaching the substrate, combined with high energy dissipation when applying transversal load. This is why we recently proposed the granular media friction pad (GMFP) as a potential universal solution for friction enhancement on a wide range of substrates [1]. When applying load to the GMFP, the granular medium undergoes the jamming transition [2,3] The result of this is fluid-like behavior [4,5] of the GMFP, when unloaded or approaching the substrate topography (see Figure 1a), and solid-like behavior, when pressed against the substrate (see Figure 1b). In contrast to previous systems employing the jamming transition to create friction or holding forces [4,15,16,17,18,19,20], no active control mechanism (such as the application of a vacuum to control the jamming transition) is needed

Methods

Results

Conclusion