An Analytical Approach to Improve Peristaltic Locomotion of Soft, Earthworm-Inspired Robots in Flexible Soil Media

Abstract

Bio-inspired geotechnics is the fast-growing, multidisciplinary field of solving geotechnical-related problems through mechanisms and processes found in nature, development of the technologies requiring input from an array of engineers and scientists. These solutions, such as those within the realm of robotics, are swiftly emerging as a viable candidate for replacing today’s underground machinery, offering energy-efficient, cost-effective alternatives paired with minimal ground disturbance compared to conventional industry standards used in subsurface exploration. Though many benefits of employing bio-inspired technology exist, the effectiveness of bio-inspired technologies functioning within real-world soil media is yet to be fully explored. Consequently, this study explored such through a soft, earthworm-inspired robot progressing within simulated soil media through utilizing peristaltic locomotion pathways. Originally developed as a peristaltic robot locomoting through rigid media by Daltorio et al. (2013), work here expanded on these developments by incorporating a simplified analytical framework which was adopted using a sub-structure approach based on soil–structure interaction (SSI) theory to improve the rigid media to one of real-word conditions in which this technology will operate. The surrounding soil was modeled using a system of independent mass-springs, which is a more appropriate alternative than rigid media in capturing compression, rebound, and deformability properties of real-world soil media. Values and calculations representing such parameters were obtained through use of ASCEND (Applications for Spherical and Cylindrical Cavity Expansion in Nonlinearly Deforming Geomaterials), a cavity expansion analysis program developed by Jaeger (2018) capable of simulating cylindrical cavity expansion across a variety of soil types, densities, consolidation histories, and drainage conditions. Results from analytical simulations yielded details in robot locomotion performance, specifically less-dense soils providing more energy-efficient results in normal force reduction and cost of transport, while higher density and consolidated soils provided robots greater anchorage and thrust capabilities. This study offered promising routes for future research into the field of bio-inspired robotics, providing a comparison evaluation of technology performance across many forms of soil proving useful in selecting burrowing mediums in experimental studies.