Inchworm-Inspired Locomotion in Untethered Soft Robots

Inchworm locomotion is comprised of a simple anchor-slip gait which has inspired a wealth of mobile robots spanning rigid, soft, composite, and foldable mechanisms. Here, we expand upon that work by introducing centimeter-scale, inexpensive, simple, and soft robots capable of forward and backward motion, as well as tight turns. The robots are based on partially antagonistic fluid elastomer actuators; using a low fidelity model and experimental verification, we reason about actuator geometry. We introduce a simple two-step manufacturing process, and test actuator longevity and payload capacity. To enable stand-alone operation, we design a lightweight, low volume electro-mechanical backpack, capable of driving up to 3 actuators. We then show how differential friction can be used to enable forward and turning motion in a single actuator, and how three actuators can be combined to additionally enable backwards motion and on-axis turns. Due to the use of miniature pumps, inflation and corresponding motion is slow. However, the robot cost, durability, and ability to maneuver in confined spaces may be beneficial in applications such as duct mapping and maintenance.