Increasing the Payload and Terrain Adaptivity of an Untethered Crawling Robot Via Soft-Rigid Coupled Linear Actuators

Fluidic Elastomer Actuators (FEAs) provide new opportunities for developing agile, adaptive, and strong mobile robots for field explorations. In this letter, we propose a soft-rigid coupled linear FEA with a bio-comparable energy density of 10.9 J/kg at 50 kPa. This actuator achieves an increased blocked force output (318%), increased energy density (183%), and increased power density (358%) by incorporating a rigid carbon-fiber telescopic shaft within its elastomeric skin. Based on this new FEA, we develop an untethered crawling robot with enhanced capability of forward locomotion and vertical load-bearing. We analyze and demonstrate how the proposed actuators increase the crawling robot's payload and terrain adaptivity. Experiments demonstrate that the robot's crawling speed with a payload of 6 kg (8.8 times of its own weight) is effectively increased compared with robot with purely soft actuators. Furthermore, we have demonstrated the robot can adapt to terrains with a wide range of roughnesses. Our design of coupling soft and rigid components provides a feasible strategy for building FEAs with higher energy density and constructing FEA-based, untethered mobile robot with better locomotion and payload performance driven by low-power pumps.