Bio-Inspired Tail Oscillation Enables Fast Crawling on Deformable Granular Terrains
Shipeng Liu, Meghana Sagare, Shubham Patil, Feifei Qian
Abstract
Deformable substrates such as sand and mud present significant challenges for terrestrial robots due to complex robot-terrain interactions. Inspired by mudskippers, amphibious animals that naturally adjust their tail morphology and movement jointly to navigate such environments, we investigate how tail design and control can jointly enhance flipper-driven locomotion on granular media. Using a bio-inspired robot modeled after the mudskipper, we experimentally compared locomotion performance between idle and actively oscillating tail configurations and found that tail oscillation increased forward speed by 17% while reducing body drag by 46%. Shear force measurements revealed that this improvement arises from oscillation-induced fluidization of the substrate, which lowers resistive forces acting on the body. Additionally, tail morphology strongly influenced the oscillation strategy: designs with larger horizontal surface areas leveraged the oscillation-induced reduction in shear resistance more effectively by limiting insertion depth. Based on these findings, we present a design principle to inform tail action selection based on substrate strength and tail morphology. Our results offer new insights into tail design and control for improving robot locomotion on deformable substrates, with implications for agricultural robotics, search and rescue, and environmental exploration.