Burrowing Locomotion via Crack Propagation of a Bio-inspired Soft Robot

Abstract

Undersea burrowing of worm-like animals involves complex hybrid dynamics with continuous-time elastic and friction forces and discrete-time events that occur when a crack forms and propagates. This paper presents a state-space model of worm-inspired burrowing locomotion using discrete elastic rod theory applied to a segmented body representing the worm’s body. The effects of soil and fracture mechanics are considered in the hybrid dynamics of crack propagation. Anisotropic friction inspired by bristle-like structures in biological systems allows the worm model to create stress concentrations and advance forward through the soil. Constant-volume segments change width as they stretch and compress, affecting the friction and fracture forces on the worm body. The model is controlled by changing the intrinsic length of each segment, with several peristaltic travelling-wave gaits considered. Simulations varying gait parameters show that some travelling-wave gaits allow the worm model to make faster progress. The derived state-space model permits improved control and estimation for worm-inspired robots and empirically shows how differing travelling-wave gaits affect the speed of locomotion.