Biophysically inspired development of a sand-swimming robot

Abstract

Abstract-Previous study of a sand-swimming lizard, the sandfish, Scincus scincus, revealed that the animal swims within granular media at speeds up to 0.4 body-lengths/cycle using body undulation (approximately a single period sinusoidal traveling wave) without limb use [1]. Inspired by this biological experiment and challenged by the absence of robotic devices with comparable subterranean locomotor abilities, we developed a numerical simulation of a robot swimming in a granular medium (modeled using a multi-particle discrete element method simulation) to guide the design of a physical sand-swimming device built with off-the-shelf servo motors. Both in simulation and experiment the robot swims limblessly subsurface and, like the animal, increases its speed by increasing its oscillation frequency. It was able to achieve speeds of up to 0.3 body-lengths/cycle. The performance of the robot measured in terms of its wave efficiency, the ratio of its forward speed to wave speed, was 0.34±0.02, within 8 % of the simulation prediction. Our work provides a validated simulation tool and a functional initial design for the development of robots that can move within yielding terrestrial substrates.

Micromechanics of intruder motion in wet granular medium

“…The motion of objects through wet granular materials consisting of athermal solids sedimented in a fluid medium is encountered in a range of chemical and food processing industries, besides the muddy bottoms of ponds and rivers [1,2]. In the quasi-static limit, the drag experienced by objects of various shapes, and their interactions, have been investigated in granular media to study fundamental granular physics and biolocomotion [3][4][5][6][7][8].…”

Phylogenetic history influences convergence for a specialized ecology: comparative skull morphology of African burrowing skinks (Squamata; Scincidae)

“…Sand burrowers, including species in the genera Acontias , Typhlosaurus , and Typhlacontias , have a unique morphology characterized by long and narrow skulls, wedge-shaped crania with flattened skull roofs, long snouts, relatively long braincases, small suborbital fenestrae, and longer dentaries with short tooth rows. Sand is a complex substrate that possesses both solid and liquid properties, is composed of smaller grain sizes, and is generally unstable [ 63 , 64 ]. Given its unique physical properties, it follows that lizards would require unique adaptations to burrow through it.…”

Towards bio-inspired robots for underground and surface exploration in planetary environments: An overview and novel developments inspired in sand-swimmers

“…The robot was able to form a sinusoidal traveling wave pattern and achieved speeds of up to 0.3 body-lengths per cycle of oscillation [58]. Experiments allowed to correlate this bio-inspired mobility with theoretical models and other techniques, and study the actual performance of lizards under soils with distinct relative densities [89]. Now, with regard to planetary exploration, the high compaction found in bottom regolith layers of extraterrestrial surfaces, suggests that subsurface slithering locomotion associated to lizards may have more potential for surface robots operating in shallow depths than for soil penetrators.…”