(Georgia Institute of Technology, 2011)
Maladen, Ryan D.; Ding, Yang; Umbanhowar, Paul B.; Kamor, Adam; Goldman, Daniel I.
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.