A robophysical model for studying obstacle navigation in sidewinders

Sidewinder rattlesnakes (Crotalus cerastes) use multiplane undulations to control their novel form of locomotion. Previous research showed that modulating amplitude or phasing of a two-wave control template—one controlling vertical lifting, the other lateral undulations—recapitulated turning gaits observed in the animals (Astley et al, PNAS 2015). With data from sidewinders interacting with pegs embedded in sand and a robophysical model, we investigate a peg-snake interaction where the animal forms a static contact with the substrate at an anatomical point anterior to the peg. This interaction mode facilitates “squeezing” the posterior body sections past the peg. Using a copper foil wrapped peg and 7 capacitive sensors along the 14-joint robot, we tested passive and active obstacle-clearing control templates. Early data shows the robot actively clears a peg using an increase in lateral wave amplitude or a reversal turn. When setting the multiplane undulations to produce two wavelengths along the robot’s body, the robot passively clears the peg if the peg interacts with a region of the robot’s body closest the head. These results will generate hypotheses for control strategies based on muscle activation patterns involved in sidewinding (Jayne, J. exp. Biol. 1988).