Meeting Abstract

112.3  Tuesday, Jan. 7 10:45  Sidewinding as a control template for climbing on sand MARVI, H.*; GONG, C.; GRAVISH, N.; MENDELSON, J.; HATTON, R. L.; CHOSET, H.; HU , D. L. ; GOLDMAN, D. I.; Georgia Tech; Carnegie Mellon; Georgia Tech; Georgia Tech and Zoo Atlanta; Oregon State; Carnegie Mellon; Georgia Tech; Georgia Tech hamid.marvi@gmail.com

Desert dwelling snakes like sidewinder rattlesnakes Crotalus cerastes sidewind to rapidly traverse granular media like loose sand. While sidewinding has been studied on hard ground, little is known of the detailed mechanics of interaction with granular media. In addition, controlling robots over such terrain remains a challenge: a field-tested limbless robot (the Modsnake) suffers significant performance loss when ascending sandy inclines. To understand how the animals effectively interact with such substrates, and to design a new control template for robots, we conduct the first study of the detailed mechanics of sidewinding on sand. We use a tiltable air fluidized bed to prepare loosely packed states of desert sand at different inclination angles. We challenge the animals to ascend these inclines and record 3D kinematics using multiple high-speed cameras. On level granular media, the contact length occupies 23±4% of the snake length (N=6). As the incline angle increases to 20 degrees, the contact length increases to 38±4% (N=6). To understand these mechanics, we measure the downhill drag forces on plates, and find that the granular yield stresses decrease by 50% over the range of incline angles. We therefore hypothesize that the increase in contact length is a neuromechanical control template such that the animals actively maintain contact stresses below the yield stress to avoid slipping. We implement the anti-slip control template in the Modsnake, and find that it generates effective climbing on granular inclines in the laboratory as well as in a simulated field environment.