Meeting Abstract
Snakes move gracefully through varied terrain, negotiating obstacles such as twigs, rocks, and grasses. Despite the seeming simplicity of this movement, the continuous interaction with the ground coupled with obstacle collisions can give rise to complex dynamics. Work in our lab that explores the interaction of the desert-dwelling sand specialist C. occipitalis with a row of vertical pegs (perpendicular to the initial direction motion) has found that the snake is least likely to apply forces to the pegs along the direction of motion. We have also observed that the snake does not substantially alter its waveform to maneuver through pegs, suggesting that positional control of shape is a reasonable neuromechanical control model. To test this, we built a 13 segment servo-motor-driven snake-like robot (1.13 kg, 80 cm long). Joint angles were commanded via the motors, and low slip translational motion of the robot was achieved by affixing wheels to each segment. To sample robot-peg interactions, the initial shape of the robot was fixed and the robot was placed at different locations within a rectangular region (dimensions set by the peg spacing and distance traveled over one period). The robot position was recorded over several cycles, and in-plane reaction forces were measured via strain gauges on each peg. The forces were complex, with multiple collisions occurring during each transit, but a simple pattern emerged: the distribution of the force orientations for the robot was similar to that of the snakes. This suggests that the animal’s interaction with obstacles is dominated by its sand-adapted body wave control mechanics. Intriguingly, video tracking of the robot after transit revealed that it was re-oriented along preferred directions, as might be predicted by wave mechanics.
