Collision-Induced Scattering of a Self-Propelled Slithering Robot

Our previous work has revealed that the interaction of a snake-like robot with a single row of evenly-spaced vertical pegs rotated the robot trajectory, and that a statistical characterization of these interactions produced a distribution of angles reminiscent far-field wave diffraction: as the spacing between the pegs was decreased, the distribution of scattering angles became multi-modal, with more large angles for smaller spacing. Here, we show that head collisions dominate this rotation, and that, because of the internal driving, they can last for significant fractions of an undulation cycle. Throughout this interaction, the robot head is pushed into but only allowed to slide along the peg surface, causing a rotation of the trajectory by an amount proportional to the interaction duration. Single-peg simulations reveal that this duration is set by the angular position on the peg and the snake undulation phase at impact, with longer-duration collisions occurring near the bottom of the peg. Multi-peg simulations show that large rotations are more frequent when spacing is small, and that the apparent ``interference” be explained by short collisions near the top of a peg becoming inaccessible and preferentially remapped to long collisions near the bottom of an adjacent peg.