  Gaits engineered for snake-like robots to rotate in-place instrumentally fill
a gap in the set of locomotive gaits that have traditionally prioritized
translation. This paper designs a Turn-in-Place gait and demonstrates the
ability of a shape-centric modeling framework to capture the gait's locomotive
properties. Shape modeling for turning involves a time-varying continuous body
curve described by a standing wave. Presumed viscous robot-ground frictional
interactions lead to body dynamics conditioned on the time-varying shape model.
The dynamic equations describing the Turn-in-Place gait are validated by an
articulated snake-like robot using a physics-based simulator and a physical
robot. The results affirm the shape-centric modeling framework's capacity to
model a variety of snake-like robot gaits with fundamentally different
body-ground contact patterns. As an applied demonstration, example locomotion
scenarios partner the shape-centric Turn-in-Place gait with a Rectilinear gait
for maneuvering through constrained environments based on a multi-modal
locomotive planning strategy. Unified shape-centric modeling facilitates
trajectory planning and tracking for a snake-like robot to successfully
negotiate non-trivial obstacle configurations.
