  Soft robots can exhibit diverse behaviors with simple types of actuation by
partially outsourcing control to the morphological and material properties of
their soft bodies, which is made possible by the tight coupling between
control, body, and environment. In this paper, we present a method that will
quantitatively characterize these diverse spatiotemporal dynamics of a soft
body based on the information-theoretic approach. In particular, soft bodies
have the ability to propagate the effect of actuation through the entire body,
with a certain time delay, due to their elasticity. Our goal is to capture this
delayed interaction in a quantitative manner based on a measure called
momentary information transfer. We extend this measure to soft robotic
applications and demonstrate its power using a physical soft robotic platform
inspired by the octopus. Our approach is illustrated in two ways. First, we
statistically characterize the delayed actuation propagation through the body
as a strength of information transfer. Second, we capture this information
propagation directly as local information dynamics. As a result, we show that
our approach can successfully characterize the spatiotemporal dynamics of the
soft robotic platform, explicitly visualizing how information transfers through
the entire body with delays. Further extension scenarios of our approach are
discussed for soft robotic applications in general.
