  In this paper, we present an approach to study the behavior of compliant
plates in granular media and optimize the performance of a robot that utilizes
this technique for mobility. From previous work and fundamental tests on thin
plate force generation inside granular media, we introduce an origami-inspired
mechanism with non-linear compliance in the joints that can be used in granular
propulsion. This concept utilizes one-sided joint limits to create an
asymmetric gait cycle that avoids more complicated alternatives often found in
other swimming/digging robots. To analyze its locomotion as well as its shape
and propulsive force, we utilize granular Resistive Force Theory (RFT) as a
starting point. Adding compliance to this theory enables us to predict the
time-based evolution of compliant plates when they are dragged and rotated. It
also permits more rational design of swimming robots where fin design variables
may be optimized against the characteristics of the granular medium. This is
done using a Python-based dynamic simulation library to model the deformation
of the plates and optimize aspects of the robot's gait. Finally, we prototype
and test robot with a gait optimized using the modelling techniques mentioned
above.
