Robotic morphing in the aquatic-to-terrestrial transition*

Amphibious robots are valuable platforms for studying the physics of locomotion in the aquatic-to-terrestrial transition. Waves, currents, rocks and vegetation, as well as dynamic flows of fluidized sediment, are physical phenomena a robotic system may encounter in this transition. We recently introduced Amphibious Robotic Turtle (ART), a turtle-inspired robot that adapts for locomotion in its environment via limbs that morph between specialized terrestrial and aquatic shapes and a variety of gaits. ART can swim underwater or at the surface, walk over different terrain, and transition between water and land. We investigated the confluence of robot gait, limb shape, and the environmental medium and found that, by adapting its shape and gait, ART can locomote in different environments with comparable, or in some cases, even better cost of transport than exclusively uni-modal robots. Generalized questions arose from these studies about how and when a robot should change its shape and behavior if transitioning between environments. Future work will investigate these questions through experiments with ART in a newly built aquatic-to-terrestrial transition tank featuring controllable waves, current, incline, substrate, and temperature.