Bioinspired Hybrid Piezoelectric-Servomotor Actuated Untethered Robotic Fish

This work presents our design, fabrication, and characterization studies of a bioinspired hybrid robotic fish as an underwater swimmer. Macro-fiber composite (MFC) piezoelectric structures strike a balance between the deformation and actuation force capabilities to generate hydrodynamic propulsion, enabling a low-form-factor actuator for the tail region. Here, by coupling the MFC actuation with a servomotor in the head region, extra inphase or out-of-phase motion (relative to the tail) is provided for improved maneuverability. This work builds upon the previous generation of piezoelectric fish, which utilized a pair of MFC laminates as a caudal fin for the robotic fish, where it acted like an artificial muscle that could be driven out of phase to expand and contract on each side of the polymer substrate to simulate bending. The coupling of the servomotor with the MFCs allows for enhancement of thrust and ease of control for turning with combined DC (head) and AC (tail) actuation. Following design, fabrication, hardware/software aspects, resonant dynamics in quiescent fluid, as well as free (unconstrained) locomotion characterizations are explored for a range of piezo and servo actuation parameters, which are ongoing.