Controlled Buckling Modes in a Slender Column used to Passively Recreate Backwards Travelling Wave in Biomimetic Robotic Fish Capable of Generating Fast-Starts

An experimental study is conducted on a robotic fish designed to emulate the fast-startle response observed in live fishes. The caudal fin, dorsal and anal fin are modeled based on the northern pike and are 3D printed in a single part using mixed materials, rigid plastic to represent bone structures and rubber for the connective tissues. The robotic model is actuated using pressurized pistons. A total of two pistons are supplied through lightweight high-capacity service lines. The source of pressure is carbon dioxide with a 4.82 MPa peak operating pressure resulting in a body response that can cycle a C-start maneuver in milliseconds. The buckling modes of a slender column in compression are used to produce organic movements in the body with only two sources of actuation. The buckling of the beam interacting with the fluid results in a backwards travelling wave in the body of the robotic fish passively that is kinematically similar to the live fish. Two column lengths are tested for performance as well as control parameters (pressure magnitude, solenoid engagement duration, and time between solenoid engagements). The prototype design is deployed in a swift moving river to validate overall performance and the ability to perform fast-starts in the field.