A Robotic Fast-Start Fish Utilizing Post-Buckling Dynamics of Slender Column Under Compression to Passively Produce Rapid Underwater Locomotion

An experimental study is conducted on a robotic fish designed to emulate the fast-start response. The fish body is constructed of 3D-printed materials and a light spring steel spine. The body is actuated using pressurized pistons. A total of two pistons are supplied with pressure through lightweight high-pressure service lines. The source of pressure is carbon dioxide with a 4.82 MPa peak operating pressure resulting in a body response that emulates a C-start maneuver in milliseconds. The motion of the fish is controlled using large bandwidth solenoids with a control signal produced by a programmable microprocessor. 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 interaction of the fluid with the underactuated structure results in a travelling wave in the body of the robotic fish that is kinematically similar to the live fish. The effect of the tail is considered using the model to test performance changes with various geometries.