LONG, JR., J.H.; HOBSON, B; PELL, C; SCHUMACHER, J; KEMP, M; Vassar College; Nekton Research LLC; Nekton Research LLC; Vassar College; Nekton Research LLC: Biorobotics: A Four-Finned Underwater Vehicle for Locomotor Research

In order to test functional predictions about fin-based swimming, we have designed and built an underwater, remotely-operated vehicle with four independently controlled fins. Modeled loosely after sea turtles, the vehicle has a dorso-ventrally compressed hull and the axes of the fins are in the mid-frontal plane, perpendicular to the midline. Each fin oscillates in pitch about its axis, generating thrust as a pitching hydrofoil. Onboard, the vehicle carries its power supply, computer, and sensors: accelerometer, current and voltage meters, and motor thermometers. These sensors allow us to correlate locomotor kinematics, videotaped from an external perspective, with internal measures of mechanical and electrical state, logged by the onboard computer. The vehicle is controlled, topside, by a human operator using a multi-axis joystick that communicates with the vehicle via a tether. In our hands, the vehicle is capable of complex three-dimensional motions, with roll, pitch, and yaw superimposed on forward or backward translation. In preliminary trials, we varied the phase of the fins, while holding oscillation frequency and amplitude constant, and produced gaits reminiscent of those seen in terrestrial mammals. While a diagonal �trot� produces balanced moments and stable forward motion, a lateral �pace� oscillates the vehicle about its roll axis as it swims. We hypothesize that the gaits that produce oscillations in roll or pitch add significant heave to the fins, thereby enhancing thrust by increasing lift. This work is supported by the National Science Foundation (BCS-0320764).