Positional control of an underwater vehicle using pectoral fins

Fine scale positioning and station-keeping of underwater vehicles inspired by fish locomotion requires understanding the forces generated by secondary control surfaces used to maneuver. Here, the unsteady maneuvering of a robotic fish is explored using an idealized, 2D fish body with two pectoral fins, where each fin is a rigid 2D flapping plate. Experiments in a water channel with a stationary fish are used to measure the forces generated by the fins as a function of their prescribed kinematics. Flow visualization (PIV) and numerical simulations are leveraged to characterize the flow structures. Next, a cyber-physical system with three degrees of freedom is used to experimentally study the dynamical response of the fish. Here, the fish is allowed to freely translate (surge and heave) and rotate (pitch) in the horizontal plane. We present the force and moment generation as a function of Strouhal number, amplitude and phase synchrony between the two fins, and discuss the implications for the maneuverability of underwater vehicles.