Dynamic modeling and experimental analysis of a two-ray undulatory fin robot

Bio-inspired undulatory fin propulsion holds considerable potential for endowing robotic underwater vehicles with low-speed manoeuvrability and stable station-keeping. Robotic fins typically comprise a number of serially arranged and individually actuated “fin rays”, interconnected by a membrane-like flexible surface. Propulsive forces are generated by the propagation of a traveling wave along the mechanism, via appropriately timed ray oscillations. The present paper describes a dynamic model for an elementary two-ray fin system, analyzed as a standard robot mechanism with additional contributions arising from the elastic deformation of the flexible membrane and from the hydrodynamic forces. The model´s main aspects, particularly with regard to the hydrodynamic effects, are explored via simulation studies, as well as via experiments with a robotic prototype. The developed model can serve a number of purposes towards optimizing the mechanical design, the control strategies, and the propulsive efficacy of robotic undulatory fins.