Hydrodynamic performance of a soft body under-actuated batoid robot

Understanding the hydrodynamics that enable the levels of maneuverability observed in biological swimming is important for designing and controlling future underwater man-made vehicles. Batoids generate waves along their pectoral fins to propel themselves and maneuver. In this study the preliminary analysis of the wake structure generated by soft body under-actuated rajiform-type batoid robots is presented. Soft body under-actuated robots have continuous flexible bodies with purposely designed material distributions. Prototype bodies are designed with the heterogeneity needed to produce modes of vibration that match the body motions needed for locomotion using minimal actuation. Characterizing achievable performance is an essential step towards design improvements. In this study, further insight into the hydrodynamics of rajiforms is also gained. Particle image velocimetry (PIV) experiments reveal complex wake structures. However, identifying the exact three-dimensional vortex configuration is challenging. The orientation of the propulsive jet produced by the wake is attributed to the fin amplitude and phase parameters.