Bioinspired tearing manipulation with a robotic fish

We present SunBot, a robotic system for the study and implementation of fish-inspired tearing manipulations. Various fish species-such as the sunburst butterflyfish-feed on prey fixed to substrates, a maneuver previously not demonstrated by robotic fish which typically specialize for open water swimming and surveillance. Biological studies indicate that a dynamic "head flick" behavior may play a role in tearing off soft prey during such feeding. In this work, we study whether the robotic tail is an effective means to generate such head motions for ungrounded tearing manipulations in water. We describe the function of SunBot and compare the forces that it applies to a fixed prey in the lab while varying tail speeds and ranges of motion. A simplified dynamic template model for the tail-driven head flick maneuver matches peak force magnitudes from experiments, indicating that inertial effects of the fish's body play a substantial role. Finally, we demonstrate a tearing scenario and evaluate a free-swimming trial of SunBot - this is important to show that the actuator that enables swimming also provides the new dual purpose of forceful tearing manipulation.