Flapping Actuator Inspired by Lepidotrichia of Ray-Finned Fishes

This paper details the design and characterization of a biomimetic flapping actuator inspired by fin-rays of fishes. The flapper design consists of two carbon fiber beams with a thin viscoelastic material sandwiched between them. When the beams are actuated to move relative to each other tangentially, the entire assembly curves out of the plane of symmetry creating a flapping motion. A model for the mechanism is presented, and the model's predictions for flapper deformation and energy consumption are verified with experiments. A closed-form solution is presented for the case of a static flapper with uniform properties along its length. The model is a powerful tool to predict the response of the flapper to changes in material parameters or dimensions. A flapper with varying dimensions along its length is also characterized experimentally, and compared with a uniform flapper.