Tunable fin stiffness patterns for improved performance in fish-inspired unmanned underwater vehicles

Nature’s swimmers show unparalleled efficiency and agility, and the ability to replicate their mechanics will result in significant improvements to the performance of unmanned underwater vehicles. The propulsive appendages of biological swimmers possess complex mechanical properties. Here, the stiffness patterns of fish caudal (rear) fins and their effect on propulsive performance are of interest. Fish are capable of actively changing the stiffness of their fins via antagonistic muscle actuation. This allows them to adapt the overall fin stiffness to swimming speed but also to tune the stiffness pattern of the fin to manipulate its flow-induced deformation and resulting flow mechanics.

In this talk, we will present results on the design, manufacturing and testing of soft robotic caudal fins with tunable stiffness distributions.  Stiffness tuning of different fin sections is achieved through two methods: pressurization of small internal cavities and layer jamming through vacuum.  The resulting fins are tested in a water tunnel to evaluate their effectiveness in manipulating the flow-induced deformation and assess their performance.