Development and experimental assessment of a flexible robot fin

Energy efficiency and motion precision are particularly important for unmanned underwater vehicles (UUVs) undertaking complex missions. To achieve these objectives, researchers consider different materials when designing UUVs. In this work, we present the development and experimental assessment of a bio-inspired flexible actuator, based on the fins used in the Autonomous Underwater Vehicle U-CAT. The novel aspect of the new fin design is that it allows manipulation of the magnitude and direction of the generated thrust vector, by increasing the flexural resistance along its front edge through a rigid insert. The potential for using the fin as a U-CAT actuator is assessed through the comparison of results from parametric studies inside a water tank, run for both the here-proposed and the original design. The results indicate that the modified fin can generate an increased overall force, with a relatively small increase in power consumption. More interestingly, the overall direction of the thrust vector is better aligned with the robot's surge axis, at the expense of reducing the sway motion capability. Overall, the new design holds considerable potential for enhancing the propulsive performance of fin-actuated underwater vehicles, while representing a simple and robust implementation of undulating flexible propulsors.