Design and Investigation of Shape Memory Alloy Driven Flexible Pectoral Fin

Fin-based propulsion systems of fishes perform well for both high-speed cruising and high maneuverability, which inspires different fin propulsors for autonomous underwater vehicles. Here, we present a novel fish-fin actuator composed of a series of shape memory alloy (SMA) plate couple. Both SMA plates, whose microstructure is either martensite or austenite, are individually arranged in parallel and operated as a bias to each other that can realize bidirectional bending. These SMA plates are specially arrayed to generate undulatory motion. In the paper the basic mechanical structure and corresponding control circuit are introduced. The relationship between the displacement of SMA plate tip and SMA curvature is analyzed and the error of this model is also discussed. Finally, the following results were achieved: (1) relationship between the tip displacement of SMA plate and the output voltage of strain gauge, (2) relationship between heating current and maximal fin tip displacement, (3) relationship between heating current and responding speed. The above results show that the SMA driven fish-fin can be well achieved through the proposed methodology.