A Biomimetic Flexible Fishtail Embedded With Shape Memory Alloy Wires

In this paper, a biomimetic flexible fishtail actuated by shape memory alloy (SMA) wires is presented. The detailed structure of the fishtail propeller is designed to mimic the muscle and bone structure of a Carassius auratus. The mechanical modeling of the biomimetic fishtail is built; then, constitutive equations and thermal models of embedded SMA wires are described. Next, experiments are carried out to analyze the propulsive performance of the fishtail. Its maximum bending angle is 50° under the conditions of a heating voltage of 14.8 V and a heating time of 175 ms at a water temperature of 24.5°C. The symmetrical characteristic of both sides of the biomimetic fishtail is good, and different fluctuation can be adjusted by changing the heating time. The bending time and recovery time are recorded, and the effect of heating time on oscillation frequency is analyzed. Finally, the propulsive forces of three different heating modes at frequencies of 0.4 Hz, 0.5 Hz and 0.6 Hz are tested and compared. A relatively good heating mode is discovered for controlling the biomimetic fishtail during the experiments. The biomimetic fishtail obtains the largest average propulsive force of 0.041 N at a frequency of 0.8 Hz with a heating time of 80 ms and a bending angle of 22°.