Initial Research on Development of a Flexible Pectoral Fin Using Shape Memory Alloy

Crucians propel themselves through the water primarily either with their body and tail (axial-based locomotion) at high swimming speed or with their greatly expanded pectoral fins (pectoral-fin-based locomotion) at low swimming speed. They also use their pectoral fins to adjust stability in still motion. In this paper, we present recent experimental research on pectoral fin structure, fin locomotion, meanwhile consider a design of pectoral fin actuator based on shape memory alloy (SMA) composites composed of a couple of plates with the opposite functions. Both SMA plates, whose microstructure is either martensite or austenite, are individually arranged in parallel and operated as a bias to each other mimicking the morphological and kinematic characters of pectoral fin of crucian. We also use strain gauge sensors for deformation control. Finally an examination was carried out to test the relationship between the tip displacement of SMA plate and the output voltage signal of strain gauge as well as the relationship between pulse width modulate (PWM) and bending angle (thetas). The results give us a confidence on the possibility of imitating pectoral fin locomotion using shape memory alloy