A Afshari - Undergraduate Student
A Yousefi-Koma - Professor
H Basaeri - Graduate. Student Center of Advanced Systems and Technologies (CAST) School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran

This contribution presents the experimental investigations on the design and fabrication of a dorsal fin of a shark robot-fish mechanism actuated by NiTi Shape Memory Alloy (SMA) actuators. The dorsal fin helps the shark not only to turn around, but also to roll. This fin consists of two main parts, a rigid part that is connected to the shark’s body and another part is mounted on the latter one which can be rotated. The rotation angle of the second part is actuated by two parallel SMA wires. In this design a new combined mechanism consists of one gear and two half-gears are employed for linking the input force of SMA wires to output shaft. To have clockwise motion, first half-gear is in contact with output gear and second half-gear is free of motion. However, in counter clockwise motion, second half-gear is in contact with output gear and the first one is free. Preload on the SMA wires occurs by torsional springs based on the axis of gears. The advantage of this design is based on independency of the two parallel actuators which decreases the load on wires and loss of energy. The experimental results show that this mechanism is more efficient in comparison with the past mechanisms. Finally the comparison showed that experimental results are nicely fit on theoretical results.

Bio-inspired robotics, Shape memory alloy, Independent parallel actuators