Use of a shape memory alloy for the design of an oscillatory propulsion system

This study investigates the potential for incorporating the elastic mechanisms found in fish propulsive systems into mechanical systems for the development of underwater propulsion. Physical and kinematic information associated with the steady swimming of the bonito and other scombrid species was used for the design. Several electroactive materials were examined for simulating muscle behavior and their relative suitability was compared. A dynamic analysis method adapted for muscle, which is a work-loop technique, would provide valuable information. However, the lack of such information on engineering materials made any direct comparison between the biological and mechanical systems difficult. Based on available information, nickel-titanium shape memory alloy (SMA) was better suited to produce relatively slow and powerful steady swimming of scombrid species. The simplified geometry of muscular systems and axial tendons was adapted. These arrangements alleviate the limited strain of the SMA by trading force for distance and provide an effective force transmission pathways to the backbone.