Bio-inspired unmanned undersea vehicle

Biological systems in ocean environment provide all the desired features required for design of unmanned undersea vehicles. We noticed the uniqueness and simplicity in the design of rowing medusa and have successfully demonstrated working prototypes of Aurelia Aurita. In this study, we demonstrate the effect of bell joints in reducing the contraction force required for deformation. The study is based on observations made for the sub-umbrella features of jellyfish. Artificial jellyfish unmanned undersea vehicle (UUV) was fabricated consisting of silicone as the matrix material and shape memory alloy (SMA) as the actuation material. UUV was characterized for its performance and tailored to achieve vertical motion. SMAs were selected for actuation material because they are simple current-driven device providing large strain and blocking force. However, electrical power requirements were found to be quite high in the underwater conditions. It was identified that by including "joints" in the structural material forming the bell, the overall power requirement can be reduced as it lowers the resistance to compression. An analytical model was developed that correlates the deformation achieved with the morphology of the joints. Experiments were conducted to characterize the effect of both joint shapes and structural materials on the motion. Results are compared with that of natural medusa gastrodermal lamella and analyzed using the theoretical model. By including the features inherently present in natural jellyfish, the required compression force was found to be decreased.