A wave energy conversion mechanism applied in robotic fish

Multi-joints robotic fish can provide great help for humans in river and sea for their excellent maneuverability and high propulsion efficiency. However, the energy problem has limited its applications severely because most developed robotic fish can only swim continuously for several hours with the storage energy itself. Fortunately, the ocean has enormous wave energy which could be captured and converted to electricity. Based on the structure of the multi-joints robotic fish, a reversible energy conversion mechanism is proposed. The mechanism not only can work as drive unit but also can work as power take-off (PTO) unit which is able to capture wave power for the robotic fish. In this paper, the PTO unit is investigated analytically and verified by experiments. Firstly, the hydrodynamic behavior of the PTO unit was analyzed and calculated with linear water wave theory. Secondly, a wave generating system and a PTO unit prototype were designed and manufactured according to the theoretical analysis. Finally, experiments on the energy conversion mechanism were conducted. The results demonstrate that the developed PTO unit is able to convert wave energy to electricity with a relative high efficiency, which provides a practical solution for the energy problem of the bionic underwater robots.