Design and experiments of a robotic fish imitating cow-nosed ray

The cow-nosed ray is studied as natural sample of a flapping-foil robotic fish. Body structure, motion discipline, and dynamic foil deformation of cow-nosed ray are analyzed. Based on the analysis results, a robotic fish imitating cow-nosed ray, named Robo-ray II, mainly composed of soft body, flexible ribs and pneumatic artificial muscles, is developed. Structure and swimming morphology of the robotic prototype are as that of a normal cow-nosed ray in nature. Key propulsion parameters of Robo-ray II at normal conditions, including the St Number at linear swimming, thrust coefficient at towing are studied through experiments. The suitable driving parameters are confirmed considering the efficiency and swimming velocity. Swimming velocity of 0.16 m·s^-1 and thrust coefficient of 0.56 in maximum are achieved in experiments.