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Design and optimization of a robotic fish mimicking cow-nosed ray

The paper is aimed at establishing a platform of robotic fish propelled by paired pectoral fins, so as to research pectoral fin propulsion. Locomotion of nature sample, cow-nosed ray, was analyzed before simplified mathematical model was obtained for design of the robotic fish. Locomotion of the pectoral fins is equivalent to the pass of oscillating motion from front to back in the form of cubic function in one plane. Tridimensional flexible skin was made according to the shape of cow-nosed ray. Mechanism with three fin rays was designed to meet the mathematical model, that is, to mimic the pass of locomotion wave on pectoral fin. A novel two stage rocker-slide mechanism was designed, which can drive the flexible skin to realize the ideal profile approximately with only one motor. In order to mimic the locomotion better, key dimension parameters were optimized based on the mathematical model of locomotion. Primary experiment was done for the two stage rocker-slide mechanism, which showed the design was valid.