Development and depth control of a robotic fish mimicking cownose ray

A robotic fish mimicking cownose ray is developed and a fuzzy depth control method is presented in this paper. With dosoventrally flattened body wich is disigned by imitating body shape of cownose ray, the robotic fish has preferable pitch stability. A tail-unit, which consists of a pair of horizontal tails and a vertical tail, is used to realize turning motion in the horizontal plane and up-and-down motion in the vertical plane. By adjusting rotation angles of the horizontal tail, the robotic fish can swim upward or downward. Due to the complex hydrodynamics and uncertaintyies exist in the environment, fuzzy logic method is applied to realize automatic depth control of the robotic fish. The experimental results on the prototype verify that the fuzzy logic depth control method is effective in design and implemention.