An Obstacle Avoidance Algorithm for an Underwater Robotic Fish with Undulating Long-Fins

L. Shang, S. Wang, and M. Tan (PRC)


Biomimetic Robotics, obstacle avoidance, Underwater Vehicles, motion control


Four motion modes of underwater robotic fish by undulating symmetrical long-fins are proposed which include marching mode, receding mode, rotating mode and side-swaying mode. Robotic fish bends the two symmetrical long-fins into different waveform and makes the fin-ray oscillating to produce hydrodynamic forces. Through hydrodynamic force’s analysis, force in different direction can be produced for fish body. Different combination of the two long-fins’ waveform produces some motion modes for the fish body. The four motion modes are basic and typical. And this paper presents an algorithm for obstacle avoidance based on switching motion modes. By switching the four motion modes, Robotic fish installing infrared sensors can achieve obstacle avoidance. The experiment shows robotic fish swims steady and smoothly. Robotic fish reduce error produced by fish’s turning in certain degree. Meanwhile the experiments also show the algorithm for obstacle avoidance is valid.

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