| Summary: | With the increasing impacts of overfishing and environmental pollution, the deep-sea cage culture of marine fishes has become an important direction of mariculture. In this paper, a tuna-like robotic fish with a three-dimensional helix path-following control system is designed for deep-sea net cage inspection. To mimic the flexibility of the fish’s movement, the kinematic model of the robotic fish adopts a tuna-like double-joint design with an additional thruster device at the tail. Since the descending interval control plays a critical role in deep-sea net cage inspection, the control system utilizes the proportion integration differentiation (PID) based fuzzy logic control method to control the descending interval and yaw angle during the helix path movement. A polar coordinate path definition method is also proposed to simplify the reference path definition during net cage inspection. The experimental results demonstrates that the proposed three-dimensional path-following model can conduct net inspection task in an interferential environment and move along predefined reference path.
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