Research On Numerical Simulation And Motion Control Of Aquaculture Robotic Fish

In recent years,although China’s aquaculture industry has achieved rapid development,it is still facing problems such as low degree of automation,aging labor force and environmental pollution.The transformation and upgrading of the aquaculture industry is urgent.With the development of science and technology,the application of underwater robots in the aquaculture industry has become possible.As a kind of underwater robot,the propulsion method of bionic robotic fish has the characteristics of higher propulsion efficiency,lower noise and stronger maneuverability,when compared with the traditional underwater robot.Besides,the robotic fish can minimize the impact on the real fish when performing underwater operations.Therefore,the robotic fish has broad application prospects in the aquaculture industry.In this paper,an aquaculture robotic fish is designed with the two-joint fish tail swing as the propulsion method,taking the trevally fish as the bionic object.In order to realize the precise underwater operation of the robotic fish,the mathematical model of robotic fish is established,and the relevant hydrodynamic coefficients of robotic fish are solved through numerical simulation,based on which,the research on the path following control method is completed.The main research contents are summarized as follows:(1)Structural design and equipment selection for key parts of the robotic fish.In order to realize the path following control of the robotic fish,the horizontal plane and threedimensional mathematical models of the robotic fish are established respectively,and the tracking error dynamics of the robotic fish are derived based on the Serret-Frenet coordinate system.(2)Numerical simulations of straight and oblique motions of the robotic fish were carried out using fluid mechanics simulation.According to the unsteady motion state of the robotic fish,a motion model is constructed,and a UDF program is written to realize the numerical simulation of the robotic fish plane motion mechanism test through the dynamic grid technology,solve the relevant hydrodynamic coefficients,and perfect the robotic fish mathematical model.(3)The research on the path following control of robotic fish is carried out.Firstly,for the horizontal tracking control task,a tracking controller based on LOS(Line-of-Sight)guidance,fuzzy sliding mode dynamics control and disturbance observer is designed,which effectively solves the problem of robust control under external disturbances;Secondly,the control task is extended to three-dimensional space,and a three-dimensional path tracking control algorithm is proposed;Then,the effectiveness of the proposed algorithm is verified by numerical simulation.The simulation results show that the designed controller can regulate the robotic fish to realize the three-dimensional path following control with uncertain model parameters and unknown external interferences,and its control accuracy and robustness are obviously better than the conventional PID and sliding mode controller.Finally,the algorithm is transplanted to the robotic fish body,and the horizontal plane experiment is carried out.It can be seen that the proposed control method can effectively track the desired path.Through the above contents,the design and motion control method of aquaculture robotic fish are completed,which lays a foundation for the popularization and application of robotic fish in aquaculture.