The Design And Motion Control Of A Biomimetic Robot Fish

With the continuous advancement of industrialization,land resources are being exploited to be utilized in large quantities and become increasingly depleted.In order to meet human's higher energy needs,we have gradually turned our attention to the ocean.Exploration of underwater resources requires underwater robots help to complete many difficult or dangerous jobs that humans cannot accomplish.Therefore,scholars at home and abroad began to explore underwater robots.Traditional underwater robots are usually propelled by conventional propellers such as the screw propeller.Prominent drawbacks of the screw propeller are low propulsion efficiency,poor sensitivity,and high noise.The ultra-high swimming performance of fish in the ocean inspires scientists to study the efficient mechanism of fish promotion,which can be applied to underwater robots through the bionics methodology.Therefore,the corresponding research on underwater bionic robotic fish is carried out in this paper.The main contents and conclusions of the paper are summarized as follows.Firstly,the achievement of the robotic fish swimming mechanism and the robotic fish prototype at home and abroad are summarized systematically in this paper.Then three-body and two-joint fish prototype machine like Carangidae is designed.The robot fish head and body parts have large rotational inertia and mass,but the overall swing range is very small.The main source of swing deduces from the tail,which contributes greater than 90% of propulsive force.Therefore,the design idea of the bionic robotic fish in this paper is that the rigid fish head and connected with the flexible caudal fin,the rigid fish head is almost not moved when the fish swims,and the thrust is mainly provided by the swing of the flexible fish tail.After,the paper designed the lifting mechanism and pitching mechanism of the bionic robotic fish.The paper simulated the forward movement and steering movement of the robotic fish prototype by MATLAB.Again,the shape of the robotic fish is an important factor in determining the resistance of the robotic fish.In this paper,we designed the shape of the robotic fish by investigating the curve contour of the robotic fish model,the maximum diameter of the cross section,the position of the largest cross section,and the effect of the fish caudal fin on the resistance of the robotic fish.At present,there are many researches on bionic robotic fish at home and abroad,but it should be noted that most existing robotic fish control algorithms are based on a simplified propulsion model,which provides only a rough prediction of the hydrodynamic effects of robotic fish.In order to accurately predict the hydrodynamics of robotic fish,it is necessary to perform dynamic analysis of the fluid around the robotic fish through computational fluid dynamics software(CFD).Using Fluent software to simulate the movement of robotic fish,the dynamic mesh technology was used to determine the hydrodynamic coefficients,and the robotic fish wall in the control domain was moved according to the specified rules.At the same time,the entrance velocity of the control body simulates the infinite flow from the far end,and simulates the pure heaving,pure pitching,pure swaying,and pure rolling motion of the robotic fish according to different movement laws of the robotic fish.The corresponding hydrodynamic coefficients were further calculated.The manipulative performance of robotic fish refers to controlling the speed,azimuth,elevation angle and ascent depth of robotic fish.The method adopted in this paper is to establish a six-degrees of freedom mathematical model for robotic fish.After obtaining the hydrodynamic coefficients,using the sliding mode control method,the sliding mode control method is simple,robust,and highly reliable.In this paper,we designed a control program to design a specific path for robotic fish,tracked and analyzed the actual path of robotic fish.The results show that the above control method can effectively control the robotic fish.Bionic robotic fish is a multidisciplinary research project aimed at researching bionic robotic fish with higher mobility,flexibility and high efficiency,which will have extraordinary significance for human exploration of the ocean.