Research On Bionic Fish Oscillating Propulsion Technology

During billions of years' evolution,fish have evolved to have the most suitable body structure and the most efficient form of exercise for underwater swimming.Biological studies have shown that fish can improve swimming performance by changing their stiffness.Based on the above characteristics of fish,this paper studies a multi-joint structure,imitation of muscle-driven mode and a new type of imitation fish swinging propulsion technology.In this paper,sturgeon has been taken as a bionic object to carry out the fish structure and movement characteristics of the theoretical study,and the rules of the sturgeon movement in a certain time series during the same period of the sturgeon in the same period have been obtained.Based on the theory of fish physiological structure and muscle drive principle,a new theory of multi-joint structure and imitation muscle drive principle are proposed.According to the variable stiffness characteristics of fish during swimming,a scheme of changing stiffness by air pressure is proposed and validated in a multi-joint series structure.The mathematic model of the variable stiffness system is established.The mathematical relation between the aerostatic load and the natural frequency is analyzed by the cantilever theory.The relationship between the pressure and the natural frequency is simulated and analyzed by the finite element method.Kinematic and kinetic studies of propulsion systems have been conducted.The mathematical model of propulsion system hydrodynamics is established.The mechanical model of propulsion system is established by using Lagrange equation.The virtual prototype of propulsion system is established by using ADAMS dynamic simulation software and the dynamics simulation of propulsion system is carried out.The relationship between propulsion performance of propulsion system and tail wobble frequency is analyzed.A new type of imitation fish swing propulsion system is developed.Multi-joint structure and imitative muscle drive mode are adopted.And the skeletal structure is a rigid body and the internal variable stiffness system is a flexible body.The control method is changing the air pressure to control the stiffness and then the speed change.The experimental prototype of the propulsion system is manufactured and assembled in this way.The prototype of the fishes swinging propulsion system is experimentally studied.Experiments show that the swinging tail of the imitation fish swinging propulsion system designed in this paper is in accordance with the swimming stance of fish during swimming.The swimming speed is linear with the driving frequency of the propulsion system,which is the same as the simulation conclusion.The influence of the stiffness of the propulsion system on the traveling speed of the system is obtained.The stiffness of the propulsion system can be increased and the range of the propulsion system can be expanded.For different speed requirements,the appropriate system stiffness can be selected to improve the efficiency of propulsion system.