Innovation Design And Analysis Of Bionic Underwater Vehicle Propelled By Multiple Undulatory Fins

With the development of ocean strategic status,underwater vehicle plays a more and more important role in maritime and military.Propeller propulsion is widely used in traditional aircraft,but it has many disadvantages such as high noise,large disturbance to environment,poor maneuverability and concealment,etc.Therefore,people have been continually searching for new propulsion modes to make up for the deficiency of propeller propulsion.While after millions of years of natural evolution and selection,fish have superior underwater performance.The undulatory fin propulsion mode is more efficient and easier to transplant than the tail fin propulsion mode,which provides a new idea for the design and research of underwater vehicle.However,due to the complex undulating fin motion forms,it is difficult for the bionic propulsion device to completely reproduce the undulating motion forms,which requires higher requirements for the control system.In order to simplify the control system of the undulatory fin bionic propulsion device and reduce design difficulty and cost,the undulatory fin is used as the bionic object in this paper.According to the structure and motion characteristics of the undulatory fin,a single driving undulatory fin bionic propulsion device is designed.Based on the bionic propulsion device,a new design scheme of multi-fin underwater vehicle is proposed,and the dynamic system model of underwater vehicle is established.Numerical simulation of hydrodynamic analysis for undulatory fin and underwater vehicle are carried out.The undulating fin propulsion mechanism is analyzed and verified,and the resistance characteristics of the vehicle under different flow velocities are studied.The main contents of this paper are as follows:(1)Aiming at the undulatory fins of Amiiformes,a summary of the morphological structure and motion characteristics,as well as a qualitative analysis of the propulsion mechanism and motion rule are carried out,which providing the theoretical basis and design criterion for the study of the bionic propulsion device of undulatory fins.The actual model is simplified properly to realize the transformation from biological model to physical model.And the kinematic and dynamic models of the undulatory fin are established,which describing the movement of the undulating fin at different moments.Starting with the hydrodynamic force of the flexible long dorsal fin,the hydrodynamic analysis and modeling of the flexible long dorsal fin are carried out.(2)According to the motion characteristics of undulatory fins,a new type of bionic propulsion device for undulatory fins is designed based on the bionic principle of structure and similarity principle.The propulsion device is composed of the basic motion unit of the fin strip and the fin surface connecting the fin strip.The basic propulsion motion unit is a crank-rocker mechanism to realize the periodic swing of a single fin in a certain angle.The crankshaft is formed by combining the crank of each movement unit,and there is a certain angle difference between the cranks,which realizes the orderly swing of each fin,and finally forms the undulatory motion of the fin surface.The parameters of the connecting rod are optimized to have good force transfer performance and wave symmetry,and the simulation is carried out with ADAMS software.(3)Considering the fixed waveform of the single-driven undulatory fin propulsion device,it is impossible to realize a variety of undulatory motion modes.Hence,a multi-wave fin cooperative control scheme is proposed.Based on the theory of bionics and the idea of fish colony movement,the four groups of undulatory fins adopt staggered and parallel configuration structure to constitute the propulsion motion system.The corresponding propulsion force,yaw moment and pitching moment can be generated by the cooperative control of each group of undulatory fins.The kinematic models of the underwater vehicle are established,and the relationship between the external force and the motion state of the vehicle is analyzed,which provides a theoretical basis for the design of the control system.From the point of view of function division,the hierarchical relationship between sub-function and total function is analyzed,and the hierarchical control scheme of undulatory fin control system is planned.(4)The hydrodynamic simulation of undulating fin and underwater vehicle was carried out to analyze and verify the mechanism of undulating fin propulsion and study the resistance characteristics of the vehicle.A simplified two-dimensional wave motion model of undulatory fin is established.The dimensionless resistance coefficient and the distribution of pressure and velocity around the fin surface are analyzed.The resistance characteristics of the vehicle are simulated by CFD,and the pressure and the surrounding flow field distribution of the vehicle are visualized,which lays a foundation for the optimization analysis of the vehicle.