Research On Propulsion Performance Of Underwater Bionic Propulsion Device Based On Active Deformation

With the development of global economy and the change of energy environment,strategic position of the national marine security has become more and more important.As an important resource reserve on the earth,marine resources have been paid more and more attention by the state.Marine transportation and marine military strategic significance also play an important role.However,the traditional underwater vehicles are large in size,heavy in weight,inefficient in propulsion and poor in maneuverability,which can not meet the growing need for marine strategy.Therefore,how to improve the propulsion performance of underwater vehicles has become an urgent problem to be solved.After hundreds of millions of years of evolution,marine organisms have evolved a unique way of swimming propulsion in the water environment.Especially the fluctuating propulsion of fish and the jet propulsion of shrimp in fast escape have the characteristics of high maneuverability,high performance,high efficiency and low interference,which coincide with the current demand of underwater bionic robots.So,the research and application of multi-functional underwater bionic vehicle with high maneuverability,high stability,high efficiency and high stealth performance are very important for ensuring national marine safety.In this paper,the influence of active deformation on the propulsion performance of Underwater Bionic Propulsion Device is studied from two aspects:wave propulsion and jet propulsion.Firstly,from the perspective of bionics,this paper takes the promotion method of BCF fish and crayfish as the research object,and studies the propulsion performance of improving fluctuating propulsion of fish and jet propulsion of crayfish.Aiming at the fluctuating propulsion of fish,the effects of different shape fins on different environments and tasks are studied firstly.Then the flexible tail fins with active deformation and experimental platform are designed.The optimal shape of flexible tail fins under different tasks is explored by means of morphological structure comparison of bionic objects,numerical study and model test.The biomimetic caudal fin can change its shape smoothly and continuously according to the nature of the task,through the morphological and structural changes of the caudal fin structure.It can respond to the changing swimming conditions and mission characteristics,that is,it has the ability of long-range,high-speed and high-maneuverability propulsion,which greatly improves the propulsion performance.For jet propulsion,creatively combines the red-white muscle movement with the traditional jet propulsion of the crayfish,so that the bionic crayfish tail can remain bent after being quickly bent to the head.The bionic crayfish can get farther displacement through this control mode which improves the performance of escape advancement.The main contents and achievements of this paper are as follows:(1)For active deformation undulatory propulsion,fish are taken as bionic research object.Firstly,the morphological structure of fish is analyzed from the perspective of bionics.The caudal fin morphology and aspect ratio of tuna,pike and butterfly were analyzed and ab active deformed flexible caudal fin is designed.By calculating the area change of the it,the relationship of the aspect ratio of the caudal fin is studied.The undulatory model of the caudal fin is established,and the theoretical total speed,undulatory efficiency and input power are calculated.The thrust theory is studied,and the formula for calculating the thrust force is deduced,which provides a theoretical basis for the study of improving the propulsion performance of the active deformed flexible caudal fin.An experimental platform for active deformation wave propulsion was designed to evaluate the effects of different control modes and parameters on propulsion performance.Based on the designed experimental platform,force feedback method is selected as the experimental measurement method,and the efficiency calculation method based on force feedback method is explored.(2)For active deformed jet propulsion,the shape and structure of crayfish were analyzed,and the motion structure of crayfish jet propulsion was understood through the cross-section of the tail of crayfish.The mechanism of red and white muscle movement was studied.By combining the movement mode of red and white muscle with the jet propulsion of crayfish,the red and white muscle propulsion mode was designed for the bionic crayfish.On this basis,the SMA flexible thruster was designed.The thruster can simulate the rapid bending of the tail of the crayfish to the head,thus realizing the jet propulsion.The basic characteristics of SMA are analyzed.By understanding the transformation mechanism of martensite and austenite and one-dimensional constitutive model,the thermodynamic analysis of SMA wire is carried out,and the heat conduction model of SMA wire during heating and cooling is deduced.The static model of SMA flexible thruster is established,and the maximum bending angle and minimum radius of SMA flexible thruster are deduced.Finally,an experimental platform was designed to compare the traditional control mode with the red and white muscle control mode and the effects of different parameters on the jet propulsion performance.(3)An experimental platform system of active deformed flexible Caudal fin was built.The propelling force curve,average propelling force and propelling efficiency of each shape of tail fin were analyzed.It was found that although the crescent tail fin had the lowest propelling force,its propelling efficiency was the highest.The kinematics parameters such as swing frequency,swing amplitude and relative inflow velocity are studied experimentally to analyze the kinematics parameters of the tail fin for optimum propulsion performance under different environments and tasks.Two kinds of tail fin control modes which can change shape continuously in the same period are designed.The experiments of two different dynamic parameters and two kinds of tail fins with fixed shape(crescent and fan)are carried out.Through comparative experiments,it is found that the continuous deformation mode in the same period can improve the propulsion force and efficiency of the tail fin and the propulsion performance in a specific environment.Experiments show that the propelling performance of deformation mode is not superior to that of fixed shape mode in all cases,and specific problems need to be analyzed.Experiments show that the propelling performance of deformation mode is not always superior to that of fixed shape mode.The robotic fin needs to change its shape in real time according to the different external environment and tasks in order to achieve the optimal fluctuating propulsion under all working conditions.(4)The whole experimental platform system of jet propulsion was set up,and the jet propulsion experiment of bionic crayfish was carried out.The movement process of shrimp during jet propulsion was analyzed.The red and white muscle propulsion mode was designed and compared with the traditional shrimp propulsion mode.By comparing the jet propulsion trajectories of the traditional model and the red-white muscle model,it is found that the red-white muscle model can effectively reduce the fluctuation of the jet propulsion.By comparing the trajectories of the bionic crayfish,it is found that the red and white muscle model can improve the X-axis displacement of the bionic crayfish jet propulsion.Then the SMA wire diameter,elastic steel sheet thickness and driving voltage of SMA driver are studied and analyzed.By comparing average thrust force,average resultant force and jet propulsion direction of X and Z axes,the average resultant force and direction of jet propulsion under the optimum propulsion performance are obtained.