Design And Research Of A Bionic Propulsion Mechanism

Underwater propeller shaft of conventional propeller produces cavitation phenomenon at high rotational speeds,resulting in blade wear and lower efficiency,which is only 40%-60% of its nomal value.In contrast,when the bionic propeller is in motion,its propulsion efficiency is high,disturbance is small and flexibility is high,making the bionic propellers become an important development trend of modern robots.The internal transmission structure of the existing bionic propeller is relatively complicated,making its motion control strategy difficult,affecting the propulsion speed and maneuverability of the bionic propeller.Therefore,a new type of double-tailed bionic robot fish is designed in the paper,which adopts a simple non-fast-return crank handle rocker mechanism.Through the cooperation of the double fish tail and the pectoral fin,it can realize linear swimming,left and right turning,floating and diving.It has been showed that the bionic fish has good speed and maneuverability in a series of underwater experiments.The main research contents of this paper are as follows:1.A new type of fishtail bionic robot fish was designed.The advantages and disadvantages of the all kind of internal transmission mechanisms of the bionic fish are analyzed and compared.Two internal transmission mechanisms are proposed,and the optimal mechanisms,crank and rocker transmission scheme,is selected.According to the internal transmission scheme,the double-tailed driving mechanism was designed,and the movement state of the caudal fin linear motion,floating and diving was analyzed.The simulated frog-type double pectoral fin structure was designed to assist the robotic fish movement,and the pectoral fins were analyzed for turning,floating and diving in auxiliary movement state.Finally,the power unit,communication unit,control unit,positioning unit and other mechanical structures of the bionic fish were designed to complete the prototype design.2.Design and simulation of the crank-free rocker mechanism without fast return.The mathematical model of the internal crank rocker transmission mechanism is established,and the computer aided optimization design of the transmission mechanism is carried out to solve the optimal value of the minimum transmission angle of the mechanism.Motion simulation was performed by MATLAB/Simulink software.3.The effects of caudal fin shape and wake structure on the propulsion efficiency of bionic fish were analyzed.Secondly,the force analysis of the caudal fin under water swing was carried out.The motion trajectory of the caudal fin was analyzed by mathematical modeling.The bionic fish model was imported into Adams software for simulation,and the motion law of the bionic fish in the straight line,turning and floating down dive was obtained.4.A GPS/BDS dual-mode underwater positioning system is designed.The system uses a data processing algorithm combining median filtering and Kalman filtering.The underwater positioning experiment shows that the positioning performance of the dualmode positioning system is significantly higher than that of the single-mode positioning system.5.The five kinds of postures of bionic robotic fish,such as linear swimming,left turn,right turn,floating and dive,are analyzed,and the control strategies are set for various kinds of postures.At the same time,the control system of bionic fish was designed.The system chose to control two motor drive modules L298 N by single chip SC89F5162 chip.The two motor drive modules control the motors of upper and lower caudal fins and left and right pectoral fins respectively.6.An underwater prototype experiment was performed on the robotic fish.The experimental positioning data is collected by the dual-mode positioning system in the robot fish,and is fitted into the swimming route of the robot fish.Underwater experiments show that when the swing frequency of bionic fin and caudal fin is 3Hz,the speed can reach 0.98m/s and the turning radius is 0.34 m.It is verified that the bionic fish has good speed and maneuverability.