Design Of Biomimetic Robotic Fish With 3 DOF Pectoral Fins And Flexible Body And Its Hydrodynamic Characteristics Analysis

In recent years,with increasing development of ocean exploration,As an important equipment for the development and utilization of underwater resources,underwater robot has received extensive attention and research.With the characteristics of high efficiency and low noise and flexible movement,the biomimetic robotic fish has become one of the future directions of underwater robot research.A robotic fish with pectoral fins which can achieve three Degree of Freedom(DOF)movements and a wire-driven flexible body and caudal fin is designed.The three DOF pectoral fin kinematics models of the robotic fish were established,using Computational Fluid Dynamics(CFD)technique,the pressure of the flow field about the robotic fish under different conditions were numerically simulated and the performance of propulsion of the biomimetic robotic fish under the conditions of multi DOF pectoral fins propulsion was obtained,the hydrodynamic characteristics were verified by experiments.The details are as follows:(1)Carangidae as the biomimetic object,a robotic fish with three DOF pectoral fins and wire-driven flexible body and caudal fin is designed.The three DOF pectoral fin propulsion mechanism includes feathering and a flapping and lead-lag motion.The mechanism can perform single and combined motions that can achieve the purpose of the complex motions of the pectoral fins.The wire-driven flexible body and caudal fin includes a wire-driven mechanism and a multi vertebrae flexible body and caudal fin that can fit fish body waves of Lighthill curves.(2)The laws of the sinusoidal motion of the unilateral pectoral fin have been studied.To establish the dynamic mesh of the pectoral fin,with the Flunet simulation software,the performance of the hydrodynamics of the linear movement of the robotic fish pectoral fins propulsion in different frequencies is analyzed,which resulted in data on continuous changes about thrust,lift and lateral coefficient,as well as pressure contours of the robotic fish.Conclusions are found from the analysis,that when the robotic fish is propelled with pectoral fins,the frequency of the pectoral fins motion has an importamt influence on the linear movement under the same DOF motions.The comprehensive analysis results demostrate that the propulsion performance is better under the condition of f=1.0Hz both single and combined motion of pectoral fins.Under the same frequency condition,the motions of the different DOF of pectoral fins has an important influence on the robot fish propulsion,the single DOF propulsion performance is poor at f=0.5,1.0Hz,and the three DOF combined motion of pectoral fins has the best propulsion performance,while f=1.5,2.0Hz,In the multi-DOF combined motion,the three DOF motion law is more complicated,in general,the two DOF motion propulsion performance is better than the three DOF,and the three DOF motion of the pectoral fin needs to be further optimized at high frequencies.The analysis results are verified by experiments,it is basically consistent with the results of the simulation analysis.(3)The laws of the sinusoidal motion of the bilateral pectoral fins have been studied.To eastablish the fish body dynamic mesh model,through the Flunet simulation software,the hydrodynamics of the turning movement of the robotic fish pectoral fins propulsion in different DOF during different frequencies is analyzed,which result in data on continuous changes about thrust,lift and lateral forces,as well as pressure contours of the robotic fish.conclusions is found from the analysis,when feathering motion of he robotic fish,the turning performance of the robot fish is poor;when the lead-lag and the combined motion,the robotic fish realizes the turning function through the thrust and the lateral force,that demonstrate the better turning performance,the robotic fish has a good turning effect at f=1.0,1.5Hz.Under the same frequency condition,the three DOF motion always has good turning propulsion performance,which fully reflects the flexible maneuverability of MPF bionic robot fish.The analysis results are verified by experiments,it is basically consistent with the results of the simulation analysis.