Studies On Kinematics,Dynamics And Control Of Flexible Pectoral Fin During Labriform Swimming

With the national demand for the exploitation of marine resources,the design of underwater propulsion equipment has attracted more and more attention from scholars.After billions of years of evolution,fish in nature have excellent underwater propulsion performance.Studying the fish's propulsion mechanism is of great significance to improve the propulsion performance and efficiency of underwater propulsion equipment.Based on the morphology of pectoral fins of fish,this paper studies the kinematics and hydrodynamics of pectoral fins when fish are swimming stably with labriform mode.The effects of kinematic parameters on pectoral fin propulsion performance are explored,kinematics,dynamics and control model of the pectoral fin are all researched in his paper.Firstly,the fish's movement patterns are briefly introduced,including the BCF movement pattern and the MPF movement pattern.In the anatomy and morphology of the fish pectoral fins,the musculoskeletal structure and the basic principles of the pectoral fins driven by their muscle tissue are explained.Based on the kinematics of the pectoral fin during stable swimming with labriform mode,a simplified pectoral fin model consisting of five-ray and membranes is determined.Each fin ray achievs its basic motion by two mutually orthogonal degrees of rotation.Combined with the D-H parameter modeling method in robotics,a ten-degree-of-freedom flexible pectoral fin kinematic model is established,and a program is written in MATLAB to simulate and analyze the pectoral fin locomotion.Then,based on the kinematic model of the pectoral fin and the basic flow resistance model,a semi-empirical theoretical model of the pectoral fin is established.Based on the basic fluid mechanics theory of objects immersed in flow,the model uses the micro-element method to analyze the force of the membrane surface,and numerical integration is used to solve the hydrodynamics of the pectoral fin.By programming a program in MATLAB to solve the model,a curve of hydrodynamic force(thrust,lift,lateral force)generated during the m ovement of pectoral fin in a cycle is obtained.At the same time,a fluid structure interaction model of pectoral fin moving in water is established in the finite element analysis software ADINA,which simulated the surrounding flow field changes during pe ctoral fin locomotion,and the fluid node forces on the interaction boundary are extracted to describe the change of hydrodynamics.The calculation results of the semi-empirical theoretical model and the fluid structure interaction numerical model are consistent with each other,which means that the correctness of the numerical model and theoretical model is verified by each other.Secondly,based on the numerical analysis method,the effects of kinematic parameters on the swimming performance were also analyzed.The parameters,which have a significant influence on the hydrodynamic force,are the frequency f and the flapping angle.As the frequency increases,the thrust and lateral forces surge and the lift force has a slight rise.The thrust force soars approximately linearly with the flapping angleincreasing,and there is no significant change in lateral force and lift force.The rowing angle ? and the phase lag have little effect on the hydrodynamic force.Therefore,the frequency and amplitude of flapping angle should be focused preferentially when a biorobotic pectoral fin is designed.Finally,based on the kinematic model of the pectoral fin and the results of numerical simulation of fluid structure interaction,the kinematic and dynamic control of a single fin ray are studied.In the control model of kinematics,the trajectory tracking of the fin ray in the Cartesian coordinate system is realized using the inverse Jacobian control method.In the control model of dynamics,a combination of feed-forward torque control and feedback control is used to implement the closed-loop control of the entire system.The hydrodynamic force obtained from the numerical simulation is added to the dynamic control system and regard as external disturbance force.The control simulation is carried out for the purpose of trajectory tracking of a single fin.