Research On The Tail Driving System Of A Bionic Carangiform Fish Based On Linear Hypocycloid

Imitating fish tail beating motion, water or underwater bionic thruster driven by motor combo with a mechanical transmission is one of main models.The driving theory of motion and power has not received sufficient attention,which is a most important factors affecting the bionic thruster performance such as propulsive velocity and force, efficiency, and even to the thruster structure. In this paper, based on the composition of tail driving system’s transmission and transformation, combined with characteristics of Linear Hypocycloid and planetary gears, the two-joint tail driving system of bionic carangiform is developed.Propulsion performance of this linear hypocycloid tail driving system is further studied from the aspects of principle design, parameter optimization, kinematics, dynamics and experimental verification.Firstly, based on Linear Hypocycloid, combined with two-joint tail driving mechanism,the two-joint tail driving system is presented to imitate lunate tail swimming of carangiform fish. The kinematics study on the tail driving system is conducted with graphical method of vector equation. The relationships of different structural parameters are studied, and further optimization of structure sizes is developed. The comparative study on the driving system with a live fish of Carp is simulated in MATLAB.Secondly, the kinematic model of the two-joint tail driving system is simplified into a simple 2D tail fin. According to the 2D model of tail fin oscillating, dynamic and hydrodynamic analysis are conducted with Momentum Theorem, Lagrange Theorem and Two-dimensional Foil Theory.At last, based on the proposed kinematic and hydrodynamic models, the visual flow-field of tail fin oscillating is presented by numerical simulation in Fluent software. The influences of motion parameters on tail fin’s propulsive performance are studied in detail.Then, the prototype and the experimental plat of this designed driving system are established. The propulsive performance from experiments compared with theoretical derivation is analyzed. The comparative results testify the feasibility and efficiency of the tail driving system, which will lay a solid theoretical foundation for developing a better bionic thruster.