The Caudal Fin And Jet Propulsion Performance Of The Bionic Robot Fish Driven By SMA And Experiment Research

As the combined point of the fish swimming mechanism and the robot technology, the bionic robot fish provides a new way to develop the new type of the underwater propeller, which has important research value and application prospect. The fish swimming modes can be divided into three types, which are caudal fin oscillatory propulsion mode, pectoral fin undulatary propulsion mode and jet propulsion mode. Currently, the majority of the bionic robot fish mimic the former two propulsion modes while fewer robot fish mimic the jet propulsion mode. Moreover, with the development of intelligent materials, the application of those materials in bionic robot fish has become to be the tendency. As a kind of the intelligent materials, SMA are the ideal actuating material for the bionic robot fish because of its greater stress and strain and lower driving voltage. In this paper, a kind of bionic caudal fin propulsor mimicing fish caudal fin propulsion and a kind of bionic jet propulsor mimicing squid jet propulsion actuated by SMA are designed respectively. Meanwhile, two kinds of bionic robot fish based above the two bionic propulor are developped to verify the feasibility.Initially, by imitating the structure and action mechanism of the caudal fin of the fish, a bionic SMA-driven caudal fin has been developed, which can achieve flexible bidirectional bending in a large range when it was driven by current. In order to analyze the driving performance of the bionic caudal fin, the driving model has been established which combined the mechanical and geometric model of the caudal fin and the thermodynamic model and the constitutive model of SMA. Through the analysis of the driving model, it can come to a conclusion that the relationship between the bending angle of the bionic caudal fin and the driving current is approximately linear when the driving current varied between a certain range. And it is verified by experiment, which provides the theoretical and experimental basis for the control of the bionic caudal fin.For further studying the propulsion performance, the CFD method was emplyed to simulate the three-dimensional flexible bending of the bionic caudal fin. The simulation results show that the flexible bending of the caudal fin can not only produce the periodic proplusive force, but also produce the periodic lateral force, and the fluctuation amplitude of the lateral force is much greater than the proplusive force.To eliminate the fluctuation of the lateral force, the twin caudal fin symmetrical swing propulsion mode was proposed. The numerical simulation was carried out and the results show that the twin caudal fin symmetrical swing mode not only effectively eliminate the fluctuation of the lateral force, but also enhance the propulsive force, which means that the propulsive force the twin caudal fin produced is greater than the sum of the propulsive force that two individual single caudal fin produced. In addition, the flow field, the pressure field and the three dimensional vorticity around the single and twin caudal fin were analyzed, and the propulsion mechanism of the caudal fin and the fluid field couple of the twin caudal fin were also analyzed. Subsequently, the propulsive force test platform was established and the propulsive force and lateral force that produce by the single caudal fin and the twin caudal fin were measured respectively. The experiment results verified the correctness of the numerical simulation.Based on the analysis of the mechanism of the cuttlefish jet propulsion, our research group developped a kind of bionic cuttlefish mantle actuated by SMA by imitating the structure of the cuttlefish mantle, through which the jet propulsion can be achieved. To further improve the action performance of the bionic mantle, we improve the arrangement of the SMA wire and put forwad a kind of bionic mantle with the V type arrangement of SMA wire. In order to anlyalze the action and propulsion performance of the V type arrangement bionic mantle, the action theory model has been established which combined the geometric deformable model, the mechanical model and the cavity pressure model of the bionc mantle and the thermodynamic model, constitutive model of SMA. Through the analysis of the model, the action amplitude of the bionic mante and the jet thrust the bionic mantle jet propeller can produce were cauculate and the impact of the SMA wire arrangement angle on the action amplitude were investigae, and the optimal SMA wire arrangement was obtained. Then the experimental study was conducted to reseach the jet thrust performane of the bionic mantle jet propeller and the results verified the correctness of the theory.Finally, a bionic robot fish based on the bionic caudal fin propulsion and a bionic robot fish based on the bionic jet propulsion were developed respectively, and a control system can realize the self-propelled swimming was also developed. Then the swimming experiment was carried out, the results show that the bionic fish can realize the straight line swimming, the turning swimming and desired trajectory self-propelled swimming. Furthermore, the experimental results also show that the twin caudal propulsion can effectively eliminate the head swinging and improve the stability of the robot fish.