Design And Experimental Study Of Flexible Biomimetic Robot Fish Base On The Vibration Propulsion Mechanism

Evolution of fish has been on for billions of years and this leads to perfect swimming features, which are high-speeding swimming, incredible flexibility and high efficiency. No under-water robots or vehicles could compare with living fish so far, as a consequence, increasing number of academic and researchers have been working on bionic robot fish. After decades of development, progress has been achieved and the robotic fish can be drove in several different ways. However, practical application is not ideal, and as a main solution of which, the driving method needs to be studied. This project applied mechanical vibration into the propulsion of the bionic mechanical fish based on the similarity of mechanical vibration and swing of fish tail, by tuning the vibration frequency to the resonance frequency of the robotic fish to acquire efficient performance. Hence, this can be considered as an investigation of alternative robotic fish driving method.This design is inspired by the bionic point of view, which leads the overall design to a solid head with a flexible tail bionic robotic fish, the vibration source is embedded in the flexible tail and drives the tail swinging. The vibration is generated by a pair of symmetric eccentric wheels, which are driven by servo motor with a set of control circuit for accurate speed tuning, for the convenience of experiment, the rotation speed of servo motor is controlled by a mobile-phone connected to the control board through Bluetooth.The main task is the analysis of the flexible robotic fish. First of all, the resonance frequency of the flexible tail was calculated and the expressions of resonance frequency were carried out with constant cross-section area of the tail, after which, qualitative analysis on the relationship between flexible tail resonance frequency and tail cross-section variables was carried out. Then finite element method was used to analyze the resonance frequency of the fish, the existence of the excitation source may result in an empty space inside the tail and the position of this empty space may have an influence on the resonance frequency, hence, FE method was used to study the relationship between the position of the excitation source and the resonance frequency of the fish. In the end, Adams was used to simulate the results of the tail swinging and to analyze the response of the tail with vary excitation frequency.Experiment study was done after simulations and analysis of the flexible bionic robot fish were carried out. Difficulties during the assembling process, such as embedding vibration source inside the flexible body, counter weight of the fish and seal of the body, have been tackled. Swimming characteristics of the robotic fish from three different excitation positions on the body with three different materials of the tails has been studied. The feasibility of vibration drove robotic fish has been verified. Hence, the conclusion can be made: in a certain range, the closer to the tail the excitation position is, the better swimming performance the robotic fish will be achieved, better performance of the robotic fish can also be acquired by choosing appropriate tail stiffness.