The Design Of A New Propulsion Mechanism Of Robotic Fish And Optimization Of Swimming Speed

Bionic robot fish is an active area of underwater robot research. The swimming speed isone of the key performance indicators in the field of bionic robot fish. For the robotic fishdriven by the body and/or caudal fin (BCF), some important factors that affect its swimmingspeed include oscillating frequency, oscillating amplitude, caudal tail fin shape and flexibility.Especially, the oscillating frequency is the most important factor among them. In this thesis, anew kind of robotic fish is designed that significantly improve the speed of the robot fishswimming by improving oscillating frequency up to8Hz. The main contents are as follows:(1) A new propulsion mechanism of robotic fish is first designed and then its shell iscompleted by evaluating the relation between the center of gravity and buoyance. Specifically,the propulsion mechanism can transform rotary motion of DC motor into high frequencyoscillation that is consistent with the requirement of robotic fish tail. Meanwhile, theconditions for robotic fish to achieve stable swimming are satisfied by modifying the shape ofrobot fish head shell. The oscillating frequency of proposed mechanism is up to8Hz.(2) The experimental scheme of swimming speed optimization is designed. Here, fourparameters, including AR, D, f and k, are selected to optimize the swimming speed. Under theconstraints of motor power, a optimization program is given as follows. Firstly, the wholeparameter space is divided into the largest regular space and the remainder space. Secondly,adopted the orthogonal method in the largest regular space, the preliminary relation ofswimming speed with these parameters are obtained by variance analysis. On this basis,further experiments are carried out by selecting some typical combination of parameters in theremainder space. By comparison with the results in the regular space, the fastest swimmingspeed is determined.(3) An experimental platform is established to optimize the swimming speed of roboticfish. In our scheme, a video image analysis method is used to measure the swimming speed.By capturing a number of video snapshots in a second, the length of trajectory is calculated.The swimming speed is equal to the product of this length and scale. Oscillating frequency isobtained indirectly by using an oscilloscope to measure the voltage fluctuation frequency.(4) The rules of swimming speed optimization under high frequency is obtained byanalysis the results of experiments, where the fastest speed of robotic fish is up to870mm/s,approximately2.6BL/s. Specifically, the swimming speed is remarkably positive correlatedto the parameters k and f. Meanwhile, the correlation of swimming speed with parameters Dand AR is nonlinear but they are not positive correlated. Therefore, only15kinds of theparameter combination are selected for further experiment and the fastest speed is obtained.