Design And Experimental Research Of A Bionic Stingray Robot Based On CPG

Since the 21 st century,the strategic position of marine resources is becoming more and more important,and mankind has been accelerating the pace of exploring the ocean,all kinds of underwater bionic robot as an important tool to explore came into being.Compared with the traditional propeller,the bionic underwater robot has the advantages of high maneuverability,high power-to-weight ratio and good stability,which has become the focus of researchers all over the world.In this thesis,stingray is regarded as a biomimetic research object.Based on the analysis of biological characteristics and swimming mechanism of stingray,a bionic stingray robot with circular long-fin was developed and a CPG method was proposed to control the fluctuation of circular long-fin.Besides,the propulsion performance of the prototype was experimentally studied.This bionic stingray robot in this thesis provides a new propulsion method and control method for the research of high efficiency and high mobility bionic underwater robot.Firstly,the mechanism of muscle and skeletal structure and fin surface fluctuation were analyzed,the kinematic model and the hydrodynamic model,based on Lighthill's ‘Large-Amplitude Elongated-Body Theory' of the pectoral fin,was established.And the influence of undulating frequency and amplitude on the propulsion force of stingray were also analyzed preliminarily.Secondly,to simulate the morphological characteristics of the stingray,the shell structure of the bionic stingray robot was designed,and the circular long-fin structure,static submerged and floating module and attitude control module,based on structural bionics and functional bionics,were designed.Then,the corresponding control system is designed.Based on the structural characteristics of the circular long-fin,three swimming strategies are proposed,which are straight-line swimming,maneuvering turn and dynamic floatation.Thirdly,a motion control method based on the central pattern generator(CPG)is proposed according to the structural characteristics and propulsion mechanism of the circular long-fin.After analyzing the characteristics of the Ijspeert's phase oscillator,we design the bionic CPG network topology of the stingray,and according to the different swimming gait,the reasonable coupling relation and the connection weight are determined,and an amplitude transition method is proposed to deal with the transition of the output signal during gait switching.And then,the CPG network output waveform is simulated and verified by MATLAB/Simulink? software,which proves the effectiveness of the CPG network model constructed for the circular long-fin structure.Finally,the swimming performance of the stingray robot was tested and the effects of the undulating frequency and amplitude on the swimming speed and propulsion force were analyzed.The simulation results were also compared with the theoretical simulation data.The experimental results show that the circular pectoral fins of the stingray robot can finish the undulating movement similar to the living creature,and the posture is stable and flexible in the process of swimming.The straight-line swimming speed and standing turning speed increase with the undulating frequency and amplitude,the maximum line swimming speed can reach 109 mm / s,the maximum standing turning speed can reach 93 ° / s,the maximum propulsive force can be 1.62 N and the maximum turning moment is 67.37 N ?mm,the propulsive force and standing turning moment are increasing with the increase of the undulating frequency and amplitude.