Dynamics and motion for three joint robotic fish
                                                               ZHANG De yi1, ZHAO Hong fei2, WANG Qi1, ZHANG Chao1
（1.School of Mechatronic and Power Engineering, Jiangsu University of Science and Technology, Zhangjiagang 215600, China;2.KTK Group, Changzhou 213000, China）


Abstract: In order to control the underwater movement of bio robotic fish, through researching on the fish body shape and movement patterns, the model structure of the robotic fish and dynamics model was established. The wave theory of liquid was used to analyze hydrodynamic motion law for robotic fish third connecting rod preliminarily. The resistance of robotic fish related to the factors just as the area under the water, the oscillation frequency and the length of connecting rod was found. Moving velocity and acceleration cloud be improved by choosing quality and length of the connecting rod properly. Swing angle was got according to the theory of large swing of slender, and Matlab was used to simulate the motion of the fish. Experiment was also carried on. Both the results of simulation and experiment indicate that with the oscillation frequency increasing, the driving force will be increased, the fish swing will be increased, the moving velocity and the stability of the movement will be affected further. There is a reasonable oscillation frequency range makes the moving velocity reach the maximum.
Key words: robotic fish; dynamics; swing motion; moving velocity