A study on the motion mechanism of articulated fish robot

Recently, the technologies of mobile robots have been growing rapidly in the fields such as cleaning robot, explosive ordnance disposal robot, patrol robot, and etc. However, the researches about the autonomous underwater robots have not been done so much, and they still remain at the low level of technology. In this paper, we studied the motion mechanism of real fishes, from which we derived the dynamic equations of a fish robot. Using the equation we developed a method to find the optimal parameters to give a maximum propulsive power for a considered fish robot. The fished robot is model as a three jointed rigid bodies and its length is chosen as about 860 mm, based on the simulation result. Two servo motors with encoders are located at link 1 and link 2, respectively. However, the fourth link is connected to link 3 with a flexible springs to imitate the smooth motion of real fishes. Finally some experiments are carried out to compare the motion characteristics between experiment and simulation.